JP2008027570A - Suspension substrate and manufacturing method thereof - Google Patents

Abstract

A main object of the present invention is to provide a suspension substrate that can be produced at low cost and can sufficiently prevent electrostatic breakdown and suppress noise.
The present invention provides a metal substrate, an insulating layer formed on the metal substrate and having an opening through which the metal substrate is exposed, and formed on the insulating layer and disposed in the vicinity of the opening. A suspension substrate having a ground wiring layer formed on the opening and a ground terminal in contact with the metal substrate and the ground wiring layer, wherein the ground terminal has a melting point of 450 ° C. or lower. The above-described problems are solved by providing a suspension substrate that is formed of metal.
[Selection] Figure 1

Description

  The present invention relates to a suspension substrate that is produced at low cost and can sufficiently prevent electrostatic breakdown and suppress noise.

  In recent years, due to the spread of the Internet and the like, there has been a demand for an increase in the amount of information processing of personal computers and an increase in information processing speed, and along with this, the capacity of hard disk drives (HDD) incorporated in personal computers has increased. Increasing information transmission speed is required. In addition, a component called a magnetic head suspension that supports the magnetic head used in the HDD also has a signal line such as a copper wiring directly formed on a stainless steel spring from a conventional type in which a signal line such as a gold wire is connected. The so-called wireless suspension has been shifted to the integrated wiring type.

  Recently, there has been an increase in demand for HDDs mounted on various small devices such as portable applications. For this reason, HDDs have become denser and magnetic heads have become smaller, and magnetic heads have become more sensitive. It is easily affected by static electricity. Therefore, there is a problem that the characteristics of the small magnetic head element are changed by the electric charge accumulated in the slider, or in the worst case, it is destroyed.

  Further, as another problem, in order to improve the signal transmission speed and accuracy of the HDD, in recent years, there has been a tendency to use a higher frequency electric signal. However, as the frequency becomes higher, the noise of the transmitted electric signal becomes smaller. There was a problem of increasing. The cause of noise is considered to be due to the potential difference between the metal substrate and the wiring layer.

  With respect to these problems, for example, in Patent Document 1, in order to prevent electrostatic breakdown of the magnetic head, an electrical connection is made between the magnetic head and the suspension using a conductive resin, and the suspension side is also protected. It discloses that a grounding electrode is formed of a conductive material such as copper by sputtering, plating, vapor deposition, or the like.

  For example, Patent Document 2 discloses that a ground terminal for short-circuiting the wiring and the suspension substrate is provided on the suspension with wiring in order to suppress noise generation. In the process of forming the ground terminal, since an additive method is used, a power feeding layer forming step by a dry process and a wiring layer forming step by an electrolytic plating method are necessary.

  According to the above-described conventional technology, it is necessary to perform a relatively time-consuming process such as sputtering, plating, or vapor deposition when forming the ground electrode and the ground terminal. Therefore, there is a problem that productivity is low and cost is high.

JP-A-8-1111015 JP 2006-12205 A

  The present invention has been made in view of the above circumstances, and has as its main object to provide a suspension substrate that is produced at a low cost and that can sufficiently prevent electrostatic breakdown and suppress noise. It is.

  In order to solve the above problems, in the present invention, a metal substrate, an insulating layer formed on the metal substrate and having an opening through which the metal substrate is exposed, formed on the insulating layer, and A suspension board having a ground wiring layer disposed in the vicinity of the opening, and a ground terminal formed in the opening and in contact with the metal substrate and the ground wiring layer, wherein the ground terminal is A suspension substrate is provided which is made of a metal having a melting point of 450 ° C. or lower.

  According to the present invention, since the melting point or liquid phase point of the metal used for forming the ground terminal is relatively low, there is an advantage that the ground terminal can be easily formed.

  In the above invention, it is preferable that the ground terminal has a convex shape having a vertex in the region of the opening in plan view. The ground terminal having such a shape can be formed, for example, by a method of quantitatively dropping a metal having a melting point of 450 ° C. or lower in a molten state, and this method can reduce the cost and simplify the process. It is easy.

  In the said invention, it is preferable that the metal which forms the said ground terminal is lead-free solder. This is because the load on the environment can be reduced.

  In the above invention, the grounding wiring layer is formed so as to surround the opening in plan view, and the grounding wiring layer suppresses an air pool generated when the ground terminal is formed. It is preferable to have a part. This is because the contact area between the ground terminal and the metal substrate can be sufficiently increased by suppressing the occurrence of air accumulation.

  In the present invention, the ground wiring layer in the vicinity of the opening is preferably in a line shape. This is because air accumulation is unlikely to occur.

  In the said invention, it is preferable that the said ground terminal is formed only in the inside of the area | region enclosed by the edge part of the said opening part. This is because the grounding wiring layer disposed in the vicinity of the opening can be reduced in size, and space and weight can be reduced.

  In the said invention, it is preferable that the intermetallic compound layer is formed in the joining interface of the said ground terminal and the said metal substrate. This is because the electrical connection between the ground terminal and the metal substrate becomes better and the electrical resistance becomes lower.

  In the present invention, a metal substrate, an insulating layer formed on the metal substrate and having an opening through which the metal substrate is exposed, and a ground formed on the insulating layer and disposed in the vicinity of the opening. A metal forming layer having a melting point of 450 ° C. or less in a molten state is quantitatively dropped into the opening to contact the metal substrate and the grounding wiring layer. There is provided a method for manufacturing a suspension substrate, comprising a ground terminal forming step of forming a ground terminal.

  According to the present invention, it is possible to reduce the cost and simplify the process by dripping molten metal into the opening to form the ground terminal.

