TWI655985B - Metal core column assembly method - Google Patents

Abstract

The present invention provides a method of assembling a metal stem which is capable of suppressing collapse of a metal stem which has been assembled once in a semiconductor wafer or the like in two-time assembly. The method of assembling the metal stem includes a step of applying a flux F on a plurality of electrodes 101 formed on the first substrate 100, and a first joint surface of a Cu core 1A of a Cu core having a cylindrical shape covered with solder. 10A is loaded onto each of the electrodes 101 coated with the flux F, heated at a temperature at which the solder is melted, and the Cu stem 1A is bonded to the electrode 101; the periphery of the Cu stem 1A to which the electrode 101 is bonded is made of a resin a step of sealing the composition 12; and a step of peeling off the surface 120 of the resin composition 12 around the Cu core column 1A to expose the second joint surface 11A of the Cu core column 1A and aligning the heights of the respective Cu core columns 1A .

Description

Metal core column assembly method

The present invention relates to an assembly method for assembling a metal stem of a metal core coated with a solder to a metal stem on a substrate.

In recent years, due to the development of small information devices, rapid miniaturization of installed electronic components is underway. The electronic component is applied to a ball grid array (hereinafter referred to as "BGA") in which an electrode is provided on the back surface, so that the connection terminal is narrowed and the assembly area is reduced due to the demand for miniaturization.

The electronic component applied to the BGA has, for example, a semiconductor package. In the semiconductor package, the semiconductor package having the electrodes is sealed with a resin. Solder bumps are formed in the electrodes of the semiconductor wafer. The solder bumps are formed by bonding solder balls to the electrodes of the semiconductor wafer. A semiconductor wafer to which the BGA is applied is placed on the circuit board such that the respective solder bumps are in contact with the electrodes of the circuit board, and the molten solder bumps are bonded to the electrodes by heating, thereby mounting the semiconductor wafer on the circuit board.

In recent years, with the development of miniaturization of electronic components, the electrode as a welded portion of an electronic component has also become small. Therefore, the area where the solder joint can be used is small, and the joint reliability using only the joint strength of the solder is insufficient.

Therefore, a technique has been proposed in which a solder ball is assembled once on a semiconductor wafer as a component fixing means for bonding by soldering, and a semiconductor wafer on which a solder bump is formed is assembled twice on a circuit board. A semiconductor wafer or the like is fixed by filling a resin called an underfill between the semiconductor wafer and the circuit board to cover the periphery of the solder joint portion (see, for example, Patent Document 1). [Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent No. 4757070

[Problems to be solved by the invention]

In recent years, with the development of miniaturization of electronic components, the solder joint portion has been miniaturized due to the reduction in the area of the assembly and the narrowing of the electrode pitch, and it has been replaced by a metal stem which is coated with a columnar metal core by solder. Spherical solder bumps.

Even in the case of using a metal stem, the semiconductor chip is assembled once on a semiconductor wafer, and the semiconductor wafer assembled with the metal stem once assembled on the board is assembled twice, on the semiconductor wafer. The resin is filled with the circuit board, and the semiconductor wafer can also be fixed by a resin.

However, in the step of assembling the semiconductor wafer in which the metal stem is assembled once on the board, the metal core of the semiconductor wafer is bonded in one assembly by heating the solder to a temperature at which it is melted. The column has the possibility of collapse.

The present invention has been made to solve such a technical problem, and an object thereof is to provide a method of assembling a metal stem which can suppress collapse of a metal stem which is assembled once on a semiconductor wafer or the like in secondary assembly. [means to solve the problem]

In order to solve the above problems, the present invention provides a method for assembling a metal stem, comprising: a step of applying a flux or a solder paste on a plurality of electrodes formed on a substrate; and a metal pillar of the metal core covered with solder 1 bonding surface is loaded onto each electrode coated with a flux or solder paste, heating at a temperature at which the solder is melted and bonding the metal stem to the electrode; using a resin combination around the metal stem to which the electrode is bonded And a step of sealing the surface of the resin composition around the sealing metal stem while exposing the second joint surface of the metal stem to align the heights of the respective metal stems. [Effects of the Invention]

In the present invention, by sealing the periphery of the metal stem bonded to the substrate in one assembly by the resin composition, the solder can be suppressed even if the solder is heated to a temperature at which it is melted in the secondary assembly. collapse.

Hereinafter, a method of assembling the Cu stem as an embodiment of the method of assembling the metal stem of the present invention will be described with reference to the drawings.

