JPH03124092A - Preflux of printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a preflux which prevents a copper circuit from being oxidized and which can enhance a soldering finish by a method wherein an antioxidant selected from a phenol-based antioxidant and a phosphite-based antioxidant or an organic sulfur antioxidant is mixed with a resin for preflux at a prescribed amount against a solid portion of a preflux. CONSTITUTION:Trisnonyl phenyl phosphite of a phosphite-based antioxidant or dilauryl-3,3'-thiodiproprionate of an organic sulfur-based antioxidant is used as triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate of a phenol-based antioxidant. Regarding a mixture ratio of the phenolbased antioxidant to other antioxidants, an addition amount of the latter in a total amount is set at 3 to 50wt.%. A total amount of the phosphite-based antioxidant or the organic sulfur-based antioxidant is set at 20 to 50wt.% in a solid portion of a preflux. By this constitution, it is possible to obtain the preflux having a remarkable effect to prevent oxidation.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to preflux for printed wiring boards.

[Conventional technology]

A printed wiring board is a circuit made of copper or the like formed on a board made of paper, glass fiber, or the like as a base material using a binder such as phenol resin, epoxy resin, or polyimide resin. Copper circuits include those in which through-holes are plated with copper, and those in which circuits are provided inside a board, etc., exist along with surface circuits. This printed wiring board includes resistors and capacitors ICs.
Electronic components such as are soldered. For this reason, a precursor of solder flux is applied to printed wiring boards in advance in order to prevent oxidation of surface circuits. This is usually called preflux. Conventionally, as preflux, rosin, which is a solid component of solder flux, has been used as it is or purified and mixed with a rust preventive agent and an activator as necessary so as not to impair soldering. Rosin is usually made of abietic acid and its derivatives, and although it has excellent soldering properties, it has poor moisture resistance and heat resistance, and if printed wiring boards are stored for a long time or heat treated, the copper circuits will oxidize and the solder will evaporate. However, the reliability of the performance was insufficient. Particularly, those that have gone through a process such as ■PS for the purpose of surface mounting have the disadvantage that the subsequent soldering properties are significantly degraded.

For this reason, Japanese Patent No. 626762, Japanese Patent No. 642075, US Patent No. 393351, British Patent No. 1250142, Japanese Patent No. 1287854, West German Patent No. 2003175,
No. 2116012, French Patent No. 7002588,
As seen in specifications such as No. 7111469, it is known that the soldering properties of copper circuits can be improved by applying alkylimidazole treatment or the like.

[Problem to be solved by the invention]

As mentioned above, printed wiring boards are becoming more and more oriented toward high-density electronic circuits based on component mounting and surface mounting.

For this reason, gases such as Freon are heated to high temperatures (240 to 250'
C) So-called ■PS( Vapor Phase Sold
ering) method is becoming popular. In this method, when soldering is performed in a post-process such as a component with leads, the surface of the copper circuit is oxidized by the heat received in the previous process, making it difficult for the solder to rise. The alkylimidazole treatment described above does not provide sufficient soldering properties, and there has been a demand for an even better preflux.

Additionally, conventionally, printed wiring boards have been coated with a rust preventive agent mainly composed of rosin to prevent oxidation of the copper surface and maintain solder connection reliability until the time of solder connection work during component mounting. . However, as the mounting density of components has become higher and more diverse, soldering is a work process, and when heat treatment such as applying adhesive and heating is performed many times, the rust preventive effect is lost and the solderability becomes poor. come. In addition, coatings using thermosetting resin as a vehicle are widely used for rust prevention, but once thermosetting resin forms a bridge on the copper surface, it becomes insoluble and infusible, making it difficult for copper and solder to bond. Connection becomes virtually impossible.

An object of the present invention is to provide a preflux for printed wiring boards that has improved prevention of oxidation due to heat treatment of copper circuits and improved solder swellability in post-processes.

[Means to solve the problem]

That is, the present invention combines a phenolic antioxidant and (a) a phosphite antioxidant or (
(b) To provide a preflux for printed wiring boards, which is characterized in that an antioxidant consisting of an organic sulfur-based antioxidant is blended such that the antioxidant content is 5% by weight or more based on the solid content. It is something to do.