  In the said invention, it is preferable that the dripping method of dripping quantitatively in the state which the said metal melt | dissolved is a method of using the metal ball which has a predetermined | prescribed diameter, melting the said metal ball sequentially, and dripping. This is because the amount of molten metal dripped can be freely adjusted by appropriately selecting the diameter of the metal ball as the raw material.

  In the said invention, when the said metal is dripped in the molten state, it is preferable that the diameter of the molten metal is smaller than the diameter of the said opening part. This is because the molten metal can be landed more reliably by making the diameter of the molten metal smaller than the diameter of the opening.

  In the present invention, there is an effect that it is possible to provide a suspension substrate that can be produced at low cost and can sufficiently prevent electrostatic breakdown and suppress noise.

  Hereinafter, the suspension substrate and the manufacturing method thereof according to the present invention will be described in detail.

A. First, the suspension substrate of the present invention will be described. The suspension substrate of the present invention includes a metal substrate, an insulating layer formed on the metal substrate and having an opening through which the metal substrate is exposed, and formed on the insulating layer and disposed in the vicinity of the opening. A suspension substrate having a ground wiring layer formed on the opening and a ground terminal in contact with the metal substrate and the ground wiring layer, wherein the ground terminal has a melting point of 450 ° C. or lower. It is formed from a metal.

  According to the present invention, since the melting point of the metal used for forming the ground terminal is relatively low, there is an advantage that the ground terminal can be easily formed. In addition, ground terminals formed by conventional sputtering methods, vapor deposition methods, plating methods, and the like have a problem that productivity is low and cost is high because of a relatively time-consuming process. In the invention, for example, as will be described later, the ground terminal can be easily formed by dropping molten metal into the opening.

  Next, the suspension substrate of the present invention will be described with reference to the drawings. FIG. 1 is a schematic plan view showing an example of a suspension substrate according to the present invention. More specifically, FIG. 1 is an enlarged schematic plan view showing a front end portion on which a magnetic head slider is mounted. The suspension substrate shown in FIG. 1 has a patterned wiring layer made of Cu (ground wiring layer 3a, write circuit) on SUS as a metal substrate 1 having a spring property via polyimide as an insulating layer 2. A wiring layer 3b for reading and a wiring layer 3c for reading are formed. Furthermore, the suspension substrate shown in FIG. 1 has a ground terminal 4 for conducting the metal substrate 1 and the ground wiring layer 3a.

  FIG. 2 is a sectional view taken along line XX in FIG. As shown in FIG. 2, the suspension substrate of the present invention is formed on a metal substrate 1, an insulating layer 2 formed on the metal substrate 1, and having an opening 5 through which the metal substrate 1 is exposed, and an insulating layer 2. And a grounding wiring layer 3a disposed in the vicinity of the opening 5 and a ground terminal 4 formed in the opening 5 and in contact with the metal substrate 1 and the grounding wiring layer 3a. In the present invention, the ground terminal 4 is formed of a metal having a specific melting point.

In the present invention, as shown in FIG. 2, the ground terminal 4 preferably has a convex shape having an apex in the region of the opening 5 in plan view (direction A in FIG. 2). . This is because the ground terminal having such a shape can be formed, for example, by a method of dropping molten metal into the opening, and this method can easily reduce the cost and simplify the process. Usually, when molten metal is dropped onto the opening, the molten metal flows after landing, so that a convex shape with the landing point as the apex is formed. In other words, the ground terminal is preferably formed by quantitatively dropping a metal having a melting point of 450 ° C. or lower in a molten state. On the other hand, when the ground terminal in the present invention is formed by plating, the shape of the ground terminal 4 has a recess near the center of the opening 5 as shown in FIG.
Hereinafter, the suspension substrate of the present invention will be described for each configuration.

1. First, the ground terminal used in the present invention will be described. The ground terminal used in the present invention is formed in an opening which will be described later, and has a function of contacting the metal substrate and the grounding wiring layer and making both conductive. Furthermore, the ground terminal used in the present invention is formed of a metal having a melting point of 450 ° C. or lower. Among them, the melting point of the metal is preferably 350 ° C. or less, particularly preferably 250 ° C. or less. This is because if the melting point of the metal is low, the metal can be easily melted and a ground terminal can be easily formed.

In the present invention, the “melting point” refers to the temperature at which a solid phase substance maintains equilibrium with the liquid phase under a constant pressure, and is also referred to as the melting point. In the case of a single metal or an eutectic composition of two or more components (a mixture of two or more crystals that crystallize simultaneously from a liquid containing two or more components), the melting point is the freezing point (the temperature at which the liquid solidifies). Matches. In the case of a metal that is not a eutectic composition composed of two or more components coexisting in equilibrium, the relationship between the composition of the liquid and solid composed of two or more components coexisting in equilibrium and the temperature, that is, the melting point When the temperature (melting point) is taken on the vertical axis and the composition (ratio of components) is taken on the horizontal axis, the temperature at which the liquid phase and the solid phase are kept in equilibrium is drawn on the liquid phase composition. A liquidus is obtained, and the liquidus point here is the melting point.
The lower limit of the melting point of the metal is not particularly limited as long as it is solid at normal temperature (25 ° C.), but is usually 100 ° C. or higher.

  The melting point of the metal can be measured by differential thermal analysis (DTA) or differential scanning calorimetry (DSC) according to JIS Z3198-1. Examples of the thermal analyzer include DSC8230 and TG8120 manufactured by Rigaku Corporation.

  The metal used in the present invention may be a single metal or an alloy as long as it is a metal having a melting point or lower as described above, but in the present invention, the metal is preferably an alloy. This is because an alloy having a low melting point can be easily obtained by mixing a metal having a low melting point, and a wide variety of metals can be used.