Figs. 1(a) to 1(e) and Figs. 2(a) to 2(b) are flowcharts showing an example of a method of assembling a Cu stem according to an embodiment of the present invention. Fig. 3 is a perspective view showing an example of a Cu stem of an embodiment of the present invention. Fig. 4 is a cross-sectional view showing an exemplary structure of a Cu core column according to an embodiment of the present invention.

In the method of assembling the Cu core of the present embodiment, after the step of bonding the Cu core column to the substrate by solder is referred to as a single assembly step, in order to avoid the Cu core column bonded to the substrate by solder in the first assembly, the second time is performed twice. In the heating during assembly, the resin is collapsed, and a step of sealing the periphery of the Cu core after the assembly by the resin composition is provided.

First, the Cu stem used in the method of assembling the Cu stem of the present embodiment will be described with reference to FIGS. 3 and 4 .

The Cu stem 1A is an example of a metal stem including a Cu pillar 2A and a solder layer 3A, and the Cu pillar 2A is a columnar metal core having a specific size and ensuring a space between a substrate constituting a semiconductor wafer and a printed circuit board or the like. As an example, the solder layer 3A is an example of a coating layer covering the Cu pillar 2A. As shown in Fig. 3, in the cylindrical configuration of the Cu stem 1A, one end surface along the axial direction of the cylinder is the first joint surface 10A, and the other joint surface is the second joint surface 11A. Further, in the present example, the Cu column 2A is formed in a columnar shape, but is not limited thereto, and may be, for example, a quadrangular prism.

The Cu column 2A may be composed of a Cu monomer or an alloy containing Cu as a main component. In the case where the Cu column 2A is composed of an alloy, the content of Cu is 50% by mass or more. Further, as the Cu column 2A, in addition to Cu, Ni, Ag, Bi, Pb, Al, Sn, Fe, Zn, In, Ge, Sb, Co, Mn, Au, Si, Pt, Cr, La may be used. A metal monomer or alloy of Mo, Nb, Pd, Ti, Zr, Mg, a metal oxide, or a metal mixed oxide.

In the case where the solder layer 3A is an alloy, it is not particularly limited as long as it is a lead-free solder containing Sn as a main component. Further, as the solder layer, a Sn plating film composed of 100% of Sn may be used. For example, Sn, a Sn-Ag alloy, a Sn-Cu alloy, a Sn-Ag-Cu alloy, a Sn-In alloy, a Sn-Bi alloy, and a material in which a specific alloying element is added as described above may be mentioned. In the above case, the content of Sn is 40% by mass or more. As the alloying element to be added, for example, Ag, Cu, In, Ni, Co, Sb, Ge, P, Fe, or the like can be given. Among the above, from the viewpoint of the drop impact characteristics, the alloy composition of the solder layer is preferably a Sn-3Ag-0.5Cu alloy. Further, a Sn-Pb-based solder containing Pb can also be used. In the Cu stem 1A, solder layer 3A is formed by solder plating on the surface of the Cu pillar 2A.

The Cu stem 1A may be provided with a diffusion preventing layer between the Cu pillar 2A and the solder layer 3A. The diffusion preventing layer is selected from one or more elements such as Ni and Co, and prevents Cu which constitutes the Cu pillar 2A from diffusing into the solder layer 3A.

The wire diameter (diameter) D2 of the Cu column 2A is preferably 20 to 1000 μm, and the length L2 is preferably 20 to 10000 μm.

The thickness of the solder layer 3A is not particularly limited and may be, for example, 100 μm or less. In general, it can be 20 to 50 μm.

The wire diameter (diameter) D1 of the Cu stem 1A is preferably 22 to 2000 μm, and the length L1 is preferably 22 to 20000 μm.

Next, a method of assembling the Cu stem of the present embodiment will be described with reference to FIGS. 1(a) to 1(e) and FIGS. 2(a) to 2(b). As shown in Fig. 1(a), the flux F is applied onto the electrode 101 of the first substrate 100 such as a semiconductor wafer. In the step of applying the flux F, the flux F is applied to the portion where the electrode 101 is provided, using a mask (not shown) provided with an opening according to the arrangement of the electrode 101.

As the flux, for example, a conventional flux containing an organic acid, an amine, a surfactant, a base, a halogen, a thixotropic agent, or a solvent can be used.