Examples of the phenolic antioxidants used in the preflux of the present invention include the following. Triethylene glycol-bis(3-(3t-7'thyl-5-methyl-4-hydroxyphenyl)propionate) (
1.6 hexanediolubis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (melting point 104-108°C),
2.4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-butylanilino)-1°3.
5-triazine (melting point 91-96°C), pentaerythrityl-tetrakis (3-(3,5-di-t-7'+-4-hydroxyphenyl)propionate) (melting point 1
10~125°CL 2,2-thiodiene bis(3
-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (melting point 63°C), octadecyl-3-(35-di-t-butyl-4-hydroxyphenyl)propionate (melting point 50-53 °C), 2.2thiobis(4-methyl-6-t-butylphenol (melting point 81-85 °C), N,N'-hexamethylenebis(
3,5-di-monobutyl-4-hydroxy-hydrocinnamamide) (melting point 156-161°C), 3,5-di-
t-Butyl-4-hydroxyhenzylphosphonate diethyl ester (melting point 116-123°C), 1
,3,5-trimethyl-2,4,6-1-lis(3,5
-dimo-butyl-4-hydroxybenzyl)benzene (melting point 240-250°C), tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-isocyanurate melting point (218-223°C), octyl diphenylamine (liquid at room temperature), N-N'bis(3-(3,
5-di-butyl-4-hydroxyphenyl)propionyl]hydrazine (melting point 210°C), 2-6-di-L-butyl-4-methylphenol (melting point 69°C),
Styrenated phenol (liquid at room temperature), 2,2'-methylene-bis-(4-methyl-6-t-butylphenol) (melting point 128°C), 2-t-butyl-6-(3' is also monobutylphenol) 5'-methyl-2'-hydroxybenzyl)
-4-methylphenylacrylate (melting point 128°C)
, 4,4'-butylidene-bis(3-methyl-6-t
-butylphenol) (melting point 209°C), 4.4'-
Thio-bis-(3methyl-6-t-butylphenol)
ld point 160”C), alkylated bisphenol (
liquid at room temperature), 1,3.5-tris(4-t,-butyl-3-hydroxy-26-dimethylhenzyl) isocyanurate (melting point 143°C), tetrakis-[methylene-3-(3', 5') - Dimomonobutyl-4'-hydroxyphenyl)propionate comethane (melting point 110°C
L3,9-bis(2-+3- (3-t-butyl-4-
Hydroxy-5-methylphenyl)propionyxy)-
1,1-dimethylethyl)-2,4,8,10-tetraoxasbiro(5,5)undecane (melting point 110°C)
and so on.

Examples of phosphite antioxidants include the following. Trisnonylphenyl phosphite (liquid at room temperature), triphenyl phosphite (melting point 16°C)
, tris(2,4-di-tert-butylphenyl) phosphite (melting point: 180°C).

Furthermore, as an organic sulfur-based antioxidant, Jilau IJ
/L/ -3,3'-thiodipropionate (melting point 37
°C), Simailistyl-3,3'-thiodipropionate (melting point 49-54 °C), Distearyl-3,3'
-thiodipropionate (melting point 59°C), pentaerythritol-tetrakis-(β lauryl-thiopropionate (melting point 46°C)), 2-mercaptobenzimidazole (melting point 285°C), and the like.

The blending ratio of these phenolic antioxidants and other antioxidants is such that the amount of the latter added is 3 to 50% of the total amount of antioxidants.
Appropriate amount is approximately % by weight. The antioxidant effect is enhanced by using these antioxidants in combination with phenolic antioxidants. This effect is small when the amount of the phosphite-based antioxidant or organic sulfur-based antioxidant is less than 3% by weight, and this effect is saturated when it exceeds 50% by weight. If the total amount of these two types of antioxidants is 5% by weight or more, preferably 20 to 50% by weight, based on the solid content of Preflux, a remarkable antioxidant effect can be obtained. If the amount added is less than 5% by weight, the effect will be small, and if it exceeds 50% by weight, the effect will be saturated.

As mentioned above, antioxidants have different melting points depending on the substance. It is practically preferable that the melting point of the mixture of these two systems is about 90 to 140°C. If the melting point of the mixture is less than 90°C, the film after being applied to the printed wiring board will easily become sticky.
Blocking occurs when wiring boards are stacked, which is a practical problem. Further, if the melting point of the mixture exceeds 140°C, it is not preferable because the soldering properties deteriorate because it takes time for the mixture to become compatible with the post flux that is sometimes applied.

Therefore, this problem can be solved by determining the blending ratio of a mixture of these phenolic antioxidants and other antioxidants so that the melting point is about 90 to 140°C.

Further, by using these two types of antioxidants in combination with a pre-flux resin such as a rosin resin or a terpene resin having a pre-flux function and adjusting the melting point to 90 to 140°C, blocking caused by stacking the wiring boards, The problem of compatibility with post flux can be solved. Preflux functional resins include commonly used rosin resins (rosin, hydrogenated rosin, asymmetric rosin, phenol-modified rosin, and their esterified products, etc.) or terpene resins (terpene polymers, aromatic modified terpenes, hydrogenated rosins, etc.). terpene resin, terpene phenol copolymer, α-pinene polymer, β-pinene polymer, etc.), and by using these together, it is possible to eliminate the sagging of the film and the compatibility with post flux, and it also has an antioxidant effect. It also improves.

