JPS617695A - Long flexible both-side printed circuit board and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a long flexible double-sided printed wiring board and a method for manufacturing the same, and in particular, the present invention relates to a long flexible double-sided printed wiring board and a method for manufacturing the same. Regarding a method of manufacturing a double-sided printed wiring board by continuously forming an electroless plating layer on both sides, a long and flexible double-sided printed wiring board suitable for continuous mounting is used, for example, in the production of IC cards, etc. It is something that can be provided.

[Conventional technology]

As a conventional technique, for example, there is the following one.

(11) Currently, the subtractive method is generally used to create a circuit by etching unnecessary parts from copper foil, and in some cases, the necessary circuit is created from the beginning. An additive method that creates only a portion, and a semi-additive method that is intermediate between the two methods are used.

Regarding insulating base materials, there are various materials such as paper, glass fiber, and synthetic fiber impregnated with epoxy resin, phenol resin, silicone resin, polyester resin, polyimide resin, Teflon resin, etc., and each has its own purpose. Depending on the situation, f-komono is used.

(2) According to Management System Research New Edition's ``High-density multifunctional packaging technology collection'' (first edition published on October 1, 1981), film carrier technology was introduced as an automatic IC assembly technology. ing. This is done by forming a lead frame from copper foil on a tape-shaped insulating film (A/m), and using holes drilled in the film for frame-by-frame feeding.
It automatically feeds and aligns the tape and automates IC assembly. This method is a method that can reduce IC production costs and increase reliability.
The book describes the process for manufacturing carrier tapes necessary for this film carrier technology, and also states that double-sided carrier tapes have been put into practical use when films are directly used as substrates.

(3) Japanese Unexamined Patent Publication No. 58-70593 states, ``A print pattern is formed on a flexible long strip-shaped printed board in which guide holes are bored at predetermined pitch intervals, and predetermined parts are attached to this print pattern. A method for manufacturing an electronic package is disclosed in which a number of attached sheets are connected and formed into a band shape, which is then cut into individual sheets.

[Problem that the invention seeks to solve]

However, the long carrier tape in the conventional technique (2) is manufactured only by the subtractive method in the conventional technique (1), and its base material is polyimide resin, glass cloth epoxy, etc. A fairly limited type of base material for printed wiring boards, in which a copper foil is preliminarily laminated on the surface of a resin or the like, is not used. Furthermore, as mentioned above, using a copper-clad laminate as a base material for a flexible printed wiring board has the following drawbacks.

(b) Due to the influence of pinholes etc. that occur during copper foil manufacturing, the minimum thickness of copper foil that can be manufactured is currently 18 μm, and considering the etch factor in the copper foil etching process, a copper foil layer of this thickness is not possible. is not suitable for creating fine patterns.

(b) Dishes made of insulating substrates that can be laminated with copper foil on both sides are limited to glass cloth, etc., and the substrate cannot be selected from a wide range depending on the purpose. Additionally, this is a factor that increases manufacturing costs.

The price of double-sided copper foil laminates is higher than that of the same type of substrate without copper foil.

2) The flexibility of the substrate is significantly impaired due to the copper foil being laminated on both sides of the substrate. This means that when attempting to downsize the manufacturing apparatus by bending the base material and continuously conveying it by taking advantage of the advantages of the flexible base material, the advantages cannot be fully utilized.

In addition, in the conventional technique (3), although the advantages of continuous mounting on a long printed wiring board are also described in the same publication, there is no specific method for manufacturing a long printed wiring board. It is not yet clear what kind of structure a printed wiring board can be obtained using this method.

The present invention aims to eliminate and improve the shortcomings of the conventional technology in the long flexible printed wiring board, and the present invention includes the long flexible double-sided printed wiring board and its The object of the present invention is achieved by a manufacturing method.

The present invention is based on the fact that the polyimide resin base material conventionally used as this type of double-sided base material has excellent properties but is expensive, while polyester, on the other hand, is relatively cheap but has poor properties. In addition, considering that double-sided glass epoxy substrates are not used industrially, various resins such as phenol, epoxy, polyimide, or triazine are used as base materials for flexible insulating materials such as glass cloth, as shown below. Another purpose is to start with something that applies adhesive.

[Means for solving problems]

According to the present invention, it is possible to manufacture a long flexible double-sided printed wiring board by the Yamia day tape method, and the drawbacks of the conventional techniques can be solved. Here, as shown in Figure 1, a long printed wiring board means that the base material not only has a circuit function as a printed circuit board, but also functions as a transport medium in the component mounting process. In the present invention, each part of a long base material is subjected to repeated processing to form a conductor circuit, and then manufactured into a product.

