JPH08181414A - Manufacture of injection molding circuit substrate - Google Patents

Abstract

PURPOSE: To improve bonding property and to make a pattern fine by roughening a surface by forming a secondary injection molded item to expose only a primary injection molded item and a pattern side of a substrate, and by applying electroless plating on a pattern side. CONSTITUTION: Resin mixed with electroless plating catalyst is used and a primary injection molded item is formed by projecting a pattern side 4. A substrate 5 is inserted and a secondary injection molded item 2 is formed of unmixed resin to expose only pattern sides 14, 54 of a primary injection molded item 1 and the substrate 5. Then, a surface is subjected to wet treatment and immersed in electroless copper plating solution, and foundation platings 16, 56 are formed as an electric conductor film in a surface of mixed resin shaped to correspond to the pattern parts 14, 54. Therefore, if upper platings 17, 57 consisting of Ni plating and Au plating are formed by an electroless plating method on the foundation platings 16, 56, good bonding success ratio of almost 100% can be realized and a fine pattern of a pitch of 0.15mm can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an injection molded circuit board having a patterned metal layer on its surface.

[0002]

2. Description of the Related Art An injection-molded circuit board having a patterned metal layer used as an electric circuit pattern or the like on its surface, for example, MCB (molded circuit board), MWB (molded).
wiring board), MID (molded interconnection boa)
rd) has attracted attention because it meets various requirements such as three-dimensionalization, reduction in wiring man-hours, weight reduction, space saving, and cost reduction.

The above-mentioned injection-molded circuit board has a resin (hereinafter, simply referred to as "difficult-to-plate resin") to which metal plating is hard to adhere, as disclosed in, for example, Japanese Patent Application Laid-Open No. 63-50482.
It is a so-called two-shot molded product that uses a resin that easily adheres to the metal plating (hereinafter simply referred to as “easy-plating resin”). A predetermined circuit pattern is formed by applying metal plating.

When manufacturing this injection-molded circuit board, as shown in FIG. 2A, the primary injection-molded body 1 having a pattern surface 4 corresponding to the pattern of the electric circuit to be formed is easily plated. 2B, the secondary injection molded body 2 is formed by surrounding the primary injection molded body 1 excluding the pattern surface 4 with the non-plating resin in the secondary molding after molding with the flexible resin. Then, the injection-molded product 3 is molded by this. After that, roughening treatment is performed with a chemical, and electroless plating treatment is performed on the patterned surface 4 after the treatment. At this time, as shown in FIG. 2D, the metal does not adhere to the portion of the difficult-to-plate resin 2, and the base plating 6 is formed only on the pattern surface 4 which is the easily-platable resin. Further, in order to protect the surface of the pattern surface and improve the wire bondability, nickel plating, gold plating, or the like is applied as the upper plating 7 on the base plating 6 thus formed, and the metal plating portion is used. To form various circuits. This method is called a two-time molding method and is characterized in that it has a high degree of freedom in pattern formation and can be formed three-dimensionally.

[0005]

However, since the above-mentioned base plating is generally copper-plated by the electroless plating method, the surface thereof becomes very rough, and Rmax (JIS The distance between the highest peak and the deepest valley bottom of the sectional curve was 30 to 50 m. Furthermore, even when the upper plating of copper, nickel or the like is thickly formed on the undercoating by an electrolytic plating method which is smoother than the electroless plating method, the surface of the upper plating becomes rough. The value is 10 to 20 μm in Rmax
Met.

If the surface of the plating is rough like this,
It is very difficult to bond a wire, especially a thin wire having a diameter of about 20 μm, onto the upper plating by a ball bonder, and conventionally, the success rate was only about 50 to 70%, which was not practical.

Therefore, in order to improve the success rate of bonding, it has been desired to improve the surface roughness of the undercoat.

Further, the width and pitch of the circuit pattern are limited in terms of molding, mold production ability, resin flow problem (for example,
If the thickness is 0.2 mm or less and the area of 3 cm square or more is large, the resin will not flow.)
In the molding method, the limit is at most about 0.5 mm, and further finer circuit patterns have been demanded in order to meet recent demands for miniaturization and high-density mounting of mounted components.

[0009]

SUMMARY OF THE INVENTION In view of the above problems, the present invention has a degree of freedom in forming a circuit pattern by a two-time molding method, particularly a three-dimensional circuit pattern, and at the same time, improves the bonding property by smoothing a plating surface. The purpose of the present invention is to provide a method for manufacturing an injection molded circuit board that can meet the demands for improvement and finer pattern.