Normally, preflux is used at a concentration of about 5% by weight, but the preflux in this book can also use alcohols, ketones, aromatics, esters, etc., which are usually used as solvents. Not restricted.

[Effect]

In the preflux of the present invention, the antioxidant acts as a rust preventive agent on the surface of the copper circuit. This anti-corrosion ability is superior to the conventionally used rosin and alkylimidazole in terms of heat resistance and stability, and this effect is enhanced when used in combination with a flux resin such as terpene resin.

This curing varies depending on the amount of antioxidant added, and a small amount does not show any effect, and as the amount added reaches a point where the effect becomes saturated, the present invention has found an appropriate amount to add.

〔Example〕

The present invention will be specifically explained below based on Examples and Comparative Examples, but the present invention is not limited thereto.

Comparative Example 1 5 g of polymerized rosin (Polyveil manufactured by Rika Vercules) was dissolved in 95 g of acetone.

Comparative Example 2 Polymerized rosin (Polyveil manufactured by Rika Bercules) 4.8g
and 0.2g of imidazole (Shikoku Kasei imidazole) to 95g of acetone? I understand.

Example 1 3 g of hydrogenated rosin ester (Arayo Kagaku HP) and the phenolic antioxidant triethylene glycol-bis(3-(
3-t-butyl-5-methyl-4-hydroxyphenyl) propionate) (Irganoylganox 2453 manufactured by CIBA GEIGY and phosphite antioxidant tris(2,4-di-tert-butylphenyl)
Phosphite (Sumitomo Chemical Sumilizer P-16) 0
．． 4 g was dissolved in 95 g of methanol.

Example 2 Phenol-modified terpene resin (S5-145 manufactured by Yaskawa Oil Co., Ltd.)
)3 and 1,6-hexanethiolubis(3-(3,5
-di-t-butyl-4-hydroxyphenyl)propionate) (Irganox 259 manufactured by CrBAGEIGY)
) 1.6 g and tris(2,4-di-tert-butylphenyl) phosphite 0.4 g to 95 g of methanol?
I understand.

Example 3 3 g of aromatic terpene resin (To-125 manufactured by Yasukawa Oil Co., Ltd.) and 1,6-hexane-thiolubis (3-(3,5-di-t-butyl-hydroxyphenyl)propionate)
1.6 g and 0.4 g of tris(2°4-di-tert-butylphenyl) phosphite were dissolved in 95 g of methanol.

Example 4 Tris(2,4-di-L-butylphenyl) of Example 1
Dilauryl-33'-thiodipropionate (Sumitomo Chemical Co., Ltd. Sumilizer TPL-R) 0.
4g was used.

Example 5.6 Pentaerythritol-tetrakis-(β-
Lauryl-thiopropionate) (Sumitomo Chemical Sumilizer TP-D) 0.4 g (Example 5), same as 2
-0.4 g of mercaptobenzimidazole (Sumilizer MB manufactured by Sumitomo Chemical) (Example 6) was used.

Example 7.8.9 Tris(2,4-di-butylphenyl) of Example 2
Instead of phosphite, 0.4 g of dilauryl-3゜3'-thiodipropionate (Sumilizer TPL-R) (Example 7) and pentaerythritol-ω-tetrakis-(β-lauryl-thiopropionate) ( Sumilizer TP-D) 0.4 g (example day), same 2-mercaptobenzimidazole-ω (Sumilizer MB) 0
．． 4g (Example 9) was used.

Each of the obtained prefluxes of Comparative Example 1.2 and Examples 1 to 10 was dip coated on an FR-4 type printed wiring board, and dried for 100"010 minutes.

This printed wiring board was transferred to the VPS flow (215°C
, 3.5 minutes per cycle) three times, and then solder frying (245° C., 15 seconds) was performed in a conventional manner, and the results shown in the following table were obtained.

Example 10 3 g of aromatic terpene resin (To-125) and NN'-hexamethylenebis(3,5-di-L-phthyl-4-hydroxy-hydrocinnamide) CCIBA GEIG
1098g of Irganox made by Y and dilauryl
3,3'-thiodipropionate (Sumilizer TP
Preflux was prepared by dissolving 0.4 g of LR) in 95.0 g of toluene.

〔Effect of the invention〕

The Breflux of the printed wiring board of the present invention prevents oxidation of the copper circuit due to heat during the surface mounting method glue flow process in soldering the printed wiring board, and has excellent solderability, allowing for diversification of mounting. Breflux can be used for various purposes, and its practical value is extremely high.

Claims (1)

[Claims] 1. A phenolic antioxidant and an antioxidant selected from (a) a phosphite-based antioxidant or (b) an organic sulfur-based antioxidant are added to the preflux resin so that the total antioxidant content is equal to that of the preflux. A preflux for printed wiring boards, characterized in that the preflux is blended in an amount of 5 to 50% by weight based on the solid content.