Next, the manufacturing method of the present invention will be specifically explained based on the drawings in the order described in the claims.

FIG. 2 is an explanatory diagram showing the main steps of the manufacturing method of the present invention.

First, in the step <8), a long flexible insulating base material (1
), with the adhesive layer (2) formed on both sides.Currently used flexible insulating materials include various base materials such as polyester film, polyimide film, and epoxy resin with a glass cloth core material. In particular, when glass cloth is used as the core material, the presence of fluff on its surface causes the applied resin to form a resin layer on that part, making it difficult to laminate the copper foil. Therefore, although the glass cloth core material has good dimensional stability, it has a thickness of 0.211 mm.
There are few products manufactured for flexible printed wiring boards below NLR. However, since this manufacturing method does not require copper foil on the surface of the printed wiring board, it is possible to select a complementary material from a wide range. A glass cloth triazine base material having higher heat resistance while maintaining dimensional stability can be used. In addition, the adhesive layer (2) uses one or more of phenol, epoxy, polyimide, and triazine resin, and is used as an insulating material to improve the adhesion between the electroless plating formed on the surface and the base material. A material having the same composition as the above material is used, and can be particularly preferably formed to a thickness of 10 to 50 μm by coating or roll coating. Furthermore, after that, heat treatment is performed under conditions suitable for the components of the adhesive layer so that the adhesive layer does not flow, and the thermosetting resin is brought into a B-stage cured state.

Next, in step (b), positioning holes and through holes are provided in the base material. These holes may be formed using an NC drill or a mold. Generally, when a drill is used, the shape of the hole wall surface can be sharp, and when a mold is used, it is possible to make many holes at the same time.

Also, as methods using a mold, there are two methods: first forming a positioning hole and then using that hole to form a through hole, and a method of forming both at the same time. The position accuracy of each hole is better.

Next, in the step (Q), the adhesive layer is brought into a semi-cured state. Here, the semi-cured state means that the adhesive layer remains in the B stage using hot air or infrared rays, but is not used in each process such as electroless plating. It is in a state where it is further slightly cured to the extent that swelling of the base material can be prevented.

If curing is allowed to proceed too much at this time, it will not be possible to obtain a circuit pattern with good adhesion between the electroless plated film and the base material. Preferably, the reaction is carried out at a temperature of ~90% for 10 to 30 minutes.

Next, in step (d), the adhesive layer is roughened. The purpose of this step is to increase the surface area and provide an anchor effect, and both of these effects improve the adhesion between the base material and the circuit pattern. Roughening methods include puff polishing, resist blasting, chemical treatment, etc., and the surface roughness is preferably 0.5 to 3 μm in 10-point average roughness according to J-Technology 5B0601.

Here, the steps ω), (c), and (d) can basically be performed in any order, but if the surface roughening of @) is done after the drilling of (b), Anaming is effective in removing pari that sometimes occurs.

Next, in step (e), an electroless plating layer is formed on the entire surface of the base material. The electroless plating may be made of any conductive material such as copper, nickel, tin, etc., but electroless copper plating is generally used in consideration of high conductivity, cost, etc. The thickness of the deposited plating is preferably 0.1 to 3 μm. If the thickness is less than this, the conductivity during electroplating in the subsequent process will be impaired, and if the thickness is more than this, the amount of etching will increase, and the semi-additive method Strengths are not fully utilized. The electroless copper plating bath solution used in the present invention includes, for example, commercially available products manufactured by Shipley Co., Ltd. and products manufactured by Hitachi Chemical Co., Ltd. It is also preferable to use these plating bath solutions with the addition of various types of surfactants in order to obtain a good plated film.

Next, in step (c), hot pressing is performed.

The purpose of this step is to improve the adhesion between the conductor layer and the base material by applying both heat and pressure to the base material. The method uses a preheated roll, an endless belt, or a press. At this time, the pressure is preferably two or more cuts, and if it is less than that, sufficient adhesion cannot be obtained. Also, the temperature.

The Tg of the base material is preferably 50 to 9096, and adhesion will not increase if it is lower or higher than that.

Next, in step (n), a conductor circuit is formed on the surface of the base material. When a semi-additive method is used to form the conductor circuit, (i) resist formation, (i) electrolytic copper pattern plating, 010 resist peeling. , 4ψ etching. In the above (:), a dry film, a liquid resist, or a resist ink is used for the resist, and the next exposure and development process or the resist ink is carried out through a printing process and then a 5th process. A negative pattern is formed to cover the areas not to be electrolytically plated with copper.In addition, in the exposure process or printing process performed at this time, the positioning holes, which are one of the features of the present invention, are used to automatically That's right,
Continuously align the exposure mask, printing screen and substrate. In (II) electrolytic copper pattern plating-I, high-speed electrolytic copper plating with a current density of 7 to 30 A/dm on the plating surface is preferred.Generally, the lower the current density, the larger the equipment, and the higher the current density. Indeed, it becomes difficult to obtain plating with good physical properties. (For ID resist removal, use a method that matches the resist material, and for track etching, form an etching resist on areas other than the area to be etched.
After that, either form a conductor circuit by etching, or simply etch the entire part, and set the amount of etching to such an extent that only the electroless copper plating part is completely dissolved. Form on top.

Incidentally, as for the etching liquid here, basically either acidic or alkaline etching liquid can be used, but when etching is to be performed after forming an etching resist, it is necessary to use a suitable liquid.

In addition to methods (1) to (4) above, as shown in FIG. 3, after electroless copper plating, electrolytic copper plating is applied to the entire surface of the base material, and the thickness of the conductor part is set to the thickness necessary for a conductor circuit.
After forming the etching resist, unnecessary portions may be removed by etching, and finally the etching resist may be peeled off to form a desired conductor circuit. In this case, −(P
Although the advantages of the 2-additive method are lost, the advantage is that the thickness of the conductor portion can be set to any thickness as required.

Next, in the step (h), the adhesive layer is cured to the C stage to be in a completely cured state to obtain the final adhesion between the base material and the conductor circuit. At this time, the base material is 50 to 9 of the Tg of the base material.
The highest adhesion is obtained by leaving it in a 0% non-oxidizing atmosphere for 1 to 2 hours.

Further, complete curing after the formation of the conductor circuit facilitates the release of gas from the adhesive layer and has the effect of increasing adhesion. The purpose of using non-oxidizing gas is to prevent oxidation of the copper surface and facilitate surface treatment in the subsequent process.
Nitrogen gas, argon gas, helium gas, hydrogen gas, etc. can be used.

The conductor circuit of the present invention is formed as described above, but if necessary thereafter, surface treatments such as solder resist, nickel plating, gold plating, tin plating, and solder plating can be performed. As described above, according to the present invention, double-sided printed wiring boards are continuously formed on a long strip-shaped base material.
A long flexible double-sided printed wiring board can be provided.

〔Example〕

Next, an example of forming a conductor circuit on a long flexible base material by the most typical semi-additive method of the present invention will be described.

First, as an insulating base material, a glass cloth core material BT resin printed wiring board base material with a thickness of 0 to 13 gg is used, and a 30 μm thick film on both sides is laminated with an adhesive film.
BT resin adhesive layer is formed and this adhesive layer is heated at 60°C1.
By heating for 15 hours, it was semi-cured to a B stage state. Next, using a mold, positioning holes of 3 ff in diameter are made at both ends of this base material at intervals of 5H, and using the holes, through holes for through holes are similarly made using the mold. Next 1
It was semi-hardened in hot air at 75°C for 15 minutes, and the surface was roughened to about 2 μm using a buff roll. The entire surface of this substrate is then coated with a commercially available electroless copper plating system at °C.
A 0.5 μm thin film conductor layer was formed in 1 minute. Next, hot pressing is performed using a hot roll press at a temperature of 17
The test was carried out at 5°C and under a pressure of 41°C while being transported at t, am, and z=. After that, pattern formation was carried out by laminating a 25 μm alkali-soluble dry film on electroless copper, and after exposure by automatic positioning of the circuit pattern,
．． After developing with 7596 sodium carbonate solution and forming a plating resist, a 20 μm thick film was applied to the conductor circuit area in a copper sulfate bath.
Electrolytic copper plating was applied. Next, the resist was peeled off with a 2% caustic soda solution, and then etched to a thickness of about 2 μm with a cupric chloride solution, leaving the conductor circuit portion on the base material.

Finally, the adhesive layer is heated in a nitrogen gas atmosphere at 175°C for 1 hour to bring the adhesive layer to a C-stage completely cured state, and finally has an average peel strength of 2 kg/ffl according to JI8C6481. A long flexible double-sided printed wiring board was obtained.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to manufacture a long flexible double-sided printed wiring board by a semi-additive method, and therefore it has the following characteristics compared to conventional long sheets.

(a) Base materials that are difficult to laminate with copper foil can also be used, and base materials can be selected from a wide range depending on the application.

(b) The base material is cheaper because there is no copper foil.

(c) Since it can be commercialized without impairing the flexibility of the base material, long double-sided printed wiring boards can be continuously produced using relatively small equipment by taking advantage of its flexibility.

2) It has a high etch factor for forming sharp patterns, which is an advantage of the semi-additive method, so it is also suitable for producing fine conductor circuits.

(e) Furthermore, by appropriately setting various conditions such as the amount of electricity for the thickness of the conductor portion, a desired thickness can be easily and freely obtained. Therefore, the overall thickness of the printed wiring board can be minimized and the thickness can be made uniform, which is economically advantageous.

As described above, amid the recent demand for smaller size and lower prices for electronic products, the film carrier method contributes to automation of component mounting and lowers product costs. However, with the long printed wiring boards produced by conventional carrier tapes, the manufacturing costs of the printed wiring boards themselves are not necessarily low, and they are not suitable for high-density wiring, and are not suitable for miniaturizing products. I couldn't contribute enough. On the other hand, according to the present invention, the cost of the printed wiring board itself is lower due to the above-mentioned reasons, the cost of mounting components is also lower, and since it is suitable for high-density wiring, it is possible to downsize electronic-related products. , which will also greatly contribute to lower prices.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the double-sided printed wiring board of the present invention, FIG. 2 is a flow sheet diagram of the main steps in the semi-additive manufacturing method, which is an example of the double-sided printed wiring board of the present invention, and FIG. FIG. 1 is a longitudinal cross-sectional view of a double-sided printed wiring board of the present invention. (1)...Flexible insulating base material (2)...B-stage adhesive layer (3)...Through holes and holes necessary for the product (4)...
・Semi-hard adhesive layer (5)...Adhesive layer with roughened surface (e)...Electroless plating layer (7)...Hot roll (8)...Plating resist (9) )...Electrolytic plating layer (1...Adhesive layer (11) in a fully cured state...Copper foil layer

Claims (1)

[Claims] 1. (a) A first step of forming an adhesive layer on both sides of a long flexible insulating material and turning the adhesive layer into a B stage; (b) leaving the long base as it is; (c) a step of bringing the semi-cured state of the adhesive layer closer to a fully cured state; (d) a step of roughening the surface of the adhesive layer; (e) on the entire surface of the base material, a fifth step of forming a conductor layer by electroless plating, (f) a sixth step of applying continuous hot pressing, (g) a seventh step of forming a conductor circuit on the surface of the base material, and (h) the adhesive layer. A method for producing a long flexible double-sided printed wiring board, comprising an eighth step of completely curing the board. 2. The flexible insulating material is made of phenol resin, epoxy resin, polyimide resin,
2. The manufacturing method according to claim 1, wherein one or more resins selected from triazine resins are coated. 3. The steps (b) to (d) above are the steps (c), (b)
3. The manufacturing method according to claim 1 or 2, characterized in that step (a) and step (d) are carried out in this order. 4. The steps (b) to (d) above are the steps (c) and (d).
4. The manufacturing method according to claim 1, wherein step (b) is carried out in this order. 5. Semi-curing in the step (c) above is performed by heating the base material surface to 50 to 90% of the glass transition point (Tg) of the thermosetting resin.
5. The manufacturing method according to claim 1, wherein the manufacturing method is carried out at a temperature corresponding to . 6. The manufacturing method according to claims 1 to 5, wherein the electroless plating in step (e) is electroless copper plating. 7. The manufacturing method according to claims 1 to 6, wherein the thickness of the electroless copper plating is 0.1 to 3 μm. 8. The continuous hot press in step (f) above is performed at a pressure of 2 kg/cm^2 or more, and the Tg of the resin is 5
8. The manufacturing method according to claim 1, wherein the manufacturing method is carried out at a temperature of 0 to 90%. 9. Complete curing in the step (h) is performed at a temperature of 50 to 90% of the Tg of the resin in a non-oxidizing atmosphere. manufacturing method. 10. A long flexible print characterized by having an electroless plating layer on both sides of a long flexible insulating material with at least an adhesive layer interposed therebetween, and having an electrolytic plating layer on the surface thereof. wiring board.