  The alloy is not particularly limited as long as it is an alloy having a melting point or less as described above. Specifically, tin (Sn), lead (Pb), zinc (Zn), silver (Ag), copper ( An alloy containing at least two kinds of metals selected from the group consisting of Cu), indium (In), bismuth (Bi), antimony (Sb), nickel (Ni), and germanium (Ge) can be given. Among these, in the present invention, the alloy includes at least two kinds of metals selected from the group consisting of tin (Sn), lead (Pb), silver (Ag), copper (Cu), and bismuth (Bi). It is preferable that

  In the present invention, it is preferable to use solder as the alloy. In general, solder can be roughly classified into lead-containing solder and lead-free solder. In the present invention, the lead-containing solder means a molten material containing lead (Pb) and tin (Sn) as main components and having a melting point equal to or lower than the above-described temperature. Lead-free solder refers to a molten material that does not contain lead (Pb), contains tin (Sn) as a main component, and has a melting point equal to or lower than the above-described temperature. Among them, in the present invention, it is preferable to use lead-free solder as the alloy. This is because the load on the environment can be reduced.

  Specific examples of the lead-free solder include Sn—Sb, Sn—Cu, Sn—Cu—Ni, Sn—Ag, Sn—Ag—Cu, Sn—Ag—Cu—Bi, Examples thereof include Sn—Zn, Sn—Ag—In—Bi, Sn—Zn, Sn—Bi, Sn—In, and Sn—Sb solders.

  Specific examples of the lead-containing solder include Sn—Pb, Sn—Ag—Pb, Sn—Pb—Bi, Sn—Sb—Pb, Sn—Ag—Sb—Pb, and the like. Can be mentioned.

  On the other hand, the single metal is not particularly limited as long as it is a metal having a melting point or lower as described above, and examples thereof include tin (Sn) and lead (Pb).

  The shape of the ground terminal is not particularly limited as long as the metal substrate and the grounding wiring layer can be conducted. The shape of the ground terminal differs depending on the shape of an opening, which will be described later.

  The resistance value of the ground terminal is not particularly limited. For example, it is preferably 5Ω or less, more preferably 1Ω or less, and particularly preferably 0.5Ω or less.

  In the present invention, when a ground terminal is formed by melting a low melting point metal and dropping it into the opening of the insulating layer, a flux is used to remove the metal oxide film formed on the metal surface such as SUS. Processing may be performed. Such flux treatment is not performed when the ground terminal is formed by plating or the like. Therefore, it is possible to determine whether or not the ground terminal is manufactured by a plating method or the like by examining the presence of the flux residue. The presence of the flux residue can be confirmed by ion chromatography, AES (Atomic Emission Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy).

  In the present invention, it is preferable that the ground terminal is formed only inside a region surrounded by the end of the opening. This is because the grounding wiring layer disposed in the vicinity of the opening can be reduced in size, and space and weight can be reduced. If the weight in the vicinity of the ground terminal can be reduced, the metal substrate can be made thinner.

  Specifically, as shown in FIG. 4A, the ground terminal 4 can be formed only inside the region surrounded by the end B of the opening 5. In the present invention, as shown in FIG. 4B, the ground wiring layer 3 a may have an opening smaller than the opening 5. Further, from the viewpoint of improving the bonding reliability, the ground terminal is preferably formed so as to fill the opening. On the other hand, from the viewpoint of weight reduction, the ground terminal may be formed so as not to partially fill the opening.

  As a method for forming such a ground terminal, for example, as described in “B. Manufacturing method of suspension substrate”, which will be described later, when the metal is melted and dropped into the opening, the molten metal A method of making the diameter smaller than the diameter of the opening can be exemplified.

  In the present invention, it is preferable that an intermetallic compound layer is formed at the bonding interface between the ground terminal and the metal substrate. This is because the electrical connection between the ground terminal and the metal substrate becomes better and the electrical resistance becomes lower. Specifically, as shown in FIG. 5, an example in which an intermetallic compound layer 21 is formed at the bonding interface between the ground terminal 4 and the metal substrate 1 can be exemplified.

The intermetallic compound layer usually has both components of the metal constituting the ground terminal and the metal constituting the metal substrate. For example, when Cu and Au are used as the metal constituting the ground terminal and SUS304 is used as the metal substrate, the intermetallic compound layer includes a Cu element, an Au element, a Sn element, and the like.
The composition of the intermetallic compound layer can be measured, for example, by EDX or AES.
The film thickness of the intermetallic compound layer is not particularly limited as long as the electrical connectivity between the ground terminal and the metal substrate can be improved. For example, the film thickness is in the range of 0.1 μm to 5.0 μm, especially 1.0 μm. It is preferable to be within a range of ˜3.0 μm.

  In addition, as a method for forming such an intermetallic compound layer, for example, as described in “B. Suspension substrate manufacturing method” described later, an oxide film is removed from an exposed metal substrate, and then, Examples include a method of bringing a molten metal into contact with an exposed metal substrate before the metal oxide film is formed on the surface of the metal substrate after cleaning.

2. Insulating Layer and Grounding Wiring Layer Next, the insulating layer and the grounding wiring layer used in the present invention will be described. The insulating layer used in the present invention is formed on a metal substrate and has an opening through which the metal substrate is exposed. On the other hand, the grounding wiring layer used in the present invention is formed on the insulating layer and disposed in the vicinity of the opening.

  The insulating layer used in the present invention has an opening through which the metal substrate is exposed at a position where the ground terminal is formed. The shape of the opening is not particularly limited as long as the ground terminal is a shape capable of electrically connecting the metal substrate and the grounding wiring layer. For example, a circular shape; an elliptical shape; a quadrangular shape, a pentagonal shape, etc. Any polygonal shape, comb shape, cross shape, rod shape and the like can be mentioned. In addition, as a shape of an opening part, circular shape is common. When the shape of the opening is a circle, the diameter is usually about 50 μm to 300 μm.