In order to achieve the above object, a method of manufacturing an injection-molded circuit board according to the present invention comprises injection-molding a compounded resin containing a catalyst for electroless plating with a pattern surface corresponding to the pattern of an electric circuit protruding. After forming a primary injection molded body, to form a secondary injection molded body by injection molding a non-blended resin not mixed with a catalyst for electroless plating around the primary injection molded body except the pattern surface, Further, in the method for producing an injection molded circuit board in which a pattern is formed by plating the surface of the primary injection molded body, after forming the primary injection molded body, smoothness of the plated surface or a fine pattern is required. A substrate on which a pattern is preliminarily formed is inserted, and a secondary injection molded body is formed so that only the pattern surface of the primary injection molded body and the substrate is exposed. After producing the goods, performs a roughening process of injection-molded article surface, is obtained by a configuration in which plating by electroless plating on the pattern surface after the treatment.

Among the above-mentioned constitutions, a polyester-based synthetic resin is adopted as a compounding resin containing a catalyst for electroless plating for forming the primary injection molded body 1, and an aromatic polyester resin is used as a thermoplastic resin. Liquid crystal polymer (LCP), polyethylene terephthalate (PET),
Polybutylene terephthalate (PBT), polyether sulfone, (PES), polyether imide (PBT)
EI), aromatic polyamide, etc.
It is not particularly limited to these. Further, palladium and ruthenium are used as the electroless plating catalyst.

On the other hand, polyphenylene sulfide (PP) is used as a non-blended resin for forming the secondary injection molded body 2.
Although S) is suitable, it is not particularly limited thereto, and any material having resistance to a chemical used for roughening the compounded resin may be used. For example, when an aromatic polyester resin is used as the compounding resin, PES, PEI, PEI, etc. which are resistant to alkali can be used in addition to PPS. The primary injection molding and the secondary injection molding are performed using a mold or the like.

The board to be inserted may be formed by a generally known method for manufacturing a printed board.
As a material for forming the substrate, phenol-impregnated paper, epoxy-impregnated paper, epoxy-impregnated glass cloth, polyimide-impregnated glass, thermoplastic resin (LCP, PET, PBT, PES)
Etc.), thermosetting resins (phenol, epoxy, etc.), polyimide films and the like. A flat plate was formed using these materials, an electric conductor coating film of copper (electrolytic copper, rolled copper) or the like was formed on the surface, and a resist film was formed on the portion of the electric conductor coating film that remained as an electric conductor circuit. After that, a circuit pattern is formed by a subtraction method of chemically removing the electric conductor coating film in the portion without the resist film.

The shape of the substrate is not limited to a flat plate, but may be a three-dimensional shape, for example, a 2.5-dimensional shape. Further, the circuit formation can be performed not only by the above method but also by an exposure method or an additive method.

Further, when the smoothness of the conductor surface is required, a copper bar punched out in the shape of the pattern may be used.

[0016]

According to the present invention having the above-described structure, the plating surface is excellent in smoothness and the bonding property is improved while having a degree of freedom in forming a circuit pattern by the double molding method, particularly a three-dimensional circuit pattern. In addition, it becomes possible to form an injection molded circuit board having a fine pattern of about 0.1 mm pitch.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a method for manufacturing an injection molded circuit board according to the present invention will be described below with reference to FIGS.

First, as a compounding resin compounded with a catalyst for electroless plating, LCP-2 which is LCP (liquid crystal polymer)
49 (manufactured by Hoechst Celanese Co., Ltd., product name) was used to project the pattern surface 4 corresponding to the pattern of the electric circuit with a mold and injection molding was performed to form a primary injection molded body 1 (FIG. )).

A MCF-5000I, which is a two-layer metal clad film in which a 25 μm-thick electrolytic copper foil is bonded onto a 25 μm-thick polyimide resin as a substrate 5 to be inserted when the secondary injection-molded article 2 is formed. (Hitachi Chemical Co., Ltd., trade name) was used to form a pattern with a pitch of 0.15 mm by the subtract method (FIG. 1).
(B)).

Next, while inserting the substrate 5,
C-100 as PPS (polyphenylene sulfide), which is a non-blended resin that does not contain a catalyst for electroless plating
HG (trade name, manufactured by Idemitsu Petrochemical Co., Ltd.) is injection-molded so that only the pattern surfaces 14 and 54 of the primary injection molded body 1 and the substrate 5 are exposed to form a secondary injection molded body 2. An injection molded product 3 was produced (Fig. 1 (c)).