The organic acid is added as an active ingredient component in the flux. Examples of the organic acid include glutaric acid, phenylsuccinic acid, succinic acid, malonic acid, adipic acid, sebacic acid, glycolic acid, diglycolic acid, thioglycolic acid, thiodiglycolic acid, and propionic acid. , malic acid, tartaric acid, dimer acid, hydrogenated dimer acid, trimer acid, and the like.

The amine is added as an active auxiliary component in the flux and affects the rate of wetting diffusion of the flux. Examples of the amine include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, polyetheramine, polyoxyalkyleneamine, and polyoxyethyleneamine. , polyoxypropyleneamine, 2-ethylaminoethanol, diethanolamine, triethanolamine, amino alcohol, and the like.

The base agent may, for example, be polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, polyoxyethylene alkyl ether, polyoxyethylene alkyl ester or polyoxyethylene tallow ester.

The solvent is selected from the conventionally known glycol ether type compounds. Examples of the solvent include hexanediol, hexyldiglycol, 1,3-butanediol, octanediol, alkylene oxide resorcinol copolymer, and 2-ethyl-1,3-hexanediol. 2-ethylhexyl diglycol, phenylethylene glycol, butyl triethylene glycol, terpineol, and the like.

Next, as shown in FIG. 1(b), the first bonding surface 10A of the Cu pillar 1A is placed on the electrode 101 coated with the flux F. In the step of loading the Cu stem 1A to the substrate 100, a mask (not shown) provided with an opening into which the Cu stem 1A is inserted is used to load the Cu stem 1A in a specific direction to the electrode 101 provided. section.

Next, as shown in Fig. 1(c), the first substrate 100 on which the Cu stem 1A is placed is heated to a specific temperature at which the solder layer 3A is melted by a reflow furnace, and the first substrate is soldered. The electrode 101 of 100 is bonded to the Cu stem 1A.

After the Cu stem 1A is solder-bonded to the electrode 101, the flux residue remaining in the joint portion of the Cu stem 1A and the electrode 101 is removed by washing. Moreover, when the flux F has no residue, the washing step is not performed.

Next, as shown in FIG. 1(d), the resin composition 12 is filled around the Cu stem 1A to which the electrode 101 of the first substrate 100 is bonded. The resin composition 12 contains a thermosetting resin which is cured by heating and a curing agent which accelerates curing of the resin.

In the case where the resin composition is in a liquid state at normal temperature, the resin composition 12 is filled around the Cu stem 1A by capillary action. When the resin composition is solid at normal temperature, it is melted by heating, and pressure is applied to fill the resin composition 12 around the Cu stem 1A. In any case, after filling the resin composition 12, the resin composition 12 filled around the Cu core column 1A is heated to a curing temperature, and by curing the resin composition 12, the Cu core is utilized by the resin composition 12. The circumference of the column 1A is sealed to form a support structure.

The thermosetting resin may, for example, be an epoxy resin or a cyanate resin. Examples of the epoxy resin include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol E epoxy resin, bisphenol S epoxy resin, bisphenol M epoxy resin, and double a bisphenol type epoxy resin such as a phenol P type epoxy resin or a bisphenol Z type epoxy resin; a novolak type epoxy resin such as a novolak type epoxy resin or a cresol novolak type epoxy resin; a biphenyl type An arylalkylene type epoxy resin such as an epoxy resin, a benzene dimethyl epoxy resin or a biphenyl aralkyl epoxy resin; a naphthalene epoxy resin, a dinaphthyl epoxy resin, a fluorene ring Oxygen resin, phenoxy type epoxy resin, dicyclopentadiene type epoxy resin, norbornene type epoxy resin, adamantane type epoxy resin, fluorene type epoxy resin, and the like.

Examples of the cyanate resin include a bisphenol type such as a novolac type cyanate resin, a bisphenol A type cyanate resin, a bisphenol E type cyanate resin, and a tetramethyl bisphenol F type cyanate resin. Cyanate resin; cyanate resin obtained by reaction between naphthol aralkyl type polyvalent naphthol and cyanogen halide; dicyclopentadiene type cyanate resin, biphenyl alkyl type cyanate resin, etc. .

In addition to the epoxy resin and the cyanate resin, the resin contained in the resin composition 12 may be a phenolic phenol resin such as a phenol novolac resin, a cresol novolac resin or a bisphenol A phenol resin, and is not modified. a soluble phenol resin, a modified phenol resin such as tung oil, linseed oil, walnut oil, etc., a phenol resin such as a soluble phenol resin, a urea resin (urea) resin, a melamine resin, etc. Pyrazine ring resin, unsaturated polyester resin, bismaleimide resin, polyurethane resin, diallyl phthalate resin, silicone resin, resin with benzoxazine ring, polyfluorene Imine resin, polyamidoximine resin, benzocyclobutene resin, and the like.