  The position of the opening is not particularly limited as long as the ground terminal can connect the metal substrate and the grounding wiring layer, and the opening can be formed at any location. For example, as shown in FIG. 1 described above, the magnetic head slider may be provided at the tip of the suspension substrate, or as shown in FIG. 6 at a portion other than the tip of the suspension substrate. Also good. In FIG. 6, the ground wiring layer 3a is formed between the write wiring layer 3b and the read wiring layer 3c, and an opening is formed in the region of the insulating layer 2 where the ground wiring layer 3a is formed. 5 is provided.

  On the other hand, the grounding wiring layer used in the present invention is formed on the insulating layer and disposed in the vicinity of the opening. In the present invention, the grounding wiring layer and the metal substrate are brought into conduction through the ground terminal. The “near the opening” means a position where the opening can be substantially grounded via the ground terminal. For example, it refers to a region within a range of 50 μm from the end of the opening.

  The shape of the ground wiring layer is not particularly limited as long as it can be electrically connected to the metal substrate through the ground terminal, and can be set to an arbitrary shape. Usually, the ground wiring layer is formed so as to surround the opening in a plan view. Specifically, as shown in FIG. 7, the ground wiring layer 3a is formed so as to surround the opening 5 formed in the insulating layer 2 in a plan view.

  As described above, the ground wiring layer is formed so as to surround the opening in a plan view, and as described later, a low melting point metal is melted and dropped into the opening. Thus, when forming the ground terminal, there is no escape of air during dripping, and air accumulation occurs, and as a result, the contact between the ground terminal and the metal substrate may be insufficient. Specifically, as shown in FIG. 8, an air reservoir 6 is generated, and there is a possibility that the contact between the ground terminal 4 and the metal substrate 1 becomes insufficient.

  Therefore, in the above case, it is preferable that at least one of the grounding wiring layer and the insulating layer has an air vent portion that suppresses air accumulation generated when the ground terminal is formed. This is because the contact area between the ground terminal and the metal substrate can be sufficiently increased by suppressing the occurrence of air accumulation. As an example of the grounding wiring layer having the air vent portion, for example, as shown in FIG. 9A, a grounding wiring layer 3a having the air vent portion 7 can be cited. Similarly, both the grounding wiring layer 3a and the insulating layer 2 may have the air vent portion 7 (FIG. 9B), or only the insulating layer may have the air vent portion (not shown). ). When the ground wiring layer is made of copper, an air vent portion of about 20 μm to 50 μm can be provided. Further, the ground wiring layer or the insulating layer may have a plurality of air vent portions.

  In the present invention, the grounding wiring layer may not be formed so as to surround the opening in a plan view. Specifically, as shown in FIG. 10A, the ground wiring layer 3 a may be simply formed in the vicinity of the opening 5. That is, the shape of the ground wiring layer in the vicinity of the opening may be a line. Even in such a case, as shown in FIG. 10B, the ground terminal 4 can sufficiently conduct the ground wiring layer 3 a and the metal substrate 1. In this case, it is not necessary to provide the above-described air vent portion in the grounding wiring layer or the insulating layer. Further, as shown in FIG. 11A, a plurality of line-like ground wiring layers 3 a may be formed in the vicinity of the opening 5. Thereby, joining reliability can be improved. On the other hand, as shown in FIG. 11B, a line-shaped grounding wiring layer 3a may be formed so as to be in contact with the opening 5 in plan view. Thereby, the freedom degree of design of the position of an opening part can be improved.

  Further, in the present invention, as shown in FIG. 12A, the ground wiring layer 3a may have an opening smaller than the opening 5, and as shown in FIG. The wiring layer 3a may have an opening having the same size as the opening 5, and the grounding wiring layer 3a has an opening larger than the opening 5 as shown in FIG. May be.

  In the present invention, as will be described later, a ground terminal in contact with the metal substrate and the ground wiring layer can be formed by quantitatively dropping a metal having a melting point of 450 ° C. or lower into the opening in a molten state. (See FIG. 16 described later). In this case, the grounding wiring layer can be reduced in size and space and weight can be reduced as compared with the conventional method of forming the ground terminal by plating or the like. From the viewpoint of preventing deterioration of the insulating layer, it is preferable to form a grounding wiring layer so that the ground terminal and the insulating layer do not contact each other. Here, as shown in FIG. 13, the distance C is the distance between the end of the opening 5 and the end of the ground wiring layer 3 a on the side away from the opening 5. In the present invention, when the ground terminal is formed using the above-described method, the grounding wiring layer can be downsized as compared with the conventional plating method or the like. In this case, the distance C can be set to 75 μm or less, particularly 50 μm or less.

  Furthermore, in the present invention, as described later, when the metal is dropped into the opening in a molten state, the diameter of the molten metal is preferably smaller than the diameter of the opening (see FIG. 17 described later). ). This is because the grounding wiring layer disposed in the vicinity of the opening can be further reduced in size. In this case, the distance C can be set to 40 μm or less, particularly 30 μm or less. On the other hand, the distance C is usually 20 μm or more from the viewpoint of securing the mechanical strength of the ground wiring layer.

  The thickness of the insulating layer is not particularly limited as long as desired insulating properties can be exhibited, but is usually about 5 μm to 10 μm. On the other hand, the thickness of the grounding wiring layer is not particularly limited as long as desired conductivity can be exhibited, but is usually about 6 μm to 18 μm.

