JPH06322546A - Composition for plating - Google Patents

Abstract

PURPOSE:To prevent the generation of blister at the soldering process after plating by most suitably selecting the composition for an electroless plating and specifying the grain size and moisture content of an inorg. filler. CONSTITUTION:The composition to be plated 2 is the composition prepared by filing 50-200pts. inorg. filler having <=5mum average grain diameter and <=0.1% moisture content into 100pts. uncured thermosetting resin or resin composition in weight. The uncured thermosetting resin or the resin composition is one among an epoxy resin and its curing agent, a polyol and an isocyanate compd. a phenol resin and unsatd. polyester. The composition 2 is applied on the matter to be plated 1, polymerized and cured, the matter to be plated 1 and the composition 2 are combined strongly, the filler 3 in the composition 2 is exposed by a chemical method, etc., and eluted and removed, and numerous fine pores 4 are obtained. When the electroless plating is applied on the surface of the composition 2, a plating metal is entered into the pores 4, a plating layer is formed in uniform thickness, and jointed integrately on the matter to be plated 1 by an anchor effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition to be plated, which is used when electroless plating is applied to a heat resistant plastic.

[0002]

2. Description of the Related Art The composition for electroless plating is known per se from JP-A-60-79075. However, since the known electroless plating composition has a weak adhesion of the metal film after plating, the applicant of the present invention intends to improve the adhesion by applying heat resistance and a strong adhesion of the metal film after plating. I have already applied for a composition to be worn (Japanese Patent Application No. 4-
69054).

[0003]

The composition for plating to be applied of the above-mentioned prior application is applied to an adherend (printed circuit board) and, after curing, the applied surface is polished and further pretreatment for electroless plating (cleaner conditioner, hot water washing). , Washing with water, soft etching, washing with water, acid activation, washing with water, etc., and then electroless plating of gold, silver, copper, nickel, zinc, etc. to form a metal film with strong adhesion as expected. However, blistering (a phenomenon in which a part of the metal film expands and peels off from the printed board) was occasionally observed in the soldering step after plating.

[0004]

As a result of intensive studies by the present inventors in order to solve such problems, there is a close relationship between the water content of the inorganic filler and the blisters in the soldering process after plating. The present invention was completed by finding out that there is.

That is, the composition to be plated according to the present invention is
100 to 100 parts by weight of an uncured thermosetting resin or resin composition is filled with 50 to 200 parts by weight of an inorganic filler having an average particle size of 5 μm or less and a water content of 0.1% by weight or less.

The composition to be coated with plating of the present invention contains an organic solvent for adjusting viscosity and a surfactant and a colorant for improving the dispersibility of the filler, if necessary.

By using the above composition to be plated, it is possible to form a metal film having a strong adhesive force and a high durability on a heat-resistant plastic substrate, thereby eliminating conventional blistering.

The uncured thermosetting resin or resin composition constituting the composition to be plated according to the present invention is any of an epoxy resin and its curing agent, a polyol and an isocyanate compound, a phenol resin and an unsaturated polyester resin. Therefore, it is desirable to select it according to the material of the plastic substrate that is the plating adherend. That is, glass
An epoxy resin and its curing agent are used for the epoxy substrate, a polyol and an isocyanate compound are used for the polyurethane resin substrate, a phenol resin is used for the paper / phenol substrate, and an unsaturated polyester resin is used for the glass / cured polyester substrate.

Calcium carbonate and / or barium sulfate is used as the inorganic filler constituting the composition to be plated.

Next, in the plating method, the composition 2 to be plated is applied to the object 1 to be plated in the coating treatment step (see FIG. 1 (A)). In the next curing treatment step, when the applied coating composition 2 is polymerized and cured, the plating object 1 and the plating composition 2 are firmly bonded.
Further, in the surface treatment step, the filler 3 in the cured coating composition 2 is exposed by a physical or chemical method (see FIG. 1 (B)).

Subsequently, in the elution processing step, the exposed filler 3 is eluted. After the filler 3 is eluted and removed, a large number of micropores 4 corresponding to the shape of the fine particles of the filler 3 are obtained as cavities (see FIG. 1C).

In the next plating step, electroless plating is applied to the surface of the composition to be plated 2 to be plated in the above state. In this treatment step, the plating metal 5 penetrates into the many micropores 4 of the composition to be plated 2, and a plating layer is formed on the surface of the composition to be plated 2 to have a uniform thickness. . When the electroless plating is completed, the plating film is integrally bonded onto the object to be plated 1 by the anchoring effect (Fig. 1 (D)).
reference).

The water content of the filler constituting the composition to be plated according to the present invention is 0.1% by weight or less, preferably 0.
It is at most 02% by weight. If the water content exceeds 0.1% by weight, the frequency of blistering after plating increases.

