JPS62229897A - Manufacture of printed wiring board - 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 <Industrial Application Field> The present invention relates to a method for manufacturing a printed wiring board. The present invention relates to a method for manufacturing a printed wiring board in which a circuit pattern is formed using a transfer printing method immediately after molding.

<Conventional technology> Conventionally, methods for manufacturing printed wiring boards include a method in which copper foil is pasted onto a base material such as glass epoxy or phenol, and a circuit pattern is formed by etching the copper foil (subtract method); A method of forming a circuit pattern on a base material using electroless plating or electrolytic plating (additive method),
There is a method of forming a circuit pattern on a base material by screen printing using conductive ink (screen printing method).

However, these methods require post-processing such as drilling holes in the printed wiring board, adding ribs, and punching out the outer shape in order to attach the printed wiring board to the product.

To solve this problem, the base material for printed wiring boards is molded by injection molding using heat-resistant thermoplastic resin, and holes and lips are formed in the base material in advance to avoid the need for post-processing. After that, there was a method of forming a circuit pattern on the surface of a substrate using an additive method or a screen printing method.

However, since the additive method and the screen printing method are techniques mainly applied to flat surfaces, they are not suitable for substrates exhibiting three-dimensional shapes. Further, the subtract method and the additive method involve many manufacturing steps such as providing and removing a resist layer, and are complicated.

Therefore, the present applicant previously developed a transfer material on which a circuit pattern layer is formed, as a method that enables the formation of a circuit pattern on a substrate for a printed wiring board exhibiting a three-dimensional shape, and also reasonably shortens the manufacturing process. , by placing it in an injection mold and then injecting a molten heat-resistant thermoplastic resin into the mold, forming a circuit pattern on the surface of the substrate at the same time as forming the substrate for the printed wiring board. We proposed a method to do this (see Japanese Patent Application Laid-open No. 121791/1983).

<Problems to be Solved by the Invention> However, in the above method, the thermoplastic resin that satisfies the mechanical strength, heat resistance, and electrical properties required as a base material for printed wiring boards is one that has a high melting temperature. Therefore, as a condition for injection molding, it is necessary to set the mold temperature and resin temperature higher than when injection molding ordinary resins, and the resin used for ordinary transfer materials is acrylic-based. and vinyl chloride, etc., which have a low melting temperature,
It had the following problems.

When a transfer material with a circuit pattern layer and an adhesive layer formed using ta+ general plastic resin as a binder is created and placed in an injection mold for simultaneous molding transfer printing, the molten material injected during injection molding is Along with resin, circuit pattern layer and adhesive F
l' melts and flows.

(b) If you create a transfer material in which the circuit pattern layer and adhesive layer are sufficiently cured using a curable resin as a binder to prevent the circuit pattern from melting, and perform molding and transfer printing in the same way, in this case, the circuit pattern layer Although the adhesive layer does not melt, the adhesive strength between the molding resin and the circuit pattern layer is so weak that it cannot be used.

(cl) If you create a transfer material with a circuit pattern and adhesive layer formed using uncured curable resin as a binder and perform molding-simultaneous transfer printing in the same way, the heat pressure of the injected resin will create a circuit pattern layer and adhesive layer. The layers are washed away and uniform adhesion is not achieved.

Therefore, we tried to perform transfer printing using the same method as general transfer painting, but if the object to be transferred is a flat plate, it can be easily transferred by pressing with a hot roll, but the shape of the object to be transferred is a little complicated. In this case, it is impossible to press with a hot roll, and it is necessary to press using a mold, and since it is impossible to match the shape 100% to the shape of the transferred object, the conditions for transfer printing are very difficult to set. It becomes difficult. Furthermore, press molds for transfer printing are also expensive.

The present invention eliminates all of the above-mentioned drawbacks, makes it possible to form a circuit pattern on a substrate for a printed wiring board exhibiting a three-dimensional shape, and improves the method of manufacturing a printed wiring board that can reasonably shorten the manufacturing process. The purpose is to provide

Means for Solving the Problems> In order to achieve the object, the present invention has the following configuration. That is, the present invention includes (8) a step of creating a transfer material in which a circuit pattern layer is provided on a base sheet and an adhesive layer is provided as necessary; (After solidifying the C1 printed wiring board base material, the mold is opened, and the transfer material is placed on the surface of the printed wiring board base material.) This method of manufacturing a printed wiring board is characterized by comprising the steps of transferring and printing a circuit pattern layer of a transfer material onto the surface of a substrate for a printed wiring board, and opening the mold again.

Next, the manufacturing process will be explained in more detail using the drawings. Note that the drawings are drawn in an exaggerated manner, ignoring the relative dimensional relationships of the constituent elements, for clarity of illustration.