  Examples of the material for the insulating layer include polyimide (PI). On the other hand, examples of the material for the grounding wiring layer include copper (Cu). Furthermore, the grounding wiring layer may be plated with nickel (Ni) or gold (Au). In particular, when gold (Au) plating treatment is performed, the bondability between the solder and the ground wiring layer is enhanced. However, if the gold plating thickness is thick, the Au of the brittle plating and the Sn of the solder are mutually bonded at the bonding interface with the solder. Preferred gold plating thickness because it can diffuse and form very brittle Au-Su intermetallic compounds, or can generate Kirkendall voids due to the difference in the diffusion rate of each metal, resulting in unstable bonding state. Is 0.5 μm or less, more preferably about 0.1 μm to 0.2 μm.

3. Next, the metal substrate used in the present invention will be described. The metal substrate used for this invention will not be specifically limited if it has electroconductivity. Since the suspension substrate of the present invention is used for suspension applications, the metal substrate usually has an appropriate spring property.

  In this invention, it is preferable that the said metal substrate has a conductive layer in the surface side in which an opening part is formed. This is because by providing the conductive layer, conduction by the ground terminal becomes more efficient. Specific examples of the material for the conductive layer include copper (Cu). The conductive layer can be formed by, for example, a plating method.

  The thickness of the metal substrate varies depending on the material of the metal substrate and is not particularly limited, but is usually in the range of 5 μm to 20 μm. Examples of the material for the metal substrate include SUS.

4). Others A suspension substrate according to the present invention includes at least the metal substrate described above, an insulating layer having an opening, a grounding wiring layer, and a ground terminal. Furthermore, the suspension substrate of the present invention usually has a cover lay (CL) on the ground wiring layer. In the present invention, as shown in FIG. 14A, the coverlay 8 may be formed so as to cover a part of the grounding wiring layer 3a. As shown in FIG. The coverlay 8 may be formed so as not to cover the wiring layer 3a for use. The former corresponds to so-called SMD (solder mask defined), and the latter corresponds to so-called NSMD (non-solder mask defined). Although it does not specifically limit as thickness of the said coverlay, Usually, it is about 5 micrometers-about 30 micrometers, and it is preferable to exist in the range of 5 micrometers-15 micrometers especially. The material of the coverlay is not particularly limited, and the same coverlay used for a general flexible substrate or the like can be used.

  FIG. 15 is a schematic plan view illustrating the structure around the ground terminal in the present invention. FIG. 15A shows the NSMD type ground terminal 4 in which the coverlay 8 does not cover the ground wiring layer 3a, and the ground terminal 4 is formed along the opening of the ground wiring layer 3a. FIG. 15B shows an SMD type ground terminal 4 in which a coverlay (grounding wiring layer coverlay) 8 covers a part of the grounding wiring layer 3a. The air vent 7 and the grounding wiring layer coverlay are shown in FIG. 8 and an insulating layer cover lay 8 '. In this case, the ground terminal 4 is formed along the opening of the ground wiring layer cover lay 8. FIG. 15C shows the SMD type ground terminal 4 in which the coverlay 8 covers a part of the grounding wiring layer 3a, and has a line-shaped grounding wiring layer 3a. In this case, the ground terminal 4 is formed along the opening of the cover lay 8. FIG. 15D shows an NSMD type ground terminal 4 in which the cover lay 8 does not cover a part of the grounding wiring layer 3 a, and has an air vent portion 7. In this case, the ground terminal 4 is formed along the opening of the ground wiring layer 3a.

  The suspension substrate of the present invention usually has a write wiring layer and a read wiring layer in addition to the ground wiring layer described above. The write wiring layer and the read wiring layer may be formed from the same material as the ground wiring layer described above or may be formed from different materials, but are usually formed from the same material. This is because the cost can be reduced.

  The use of the suspension substrate of the present invention is not particularly limited, but it is used for a magnetic head suspension of a hard disk drive (HDD), for example.

B. Next, a method for manufacturing a suspension substrate according to the present invention will be described. The method for manufacturing a suspension substrate according to the present invention includes a metal substrate, an insulating layer formed on the metal substrate and having an opening through which the metal substrate is exposed, the insulating layer formed on the insulating layer, and the opening. A substrate forming member having a grounding wiring layer disposed in the vicinity, and quantitatively dropping the metal having a melting point of 450 ° C. or lower into the opening in a melted state, whereby the metal substrate and the ground A ground terminal forming step of forming a ground terminal in contact with the wiring layer.

  According to the present invention, it is possible to reduce the cost and simplify the process by dripping molten metal into the opening to form the ground terminal. For example, when forming a ground terminal by a conventional plating method, a step of laminating a dry film, a step of exposing a dry film, a step of developing a dry film after exposure, and an SUS surface of an opening for forming a ground terminal Many processes such as a process of removing the oxide film, a process of plating the opening, and a process of peeling off the dry film are necessary. Furthermore, in order to plate the minute openings, it is necessary to mask many other areas, which is a very inefficient operation. On the other hand, in the present invention, the ground terminal can be formed only by the process of dripping molten metal and the pretreatment process of the metal substrate, which is performed as necessary, thereby reducing the cost and simplifying the process. Can be achieved.

  Furthermore, in the present invention, heating is required to melt the metal, but in principle, heating is not required for the suspension substrate (substrate forming member) before the ground terminal is formed. Therefore, it is possible to prevent deterioration of polyimide used as an insulating layer, for example. Further, for example, when the shape of the opening is complicated, if the ground terminal is formed by a conventional plating method, the obtained ground terminal becomes brittle and may not have sufficient strength. On the other hand, in this invention, since a metal is dripped in a molten state, it has the advantage that the obtained ground terminal does not become weak like a plating method. Further, according to the present invention, a ground terminal can be formed for an opening having an arbitrary shape.