The resin contained in the resin composition 12 may be used alone or in combination of two or more kinds thereof, or one or more of the above-mentioned prepolymers may be used in combination.

Examples of the curing agent include dicyandiamide, an organic acid dioxime, an imidazole, an amine addition curing agent, a vinyl ether block carboxylic acid, a phosphonium salt, a ketimine compound, a microencapsulated imidazole, an acid anhydride, and a phenol. Wait. Examples of the acid anhydride include phthalic anhydride, maleic anhydride, citraconic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 4-methylhexahydrophthalic anhydride. Hexahydrophthalic anhydride, methylbicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride, bicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride, 1,2,3 ,6-tetrahydrophthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, ethylene glycol dihydrogen trimellitate, glyceryl trimellitic anhydride monoacetate, tetrapropylene amber Anhydride, etc.

Next, as shown in Fig. 1(e), the surface 120 of the cured resin composition 12 filled around the Cu stem 1A is scraped off, and the second joint surface 11A of the Cu stem 1A is removed from the resin composition. 12 is exposed, and the heights of the respective Cu pillars 1A are aligned, and the second joining surface 11A and the surface 120 of the resin composition 12 are smoothed. Further, as a method of polishing the surface 120 of the resin composition 12, a polishing technique using a silicon wafer can be applied, and a polishing technique using a diamond grinding wheel or the like can be applied to the present invention. The polishing processing method used in the present invention is not limited to the above.

Next, as shown in FIG. 2(a), the bonding layer 112 is formed on the electrode 111 of the second substrate 110 such as a circuit board. For example, a solder layer composed of 100% of Sn or a solder containing Cu or the like having Sn as a main component may be formed on the electrode 111 by a conventional plating method, and coated on the solder layer. The flux is formed to form the bonding layer 112.

Next, as shown in FIG. 2(b), the second bonding surface 11A of the Cu pillar 1A assembled once on the first substrate 100 as described above is mounted on the electrode 111 on which the bonding layer 112 is formed, and used. The reflow furnace is heated to a specific temperature at which the solder constituting the bonding layer is melted, and the Cu stem 1A and the electrode 111 of the second substrate 110 are solder-bonded.

As shown in the second (a) and the second (b), after the Cu core 1A is joined to the first substrate 100 by soldering, the second bonding surface 11A of the Cu pillar 1A is loaded. In the second assembly step of soldering the second substrate 110 to the second substrate 110 by soldering, the bonded portion of the bonded Cu pillar 1A and the electrode 101 of the first substrate 100 in the primary assembly is also heated. In the second assembly, the first substrate 100 to which the Cu stem 1A is bonded is mounted on the second substrate 110 such that the Cu stem 1A faces downward. In addition to the printed circuit board, any material may be used for the second substrate 110, and any conventional substrate such as an interposer may be used, and an electronic component may be used in addition to the substrate. Further, a method of laminating an electronic component or the like at the time of assembly twice may be used.

After the Cu core column 1A is solder-bonded to the first substrate 100 once, the Cu core column 1A is assembled when the support structure composed of the resin composition 12 is not provided around the Cu core column 1A and the assembly is performed twice. The upper solder flows to the lower peripheral portion along the side of the Cu stem 1A upon melting, resulting in a decrease in the amount of solder on the upper portion of the Cu stem 1A, and the intermetallic compound (IMC) is in the upper portion of the Cu stem 1A in which the amount of solder is reduced. Growing. Since the intermetallic compound and the solder cannot be joined, the bonding property in the secondary assembly is lowered in the upper portion of the Cu stem 1A in which the amount of solder is reduced and the intermetallic compound which is not bonded to the solder is formed. In this state, the Cu core column 1A may be collapsed by heating to a temperature at which the solder is melted in the second assembly. Further, in the case where the solder on the upper portion of the Cu stem 1A flows to the lower periphery at the time of melting, the solder gathers to the lower periphery of the Cu stem 1A by gravity, and the supply amount of the solder on the periphery of the lower portion of the Cu stem 1A becomes excessive. In the substrate of a narrow pitch, it also serves as a cause of bridging between the Cu pillars 1A by solder connection.

