JPH0425348B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to chemical copper plating, and particularly to a chemical copper plating solution suitable for use in printed wiring boards. [Prior Art] Conventional chemical copper plating solutions generally contain copper sulfate as a copper source, sodium potassium tartrate, ethylenediaminetetraacetic acid or its sodium salt as a complexing agent, formalin, paraformaldehyde, or
Sodium hydroxide or the like is used as the alkali. However, copper films obtained with chemical copper plating solutions consisting of the above-mentioned combinations as main components are generally brittle and lack ductility. If the film plated on the conductor portion of a printed wiring board is brittle, the circuit may break due to processing or thermal strain. In consideration of this point, a method of improving the ductility of a copper-plated film by further adding a cyanide compound, dipyridyl, polyethylene glycol, etc. to the plating solution has been put into practice. The plated film obtained using such a plating solution has a ductility of 3 to 7% and a ductility of 30 to 30%.
It has a tensile strength of 50 Kgw/mm ² and can be used practically as a conductive film for printed wiring boards. However, as demand for high-density or multilayer wire boards increases in recent years, there is a current demand for copper-plated films with even better ductility. In addition, when forming a thick copper film of 30 to 40 μm on this printed wiring board, copper, reducing agent, alkali, etc. must be sequentially replenished to maintain the plating reaction. In this case, the ductility of the deposited copper film tends to decrease, and the stability of the plating solution is also impaired. To solve this problem, 1) Separate reaction byproducts using an ion exchange membrane. 2) A method has been proposed in which an EDTA-Cu complex is prepared by dissolving copper in an aqueous solution of ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA) using diaphragm electrolysis, but method 1) has low extraction efficiency and is therefore not practical. poor. Method 2) is not efficient as it takes a long time to bring the copper concentration to 20 to 25 g/l. Furthermore, since both 1) and 2) involve electrolysis, it is necessary to operate the apparatus in conjunction with the chemical plating process, which has disadvantages such as complexity and high cost. [Problems to be Solved by the Invention] An object of the invention is to provide a chemical copper plating solution and a chemical copper plating method that do not have the above-mentioned drawbacks and can provide a copper film having excellent ductility and physical properties. be. [Means for solving the problem] In order to achieve this objective, the present inventors have conducted intensive research and have developed conventional complexing agents, reducing agents, PH adjusters,
A chemical copper plating solution has been found in which a predetermined amount of copper oxide powder is added as a copper source to a main composition such as 2,2' dipyridyl and polyethylene glycol. That is, as the copper source of the present invention, copper oxide powder, preferably cupric oxide powder that is easily soluble in mineral acids and organic acids, more preferably electrolytic copper and a cathode, are stored in a diaphragm bag, and 0.3 to 1.1 mol/ 1 of sodium sulfate aqueous solution as the electrolyte, pH5-13, liquid temperature 55-75℃,
A predetermined amount of cupric oxide powder produced under the conditions of a cathode current density of 150 to 300 A/m ² is used, and an aqueous solution having a known composition can be used for the rest. One example is the first
It is as shown in the table. Table 1 Sodium hydroxide (amount required for pH adjustment) CuO powder 20g/l as Cu EDTA4H 110g/l Paraformaldehyde 6g/l (p-HCHO) 2,2'-dipyridyl 0.005-0.02g/l Polyethylene glycol 0.05-0.02g/l Balance Water PH 11.5-13 (Initial PH5.0) [Function] As mentioned above, the main components other than copper in the present invention are known ones used within the specified range. However, it is preferable to use a predetermined amount of copper oxide powder of as high purity as possible as the copper content. Generally available commercially available cupric oxide powder, copper hydroxide, etc., when dissolved in a complexing agent such as EDTA, leave undissolved matter behind and require a long time to dissolve. Such a copper source is particularly inconvenient for preparing or replenishing plating baths. Mineral acids such as hydrochloric acid and nitric acid recommended in the present invention,
Using cupric oxide, which is easily soluble in organic acids such as EDTA, a highly concentrated EDTA-Cu solution (20g/Cu)
As an example of creating an EDT
A.4H 110g was added with as high concentration sodium hydroxide aqueous solution as possible, stirred, adjusted to PH5.0, and EDTA4H
completely dissolve. Next, 25 g (20 g as Cu) of the cupric oxide powder described above is added to the solution and, for example, aeration is performed to obtain an EDTA-Cu complex in about 20 minutes. This reaction seems to follow the formula below. EDTA・2H・2Na+CuO+H ₂ O → [EDTA−Cu]2H+2NaOH As can be seen from the reaction formula, the initial pH5.0 usually increases to 10.5 to 11.0 due to this complexation reaction. In this way, to obtain the same Cu EDTA complex salt,
Comparing the electrolytic method described in 2) of the conventional technology with the method of the present invention, the required time is reduced to about 1/10, the amount of undissolved residue is extremely small, and the physical properties of the film deposited on the coated object are greatly improved. improves. Next, the plating operation is carried out at a temperature of 60°C or higher, preferably 80°C or lower, because at lower temperatures the time required for plating is longer, and at higher temperatures, the reduction reaction becomes too strong and the bath decomposes, which is undesirable. It's for a reason. The activation of the board before plating can be carried out using the usual methods, but as an example, a paper phenol board or a board made by impregnating glass cloth with epoxy resin and laminating them is degreased by the usual method. After etching, the etching is performed by lightly etching, attaching a small amount of tin to the etched area, and then immersing it in an aqueous palladium solution to replace the palladium. The pH range during plating should be 11.5 to 13.0. This is because, outside this range, a suitable plated film cannot be obtained and may cause corner cracks in the plated film. [Example] Examples will be described below. Using the combinations shown in Table 2, first, add easily acid-soluble cupric oxide powder (manufactured according to claim 3) or various copper sources, EDTA4H, and aqueous sodium hydroxide solution to obtain an initial pH of 5.0. to obtain an EDTA-Cu complex,
Each additive and water were added to this to prepare chemical copper plating solutions shown in Table 2.