  Next, a method for manufacturing a suspension substrate according to the present invention will be described with reference to the drawings. FIG. 16 is a process diagram showing an example of a method for manufacturing a suspension substrate according to the present invention. The manufacturing method of the suspension substrate shown in FIG. 16 is formed on the metal substrate 1, the insulating layer 2 formed on the metal substrate 1 and having the opening 5 through which the metal substrate 1 is exposed, and the insulating layer 2. In addition, a substrate forming member 10 having a grounding wiring layer 3a disposed in the vicinity of the opening 5 is prepared (FIG. 16A). Next, the molten metal 12 is opened using the dropping device 11. It has a ground terminal forming step of forming the ground terminal 4 in contact with the metal substrate 1 and the ground wiring layer 3a by quantitatively dropping it on the part 5 (FIG. 16B) (FIG. 16C). )).

1. First, a ground terminal forming process in the present invention will be described. In the ground terminal forming step in the present invention, the above-described substrate forming member is used. The substrate forming member has at least a metal substrate, an insulating layer having an opening, a grounding wiring layer, and a ground terminal. Since these constituent members are the same as those described in “A. Suspension substrate”, description thereof is omitted here. In this step, a metal having a specific range of melting point is used. Since this metal is the same as that described in “A. Suspension substrate”, the description thereof is omitted here.

  The dropping method for dropping the metal in a molten state is not particularly limited as long as it can drop the molten metal quantitatively. For example, a metal ball having a predetermined diameter is used. Examples thereof include a method in which the metal balls are sequentially melted and dropped, and a method in which the metal is stored in a melted state in a predetermined container and quantitatively dropped from the container little by little.

  In particular, in the present invention, the dropping method is preferably a method in which a metal ball having a predetermined diameter is used and the metal ball is sequentially melted and dropped. This is because the amount of molten metal dripped can be freely adjusted by appropriately selecting the diameter of the metal ball as the raw material. The diameter of the metal ball is not particularly limited, but is usually about 100 μm to 250 μm. In the present invention, it is preferable to determine the diameter of the metal ball in consideration of the size of the opening.

Examples of the dropping device that performs dropping using the metal ball include, for example, a raw material supply unit that supplies the metal ball, a melting unit that melts the supplied metal ball, and a dropping unit that drops the molten metal ball And the like. In such an apparatus, first, a metal ball as a raw material is filled in the raw material supply unit, and thereafter, the metal ball is sequentially supplied from the raw material supply unit to the melting unit to melt the supplied metal ball. Examples of the melting method include a YAG laser. Thereafter, the molten metal ball is dropped from the dropping portion to the opening. Examples of the method of dropping the molten metal ball include a method of extruding the molten metal ball with an inert gas such as N ₂ . Such dropping apparatus, specifically, PAC-TECH PACKAGING TECHNOLOGIES Gmbh Co., can be mentioned SB ² -jet like.

  In the present invention, a predetermined amount of molten metal necessary for forming the ground terminal may be dropped once, or may be dropped several times. When dripping at once, there is an advantage that the number of steps is small, and when dropping at a plurality of times, there is an advantage that the occurrence of air accumulation can be suppressed by dripping little by little. That is, when the molten metal is dropped in a plurality of times, there is an advantage that it is not necessary to provide the air vent portion described in the above “A. Suspension substrate” in the ground wiring layer or the insulating layer.

  Moreover, in this invention, when the said metal is dripped in the molten state, it is preferable to set the diameter of the molten metal so that contact with the edge part of an opening part does not arise. Specifically, when the metal is dropped in a molten state, the diameter of the molten metal is preferably smaller than the diameter of the opening. This is because the molten metal can be landed more reliably by making the diameter of the molten metal smaller than the diameter of the opening. Thereby, generation | occurrence | production of an air pool can be suppressed, the joining area of a metal substrate and a ground terminal increases, and joining reliability improves. Furthermore, by improving the landing accuracy, the grounding wiring layer disposed in the vicinity of the opening can be reduced in size, and space saving and weight reduction can be achieved. If the weight in the vicinity of the ground terminal can be reduced, the metal substrate can be made thinner.

  Specifically, as illustrated in FIG. 17A, when the molten metal 12 is dropped onto the opening 5 using the dropping device 11, the horizontal diameter 12x of the molten metal 12 is changed to the opening 5. Smaller than the diameter of. As a result, as shown in FIG. 17B, the molten metal 12 can be easily landed on the surface of the metal substrate 1 exposed from the opening 5. Further, as shown in FIG. 17C, the obtained ground terminal 4 is formed only inside the region surrounded by the end of the opening 5. The obtained ground terminal is the same as the content described in “A. Suspension substrate”, and the description thereof is omitted here.

In the present invention, the diameter of the molten metal refers to the size in the horizontal direction when the molten metal dropped from a dropping device or the like enters the opening (reference numeral 12x in FIG. 17A). On the other hand, the diameter of the opening varies depending on the shape of the opening. For example, when the shape of the opening is a circle, the diameter is the diameter. In the present invention, the diameter of the molten metal (actually, only the solder ball size before melting can be specified, and the metal system during melting cannot be measured) is preferably smaller than the diameter of the opening by, for example, 10 μm or more. Especially, it is preferable that it is small in the range of 15 μm to 30 μm.
For example, as shown in FIG. 16A, when the diameter of the ground wiring layer 3a is smaller than the diameter of the opening 5, the diameter of the molten metal is compared with the diameter of the ground wiring layer. It is preferable that it is small within the said range.

  If the diameter of the molten metal is too small, the formed ground terminal may not be able to sufficiently connect the metal substrate and the grounding wiring layer. Therefore, when forming the ground terminal by one drop, it is preferable to set the diameter of the molten metal so that the metal substrate and the ground wiring layer can be sufficiently connected. At this time, it is preferable to consider the relationship between the volume of the molten metal and the area of the opening. On the other hand, even when the diameter of the molten metal is too small, as described above, the metal substrate and the ground wiring layer can be sufficiently connected by dropping in a plurality of times.

