JPS63192589A - Soldering paste - Google Patents

Abstract

PURPOSE:To improve joining strength and storage characteristic of a paste by containing alloy powder, which is rapidly cooled and solidified, and amine- halogen hydroacid salt and the specific radical generating agent. CONSTITUTION:By dropping molten metal 1 of a solidering alloy composing of tin-lead or indium-tin to the high speed rotary disk 2, it is scattered, and by blowing insert gas 3 against this droplet, it is rapidly solidified to form the alloy powder. Next, the amine-halogen hydroacid salt as an activator and 1,1'-azobis (cyclohexane-1-carbonic nitrile) as the radical generating agent are added to form the soldering paste. As the soldering alloy has fine and uniform crystal quality, the joining strength of the solder is improved. Further, by adding of the radical generating agent, hardening of the paste during storage is prevented and the storage characteristic of the paste is improved.

Description

[Detailed Description of the Invention] [Summary] For the solder alloy, an alloy powder that is rapidly solidified into a homogeneous microstructure is used. A solder paste prepared by adding the radical generator 1,1′-7zobis(cyclohexane-1-carbonitrile) to improve the effect and reducing the amount of activator.

This makes it possible to improve the solder joint strength and to control the hardening of the paste due to the chlorine ions of the activator.

[Industrial application field]

The present invention relates to a solder paste that can be used for high-density mounting of electronic components.

[Conventional technology]

The background of the technology is that conventionally, when electronic components are mounted on a printed circuit board, lead terminals of IC, LSI packages, or resistor capacitors are inserted into through holes of the printed circuit board, and methods such as dip soldering and flow soldering are used. was used to perform solder joints. However, in recent years, in order to respond to the miniaturization and higher performance of electronic devices, there has been a strong desire to mount electronic components used in these devices at even higher density. As a method for realizing high-density mounting, the surface mount method has been adopted, in which leadless chip carriers or components are soldered to the surface of the circuit board using the reflow method. It has become more and more minute. In order to meet this demand, a solder paste that has high bonding strength and can provide highly reliable bonding has become necessary. Generally, solder paste is a cream-like material containing solder alloy powder, flux, activators, thixotropic agents, and organic solvents. Flux and activator remove the oxide film on the joint surface to give good solderability, thixotropic agent gives fluidity to the paste and makes it possible to screen print the paste, and organic solvent adjusts the viscosity of the paste. used for

Usually, the solder alloy powder is a low melting point alloy manufactured by gas atomization, such as indium-soot or tin-lead alloy, as shown in Figure 4, the flux is rosin, and the activator is diethylamine hydrochloride or the like. Hydrogenated castor oil is used as the amine hydrohalide salt and thixotropic agent, and the trade name Calpitol is used as the organic solvent diethylene glycol monoethyl ether.

The solder alloy produced by the gas atomization method is produced by dispersing the molten alloy 1 with a spray gas 4 as shown in FIG. 4, but as shown in FIG. Therefore, the solder joint strength is not sufficient. The activator liberates hydrohalic acid by the heat generated during soldering and removes the oxide film on the joint surface. However, even during storage, hydrogen halides are liberated and the oxide film on the surface of the solder powder is removed, causing the solder powder to aggregate and hinder screen printing of the paste.

[Problem that the invention seeks to solve]

A solder paste made of a solder alloy with a coarse crystal structure has a problem in that the bonding strength is low, and the aminohydrohalide salt of the activator releases hydrogen chloride during storage, causing the paste to harden.

[Means for solving problems]

The above problem is caused by the alloy powder, which is made by spraying molten solder alloy onto the disk surface rotating at high speed and scattering the powder, then spraying an inert gas to rapidly cool and solidify the powder, and the activator, amine hydrohalide acid. This problem can be solved by a solder paste characterized by containing a salt and a radical generator, 1,1'-azobis(cyclohexane-1-carbonitrile).

[For production]

Solder alloys, such as tin-lead or indium-soot alloys, are made by blowing molten metal 1 onto a rotating disk 2 to scatter it, and then blowing an inert gas onto the powder to rapidly solidify it, as shown in Figure 3. As shown in Figure 1, its structure is a homogeneous collection of fine crystals, which increases the solder joint strength. Amine hydrohalides are compounds in which a hydrohalic acid is bound to an amine such as diethylamine, and the bond releases the hydrohalic acid by heat and radicals.

At this time, the effect of the activator is promoted by adding cyclohexanone-1-carbonitrile as a radical generator to the flux.

〔Example〕

FIG. 3 shows the manufacturing operation of rapidly solidified powder. A solder alloy of a predetermined composition is melted in a crucible, gas pressure is applied from the top of the crucible, the molten metal is jetted out from a small hole drilled at the bottom of the crucible, and the powder is blown onto a disk 2 rotating at high speed. The powder is dispersed as it becomes solid, and the dispersed powder is rapidly cooled by blowing an inert gas 3 onto it.

The solder alloy is (52 wt% indium - 48 wt% tin) + 5 wt% silver, and 500 g of this alloy is
Heated to 00'C and cooled for 2 hours with argon (not shown).
The molten metal 1 is pushed and ejected with a pressure of kg/c-, and the carbon disk 2 is rotated at 20.00 rpm and sprayed onto it to scatter it. It was made into a powder by blowing at 0OOn/min. 500 g of molten solder alloy was processed in 5 minutes.

The obtained solder alloy powder was kept at 150° C. for 30 seconds to melt it, and even after being solidified again at room temperature, it exhibited a fine homogeneous structure as shown in FIG.

100 g of vehicle was obtained by mixing 52 g of water-white rosin as a flux, 1 g of diethylamine hydrochloride as an activator, 10 g of cyclohexanone-1-carbonitrile as a radical generator, 2 g of hydrogenated castor oil as a thixotropic agent, and 35 g of diethylene glycol monoethyl ether as a solvent. , previously manufactured (52 wt% In-48 wt% Sn) + 5 wt%
25 g of Ag alloy powder was mixed to prepare 125 g of paste.

Using this paste, we ramp-joined two copper plates and measured the shear strength of the joint, which was 2.5 kg/Ryu2.
The value was approximately twice that of a paste prepared using commercially available powder.

Note that even after this paste was stored at room temperature for two months, it did not harden and screen printing could be performed satisfactorily.

〔Effect of the invention〕

The solder paste of the present invention has high bonding strength and reliability, and can be stored for a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a micrograph showing the fine crystal structure obtained by the rapid solidification method, Fig. 2 is a micrograph showing the coarse crystal structure obtained by the conventional gas atomization method, and Fig. 3 is an explanation showing the operation of the rapid solidification method. FIG. 4 is a diagram showing the operation of the conventional gas atomization method. ■...) Hot water, 2... Rotating disk, 3
Cooling gas, 4... Spraying gas. Coarse crystals by gas atomization method 1pm No. 20 Figure 3 shows suatomized vinegar o ”. 1... Molten metal 2... Rotating disk 31. Cooling gas 4... Spraying gas

Claims (1)

[Claims] 1. The molten solder alloy is sprayed onto the disk surface rotating at high speed, and the powder is then sprayed with an inert gas to rapidly cool and solidify the alloy powder, the activator amine hydrohalide, and the radical generation. 1. A solder paste comprising 1,1'-azobis(cyclohexane-1-carbonitrile) as an agent.