KR100452023B1 - Lead-free Cream Solder - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cream solder used for bonding electronic components, and in particular, by adding wax having a high softening point to the flux contained in the cream solder, from a rosin which is a main component of the flux during preheating during reflow soldering. It is possible to prevent the generation of scattering, and due to the fluidity of the rosin during the preliminary heating process, it is possible to prevent the flux flowing down unnecessarily, so as to ensure the required reliability when soldering electronic components Is about cream solder.

Description

Lead-free Cream Solder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cream solder used for bonding electronic components, and in particular, by adding wax having a high softening point to the flux contained in the cream solder, from a rosin which is a main component of the flux during preheating during reflow soldering. It is possible to prevent the generation of scattering, and due to the fluidity of the rosin during the preliminary heating process, it is possible to prevent the flux flowing down unnecessarily, so as to ensure the required reliability when soldering electronic components Is about cream solder.

The cream solder used for joining the electronic components is formed by uniformly mixing a solder in a powder state and a flux in a liquid or paste state at a predetermined ratio. By the way, as described above, the flux contained in the cream solder has long been produced based on rosin resin produced by removing volatile terepine oil from terfetin secreted from pine family plants, Rosin resin is based on abietic acid (abietic acid). In particular, such rosin resins have excellent heat resistance, safety, and economy, and have been used not only in the flux but also in various applications. Among them, in the flux for soldering, most of the rosin resins have the above-mentioned rosin resin as a main component. Rosin-based fluxes have been used. With respect to the composition of the rosin-based flux, in more detail, the conventional flux is generally composed of active agents such as rosin resins, inorganic salts and organic salts, thixotropic agents such as castor oil, solvents such as higher alcohols, glycols, etc. In addition, some other ingredients may be added.

On the other hand, when looking at the powder solder constituting the cream solder together with the flux, in the past has been using an alloy composition containing lead (Pb) as such a solder, as the environmental pollution problem caused by lead in recent years, There is an urgent need for development of a solder alloy that does not use harmful lead, and accordingly, various lead-free solder alloy compositions have been developed. However, in the powdered solder alloy as described above, lead is a material that serves to lower the melting point of the alloy, so that soldering can be performed at a low temperature, and thus, lead-free solder alloy that has not been used recently is used. As a result, the melting point of the solder alloy is increased, and therefore, the soldering is forced to proceed at a higher temperature than before. For this reason, problems such as damage to electronic parts to be joined due to high temperature heat generated during soldering have been derived. Due to the problems of the lead-free solder alloy, efforts to lower the melting point of the lead-free solder alloy are continuously performed. It is becoming.

However, despite these efforts, the current melting point of lead-free solder alloys has reached 220-300 ° C., which is about 50 ° C. higher than the melting point of conventional solder alloys including lead, which leads to soldering at this temperature. In some cases, damage to the electronic component due to heat may be prevented to some extent, but due to the fluidity of the flux at a high temperature, a problem may occur that may impair the reliability of the electronic component. That is, the conventional soldering process proceeds at a relatively low temperature, so that the flowability of the flux did not occur, but in the current soldering process using the lead-free solder alloy, the soldering process and the pre-heating process for such a high temperature Because of the high temperature during the pre-heating process as described above, the flowability of the rosin resin is increased, the cream solder flows to the unnecessary portion instead of the joint portion, so that bridges between circuits are generated. For example, the reliability of the electronic component may be impaired, and due to the scattering generated by the volatile material contained in the rosin resin during the heating process, the reliability of the electronic component may also be impaired.

In addition, the rosin resin has a softening point of about 80 ° C. Since the rosin remaining as a residue after solidification has brittleness, cracks may occur due to vibration generated when using electronic components. As a result, foreign matters such as moisture penetrate into such a gap and cause problems such as corrosion of the electronic component.

Due to the problems of the prior art, development of a flux and a cream solder using the same, which have no fluidity even at high temperatures and do not generate scattering, can improve the reliability of electronic components.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above, since a wax having a high softening point is included as an additive, the fluidity does not increase even at high temperatures, and does not generate scattering by the volatile components of the rosin resin. In the high-temperature soldering process, the present invention provides a flux and a cream solder including the same, which can prevent the reliability of electronic components from being lowered.

In order to achieve the above object, the present invention is a cream solder consisting of a solder in a powder state and a flux in a liquid or paste state, wherein the flux is characterized in that it comprises a wax having a high temperature softening point as an additive Provide cream solder.

According to the present invention, in the cream solder according to the present invention, since the wax having a high softening point is included as an additive in the flux constituting the flux, the heat resistance of the flux can be further improved. Since the amount of scattering generated by heat can be minimized and the flowability of the flux does not increase even at a high temperature, it is possible to prevent the flow of cream solder unnecessarily. Therefore, by using a lead-free solder alloy, Even if the soldering process is performed at, the reliability of the electronic component may not be lowered due to the fluidity of the flux as described above.