Further, the surface of the injection-molded article 3 is wet-processed, specifically, after roughening for 30 minutes in a potassium hydroxide solution at 11 mol / l and a temperature of 70 ° C., it is neutralized with hydrogen chloride. (FIG. 1 (d)), the injection-molded article 3 after the wet treatment was treated with an electroless copper plating solution (562) (KOLLMO).
RGEN CO. Manufactured, product name), and base plating (copper plating) 16 and 30 μm was formed as an electric conductor coating on the surface of the compound resin having a shape corresponding to the pattern portions 14 and 54 by an electroless plating method (Fig. 1 (e)).

At this point, the surface roughness of the undercoating was measured. As a result, the undercoating 16 which was directly plated on the plastic molded product had an Rmax (JIS: maximum height) of 3
0-50 μm, Rz (JIS: 10-point average roughness) 20 μ
m, Ra (JIS: center line average roughness) was 3 μm, whereas the base plating 56 applied on the electrolytic copper foil was Rm.
The ax was 7 μm, the Rz was 5 μm, and the Ra was 0.5 μm, and the plated surface was much smoother than the former.

The difference in surface roughness between these two is that the Rmax is already several tens of μm for obtaining the peel strength on the plastic surface before undercoating (FIG. 3), whereas that of the copper foil surface is about 5 μm. Yes (Fig. 4). Regarding the start of plating deposition, in the case of deposition on the plastic surface, partial growth occurs from the catalyst scattered on the plastic (Fig. 5 (a)), and planar growth is achieved by fusing with adjacent growth parts. Because ((b) to (c))
While the unevenness remains on the plating surface, in the case of deposition on the copper foil surface, the deposition starts at all points and the plating surface becomes flat (Fig. 6 (a) to (c)). to cause.

Further, Ni plating 3 μm, Au plating 0.3 on the undercoat plating 16, 56 by electroless plating.
The upper plating 17, 57 of μm was formed to obtain an injection molded circuit board.

When a gold wire having a diameter of 20 μm was bonded onto the pattern of the injection molded circuit board thus formed, the upper plating 1 applied on the primary injection molded body 1
While the success rate of bonding to 7 was 20%,
The success rate of bonding to the upper plating 57 applied on the inserted substrate 5 was good at almost 100%.

Since the pattern formed on the substrate 5 is the final pattern as it is when it is inserted, a fine pattern with a pitch of 0.15 mm can be formed.

[0027]

According to the present invention having the above-mentioned constitution,
Despite having the freedom to form a circuit pattern, especially a three-dimensional circuit pattern by the double molding method, the plating surface is excellent in smoothness, bonding property is improved, and a fine pattern of about 0.1 mm pitch is provided. It becomes possible to form an injection molded circuit board.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing a manufacturing process of an injection molded circuit board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional explanatory view showing a manufacturing process of a conventional injection molded circuit board.

FIG. 3 is an enlarged cross-sectional explanatory view of a plastic surface.

FIG. 4 is an enlarged cross-sectional explanatory view of a copper foil surface.

FIG. 5 is a schematic explanatory view showing the growth of plating on the plastic surface.

FIG. 6 is a schematic explanatory view showing the growth of plating on the surface of a copper foil.

[Explanation of symbols]

 1 Primary injection molded product 2 Secondary injection molded product 3 Injection molded product 4,14,54 Pattern surface 5 Substrate 6,16,56 Undercoat 7,17,57 Top plating 8 Plastic 9 Copper foil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Ichige 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Hidaka Plant (72) Inventor Shinichi Takaba Hidaka, Hitachi City, Ibaraki Prefecture 5-1-1, Machi, Hitachi Cable, Hidaka Factory (72) Inventor Toshiyuki Oaku 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Hitachi Cable, Hidaka Factory

Claims (1)

[Claims] 1. A primary injection molded article is formed by injection molding a compounded resin containing a catalyst for electroless plating with a pattern surface corresponding to the pattern of an electric circuit protruding to form a primary injection molded body, and then primary injection molding excluding the pattern surface. A non-blended resin that does not contain a catalyst for electroless plating is injection molded around the body to form a secondary injection molded body, and a pattern is formed by plating the surface of the primary injection molded body. In the method of manufacturing an injection-molded circuit board, which comprises:
Insert a substrate on which a pattern is formed in advance on the surface of the plating where smoothness or a fine pattern is required, and form a secondary injection molded body so that only the primary injection molded body and the pattern surface of the substrate are exposed. After producing an injection-molded product by performing the roughening treatment of the injection-molded product surface,
A method for manufacturing an injection molded circuit board, characterized in that the pattern surface after the treatment is plated by an electroless plating method.