In using the composition to be plated-plated according to the present invention, first, the undercoating agent 1 is applied to the surface of the printed board 10 made of glass epoxy having the copper foil circuit 11 in the X-axis direction.
2 is applied by screen printing to a thickness of 20 to 30 μm. After application, the primer is dried and cured at 150 ° C. for 30 minutes.

Thereafter, the thermosetting plating composition 2 of the present invention is applied to the surface of the printed circuit board 10 in the Y direction.
It is evenly applied by screen printing to a thickness of 20 to 30 μm in the axial direction. After coating, the composition to be plated is dried at 150 ° C. for 30 minutes to be cured (FIG. 2 (A)).

As the undercoating agent 12, a solder resist S-222 manufactured by Taiyo Ink Co., Ltd. was used.

When the undercoating agent 12 is undercoated in this way,
Adhesion with the copper foil circuit 11 is improved, and circuit insulation can be secured. Furthermore, after the primer 12 is applied by screen printing in the X-axis direction of the printed circuit board 10, the plating adhered composition 2 is applied by screen printing in the Y-axis direction of the printed circuit board 10. Can be prevented, and the coated surface can be smoothed.

When the filler 3 in the composition 2 to be plated is exposed after the composition 2 to be plated is thus cured, the surface becomes as shown in FIG. 2 (B). This filler 3
The exposure is generally performed by buffing the surface of the composition to be plated 2, but the surface treatment may be other physical or chemical polishing.

Next, a pretreatment for a usual electroless plating treatment,
In other words, cleaner conditioner, hot water wash, water wash,
Each process such as soft etching, washing with water, acid activity, and washing with water is performed in sequence, but the exposed large number of fillers 3 are eluted by sodium persulfate used for soft etching and crude sulfuric acid used for acid activation. , As shown in FIG. After the eluent removal of the filler 3 in this manner, a large number of cavities of micropores 4 corresponding to the shape of the fine particles of the filler 3 are obtained.

Subsequently, electroless plating of gold, silver, copper, nickel, zinc or the like is applied to the surface of the composition 2 to be plated in the above state. As the electroless plating solution, product number “328A” of Secret Japan Co., Ltd. is used here, and the plating condition is that the plating temperature is 19 ° C. to 22 ° C. and the plating time is 20 minutes.

By this electroless plating treatment step, the plating metal 5 penetrates into the innumerable micropores 4 of the composition 2 to be plated, and a plating layer is uniformly formed on the surface of the composition 2 to be plated. Will be done.

When the electroless plating is completed, a plating film having a predetermined thickness is formed as shown in FIG. Next, after each step of washing with water, drying, acid activation, and washing with water in this order, electroplating is performed. This electroplating uses a chemical such as copper sulfate pentahydrate as in the conventional case, and the plating condition is that the temperature is 22 ° C. to 28 ° C. and the plating time is 50 to 70 minutes. Then, after the electroplating is finished, each process of rust prevention and drying is performed, and the whole process is finished.

In this way, after the composition to be plated 2 is applied on the copper foil circuit 11 and after the plating treatment, the plated layer is etched into a predetermined circuit pattern if necessary, so that the plated material is plated. A multilayer printed circuit board having the composition 2 as an insulating layer can be formed, but if the composition to be plated 2 is selectively applied without being applied to the entire surface of the copper foil of the printed board as described above, it is not applied to a round portion. Is directly connected to the copper foil circuit 11 in the lower layer, and interlayer conduction can be performed without through holes.

[0024]

It is presumed that the size of the micropores formed after the elution of the filler can contribute to the improvement of the anchoring effect after plating. In the formed plating layer, the peeling strength of the plating film is improved by improving the anchoring effect and, in addition, the improvement of the anchoring effect can prevent blistering and poor adhesion of the plating layer under heating. Further, the improvement of the anchoring effect suppresses the thermal expansion and thermal contraction of the plating layer. Further, it is speculated that the density of the micropores formed per unit area after the elution of the filler is proper and is an appropriate size that can contribute to the improvement of the anchoring effect after plating.

[0025]

EXAMPLES Next, the composition to be plated according to the present invention will be specifically described with reference to Examples and Comparative Examples.

[0026]

[Table 1] The thermosetting resin, the filler, the dispersant, the colorant and the viscosity adjusting solvent shown in Table 1 were weighed according to the weight ratio in Table 1, put in a container with a stirrer and kneaded to prepare a composition to be plated. The rotation speed of the stirrer is 1200 rpm and kneading is performed for 6 hours.

Examples 1 to 3 and Comparative Examples 1 to 2 Compositions shown in Table 1 were prepared, except that the water content of the inorganic filler was changed as shown in Table 2 below to prepare compositions to be plated. The water content of the inorganic filler is 100 ° C of the sample at 200 ° C.
It was determined by weight reduction after hot air drying for 5 hours.

Comparative tests as shown in Table 2 were conducted to compare the plating states. That is, this comparative test
The composition to be plated is as shown in Table 1,
Only in the case of the inorganic filler, the water content was changed, and the plating was performed by the same process as above. The results are shown in Table 2.

