JPS6147182B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flame retardant resist ink for electroless plating. In particular, the present invention provides a resist ink that can withstand long-term plating with a strong acid and high-temperature strong alkaline electroless copper plating solution for plating pretreatment, has soldering heat resistance, and is flame retardant. One conventional method for manufacturing printed circuit boards is the additive method, in which only the necessary circuits are formed using electroless copper plating. In this method, a resist ink having chemical resistance is applied to areas other than the circuit forming area, that is, areas where no plating is desired. An example of this type of resist ink is an epoxy type resist ink disclosed by some of the present inventors in Japanese Patent Laid-Open No. 13574/1983. These resist inks are applied by screen printing. Generally, the thickness of the printed circuit board is at least 20
μm or more is required. When this circuit is formed by electroless copper plating, the physical properties of the deposited copper plating film must be such that the elongation rate of the film is 3% or more and the tensile strength is 21Kg/mm ² or more, as proposed by the American Printed Board Council (IPC). Otherwise, a highly reliable circuit cannot be obtained. The electroless copper plating solution that deposits a plated film having such physical properties generally contains special additives, as exemplified in Japanese Patent Application No. 50-30147.
It is a strong alkaline with a pH of 12 to 13 (at 20℃) and can only be obtained at high temperatures of 60 to 80℃. Since the plating deposition rate of this type of electroless copper plating solution is 0.5 to 5 μm/h, plating must be carried out for a long time to obtain a thickness of, for example, 30 μm. Therefore, the resist ink applied to areas other than the circuit forming area is immersed in the electroless copper plating solution for a long time, and it may dissolve into the solution, reducing the deposition rate or affecting the stability of the solution. It must not impair the properties of the deposited plating film or reduce the physical properties of the deposited plating film. Resist ink not only has such chemical resistance, but also requires resistance to soldering heat when parts are attached because it remains as a permanent resist after plating. Although the above-mentioned epoxy resist ink had chemical resistance, it did not have flame retardancy. On the other hand, conventionally flame-retardant inks include solder resist inks that are applied to areas of printed circuit boards where soldering is not desired. However, this type of ink does not satisfy the various characteristics of electroless copper plating described above. For example, the applied ink film may change in quality during plating, or a part of the composition may be eluted into the plating solution, reducing the plating deposition rate and further reducing the physical properties of the deposited plating film. Therefore, even if it had flame retardancy, it could not be used as a resist ink for electroless copper plating. An object of the present invention is to provide flame retardance without impairing the chemical resistance characteristic of conventional resist inks. In order to achieve the above object, as a result of various studies, it was found that it is better to use a brominated epoxy resin as the epoxy resin that is the main component of the resist ink. In the method of adding halogen compounds, antimony compounds, etc. to resist ink as a flame retardant method, these flame retardants and auxiliary agents are not added.
It also requires 30-40%. As a result, problems arise in that the adhesion to the insulating laminate, which is the starting material for the printed board, deteriorates and the printability of the ink deteriorates.
Furthermore, these additives are eluted from the ink film during plating, stopping the plating reaction or deteriorating the physical properties of the precipitated plating film. Therefore, we next performed a plating film deposition experiment using brominated epoxy resin, which is well known as a flame retardant resin. Initially, this experiment was conducted using only brominated epoxy resin from the viewpoint of flame retardancy. However, as will be described later, it was found that the elongation of the plated film was significantly insufficient. Therefore, as a result of various studies to improve this point, the following completely unexpected effects were obtained. In other words, the elongation of the plated film can be improved by combining non-Br epoxy resins, especially bisphenol A type or phenol novolac type epoxy resins, and the Br content in the total epoxy resin can be improved.
It has been found that the best elongation can be achieved by setting the content to 10 to 25% by weight. However, the plating resist ink of the present invention is
Contains (a) a non-brominated epoxy resin selected from bisphenol A type epoxy resin and phenol novolac type epoxy resin, and (b) a brominated epoxy resin, and the Br content in the total epoxy resin is 10 to 25% by weight. It is characterized by the following. If it is less than 5% by weight, the desired flame retardance cannot be achieved. In addition, as will become clear from the examples described below, if the amount is less than 10% by weight or more than 25% by weight, the laminate printed with ink may be immersed in an electroless copper plating solution to perform plating. , a phenomenon is observed in which the elongation rate of the deposited film decreases. Therefore, the appropriate range of the Br content contained in 100 parts by weight of the epoxy resin of the present invention is 10 to 25% by weight (hereinafter simply referred to as %). In order to create the main component of the desired resist ink using an epoxy mixture with this Br content range as the main component, smoothing agent, filler (thixotropic agent, plate release improver), coloring agent, antifoaming agent, etc. , wetting agents, and solvents must be added as essential ingredients. These additives need to be selected so that they do not dissolve into the plating solution. As a result of various studies conducted by the present inventors, we found that 0.5 to 3.5 parts by weight of an acrylic ester copolymer was used as a smoothing agent and 4 parts of silicon oxide having an -OH group was used as a thixotropic agent to 100 parts by weight of the above-mentioned epoxy resin. ~7 parts by weight, 4 to 6 parts by weight of zirconium silicate and 4 to 6 parts by weight of aluminum silicate as plate release improvers, and 5 to 20 parts by weight of Cr ₂ O ₃ for green coloring agents. , or 2 to 5 parts by weight of phthalocyanine green, and 0.5 to 1.5 parts of silicone oil as an antifoaming agent.
Part by weight, wetting agent: 0.3 n ^- sarcosine oleate
~2.0 parts by weight, and 10 to 60 parts by weight of cellosolves or carbitols as a solvent were found to be a good range. The amount of solvent added is adjusted so that the viscosity when mixed with the curing agent described below is 150 to 600 poise (at 25°C). Cellosolves include methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc., but butyl cellosolve is preferred from the viewpoint of volatility due to heat during curing. Examples of carbitol include n ^- butyl carbitol, ethyl carbitol, and methyl carbitol, and methyl carbitol is similarly preferred. As a method for preparing a resist ink using these above-mentioned additives, a known method is used in which the mixture is mixed in a crusher and then refined using a triple roll. The main component of the resist ink thus prepared is used by sufficiently mixing it with a curing agent immediately before printing. This curing agent is not particularly limited, but
It is preferable that the printed film is cured in a short time at low temperature and a cured film having chemical resistance can be obtained. Diaminodiphenylmethane is a suitable curing agent having such characteristics. Although diaminodiphenylmethane is effective when used alone, since it is a powder, when mixed with the main component of the ink, it is easier to mix it when used as a liquid curing agent. In order to use diaminodiphenylmethane as a liquid curing agent, it may be simply dissolved in a solvent. It can also be used by reacting with phenyl glycidyl ether. As the curing accelerator, 2-ethyl-4-methylimidazole, benzyldimethylamine, N.N.N'.N'-tetramethyl-1.3-diaminobutane, etc. are used.
As the solvent, the same solvent as the ink main component can be used. The thus obtained flame-retardant masking ink for electroless copper plating of the present invention can be applied to areas other than the circuit forming portions of the insulating plate by a known screen printing method. Curing conditions are 130~
30-60 min at 160℃ is sufficient. The properties of the printed film cured under these conditions not only exhibit excellent screen printability, but also meet UL94 and V1 standards for flame retardancy without compromising conventional chemical resistance. In addition, there is no discoloration or deterioration in soldering heat resistance (at 260°C for 10 seconds), and the adhesion to the base is sufficient. Hereinafter, the present invention will be explained in detail with reference to specific examples. Example 1 As a flame-retardant resist ink for electroless plating,
Based on two types of bisphenol A type epoxy resin (manufactured by Shell Chemical Co., Ltd., trade name: Ep1004) and phenol novolac type epoxy resin (manufactured by Dow Chemical Company, trade name: DEN438), brominated epoxy resin manufactured by Toto Kasei Co., Ltd. Using YDB400 (Br content approx. 50%) and YDB700 (Br content approx. 25%),
By changing the amount of each addition, the Br content is 5 to 100 parts by weight of the epoxy resin in the masking ink.
I created a masking ink with 30%. These are shown in Table 1. Table 1 shows a conventional resist ink for electroless plating that does not contain Br as a comparative example.