On the other hand, after one assembly, the periphery of the Cu stem 1A is sealed by the resin composition 12, and a support structure is formed around the Cu stem 1A, even in the second assembly, the temperature is heated to melt the solder. The solder is melted, and the Cu core column 1A is prevented from physically moving through the resin composition 12, and the periphery of the Cu stem 1A is sealed by the resin composition 12, whereby the solder on the upper portion of the Cu core column 1A can be prevented from being melted. The flow to the lower peripheral portion further suppresses the collapse of the Cu stem 1A and the occurrence of solder bridging.

Further, in the present invention, after one assembly, the resin-sealed substrate such as a ruthenium wafer may be further processed to be processed as a package.

In the above, the case where the flux F is applied to the electrode 101 of the first substrate 100 will be described. However, even if the solder paste obtained by kneading the solder powder and the flux is applied instead of the flux F, The assembly method of the present invention can also be applied. The composition of the solder powder used for the solder paste is not particularly limited as in the composition of the solder layer 3A, and the same composition as that of the solder used for the solder layer 3A may be used, and other compositions may be used. The solvent of the flux or the like used for the solder paste is not particularly limited as long as it can be used in the form of a paste.

In addition, the bonding layer 112 formed on the electrode 111 of the second substrate 110 is described above in the case where the flux F is applied to the solder layer, but the solder paste is applied to the electrode 111 and formed. In the case of the bonding layer 112, the above-described secondary assembly can also be performed. The solder paste for forming the bonding layer 112 is not particularly limited as long as the composition of the solder layer 3A, and the composition of the solder powder used for the solder paste is not particularly limited, and the same composition as that of the solder used for the solder layer 3A may be used. composition. The solvent of the flux or the like used for the solder paste is not particularly limited as long as it can be used in the form of a paste.

Further, in addition to the prior art, as a method for solving the technical problem of collapse of the Cu core column 1A, in addition to the method of the present invention, the following method may be employed: a solder having a high melting point is used in the solder layer 3A, and in two assembly operations, A solder paste of a solder having a melting point lower than that used in one assembly is used to bond the Cu pillar 1A. In the case of assembling by the above method, since the heating temperature at the time of the second assembly is lower than the heating temperature at the time of the first assembly, the solder layer 3A hardly melts at the time of the second assembly, and the collapse of the Cu core column 1A can be suppressed. .

In the present invention, after the first assembly, the above-described assembly method of sealing the periphery of the Cu core 1A with the resin composition 12 is applied, using solder or solder paste having a melting point lower than that of the solder layer 3A coated on the Cu pillar 1A. When the bonding layer 112 is formed to be assembled twice, the problem of the present invention can be more effectively solved. Further, instead of solder or solder paste, a conductive adhesive may be used as the bonding layer 112 in the secondary assembly. Since the conductive adhesive is cured by heating at a temperature lower than the melting point of the solder layer 3A coated on the Cu stem 1A, the problem of the present invention can be more effectively solved. [Industry Utilization]

The present invention is applicable to a process of assembling a columnar metal stem coated with solder to a substrate.

1A Cu-column 2A Cu-pillar 3A Solder layer 10A First joint surface 11A Second joint surface 12 Resin composition 100 First substrate 101 Electrode 110 Second substrate 111 Electrode 112 Bonding layer 120 Surface F Flux D1, D2 Wire diameter L2 , L2 length

1(a) to 1(e) are flowcharts showing an example of a method of assembling a Cu core according to an embodiment of the present invention. 2(a) to 2(b) are flowcharts showing an example of a method of assembling a Cu core according to an embodiment of the present invention. Fig. 3 is a perspective view showing an example of a Cu stem according to an embodiment of the present invention. Fig. 4 is a cross-sectional view showing an exemplary structure of a Cu stem according to an embodiment of the present invention.

Claims (2)

A method for assembling a metal stem, comprising: a step of applying a flux or a solder paste on a plurality of electrodes formed on a substrate; and loading the first joint surface of the metal stem of the metal core coated with the solder to the coating a step of heating the respective electrodes of the flux or the solder paste at a temperature at which the solder is melted and bonding the metal stem to the electrode; and sealing the periphery of the metal stem to which the electrode is bonded with a resin composition And a step of cutting the surface of the resin composition surrounding the metal stem to expose the second joint surface of the metal stem and aligning the heights of the respective metal stems. The method of assembling a metal stem according to claim 1, further comprising: sealing a periphery of the metal stem with a resin composition to expose the second joint surface of the metal stem and each of the metal cores The substrate in which the height of the pillars are aligned is loaded onto another substrate, and the second bonding surface of the metal stem is bonded to the other substrate.