JPH0313293A - Solder paste - Google Patents

Abstract

PURPOSE:To allow the best soldering by using the subject material coated with rosin on the surface by which the surface of the solder particles in the paste are maintained in a nonoxidation state without being corroded. CONSTITUTION:The solder powder coated with the rosin consists of the solder particles coated with the rosin on the surface. The rosin, therefore, comes into contact always with the surface of a circuit board at the time of soldering and the solder melts to progress joining after the oxide film on the circuit board is removed. The spreadability of the solder, is, therefore, improved and solder balls are less generated. The alloying property of the circuit board and the solder is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a "solder paste" used in the electronic industry field, and more specifically, the present invention relates to a "solder paste" used in the electronic industry field, and more specifically, a solder paste containing corrosion-prevented solder and improved product separation stability. This invention relates to a rosin-based solder paste.

[Conventional technology]

In recent years, the electronic industry has focused on miniaturizing products and increasing the speed of electronic circuits. However, miniaturization of products and increase in speed of electronic circuits conflict with each other in terms of product reliability, and it is not easy to satisfy both demands at the same time. In particular, miniaturization of products makes it difficult to solder circuit boards and electronic components. As the contacts between electronic circuits become more complex, poor soldering can cause short circuits and poor connections.

Of course, complex circuits cannot be soldered using the traditional method of soldering one part at a time with a soldering iron.

Therefore, the method of soldering electronic components to a circuit board is to first treat the board surface (copper) with flux to remove the oxide film, and then immerse the board surface (copper) in a bath of molten solder. It's here.

However, this method requires two steps, and it cannot be said to be an excellent method due to problems such as dropping of electronic components attached to the board and workability.

Therefore, a method using solder paste has been proposed as a method that converts this two-step method into one step. In this method using solder paste, a certain amount of cream solder is applied to the parts of the electronic board to be soldered using a dispenser method or a silk printing method. The electronic components are fixed by the effect of the chicken agent contained in the cream solder.

Next, the rosin flux is activated by irradiation with heat or infrared rays, removes oxides from the metal surface, melts the fine solder, and completes soldering. Therefore, according to this method, electronic components do not fall, and the process is extremely simple, making this method an ideal soldering method.

[Problems to be solved by the invention]

However, this solder paste also has problems that must be solved. Solder paste is a uniform mixture of rosin for removing metal oxides to be soldered, an activator, a paste flux prepared by dissolving chicken powder, etc. in a solvent, and solder powder. However, quality deterioration occurs due to contact between the activator in the solder paste and the solder paste with oxygen in the air. When paste flux and solder powder are mixed, the solder powder reacts with the activator and the surface of the solder powder corrodes. Furthermore, during storage in the container, the solder powder on the surface that is in contact with air is oxidized by oxygen in the air. Solder paste whose solder powder surface is corroded and oxidized causes viscosity changes and separation during storage, resulting in screen printing defects and dispenser discharge defects, the formation of solder balls during soldering, and defective soldering properties.

Therefore, an object of the present invention is to prevent the surface of solder particles in a solder paste from being corroded and to maintain a non-oxidized state.
The best way to solder is to provide a solder paste that is effective and has excellent storage stability.

[Necessary Means for Solving the Problems] The present invention relates to solder particles whose surfaces are coated with rosin, and a solder paste containing the solder particles and a solvent that does not substantially dissolve the rosin.

In the present invention, solder includes a mixture of tin, lead alloy, silver, bismuth, gold, iridium, etc., but is not particularly limited to the above components.

The solder powder used in the present invention may have any shape, but it is suitable that the particle size is 10 to 1000 mesh, preferably 250 to 400 mesh.

Further, the amount of rosin coated is suitably in the range of 1 to 200 parts by weight, preferably in the range of 20 to 60 parts by weight, per 100 parts by weight of powdered solder.

Any rosin can be used as the rosin in the present invention. Examples include maleic acid-modified rosin, maleic acid-modified rosin ester, hydrogenated rosin, disproportionated rosin, polymerized rosin, gum rosin, wood rosin, tall oil rosin, and the like.