  Although it does not specifically limit as a diameter of the fuse | melted metal, Usually, it exists in the range of 40 micrometers-150 micrometers, and it is preferable to exist in the range of 60 micrometers-100 micrometers especially. On the other hand, as described in the above “A. Suspension substrate”, the diameter of the opening is usually about 50 μm to 300 μm, but when the diameter of the molten metal is made smaller than the diameter of the opening, for example, 80 μm It is preferable to be within a range of ˜150 μm.

  Further, in the present invention, the metal substrate exposed at the opening is subjected to an oxide film removal process, and then melted before the metal oxide film is formed on the surface of the metal substrate after cleaning. It is preferable to contact the metal and the exposed metal substrate. This is because a ground terminal having a low resistance can be obtained by forming the ground terminal before forming the metal oxide film. Further, compared with a method using a flux which will be described later, the flux application process and the flux cleaning process are unnecessary, and therefore the process can be simplified. Furthermore, when using a flux, if molten metal is dropped, the flux may scatter and at the same time the ground terminal may scatter. On the other hand, if the oxide film removal process is performed, problems such as flux scattering do not occur, and ground terminal scattering can also be prevented.

  In general, when an oxide film removal process is performed on a metal substrate, the metal oxide film present on the surface of the metal substrate can be removed. However, after the oxide film removal process, the metal substrate is left in the atmosphere or the like. It is considered that a metal oxide film is formed again on the surface of the metal substrate. Since this metal oxide film is a component that increases the resistance of the ground terminal, it is preferable to form the ground terminal before the metal oxide film is formed.

  In the present invention, “before the metal oxide film is formed on the surface of the metal substrate” means a state in which the metal oxide film is not formed to such an extent that the ground terminal can exhibit the target resistance value. The target electrical resistance value varies depending on the use of the suspension substrate, but is preferably within a range of, for example, 1.0Ω or less, and more preferably 0.3Ω or less.

  In addition, it is thought that an intermetallic compound layer is formed at the bonding interface between the ground terminal and the metal substrate by forming the ground terminal before forming the metal oxide film. The intermetallic compound layer is the same as the content described in the above “A. Suspension substrate”, and the description thereof is omitted here. In the present invention, it is a time during which an oxide film is removed from the metal substrate exposed at the opening, and then an intermetallic compound layer can be formed at the bonding interface between the ground terminal and the metal substrate. Preferably, the molten metal and the exposed metal substrate are brought into contact with each other within the range in which the intermetallic compound layer can be formed.

  In the present invention, when SUS304 is used as the metal substrate, the elemental composition ratio of Fe / Cr is less than 1 when the elemental composition on the surface of SUS304 before the oxide film removal treatment is measured. This is probably because a chromium oxide film is formed on the surface of SUS304. On the other hand, when an oxide film removal process is performed on SUS304, the chromium oxide film on the surface of SUS304 is removed, and the elemental composition ratio of Fe / Cr tends to increase.

  Further, in the present invention, the ground terminal may be formed by previously arranging a metal ball as a raw material in the opening and melting the metal ball. This method is similar to so-called SBB (solder ball bonding).

2. Other Steps In the present invention, the substrate forming member may be pretreated before dropping the molten metal into the opening. Specifically, as the pretreatment, a flux treatment process for removing the metal oxide film on the surface of the metal substrate exposed at the opening, and a pickling process for removing the metal oxide film on the surface of the metal substrate exposed at the opening. Examples thereof include a plasma cleaning step for removing organic substances remaining on the surface of the metal substrate exposed at the opening, and a degreasing step for removing oil remaining on the surface of the metal substrate exposed at the opening. In particular, in the present invention, it is preferable to perform a plasma cleaning step as the pretreatment step. In the present invention, two or more kinds of the pretreatments may be combined.

  In the said flux treatment process, it does not specifically limit as a flux agent used, It is preferable to select suitably according to the kind of metal substrate. As such a fluxing agent, the same fluxing agent used for general solder or the like can be used.

In the plasma cleaning step, the organic residue on the metal substrate is removed, and at the same time, the oxide film on the metal substrate is removed. The processing gas is selected from He, N ₂ , and Ar alone or a hydrogen mixed gas of 3% or less, and the plasma apparatus is preferably a high energy efficient type such as a parallel plate type or a magnetron type.

  Examples of the pickling solution used in the pickling step include hydrochloric acid, sulfuric acid, hydrogen peroxide solution, phosphoric acid, and ammonium ammonium fluoride. These can be used alone or in a mixture.

  In the above degreasing step, the degreasing method used is not particularly limited. For example, alkaline degreasing using sodium carbonate, sodium hydroxide, etc .; emulsion degreasing; solvent degreasing; phosphoric acid, silicate, etc. Acid degreasing used; degreasing using a surfactant, a chelating agent and the like can be mentioned, and these can be used alone or in combination of two or more.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Example 1]
(Production of substrate forming member)
Prepare a laminate in which a SUS304 (metal substrate) with a thickness of 20 μm, a polyimide layer (insulating layer) with a thickness of 10 μm, and a Cu wiring layer (wiring layer) made of an electrolytic copper foil with a thickness of 18 μm are laminated in this order, The laminated body was subjected to chemical etching described below to obtain a substrate forming member. First, the region of the Cu wiring layer (grounding Cu wiring layer) where the ground terminal is formed is processed into a shape having an outer diameter of 250 μm and an inner diameter (opening diameter) of 100 μm by chemical etching, and then the outer shape of the suspension substrate is defined. For this purpose, SUS was chemically etched, and then the polyimide layer was chemically etched to form openings having a diameter of 100 μm. Thereafter, Ni was electroplated on the surface of the grounding Cu wiring layer by about 0.2 μm, and Au was electroplated by about 0.5 μm. Furthermore, a photosensitive coverlay for protecting the wiring was applied, exposed and developed to form a coverlay having a predetermined shape, thereby obtaining a substrate forming member.

