JPH05123891A - Solder paste - Google Patents

Abstract

PURPOSE:To prepare the solder paste which enables soldering at a low temp. and can save a washing stage after soldering by using solder powder, polyalkylene carbonate, org. carboxylic acid, and a solvent. CONSTITUTION:The powder of the solder selected in the range of grain sizes and the component ratios of lead and tin so as to meet purposes is used. The polyalkylene carbonate is represented by polypropylene carbonate and polybutylene carbonate. The org. carboxylic acid is selected from 1 to 30C org. carboxylic acids or polyvalent org. carboxylic acid. The solvent is selected from esters and glycol ethers. The polyalkylene carbonate is well mixed at 0.001 to 0.5, the org. carboxylic acid at 0.001 to 0.5 and the solvent at 0.5 to 10 with 1 solder powder.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a solder paste. More specifically, it relates to a solder paste having a specific composition that is easy to handle and that decomposes and removes the binder at low temperatures.

[0002]

2. Description of the Related Art Paste-like solder is used in large quantities for the purpose of screen-printing and soldering a number of parts to a print substrate at once.

[0003]

[Problems to be Solved by the Invention]
For soldering, and because each electric component has low heat resistance, it can be soldered at a lower temperature.Furthermore, it is not necessary to wash and remove binder residues after soldering. What is possessed is required to protect resources and simplify processes.

[0004]

Means for Solving the Problems The present inventors have completed the present invention by intensively searching for a solder paste which can solve the above problems and which can be soldered at a low temperature and which does not require cleaning after welding. That is, the present invention is a solder paste composed of solder powder, polypropylene carbonate, an organic carboxylic acid and a solvent.

In the present invention, as the solder powder, fine powder of an alloy of lead and tin which has been conventionally used for a solder paste can be used as it is, and a powder having a particle size of several μm to several tens μm is usually used. . The particle size, alloy composition, etc. can be changed according to the purpose.

In the present invention, the polyalkylene carbonate is obtained by copolymerizing alkylene oxide and carbon dioxide using a catalyst. The molecular weight is from 1000
1000000, usually about 5000 to 500000 can be used.
Propylene oxide as the alkylene oxide,
Butylene oxide, pentylene oxide, hexylene oxide, heptylene oxide and the like can be used.

In the present invention, as the organic carboxylic acid, one having 1 to 30 carbon atoms, preferably about 2 to 20 carbon atoms or a polyvalent organic carboxylic acid can be used, which is present in the paste until the solder is welded and finally Those that scatter are preferably used.

In the present invention, the above three components are mixed with a solvent to form a paste. As the solvent, first, polypropylene carbonate and an organic carboxylic acid are dissolved, and when the paste is prepared, the flow of the paste is good. Such compounds are used, esters and glycol ethers can be preferably used, and halogenated hydrocarbons can also be used in some cases. Alcohols may be used in combination with these good solvents of polyalkylene carbonate in order to improve the flowability of the paste.

In the present invention, the use ratio of polyalkylene carbonate, organic carboxylic acid and solvent to the solder powder is 0.001 to 0.5 and 0.001 to 1 of the solder powder, respectively.
It is about 0.5, about 0.5 to 10, and it is more preferable to use as little as the properties of the paste can withstand use.

[0010]

EXAMPLES The present invention will be further described with reference to the following examples.

Example 1 10 parts by weight of polypropylene carbonate having a molecular weight of 80,000 obtained by polymerizing 100 parts by weight of solder powder having an average particle diameter of about 20 μm with propylene oxide and carbon dioxide using diethylzinc as a catalyst, sebacic acid A paste was obtained by thoroughly mixing 1 part by weight and 20 parts by weight of phenylpropylene glycol. When a circuit was printed on the alumina plate by screen printing with this paste, the intended circuit could be drawn.
When air-dried and then heated in an electric furnace at 300 ° C, the printed circuit melted and almost no decomposition residue was observed.

Example 2 Polypropylene oxide was replaced by polybutylene carbonate having a molecular weight of 6500, and the temperature of the electric furnace was changed to 280 ° C. The same procedure as in Example 1 was carried out. No decomposition residue was observed.

[0013]

EFFECT OF THE INVENTION The paste of the present invention has good flowability, can be melted at a low temperature, has almost no decomposition residue, and is industrially extremely valuable.

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[Procedure amendment]

[Submission date] March 18, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

3. The solder paste according to claim 1, wherein the polyalkylene carbonate is polybutylene carbonate. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 10, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Example 2 Polybutylene carbonate having a molecular weight of 6500 was used instead of polypropylene carbonate, and the temperature of an electric furnace was set to 280.
When the same procedure as in Example 1 was carried out except that the temperature was set to 0 ° C., no decomposition residue was similarly observed.

Claims (3)

[Claims] 1. A solder powder, a polyalkylene carbonate,
Solder paste consisting of organic carboxylic acid and solvent. 2. The method according to claim 1, wherein the polyalkylene carbonate is polypropylene carbonate. 3. The method according to claim 1, wherein the polyalkylene carbonate is polybutylene carbonate.