Especially when considering the corrosivity of solder, it is preferable to use esterified rosin. However, the main component of the rosin used in the present invention is abietic acid. Abietic acid has an excellent oxide film removal effect as an activator, but
Abietic acid in rosin has the property of becoming active only when heated and dissolved at 90°C or higher. Therefore, at the normal temperature at which the solder paste is stored, it shows no activity and is not corrosive; therefore, any rosin can be used.

A coupling agent may also be used to improve the adhesion between the solder and the rosin. Examples of coupling agents include γ-aminopropyltriethoxysilane, N-β
Examples include -(amino)ethyl-r-ami/propyltrimethoxysilane, β-(34-evaxycyclohexyl)ethyltrimethoxysilane, and T-glycidoxypropyltrimethoxysilane. The coupling agent is suitably used in an amount of 0.001 to 5 parts by weight per 100 parts by weight of gin.

Furthermore, in order to increase the plasticity of the rosin and improve cracking and falling off due to impact between particles, it is also possible to use a plasticizer that is highly compatible with the rosin. Examples of the plasticizer include hardened beef tallow oil, dioctyl phthalate, and dioctyl adipate. Plasticizer: Rosin 100
It is appropriate to use 0.1 to 100 parts by weight.

The rosin-coated solder particles of the present invention can be manufactured by various methods, such as a spray method, a dipping method, or a combination of the two methods.

The spray method is a method in which rosin-coated solder particles are obtained by spraying an alcoholic solution of rosin (e.g., isopropyl alcohol) onto solder powder in an inert atmosphere, and then heating to remove the solvent (alcohol). It is.

In the immersion method, solder powder is immersed in an alcohol solution of rosin, and the solvent (alcohol) is evaporated off while being mixed (stirred) to obtain rosin-coated solder particles.

The combination of the spray method and the dipping method is to obtain rosin coating by further coating the rosin-coated solder particles obtained by the spray method with rosin by the dipping method, or by further coating the solder particles coated with rosin by the dipping method with rosin by the spray method. This is what we do. Incidentally, the spray method or the dipping method may be repeated multiple times.

The rosin-coated solder powder thus obtained is
It can be mixed with flux to form a solder paste. The activator in the flux is intended to remove the oxide layer. Its components include monocarboxylic acids (formic acid,
acetic acid, propionic acid) dicarboxylic acids (oxalic acid, malonic acid, succinic acid) oxycarboxylic acids (oxysuccinic acid, citric acid, tartaric acid) amines (ethylenediamine, ethylenetriamine, hexylamine, ethanolamine, ethylamine, dimethylamine, aniline, cyclohexyl) amines) Amine hydrohalides (ethylamine hydrochloride, dimethylamine hydrochloride, aniline hydrochloride, diethylamine hydrobromide, cyclohexylamine hydrochloride, etc.)
can be mentioned.

Chicken powder can also be added to the pesto.

Chicken agents include polymer resins (polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone, alginate, alginate propylene glycol ester,
Starch glycolate, starch phosphate ester salt,
Polyacrylic acid salts, etc.) Surfactants (polyethylene alkyl ether, polyethylene glycol, alkylamides, etc.) Natural synthetic waxes (Carnauba wax, BA5 fin wax, polyethylene wax, etc.) Oils and fats (hardened castor oil,
fatty acid esters, etc.).

Any solvent may be used as long as it does not substantially dissolve the rosin. Further, for soldering, a solvent having a boiling point lower than the melting temperature of the solder is preferably used, such as pure water, Freon solvent, and cyclic dimethylpolysiloxane.

Furthermore, even if the solvent is a solvent that dissolves rosin (aliphatic, aromatic, ester, ketone, alcohol, etc.), mixing or emulsifying it with a solvent that does not dissolve the rosin can substantially dissolve the rosin. Any solvent that does not dissolve in the solvent can be used as a solvent in the present invention.

In addition, when considering the dispersibility of solder paste and wettability to circuit boards, surfactants with excellent dispersibility and wettability (
It is also possible to add nonionic, anionic, cationic, amphoteric, etc.