[0029]

[Table 2] In Table 2, the thickness of the formed plating layer was obtained by peeling off the formed plating layer and measuring the thickness with a micrometer. The peel strength is obtained by cutting the plated layer having a width of 25 mm into a strip shape with a cutter knife, and forcibly peeling a part of the plated layer in a direction of 180 ° by a tensile tester. The pulling speed at this time is 50 mm / min. For the observation of the surface condition, the gloss of the plating surface was observed with the naked eye, and the good one was "A", and the diffuse reflection was "B".
Further, the presence or absence of pinholes was examined by observing the peeled plating layer with a microscope of 30 times and inspecting the presence or absence of pinholes. The blister of the plating layer is indicated by the number of printed boards having blister defects per 10 printed boards of 20 cm × 12 cm after being immersed in a solder bath at 260 ° C. for 20 seconds.

Examples 4 to 6 and Comparative Examples 3 to 4 The same as Example 1. However, the same evaluation as in Example 1 was performed using barium sulfate having a different water content instead of calcium carbonate, and the results shown in Table 3 were obtained.

[0031]

[Table 3]

[0032]

INDUSTRIAL APPLICABILITY When performing electroless plating by using calcium carbonate or / and barium sulfate as an inorganic filler,
A uniform and relatively thick plating layer without pinholes can be formed in a short time.

Since the amount of the water content of the inorganic filler added in a large amount in the composition to be plated of the present invention is controlled to 0.1% by weight or less, the appearance without blisters and pinholes is good and the adhesive strength is high. A high metal film can be formed on a printed circuit board.

By setting the particle size of the filler to 5 μm or less, the filler can be eluted in a short time when the filler exposed on the surface is eluted with the treatment liquid. Since elution is easy in this way, no special elution step is required,
The filler can be sufficiently eluted even in the usual pretreatment process (soft etching or the like) in the conventional well-known electroless plating. In addition, in the present invention, it is presumed that the size of the micropores formed after the elution of the filler can contribute to the improvement of the anchoring effect after plating, which can contribute to the improvement of the peel strength of the plating film.

Moreover, the formed plating layer improves the peeling strength of the plating film due to the improved anchoring effect, and
By improving the anchoring effect, it is possible to prevent swelling and poor adhesion of the plating layer under heating. Further, since the anchoring effect is improved, the thermal expansion and the thermal contraction of the plating layer are suppressed, so that the thermal cycle of 150 ° C. to −40 ° C. can be endured.
Therefore, it is possible to form a plated layer that can be practically used for heat-resistant plastic.

Furthermore, since the filler is filled in the cured composition to be plated on the basis of 50 parts by weight to 200 parts by weight, the density per unit area of the micropores formed after the elution of the filler becomes appropriate. Inferred. Therefore, by optimizing the density of the micropores, the anchoring effect after plating is improved,
It can contribute to prevention of poor adhesion of the plated layer under heating.

In addition, the thermal expansion and contraction of the plated layer is suppressed by the improvement of the anchoring effect after the plating described above, so that it is possible to endure the heat cycle of 150 ° C to -40 ° C.

In the plated product thus obtained, a large number of micropores 4 obtained after the elution of the filler 3 in the composition 2 to be plated has an appropriate size capable of contributing to the anchoring effect after plating. It is presumed that the peel strength of the plated film can be improved.

[Brief description of drawings]

FIG. 1 is a process diagram illustrating a plating method of the present invention.

FIG. 2 is a process diagram when the plating method of the present invention is applied to a printed circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plated object 2 Plated composition 3 Filler 4 Micropores 5 Plated metal 10 Printed circuit board 11 Copper foil 12 Undercoat agent

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical indication location H05K 1/03 F 7011-4E 3/18 A 7511-4E (72) Inventor Shingo Sasaki Aikawa-cho, Aiko-gun, Kanagawa Nakatsu 4085 Diabondo Kogyo Co., Ltd. Atsugi Plant (72) Inventor Tomohisa Uemura 7-5-17 Kamimizo, Sagamihara City, Kanagawa Prefecture (72) Inventor Toshiaki Hagino 5850, 1850 Shinba-cho, Kohoku-ku, Yokohama, Japan Inside the drawing

Claims (3)

[Claims] 1. An uncured thermosetting resin or resin composition 1
In 100 parts by weight, the average particle size is 5 μm or less and the water content is 0.1
A composition to be plated-plated, which comprises 50 to 200 parts by weight of an inorganic filler of 50% by weight or less. 2. The uncured thermosetting resin or resin composition according to claim 1 is selected from the group consisting of an epoxy resin and its curing agent, a polyol and an isocyanate compound, a phenol resin, and an unsaturated polyester resin. Composition to be plated, which is a resin or a resin composition prepared according to claim 1. 3. A plating adhered composition in which the inorganic filler according to claim 1 is calcium carbonate and / or barium sulfate.