In the cream solder according to the present invention, the wax having a high temperature softening point is LC 121N (softening point 109 ° C) which is a polyethylene wax (POLYETHYLENE WAX), and LEBAX-140P (softening point 144 ° C) which is an amide wax (AMIDE WAX) LC 701S (softening point 145 ° C), hydroxy bisamide wax (HYDROXY BIS AMIDE WAX), LC 503NC (softening point 148 ° C), polypropylene wax (POLY PROPYLENE WAX), LC 502N (softening point 160 ° C), LC 502NC (softening point) 151 ° C.) and LC 525N (softening point 162 ° C.), preferably one material selected from the group consisting of or a mixture of two or more. (However, the name of the wax is a product name of the wax sold by Lion Chemical Co., Ltd., which is widely known to those skilled in the art having ordinary knowledge in the technical field to which the present invention belongs.)

That is, in the cream solder according to the present invention, by adding the above-mentioned wax to the flux as an additive, the softening point of which is significantly higher than that of the rosin resin, which is the main component of the flux, prevents the flux from flowing unnecessarily at high temperatures. At the same time, by improving the heat resistance of the flux, it is possible to minimize the amount of scattering generated from the flux at high temperatures. Because of this, it is possible to ensure the reliability required during soldering, and in particular, while using a lead-free solder alloy containing no harmful to the human body, it is possible to solve all the disadvantages of the prior art.

Hereinafter, through the preferred embodiment of the present invention, the operation of the present invention will be described in more detail. However, the scope of the present invention is not defined thereby, but is presented as an example.

The flux for the cream solder according to the present invention was prepared by blending the composition ratio as shown in Tables 1 and 2 below, using a cream solder containing the same, and measuring the properties when the soldering was carried out, the conventional cream The flux for solder was measured similarly and the quantity measurement result was compared. These measurement results are as shown in Table 1 and Table 2 below.

Classification Example Comparative example One 2 3 4 5 6 One Suzy rosin 50 50 50 50 50 50 50 solvent Advanced Alcohol 43 43 43 43 43 43 43 Active agent Organic salt One One One One One One One additive ①L-C 121N 6 ②LEBAX-140P 6 ③L-C 701S 6 ①: ② = 1: 1 6 ①: ③ = 1: 1 6 ②: ③ = 1: 1 6 Hydrogenate Castor Oil 6 Flux content (%) 11 11 11 11 11 11 11 Evaluation results Printability ◎ ◎ ◎ ◎ ◎ ◎ ○ Slump at the time of print ○ ◎ ◎ ○ ○ ◎ × Slump at the time of heating ○ ◎ ◎ ○ ○ ◎ × Solubility in Solvents ◎ ◎ ◎ ◎ ◎ ◎ ○ Corrosion ◎ ◎ ◎ ◎ ◎ ◎ ◎ Discoloration Nil Nil Nil Nil Nil Nil With Solder ball 2 One One 2 2 One 4 Generation of scattering Nil Nil Nil Nil Nil Nil Small Crack Nil Nil Nil Nil Nil Nil Small Solderability ◎ ◎ ◎ ◎ ◎ ◎ ◎

◎: Excellent, ○: Good, ×: Poor

Classification Example Comparative example One 2 3 4 One Suzy rosin 55 55 55 55 55 solvent Carbitol 40 40 40 40 40 Active agent Amine salt One One One One One additive ①L-C 503NC 4 ②L-C 502N 4 ③L-C 502NC 4 ④L-C 525NC 4 Hydrogenate Castor Oil 4 Flux content (%) 11 11 11 11 11 Evaluation results Printability ◎ ◎ ◎ ◎ 0 Slump at the time of print ◎ ◎ ◎ ◎ △ Slump at the time of heating ◎ ◎ ◎ ◎ × Solubility in Solvents ◎ ◎ ◎ ◎ 0 corrosion ◎ ◎ ◎ ◎ ◎ discoloration ◎ ◎ ◎ ◎ 0 Solder ball 2 One One 2 4 Generation of scattering Nil Nil Nil Nil Small Crack Nil Nil Nil Nil Small Solderability ◎ ◎ ◎ ◎ ◎

◎: Excellent, ○: Good, ×: Poor

As can be seen from the above table, as a result of adding a wax having a high temperature softening point to a conventional rosin flux, it was possible to prevent the generation of scattering, and after the cream solder was solidified, the rosin brittleness remained as a residue. The occurrence of cracks was also not observed. Particularly, in the case of the conventional rosin-based flux, the fluidity of the rosin may increase due to the heat generated during heating, and may flow to an unnecessary place, resulting in a defect, whereas it includes a flux with a wax having a high softening point. In the cream solder according to the present invention, it can be seen that such a problem does not occur at all.

As can be seen from the above, according to the present invention, a flux containing a wax having a high temperature softening point is included, so that the flow of rosin at a high temperature can prevent the cream solder from flowing to an unnecessary place. In addition, since the amount of scattering generated by the volatile material contained in the rosin may be minimized, a cream solder may be provided to secure reliability required for soldering the electronic component.

In addition, according to the present invention, it is possible to prevent the occurrence of cracks due to the brittleness of the rosin remaining as a residue after the solidified solder, it is possible to prevent problems such as corrosion, discoloration, etc. of the electronic components due to the cracks, soldering Cream solders can be provided to ensure very high reliability.

Claims (2)

A lead-free cream solder composed of a lead-free solder alloy in powder form and a flux in liquid or paste form, The flux is a lead-free cream solder containing any one wax selected from the group consisting of LEBAX-140P, L-C 701S, L-C 503NC, L-C 502N, L-C 502NC and L-C 525N. delete