【table】

[Table] Special grade reagents were used. Printed wiring boards made by impregnating glass cloth with epoxy resin and laminating them were immersed in the plating solution shown in Table 2 after being degreased by a conventional method and activated with palladium. After 15 hours, they were pulled out to a thickness of 20 to 40 μm. A copper film was formed, and the mechanical properties of the deposited film were measured using a tensile test manufactured by Toyo Sokki Co., Ltd. Table 3 shows the results, and Table 4 shows the results of a 260°C soldering test. The results are shown in comparison with the case where plating liquid is used. Table 5 shows the results of a long-run test in a tank with a capacity of 50 while controlling the composition of the plating solution using a microcomputer as reference values. The temperature during plating was kept constant at 70°C.

【table】

【table】

[Table] As is clear from Table 3, the ductility of the plating film using the plating solution of the present invention was dramatically improved, and the other physical properties were almost the same. In particular, the difference in ductility shown in Table 5 increased over time. Tables 4 and 5 compare the occurrence of cracks in the corners of the holes of the plated films, and it is shown that the plated films of the present invention are superior here as well. (Effects) Simply using acid-soluble or high-purity cupric oxide powder as the copper source for chemical copper plating solution,
Not only is the plating solution easy to prepare and an excellent plating film can be obtained, but there are also fewer by-products during the preparation of the EDTA-Cu complex salt, so the plating solution has advantages such as a long service life.

Claims (1)

[Claims] 1. Copper source, complexing agent, reducing agent, PH regulator, 2,2'
A chemical plating solution containing dipyridyl and polyethylene glycol, characterized in that it uses copper oxide powder as a copper source. 2. The chemical plating solution according to item 1, wherein the copper oxide powder is a cupric oxide powder that is easily soluble in acids. 3. A first method characterized in that ethylenediamineacetic acid is used as the complexing agent, completely dissolved in an aqueous sodium hydroxide solution, and the cupric oxide is added to the solution to form an ethylenediamineacetic acid-copper complex. Chemical plating solution described in section. 4 The cupric oxide powder is prepared by using electrolytic copper as an anode, both negative and anode electrodes housed in a diaphragm bag, and using a 0.3 to 1.1 mol/1 sodium sulfate aqueous solution as an electrolyte.
2. The chemical plating solution according to item 2, which is obtained by electrolysis while regulating the pH, temperature, and cathode current density of the electrolyte. 5 In a chemical copper plating method in which the board surface is degreased, activated, and then plated with a chemical copper plating solution, the composition of the chemical copper plating solution includes a complexing agent, a reducing agent, and a PH adjuster. , 2,2' dipyridyl, polyethylene glycol, and copper oxide powder.
A chemical copper plating method characterized by being carried out as 13.0.