[Table] In Table 1, Nos. 1 to 6 are those in which the blending amounts of bisphenol A type epoxy resin (Ep1004) and brominated epoxy resin (YDB400Br content: about 50%) were changed. Nos. 7 to 10 have different amounts of phenol novolak type epoxy resin (DEN438) and brominated epoxy resin (YDB700Br content of about 25%). Example 2 A known phenol-modified acrylonitrile butadiene rubber adhesive was applied to a paper phenol laminate (LP437F manufactured by Hitachi Chemical Co., Ltd.) as an insulating board, and the mixture was heated at 160°C.
A sample cured for −70 min was prepared. The comparative conventional ink prepared in Example 1 and flame-retardant resist inks No. 1 to No. 10 of the present invention were applied to the insulating plate by screen printing. At this time, we evaluated the indistinguishability of the versions. Next, the printed ink film was cured at 150° C. for 40 minutes, and the film was evaluated for sagging, bleeding, and gloss. Next, as a chemical resistance test of the cured film, an acid resistance test and an alkali resistance test shown in Table 2 were conducted.
The acid resistance test is a chromium sulfuric acid mixture. In addition, the alkali resistance test was performed using an electroless copper plating solution.

[Table] The cross-cut tape that has undergone the alkali resistance test shown in Table 2 was floated on a solder bath at 260℃ for 10 seconds with the resist ink surface in contact with the solder bath, and cross-cut tape was tested for adhesion. I did this. In addition, as a flame retardant test, evaluation was conducted according to UL94 standard V1. Among the above test results, the
Figure 1 shows the relationship between the Br content and the elongation rate of the plating film deposited on the stainless steel plate from the electroless copper plating solution.
It was shown to. Other test results are shown in Table 3.

【table】

【table】

[Table] As is clear from Figure 1 and Table 3, in the flame retardant resist ink for electroless plating of the present invention, if the Br content in 100 parts by weight of the epoxy resin is 10 to 25%, It can be seen that it satisfies the UL94 standard V1 for flame retardancy without impairing the chemical resistance of conventional inks, and also has sufficient soldering heat resistance. As described above, the flame-retardant resist ink for electroless plating of the present invention can not only be used in the manufacturing method of printed boards by an additive method, but also can be used to form circuits by etching using a copper-clad laminate as a starting material and then making holes. It can also be used in a process in which a hole is drilled and electroless copper plating is performed only on the inner wall of the hole.
It can also be used as a simple solder resist ink, and can also be used as a general baking paint. The color tone at this time can be changed by arbitrarily selecting a colorant.

[Brief explanation of the drawing]

The figure is a diagram showing the test results of the present invention. 1 to 10...Resist inks No. 1 to No. 10 in Table 1.

Claims (1)

[Claims] 1 Contains (a) a non-Br epoxy resin selected from bisphenol A type epoxy resin and phenol novolac type epoxy resin, and (b) a Br epoxy resin, and contains Br in the total epoxy resin.
A flame-retardant resist ink composition for electroless copper plating, characterized in that the content is 10 to 25% by weight.