JPS63161178A - Release solution for tin or tin alloy - Google Patents

Abstract

PURPOSE:To reduce the title novel release soln. capable of selectively releasing the tin on a copper matrix by preparing the soln. consisting of thiourea, a halogon-substituted fatty carboxylic acid, a release accelerating agent. CONSTITUTION:The thiourea selected from thiourea, an alkyl thiourea (thiosemicarbazide, etc.) and an aromatic thiourea [1-phenyl-3-(2-thiazolyl)-2- thiourea, etc.], and at least one kind of compd. selected from a halogen- substituted fatty carboxylic acid (dichloroacetic acid, etc.) having at least one halogen atom, the same sulfonic acid, the same aromatic carboxylic acid (trichlorobenzoic acid, etc.) the same halogen-substituted aromatic sulfonic acid (trichloro benzene sulfonic acid, etc.), or their esters and salts, and the inorg. acid (hydrochloric acid, etc.) and/or org. acid (citric acid, etc.) for accelerating the release, as required, are dissolvent in specified amts. in water to prepare the release soln. The novel and useful release soln. capable of selectively releas ing the tin or tin alloy on a copper matrix is thus obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a novel method for selectively peeling off tin or tin alloys on a copper substrate in the circuit forming process of a printed circuit board.
There is one article regarding a useful stripping solution.

[Prior Art/Problems to be Solved by the Invention] In the manufacture of printed circuit boards, solder plating (tin or tin alloy plating) is often applied as an etching resist on the steel of the circuit portion.

This tin or tin alloy plating may have to be removed in a subsequent step. In order for the entire process to proceed smoothly, the solder must be peeled off quickly from the substrate and the dissolution loss of the copper substrate must be kept to a minimum.

Traditionally, acidic solutions containing peroxides and inorganic acids, such as hydrogen peroxide, have been used to selectively strip tin or tin alloys over steel substrates, which often corrode copper substrates. Sometimes. In addition, peroxides are unstable,
Decomposition is accelerated by metal ions, which can lead to a rapid rise in liquid temperature, and peroxide itself is a dangerous substance that has a significant negative impact on working conditions. There are also tin or tin alloy strippers that contain metal ions such as ferric nitrate or ferric chloride in addition to peroxide, but these can significantly corrode the copper substrate due to the metal ions they contain. , not suitable for practical use.

The tin or tin alloy stripping solution of the present invention does not contain peroxides, is less dangerous, and does not contain metal ions, so it is extremely unlikely to corrode the copper substrate and is advantageous. The copper substrate surface has a high gloss.

A selective stripping agent for tin or tin alloys from copper substrates that does not contain peroxides or metal ions was published in Japanese Patent Publication No. 50-173.
However, this stripping agent is such that precipitates begin to precipitate within a few hours after tin or tin alloy is introduced, and often the entire liquid solidifies. It is hard to say that it is practical.

[Structure and operation of the invention]

The stripping solution for selectively stripping tin or tin alloys from the copper substrate of the present invention is composed of the following three components: (1) selected from the group consisting of thiourea, alkylthiourea, and aromatic thiourea; (2) (a) halogen-substituted aliphatic carzenic acid or halogen-substituted aromatic carzenic acid or ester or salt thereof containing at least one halogen group; (b) at least one halogen group; halogen-substituted fatty acids, group sulfonic acids or halogen-substituted aromatic sulfonic acids, or salts thereof, containing a halogen group, one or more compounds selected from the following groups, and optionally (3) stripping of tin or tin alloys. Acids selected from inorganic and/or organic acids for promoting.

The first component is a thiourea component that forms a water-soluble addition compound with the tin or tin alloy and quickly dissolves the tin or tin alloy into the stripping solution.

Such thiourea components include thiourea; alkylthiourea such as thiourea, thiothesicalpazide, allylthiourea (thiocinamine), thioacetamir, ethylenethiourea, 1,3-bis(dimethylaminozorobyl);
-2-thiourea, 1,3-dimethyl-2-thiourea, 1
, 3-dipropyl-2-thiourea, malonylthiourea, etc.; aromatic thiourea 1, such as phenylthiocarpant (
N-phenylthiourea), 1-phenyl-3-(2-thiazolyl)-2-thiourea, and the like.

However, since thiourea has reducing properties, it tends to precipitate dissolved tin or tin alloys onto the copper substrate. The amount added is preferably 1 to 251) A9. 1 f! /
If the value is less than 9, sufficient peeling speed cannot be obtained, and 2S&A9
The above f is undesirable because the reducing property of the stripping solution becomes too strong. The third component is a nitrogen-substituted organic compound component as an oxidizing agent. Examples of halogen-substituted organic compounds include halogen-substituted aliphatic carzenic acids such as dichloroacetic acid, trichloroacetic acid, dibromoacetic acid, tribromoacetic acid, difluoroacetic acid, and trifluoroacetic acid; halogen-substituted aromatic carzenic acids such as trichlorobenzoic acid, tribromobenzoic acid, etc. 294!5-Trichlorophenoxyacetic acid and the like; also halogen-substituted aliphatic sulfonic acids, and halogen-substituted aromatic sulfonic acids 1 such as tricumylobenzenesulfonic acid,
and esters and salts of these acids.