(Production of suspension substrate)
Next, in order to activate the SUS surface in the opening, treatment (pickling) was performed using phosphoric acid as a pretreatment. Thereafter, Sn-3.0Ag-0.5Cu lead-free solder (solder ball) having a diameter of 0.1 mm is prepared, and the opening is formed while melting the solder ball using SB ² -JET made by Pac-Tech. A plurality of suspension substrates of the present invention were obtained by dropping the solution onto the suspension. The resistance value of the ground terminals of these suspension substrates was an average of 6.10Ω, of which 40% was 5Ω or less and 5% was 1Ω or less.

[Example 2]
Before dripping the molten solder, instead of pickling, a parallel plate type plasma cleaning device manufactured by March Plasma Systems, Inc., treated with Ar gas for 5 minutes to activate the SUS surface, A plurality of suspension substrates were obtained in the same manner as in Example 1. The resistance value of the ground terminals of these suspension substrates was 1.25Ω on average, of which 90% was 5Ω or less and 65% was 1Ω or less.

[Example 3]
Suspension was performed in the same manner as in Example 1 except that SUS flux (NS-23 manufactured by Nippon Superior Co., Ltd.) was applied instead of pickling before the molten solder was dropped and activated the SUS surface. A plurality of substrates were obtained. The resistance value of the ground terminals of these suspension substrates was an average of 5.55Ω, of which 60% was 5Ω or less and 5% was 1Ω or less.

[Example 4]
First, the same substrate forming member as in Example 1 was prepared (opening diameter was 100 μm). Then, prepare a lead-free solder of Sn-3.0Ag-0.5Cu diameter 0.1 mm (solder balls), using Pac-Tech Co. ^SB 2 -jet, horizontal direction of the molten solder balls The diameter was adjusted to 80 μm and dropped into the opening to form a ground terminal.

It is a schematic plan view which shows an example of the board | substrate for suspensions of this invention. It is XX sectional drawing of FIG. It is a schematic sectional drawing which shows the shape of the ground terminal formed by the plating method. It is a schematic sectional drawing explaining the ground terminal in this invention. It is a schematic sectional drawing explaining the ground terminal in this invention. It is a schematic plan view which shows the other example of the board | substrate for suspensions of this invention. It is a schematic plan view explaining the grounding wiring layer used for this invention. It is a schematic sectional drawing explaining an air reservoir. It is a schematic plan view explaining an air vent part. It is explanatory drawing explaining the wiring layer for grounding used for this invention. It is a schematic plan view explaining the grounding wiring layer used for this invention. It is a schematic sectional drawing explaining the wiring layer for grounding used for this invention. It is a schematic sectional drawing explaining the magnitude | size of the wiring layer for grounding used for this invention. It is a schematic sectional drawing explaining the coverlay used for this invention. It is a schematic plan view which illustrates the structure around the ground terminal in the present invention. It is process drawing which shows an example of the manufacturing method of the board | substrate for suspensions of this invention. It is process drawing which shows the other example of the manufacturing method of the board | substrate for suspensions of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Metal substrate 2 ... Insulating layer 3a ... Grounding wiring layer 3b ... Writing wiring layer 3c ... Reading wiring layer 4 ... Ground terminal 5 ... Opening 6 ... Air reservoir 7 ... Air vent part 8 ... Coverlay 10 ... Substrate formation Member 11 ... Dropping device 12 ... Molten metal

Claims (10)

A metal substrate; an insulating layer formed on the metal substrate and having an opening through which the metal substrate is exposed; a grounding wiring layer formed on the insulating layer and disposed in the vicinity of the opening; A suspension substrate having a ground terminal formed in the opening and in contact with the metal substrate and the ground wiring layer,
The suspension substrate, wherein the ground terminal is made of a metal having a melting point of 450 ° C. or lower.   The suspension substrate according to claim 1, wherein the ground terminal has a convex shape having an apex in a region of the opening in a plan view.   The suspension substrate according to claim 1 or 2, wherein the metal forming the ground terminal is lead-free solder.   The grounding wiring layer is formed so as to surround the opening in a plan view, and the grounding wiring layer has an air vent portion that suppresses an air pool generated when the ground terminal is formed. The suspension substrate according to any one of claims 1 to 3, wherein the suspension substrate is provided.   The suspension substrate according to any one of claims 1 to 3, wherein a shape of the grounding wiring layer in the vicinity of the opening is a line shape.   The suspension substrate according to any one of claims 1 to 5, wherein the ground terminal is formed only inside a region surrounded by an end of the opening.   The suspension substrate according to any one of claims 1 to 6, wherein an intermetallic compound layer is formed at a bonding interface between the ground terminal and the metal substrate. A metal substrate; an insulating layer formed on the metal substrate and having an opening through which the metal substrate is exposed; a grounding wiring layer formed on the insulating layer and disposed in the vicinity of the opening; Using a substrate forming member having
A ground terminal forming step of forming a ground terminal in contact with the metal substrate and the ground wiring layer by quantitatively dropping a metal having a melting point of 450 ° C. or less into the opening in a melted state; A method for manufacturing a suspension substrate.   9. The dropping method of quantitatively dropping the metal in a melted state is a method of using a metal ball having a predetermined diameter and sequentially melting and dropping the metal ball. A method for manufacturing a suspension substrate.   10. The method for manufacturing a suspension substrate according to claim 8, wherein when the metal is dropped in a molten state, the diameter of the molten metal is smaller than the diameter of the opening.

Images