JPS59219458A - Solution for holding activity of electroless plated copper film - Google Patents

Abstract

PURPOSE:To obtain the titled soln. retardind the rusting of an electroless-plated copper film by properly adjusting the pH of an aqueous soln. contg. adequate amounts of formaldehyde and a cupric ion complexing agent and by regulating the concn. of dissolved oxygen in the soln. to a prescribed value or less. CONSTITUTION:The pH of an aqueous soln. contg. >=4g/l (para)formaldehyde and >=5g/l N,N,N',N'-tetrakis-2-(2-hydroxypropyl)ethylenediamine or cyclohexane- 1,2-diamine-N,N,N',N'-tetraacetic acid as a cupric ion complexing agent is adjusted to >=11 with an aqueous soln. of NaOH or KOH, and the concn. of dissolved oxygen in the soln. is regulated to >=3ppm by blowing gaseous nitrogen or by other method to obtain a soln. for holding the activity of an electroless- plated copper film. When a printed wiring board subjected to through hole electroless copper plating is immersed in the soln., the oxidation of the electroless- plated copper film is inhibited, and the film can be held active until copper electroplating is carried out.

Description

[Detailed Description of the Invention] The present invention relates to an active retention solution for a plating film that does not need to be decomposed. This invention relates to a solution that keeps an electroless copper plating film active.

In general, through-hole printed wiring boards start with a copper-clad laminate with a copper layer provided on an insulating board, and then drill holes in the desired positions of the copper-clad laminate. An electroless copper plating film with a thickness of 0.2 to 0.5 μm is deposited on the surface and the hole wall, and then an electrolytic copper plating film with a desired thickness is deposited on the electroless copper plating film, and then printed and printed. It is manufactured by forming a conductive circuit by etching means. Thickness of 0.2 to 0 on the surface of copper clad laminate and hole wall
The copper clad laminate was then deposited with a 5 μm μm electroless plating film and washed with water. The copper clad laminate was stored in pure water until electrolytic copper plating was performed. However, the electroless copper plating film deposited on the surface and hole walls of copper-clad laminates stored in pure water is susceptible to rust, and the next electrolytic copper plating film must be removed within several hours after electroless copper plating. If this is not done, the electrolytic copper plating film will not be uniformly deposited on the surface of the copper-clad laminate and on the hole walls. In particular, pinholes often occur in the electrolytic copper plating film deposited on the hole walls. Therefore, it was not possible to make a product using electroless 1:1) plating, and it was not possible to make effective use of the 1L electrolytic plating system.

Therefore, the present invention provides a seamless plating process in the production of through-hole printed wiring boards, that is, even if the waiting time until the next electrolytic copper plating knee m t 1° is extended, the surface of the copper-clad laminate is Another object of the present invention is to provide a bath solution that suppresses the passage of rust through the electroless copper plating film on the hole wall and maintains the activity of the pyroelectric copper plating film.

Ignorance of the present invention, the layered membrane active retention solution (hereinafter referred to as activity retention solution) contains formaldehyde of 4 V or more per aqueous solution 11, N, N, as a complexing agent for cupric ions.
N', N'-tetrakis-2-(2-hydroxyprovir)ethylenediamine or cyclohexane-1,
2-diamine-N, N, N', N'-tetraacetic acid was added to the gold mine with 5 V or more, and the pt-i of the aqueous solution was 1.
1 or more, and the concentration of dissolved oxygen in the aqueous solution is 3 ppm
It is characterized by:

As formaldehyde, a 37% by weight formalin aqueous solution or paraformaldehyde can be used, and the concentration of formaldehyde in the active retentate is 4? ,#
The above is effective, and the concentration of formaldehyde is 4Y/l.
When the pH value decreases more than 1, the oxidation inhibiting effect of the electroless (1i1 plating film) decreases significantly.The pH of the active retentate is adjusted using an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution.The pH of the oil-based retentate is 1] The above is valid,
Usually, the pH of the oily retentate is adjusted to 11 to 12.5. When the pH of the activated retentate decreases below 11, the oxidation inhibiting effect of the activated retentate on the electroless pulverized plating film is significantly reduced, regardless of the formaldehyde concentration. Complexing agents for cupric ions include N, N, N', N'-tetrakis-2-(2-hydroxypropyl)ethylenediamine or cyclohexane-1,2-diamine-N, N,
N', N'-tetraacetic acid is used, and the amount added to the active retentate is 57/1 or more.
The copper ion complexing agent is used to remove the oxide film formed on the electroless copper plating surface during the water washing process after electroless copper plating 9, and to remove the hydroxide caused by iron ions, etc., which are brought into the active retaining solution along with the number of copper plating layers. It has the effect of suppressing the formation of copper plating and maintaining the activity of the phaseless copper plating surface. The dissolved oxygen concentration in the activated retentate must be controlled to 3 ppm or less, and when the dissolved oxygen concentration is 3 ppm or less and the pH of the activated retentate is 11 or higher, the formaldehyde copper plating film has the greatest oxidation inhibiting effect.

Hereinafter, the present invention will be specifically explained based on the Fuji side.

(Example) Pour approximately 81 liters of pure water into a plastic container, then add N, N
, N', N'-Tetrakis-2-(2-hydroxypropyl)ethylenediamine (10 liters) was added and completely dissolved.

Next, add 200 FTll of formalin aqueous solution of 37 liters, and add 11 pl(
About 12 lessons! After this, the whole was diluted with pure water to prepare an active retentate. Here, the concentration of formaldehyde in the active retentate is 8 t/l, N, N, N'
, the concentration of N'-tetrakis-2-(2-hydroxypropyl)ethylenediamine is 10 Y/l.

Next, nitrogen gas was blown into the active retentate to make the ('1 length of the dissolved oxygen in the active retentate less than appm.) Next, the epoxy glass t1 with holes drilled in the active retentate.
After immersing a sample of a clad laminate plate with electroless copper plating to a thickness of about 0.4 μm for 10 days, we observed the oxidation state of the electroless copper plating film on the hole walls of the copper clad laminate. no no 1
It was found that the progress of smelting of the L-copper plating film was inhibited. In addition, as a cupric ion complexing agent for the above active retentate, cyclohexane-1,2-diamine-N,
A similar effect was observed when using N,N',N'-tetraacetic acid (rotation of 10?/l in the active retentate).

First, for comparison of the present invention, a sample of a copper-clad laminate immersed in pure water had no 1L copper plating g<% (the thickness of the plating was approx.
．． 4Ixm) was completely oxidized in the zeolite state after being immersed in pure water for one day.

As described above, the present invention has the following effects.

(1) Rust caused by oxidation of the electroless copper plating film on the hole walls of the copper-clad laminate hardly occurs.

(11) Therefore, it is possible to lengthen the waiting time until electrolytic copper plating, so it is possible to stock up on products.

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Claims (1)

[Claims] An aqueous solution of 116 cyformaldehyde with 4f or more and N, N, N', N'-tetrakis-2-(2-hydroxypropyl)ethylenediamine as a complexing agent for cupric ions and cyclohexane-1,2-diamine-N ,
An electroless solution containing N, N', N'-tetraacetic acid of 59 or more, an aqueous solution having a pi-i of 11 or more, and a dissolved oxygen concentration in the aqueous solution of 3 ppm or less. Active retention solution for copper plating films.