The solder paste of the present invention covers the surface of the solder particles with a non-corrosive rosin to avoid direct contact with the activator in the flux and oxygen in the air.

When solder powder is corroded by oxygen in the air, activators in flux, etc., the following drawbacks occur.

(1) Solder spreadability is reduced.

(2) More solder balls occur.

(3) Decrease in alloying properties between the circuit board (copper plate) and solder.

(4) Decrease in coating properties and printing defects due to changes in product viscosity.

However, in the rosin-coated solder powder of the present invention, the surfaces of the solder particles are coated with rosin. For this reason, during soldering, the rosin always comes into contact with the circuit board (copper plate), removes the oxide film on the board, and then melts and joins the solder, which eliminates all of the above-mentioned drawbacks.

The present invention will be explained in more detail below with reference to Examples.

Example 1 (Production of rosin-coated solder powder) Rosin-coated solder powder was produced according to the recipe shown in Table 1 by the following method a, b, or C.

(Reference Example) Rosin-coated solder powder manufacturing method Method a (spray method) (1) Place the solder powder in a nitrogen reflux airtight container equipped with a stirrer and start stirring.

(2) Dissolve rosin in isopropyl alcohol and
Prepare a 0% solution.

(3) While stirring the solder powder from (1), (
Spray a certain amount of the rosin solution from 2) uniformly from the nozzle.

(4) The temperature of the stirring device is raised to 50° C. and the solvent is removed to obtain the solder powder of the present invention whose surface is coated with rosin resin.

Method b (immersion method) (1) Dissolve rosin in isopropyl alcohol.
Prepare a 0% solution.

(2) Solder powder is immersed in the rosin solution of 1, stirred while evaporating the solvent in a turbulent manner, and the surface of the solder powder is coated with rosin to obtain the solder powder of the present invention.

Method C (spray method + dipping method) (1) Place the solder powder in a nitrogen reflux airtight container equipped with a stirrer and start stirring.

(2) Spray a γ-aminopropyltriethoxysilane solution diluted to 1% with isopropyl alcohol and spray it uniformly onto the solder powder.

(3) After raising the temperature of the stirring device to 50° C. and removing the solvent and isopropyl alcohol, the same operation as in the method is carried out to coat the surface of the solder powder with rosin to obtain the solder powder of the present invention.

Table 1 (Unit double placement part) (Note 2) Rosin type table 2 Note 1) (a) (b) (c) (d) Shape and particle size of solder powder: spherical, 50 to 150 mesh irregular shape, 100-250 micron spherical, 150-400 micron spherical, 100-250 micron (60%) + amorphous, 5
0 to 150 microns (40%) (E) Spherical, 50 to 1
50 microns (80%) + amorphous, 150-400 microns (20%) (Note 3) Coupling agent: γ-aminopropyltriethoxysilane Example 2 (Production and evaluation of solder paste) Heating and cooling device, stirring Solder paste was manufactured according to the recipe in Table 3 using a sealed flask with a capacity of 5β equipped with a machine and a thermometer.

Operation method (1) Set a stirrer, thermometer, and heating and cooling devices in a 5 liter flask.

(2) Put the solvent into the flask, raise the temperature to 50°C, and start stirring.

(3) After confirming that the temperature has risen to 50°C, add the thixotropic agent (or rosin powder) and completely dissolve the thixotropic agent (rosin is dispersed).

(4) After confirming that the chicken powder is completely dissolved, add the solder powder and continue stirring until it is uniformly dispersed.

(Note 2) Paste Flags Table 4 (Unit: parts by weight) Separability of the product and changes in viscosity over time were also evaluated. The results are shown in Table 5.

(Note 3) Polyoxyethylene nonyl phenyl ether (EO
2 40) Performance evaluation

Claims (2)

[Claims] (1) Solder particles whose surfaces are coated with rosin. (2) A solder paste comprising the solder particles according to claim 1 and a solvent that does not substantially dissolve rosin.