First, a transfer material for forming a circuit pattern is created.

FIG. 1 is a sectional view showing an embodiment of a transfer material according to the present invention. 1 is a base sheet, 9 is a circuit pattern layer,
This circuit pattern layer 9 is composed of conductive pattern layers 2, 4.6 and an insulating layer 3.5.

As the base sheet 1, a single film or a laminated film of flexible and heat resistant polyester, polyimide, polyethersulfone, polyetheretherketone, polyphenylene sulfide, polymethylpentene, polyethylene, polypropylene, etc. is used. do. Furthermore, if necessary, a mold release treatment such as silicon treatment is used.

The conductive pattern layers 2, 4, and 6 constituting the circuit pattern 9 are formed by printing conductive ink. The conductive ink is prepared by uniformly mixing a binder and conductive powder in an appropriate solvent. As a binder, thermoplastic resins such as heat-resistant polyethersulfone or polysulfone, polyetherimide, polyamideimide, polyallylsulfone, polyarylate, polyphenylene oxide, polyphenylene sulfone, polycarbonate, polyamide, etc., or epoxy or non-plastic resins are used. Curing resins such as saturated polyester, urethane, phenol, acrylic, or mixtures thereof are used. Conductive powders include silver, aluminum, copper, nickel, gold, carbon, graphite,
Metal or inorganic conductive powder, such as one coated with metal on the surface of glass beads, is used. The conductive ink may contain a certain amount of surfactant, hydrating agent, etc. to improve its performance as a printing ink.

Further, the insulating layers 3 and 5 are formed on the entire surface or in a pattern by printing or coating with insulating ink. The insulating ink is prepared by uniformly mixing a binder with an appropriate solvent. As for the binder, polyethersulfone or polysulfone, polyetherimide, polyamideimide, polyallylsulfone, polyarylate, polyphenylene oxide, etc.
Thermoplastic resins such as polyphenylene sulfone, polycarbonate, and polyamide, curable resins such as epoxy, unsaturated polyester, urethane, phenol, and acrylic, or mixtures thereof are used. Insulating powder may be added to the insulating ink if necessary. This @-related powder includes nichrome oxide, alumina, silicon dioxide, zirconium oxide, magnesium oxide, beryllium oxide, boron nitride, mica, magnesium silicate,
Inorganic powders such as steatite can be used. Furthermore, to improve the performance as a printing ink, the insulating ink may contain a small amount of surfactant, a chicken-like filler, and the like.

In addition, when a curable resin is used as the outermost surface layer or the matrix of the outermost surface layer, the above-mentioned transfer material is composed of a resin whose main component is a resin in which unreacted reactive groups remain. This is because if a completely cured resin is used, the surface will not melt and the injection molding resin and the printed wiring board substrate will not adhere firmly. When a curable resin is used, heat-resistant adhesive strength can be obtained. In addition, when using a thermoplastic resin as the outermost surface layer or the matrix of the outermost surface layer, 120°C to 300°C, preferably 150°C to 200°C
It is made of a resin that starts deforming due to heat at 50°C. This is because the injection molding resin functions as an adhesive, and when the circuit pattern layer 9 of the transfer material and the injection molding resin come into contact, the circuit pattern layer 9 softens only slightly, and the circuit pattern layer 9 does not melt. This is to ensure strong adhesion.

The transfer material according to the present invention has the above-described structure, but as another aspect, an adhesive layer 8 is provided on the circuit pattern layer 9.
(See Figure 2). This adhesive layer 8 can be made of the same binder as the conductive ink or insulating ink, but since it will be the outermost layer of the transfer material, if a curable resin is used, unreacted reactive groups When a thermoplastic resin is used, it is necessary to use a resin that starts thermal deformation at a temperature of 120°C to 300°C, preferably 150°C to 250°C.

Note that the circuit pattern layer 9 that does not constitute the outermost layer of the transfer material
are formed as appropriate, taking into consideration conductivity, insulation, adhesion with adjacent layers, heat resistance, etc., respectively.

While creating the transfer material, a printed wiring board base material is molded in an injection mold. Injection molding resins that can be used in the present invention are resins with sufficient heat resistance and electrical properties, such as polyethersulfone, polyetherimide, polyetheretherketone, polysulfone, polyarylate, and polysulfone. Thermoplastic resins such as butylene terephthalate and polyethylene terephthalate can be used. In addition, glass fiber, mica, talc, etc. are added to these resins as appropriate to adjust the material properties.
Additives such as titanium oxide may also be added. Injection conditions vary depending on the type of resin and the shape of the mold, and the mold temperature is approximately 40°C.
~180°C, and the resin temperature ranges from 250 to 400°C.

