JPS5949305B2 - Chemical plating pretreatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chemical plating pretreatment method, and more particularly to a chemical plating pretreatment method for improving the resistance value accuracy of a resistive film in a printed circuit board with a resistor.

When chemical plating is performed, a catalyst such as palladium, which serves as an initiator for the plating reaction, must be attached to the surface of the object to be plated prior to plating. Chemical plating is then carried out, but if left as is, the attached catalyst is likely to drop into the plating solution and cause decomposition of the plating solution. Therefore, treatment to prevent this is usually performed in a step after the catalyst is applied. As such pretreatment liquids, aqueous solutions of hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, hydrofluoric acid, fluoroboric acid, sodium hydroxide, and the like are mainly known. however,
When forming a resistive film by chemical plating, uniformity of the resistive film is required, but it has not been possible to obtain sufficient uniformity with the above-mentioned processing liquid. Possible causes of this are that the surface of the insulating substrate on which the resistor is formed is non-uniform, that the action of the pretreatment liquid is non-uniform, or that the amount of catalyst deposited is non-uniform. The present invention has been made in view of the current situation, and its purpose is to solve the above-mentioned drawbacks of the prior art, and to form a resistive film by chemical plating on the surface of a substrate whose resistive portion is an insulator. In this case, it is an object of the present invention to provide a chemical plating pretreatment method for obtaining a resistive film having a uniform thickness, that is, a resistive film having a constant area resistance value.

To summarize the present invention, the chemical plating pretreatment method of the present invention uses an inorganic acid and aliphatic This method is characterized by treating the substrate surface with a mixed acid such as carbonic acid.

The present inventors have investigated various pretreatment methods in order to make the resistive film uniform.

Conventionally, methods have been known in which amines and alkali or hydrochloric acid and oxalic acid (see, for example, JP-A-51-1327) are used in combination after the catalyst adhesion process in order to improve the adhesion between the metal and the chemically plated film. ing. As a result of focusing on this point and proceeding with research, the present inventors completed the present invention by discovering that a mixed acid containing various inorganic acids and various aliphatic carboxylic acids is extremely effective in achieving the object of the present invention. This is what I did. That is, according to the present invention, in chemical plating for forming a resistive film, after attaching a catalyst necessary for chemical plating to the substrate surface, an appropriate amount of a mixed acid such as an inorganic acid and an aliphatic carboxylic acid is added. further treat the substrate surface with
By subsequently applying chemical plating, a resistive film with a uniform thickness can be obtained, and the accuracy of the resistance value of the resistive film can be significantly improved. As the substrate of the circuit board for forming the resistor according to the present invention, almost any insulating board such as a ceramic board, an epoxy laminate, a phenol laminate, etc. can be used.

Further, as a plating film for forming a resistive film that can be applied to the present invention, Ni-P. Ni-B, Ni-CO-P, . Ni-W-
P. Ni-Fe-PlCO-P,. Examples include those having compositions such as CO-W-P and Ni-Cr-P.
As mentioned above, the pretreatment liquid in the present invention is a mixed acid of an inorganic acid and an aliphatic carboxylic acid.

As the inorganic acid, well-known hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, etc. can be used, but hydrochloric acid is suitable from the viewpoint of ease of handling, cost, etc. In addition, examples of aliphatic carboxylic acids include formic acid, acetic acid, oxalic acid, succinic acid, citric acid, Dt-malic acid,
Tartaric acid, glycolic acid, malonic acid, maleic acid, etc. can all be used, but oxalic acid is particularly effective and cost-effective. The concentration of the inorganic acid as the pretreatment liquid of the present invention is at least 1 t equivalent in the case of hydrochloric acid) 35 (F6 hydrochloric acid 10
The concentration of aliphatic carboxylic acid must be at least 0.3 f/t, which is at least 30 p/t in the case of mt or more sulfuric acid.

If these amounts are less than the numerical values of the above conditions, the effects of the present invention will not be sufficiently achieved and a uniform resistive film will not be obtained. In carrying out the present invention, the surface of the substrate to be chemically plated is degreased, washed with water, treated with hydrochloric acid, and then immersed, coated, or sprayed with a catalyst solution containing palladium to deposit palladium. Treat with processing solution.

This treatment can be done by simply dipping or painting. The treated surface can be transferred to a conventional chemical plating process by simply washing with water. Next, the present invention will be explained using Examples, but the present invention is not limited to these in any way.

Example 1-1050? The square alumina substrates were degreased for 10 minutes each with trichlene vapor and a 10% aqueous sodium hydroxide solution at 80° C., and after washing with water, they were immersed in 15% hydrochloric acid for 2 minutes at room temperature.

Next, it was immersed in a catalyst solution (HSlOlB manufactured by Hitachi Chemical Co., Ltd.) consisting of palladium, stannous chloride, and hydrochloric acid for 10 minutes at room temperature, and then washed with water. Ten alumina substrates were prepared in this manner. Next, each of these alumina substrates was immersed in a pretreatment solution with the composition shown in Table 1 below for 5 minutes at room temperature. After washing with water, the substrates were immersed in a chemical plating solution with the composition shown in Table 2 below, and the plating temperature was adjusted. Plating was carried out at 40±2° C. for 8 minutes so as to obtain a resistive film with a sheet resistance value of 50 Ω/hole.

The amount of plating liquid was 3 tons, and stirring was performed using a stirrer. The resistance plated films thus obtained were washed with water and dried, and the area resistance of each plated film was measured to examine variations in resistance values. Measurements were made at nine locations on one side of the resistive film using a four-terminal resistance meter. Table 1 shows the results obtained.
Also listed in Examples 11 to 15 Selecting hydrochloric acid or sulfuric acid as the inorganic acid and oxalic acid as the aliphatic carbonaceous acid,
Example 1 was carried out using a treatment solution with the following composition (addition 1 was different).
~10 and Mr. Le's experiments were conducted.

The composition and results are shown in Table 3. Comparative Examples 1 to 8 As comparative examples, a treatment liquid having a composition outside the scope of the present invention was used, and Example 1
Experiments similar to ~15 were conducted (using hydrochloric acid and oxalic acid alone or in combination and sodium hydroxide alone).
.

Its composition and the results obtained are shown in Table 4. As is clear from the above results, it can be seen that according to the method of the present invention, there is little variation in resistance value.

On the other hand, when using only an inorganic acid, only an aliphatic carboxylic acid, or only an alkali as a treatment liquid, or when using a combination of an inorganic acid and an aliphatic carboxylic acid that are outside the scope of the present invention,
It can be seen that a satisfactory sheet resistance value without variation cannot be obtained. As described above, the chemical plating pretreatment method of the present invention particularly improves the accuracy of the resistance value of a resistive film in a printed circuit board with a resistor, and makes a significant contribution to reducing manufacturing costs and other aspects. be.

Claims (1)

[Claims] 1. In the production of printed circuit boards with resistors in which resistance is formed by chemical plating on the substrate surface, the substrate surface is treated with a mixed acid consisting of an inorganic acid and an aliphatic carboxylic acid as a pretreatment step for chemical plating. A learning preprocessing method characterized by the following. 2. The method according to claim 1, wherein the inorganic acid is hydrochloric acid or sulfuric acid and the aliphatic carboxylic acid is oxalic acid. 3 The concentration of hydrochloric acid is at least 10 ml as 35% hydrochloric acid per liter, and the concentration of oxalic acid is at least 0.3 g/l.
2. The method according to claim 2, wherein: l. 4. Process according to claim 2, wherein the concentration of sulfuric acid is at least 30 g/l and the concentration of oxalic acid is at least 0.3 g/l.