This component has the effect of preventing redeposition due to the reducing power of the thiourea component of tin or tin alloy. Addition amount is 10-5
00, 9 is desirable for li'/.

1) If the content is less than 09A, the redeposition of tin or tin alloy cannot be sufficiently prevented, and even if 9A or more is added to 3001/, the performance will not improve and it will be economically disadvantageous. It is an essential component of the stripping solution.

The third component is optionally added to improve the peeling speed, since the reaction between the first and second components is significantly accelerated in an acidic solution. Inorganic acid and/or organic acid component. Such inorganic acids include hydrochloric acid, nitric acid,
Examples of organic acids include sulfuric acid, phosphoric acid, sulfamic acid, boric acid, hydrofluoric acid, etc., and citric acid, acetic acid, lactic acid, etc. The amount added is 50! i~3009/
'9 is desirable. 50I/! ? If it is less than 9, there will be no effect, and if it is 3001//9 or more, the corrosion rate of copper will increase, which is not preferable.

It is possible to further improve the performance by adding a copper layer inhibitor or a surfactant to the stripping solution of the present invention.

In the stripping solution of the present invention, the solution is translucent and no precipitates will settle out until the solution is exhausted and becomes unusable.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Trichloroacetic acid 1001)/it nitric acid
1501/1 sulfamic acid
401)/1 thiourechord 2
01/1 Wednesday Nuzu 60% was added to the epoxy glass substrate patterned with copper added until the total amount was 1).
and a plate plated with solder f containing 40% lead (solder thickness 10
μ77L) was immersed in a stripping solution having the above composition at 40° C. f1, and the solder was completely removed from the f plate for 45 seconds. After the solder was removed from the board, the patterned epoxy glass substrate was continued to be immersed in the stripper solution for an additional 10 minutes.

As a result of removing the board from the stripping solution and inspecting it, the copper surface was shiny and no abnormalities were observed on the epoxy glass board. It continues to dissolve in the liquid, and the amount of solder dissolved is 9
Even when the solution was dissolved until it reached 01)/l, no precipitate was formed and the liquid remained translucent.

Example 2 Trichloroacetic acid 100F/A! Thio urine accumulation
209/1 Water A solder board that had been plated under the same conditions as in Example 1 was immersed in the above stripping solution at 40°C until the total amount reached 1), and the solder was completely removed from the board for 60 seconds. After removal from the substrate, the nosoturned epoxy glass substrate was continued to be immersed in the stripping solution for an additional 10 minutes. When the substrate was removed from the stripping solution and inspected, the copper surface was shiny and no abnormality was observed on the epoxy glass substrate.

Example 3 Nitric acid 150g/l Sulfamic acid 401! /1thioluria:X
20171 Water A solder plate plated under the same conditions as Addition Example 1 was immersed in the above stripping solution at 0°C until the total amount reached 1). Even after 10 minutes, some copper surface still appeared. , most of the solder was not removed.

Comparative example trichloroacetic acid 1001/1 nitric acid
150Ii/l sulfamic acid
401)/1 water Added up to 5 where the total amount becomes 1) Same conditions as Example 1. Plated solder plate at 40'C-t.
'When immersed in the above stripping solution, most of the solder was removed after 10 minutes. However, the copper surface was burnt red and had no luster at all.

From the above Examples and Comparative Examples, the first component thiourea component and the second component halogen-substituted organic compound component are essential components in the stripping solution of the present invention, and the third component inorganic acid and/or Alternatively, it is clear that organic acids have the effect of promoting peeling.

〔Effect of the invention〕

The stripping solution of the present invention dissolves the copper substrate very little during stripping, and the copper surface after stripping is shiny and clean without any residue, and almost no precipitation occurs even during long-term use. First, the solder removal speed is extremely slow.

The stripper dissolves a large amount of solder per unit volume, and does not use dangerous peroxides. 1) There is no negative effect on working conditions (for example, a sudden rise in liquid temperature due to decomposition of peroxides). It has many advantages.

Claims (3)

[Claims] (1) a thiourea selected from the group consisting of thiourea, alkylthiourea and aromatic thiourea; (2) (a) Halogen-substituted aliphatic carboxylic acid or halogen-substituted aromatic carboxylic acid containing at least one halogen atom and their esters or salts; (b) Halogen-substituted fat containing at least one halogen atom at least one compound selected from the group consisting of group sulfonic acids or halogen-substituted aromatic sulfonic acids and their esters or salts, and optionally, (3) A stripping solution for tin or tin alloy consisting of an inorganic acid and/or an organic acid for promoting stripping of tin or tin alloy.