After solidifying the printed wiring board base material, the mold is opened and the transfer material is placed on the surface of the printed wiring board base material. In this mold opening step, the gate portion is left in the mold without being completely opened, and the transfer material is aligned and placed inside the mold. The circuit pattern layer of the transfer material faces the printed wiring board substrate side. At this time, it is an effective method for transfer printing on three-dimensional objects to form appropriate notches or punch holes in the transfer material according to the shape of the printed wiring board base material and the shape of the mold. be.

Next, by closing the mold, the circuit pattern layer 9 of the transfer material is transferred and printed on the surface of the printed wiring board base material. The heat required for this transfer printing can be generated using the heat of the mold and the heat of the injection molding resin. When a curable resin is used as the outermost layer, curing can also proceed at the same time.

After that, the mold is opened again.The mold is opened and the molded printed wiring board base material is taken out.If the adhesion between the printed wiring board base material and the circuit pattern layer 9 of the transfer material is sufficient, this step is performed. It is preferable to peel off the base sheet 1 at this point. If this is insufficient, the residual heat of the resin may be used or additional heat may be applied to promote adhesion, and then the base sheet 1 is peeled off.

<Example> Examples of the present invention are shown below.

Silver paste (thermosetting phenol binder), insulation paste of thermosetting epoxy resin, silver paste (thermosetting phenol) were printed on a base sheet with mold releasability made by coating a 38 μm thick polyethylene terephthalate film with epoxy resin. binder)
were successively screen printed, and finally an epoxy resin adhesive ink was printed on the entire surface, followed by heat treatment to create a transfer material for a printed wiring board (see Figure 3).

Polyether sulfone resin was injected using an injection molding machine under the following conditions. After solidification of the resin, the mold was opened, the transfer material was fixed in the mold, and the mold was closed again.

The transfer material and the molded product were kept in close contact with each other for 10 seconds, the mold was opened again, the molded product was taken out, the base sheet was peeled off, and the resin was further heated at 150° C. for 30 minutes to completely cure the cured resin.

As a result, a printed wiring board was obtained in which a conductive pattern layer was formed on two strongly adhesive layers.

Continuity between the conductive pattern layers was tested and found to be good.

Moreover, all the parts that should be insulated were insulated, and the resistance value was 1X10''Ω or more.

Injection conditions (Japan Steel Works type JC150S^) mold temperature
100~120℃ cylinder temperature
350~380℃ injection pressure
99% holding force 70
~73% injection speed 99% screw rotation speed 50rpa+ <Effects of the invention> Since the present invention has the above configuration,
It has the following effects. That is, since transfer printing is performed inside the mold immediately after the +al printed wiring board base material is molded, it is possible to form a circuit pattern on the printed wiring board base material exhibiting a three-dimensional shape. (b) By forming a circuit pattern on the surface of the substrate immediately after forming the printed wiring board substrate, the manufacturing process can be rationally shortened. (C) Transfer printing of the circuit pattern layer is performed immediately after the injection molding of the printed wiring board substrate, so even resins that would otherwise flow in the simultaneous molding transfer method can be used for the circuit pattern layer. (d) Since transfer printing is performed within a mold, a press mold can be omitted compared to general transfer printing methods. (e) During transfer printing, the residual heat from molding can be used, reducing costs.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a transfer material for printed wiring boards according to the present invention. FIG. 2 is a sectional view showing another embodiment of the transfer material for printed wiring boards according to the present invention. FIG. 3 is a sectional view showing a transfer material for a printed wiring board according to an embodiment of the present invention. 1... Base sheet 2.4.6... Conductive pattern layer 3.5... Insulating layer 8... Adhesive layer 9... Circuit pattern layer

Claims (4)

[Claims] (1) (a) A process of creating a transfer material in which a circuit pattern layer is provided on a base sheet and an adhesive layer is provided as necessary; (b) A printed wiring board substrate is placed in an injection mold. (c) After solidifying the printed wiring board base material, opening the mold and placing the transfer material on the surface of the printed wiring board base material; (d) Closing the mold. (e) opening the mold again; Manufacturing method for wiring boards. (2) The outermost surface layer and/or the matrix of the outermost surface layer of the transfer material is composed of a thermosetting resin in which unreacted reactive groups remain. A method for manufacturing printed wiring boards. (3) Claim 1, characterized in that the outermost surface layer and/or the matrix of the outermost surface layer of the transfer material is made of a thermoplastic resin that starts thermal deformation at 120°C to 300°C. The method for manufacturing a printed wiring board described in . (4) After peeling off the base sheet from the printed wiring board on which the circuit pattern layer has been transfer-printed, the printed wiring board is heated to strengthen the adhesion between the printed wiring board base material and the circuit pattern layer. The method for manufacturing a printed wiring board according to claim 1, further comprising: