JP2002283097A - Solder paste composition and reflow soldering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder paste formed by using unleaded solder powder which does not give rise to the thermal deterioration of solder powder and flux film in reflow and does not degrade solderability and a reflow soldering method. SOLUTION: The solder paste composition formed by using an antioxidant consisting of a hindered phenolic compound in conjunction with the unleaded solder powder and the reflow soldering method using the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder paste composition particularly suitable for using a solder alloy powder containing no lead and zinc, and a reflow soldering method using the same.

[0002]

2. Description of the Related Art In recent years, multifunctional wiring boards for electronic devices have been developed.
The surface mounting technology has been rapidly developed along with the miniaturization, and the reflow soldering method using a solder paste has been mostly used for the surface mounting of electronic components. The solder powder used for the solder paste is Sn-P
Most of the b type is used. However, when an electronic device is discarded because it has been used, etc., although it is disassembled and a part of it is collected, the mounting board on which the electronic components are mounted is hardly collected and crushed and buried and disposed of. Currently, some are left abandoned in the natural world. Since electronic components are soldered to the mounting board that has been dumped in the nature, if this solder contains lead, this lead will elute as a soluble lead compound due to acid rain and contaminate the nature. As well,
Contaminated water and foods of animals and plants may be ingested by humans through groundwater and the like, which is becoming a serious problem due to its high toxicity. Accordingly, lead-free solder materials have been developed, and so-called lead-free solder alloy powders such as Sn-Ag alloys and Sn-Ag-Cu alloys have been used.

[0003]

However, the above-mentioned lead-free solder alloy powder has a melting point of about 200 to 220 ° C.
Therefore, in the reflow soldering method using the solder paste containing the solder powder, the peak temperature at the time of heating needs to be 230 to 240 ° C., and the lead-based Sn-P
In the case of alloy b, its eutectic composition (63Sn / 37Pb)
In the reflow soldering method using a solder paste containing the solder powder, the peak temperature of the heating may be about 230 ° C., and it is possible to solder heat-sensitive electronic components without damage. On the other hand, there is a problem that functional deterioration or the like is caused by the thermal damage. In order to solve this problem, the peak temperature at the time of reflow soldering is set low at 230 to 240 ° C. using a solder paste containing the above-mentioned lead-free solder alloy powder. Attempts have been made to mitigate thermal damage to electronic components by changing the so-called heat pattern, in which the powder is heated at a higher temperature during preheating so that the powder can be efficiently melted. Since the amount of heat during heating increases, the solder alloy powder and the flux of the solder paste film applied to the soldered portion of the printed wiring board are excessively heated, so that thermal deterioration due to oxidation is likely to occur, and the flux film during reflow And insolubility in the solder powder, lowering the soldering properties such as lowering the soldering strength. To cause another new problem that has come to be known.

A first object of the present invention is to provide a solder paste composition and a reflow soldering method capable of preventing the lead-free solder powder and the flux film from being thermally degraded even during high-temperature reflow. Second embodiment of the present invention
It is an object of the present invention to provide a solder paste composition and a reflow soldering method in which the solderability characteristics do not decrease even when a lead-free solder powder is used. A third object of the present invention is to provide a solder paste composition and a reflow soldering method capable of avoiding heat damage to electronic components that are vulnerable to high temperatures by changing a heat pattern during reflow when using a lead-free solder powder. Is to do. A fourth object of the present invention is to provide a solder paste composition and a reflow soldering method capable of obtaining a mounting board having high circuit reliability even when a lead-free solder powder is used.

[0005]

Means for Solving the Problems The present inventor has conducted intensive studies in order to solve the above-mentioned problems, and as a result, as for a solder paste in which a hindered phenol compound is used in combination with a lead-free solder powder, a lead-free solder is used. The present inventors have found that deterioration during reflow of the powder and the solder paste film is prevented, and have led to the present invention. Therefore, the present invention
(1) An object of the present invention is to provide a solder paste composition containing a lead-free solder powder, a rosin resin, an activator and a solvent, which contains an antioxidant composed of a hindered phenol compound. The present invention also provides (2) a solder paste composition according to (1), wherein the molecular weight of the hindered phenol compound is at least 500; (3) an electronic component for a soldered portion of a printed circuit board. An object of the present invention is to provide a reflow soldering method for performing reflow soldering using the solder paste composition according to item 1 or 2. The lead-free solder powder may be a solder alloy powder containing neither lead nor zinc.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a lead-free solder powder is a solder powder having no lead component, for example, a solder powder containing no lead and zinc is preferable, such as Sn-Ag, Sn- Ag-Cu, Sn-Ag-Bi, S
n-Bi, Sn-Ag-Cu-Bi, Sn-Sb and S
There is no particular limitation as long as it is a solder alloy that does not include lead and zinc, such as n-Cu. Sn-Zn based alloy solder powder may be used. Lead-free solder powder is used in the solder paste in an amount of 85 to 92% (flux: 8 to 15%), and a spherical solder powder having a particle size of 300 to 700 mesh has recently become narrower in pitch of soldering lands. For reflow soldering to a printed circuit board.

The rosin-based resin used in the present invention includes rosin and derivatives thereof such as modified rosin, and these can be used in combination. Specifically, for example, gum rosin, wood rosin, polymerized rosin, phenol-modified rosin, These derivatives are mentioned. The content of the rosin-based resin can be 30 to 70% in a so-called flux, which is a component other than the solder powder of the solder paste composition. If the amount is less than this, the oxidation of the copper foil surface of the soldering land is prevented, and the molten solder is easily wetted on the surface, so-called solderability is reduced, and solder balls are easily generated. More.

Examples of the activator include a hydrogen halide of an organic amine and an organic acid. Specific examples include diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine hydrochloride, and triethanol. Amine hydrobromide, monoethanolamine hydrobromide, adipic acid, sebacic acid, etc., which suppress the corrosiveness of the residue and do not impair insulation resistance From the viewpoint of preventing the formation of solder balls, 0.1 to 3% of the flux is preferable.

[0009] A thixotropic agent may be used. For example, hydrogenated castor oil, fatty acid amides, oxy fatty acids, etc. can be used so that the solder paste can be adjusted to a viscosity suitable for its printability. Is preferably contained in the flux at 3 to 15%. Examples of the solvent include those used in ordinary solder pastes. For example, hexyl carbitol (boiling point: 260
° C), butyl carbitol (boiling point: 230 ° C) and the like.

In the present invention, an antioxidant composed of a hindered phenol compound (which may contain a trace amount of other components) is used. The flux is used by stirring and mixing with a lead-free solder powder. The hindered phenol compound is not particularly limited,
Specifically, triethylene glycol-bis [3- (3
-T-butyl-5-methyl-4-hydroxyphenyl)
Propionate], 1,6-hexanediol-bis-
[3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino ) -1,3,5-Triazine, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2
-Thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N , N'-Hexamethylenebis (3,5-di-t-butyl-4-hydroxy-
Hydrocinnamamide), 3,5-di-t-butyl-4-
Hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl)
Benzene and the like can be mentioned. Of these, the molecular weight is 50
Those having 0 or more are particularly preferred because of their excellent thermal stability.

The antioxidant comprising a hindered phenolic compound accounts for 10% or less (at most 10%) of the flux.
%) Is preferred. If the addition amount is larger than this, the solderability may decrease. The reason why the antioxidant composed of the hindered phenol compound exhibits the effect of preventing the flux film of the solder paste film and the lead-free solder powder from deteriorating has not been clearly elucidated. Hydrogen is given to radicals of decomposed products generated when heat or light is applied to high molecular hydrocarbons, and the activation of the radicals is lost and stabilized. It can also be considered that the progress of the degradation reaction in which some insolubles are generated by the reaction is prevented. In the case of a lead-free solder powder, it can be considered that oxygen in an atmosphere in which the metal is to react is stabilized.

[0012]

EXAMPLES Examples will be described below, but the present invention is not limited by the following examples.

Example 1 A solder paste having the following composition was prepared. Hydrogenated rosin (rosin-based resin) 55.0 g Adipic acid (activator) 2.0 g Hydrogenated castor oil (thixotropic agent) 6.0 g Triethylene glycol-bis [3- (3-t-butyl-5-methyl-) 4-Hydroxyphenyl) propionate] (antioxidant) 5.0 g Hexyl carbitol (solvent) 33.0 g (flux 100 g) Flux 11.0 g Solder powder 89.0 g (Sn / Ag / Cu = 96. (5/3 / 0.5) (Solder paste: 100 g) A solder paste was obtained by stirring and mixing the above flux and solder powder. When this solder paste was measured with a Malcolm viscometer, it was 230 Pa · s (measuring temperature 25 ° C.). Further, using this solder paste, a printability test (a test for inspecting whether or not blurring or bleeding is visually observed on a printing surface by screen printing using a metal mask having a thickness of 0.15 mm), an adhesiveness test ( The purpose of this study is to examine the peelability of a metal mask after printing.
Z 3284), sagging test during heating (testing the protrusion of the coating film from a predetermined position during heating, test according to JIS Z 3284), and insulation test (resistance value of flux film separated from solder) It measures and evaluates the test according to JIS Z 3284, and furthermore, the soldering condition test (in the reflow soldering apparatus, the preheat temperature is set to 150 ° C., 12
In the case of 0 seconds, and in the case of 200 ° C. and 120 seconds, respectively, the state of soldering when the main heating was performed at 240 ° C. for 30 seconds was changed to a state in which no unmelted material was found in the solidified solder after melting. Table 1 shows the results of a test in which the most common one was evaluated as 1 and three or more were evaluated as being practical by a five-step method.

Example 2 The antioxidant was 1,6-hexanediol-bis- [3-
(3,5-t-butyl-4-hydroxyphenyl) propionate] was used in the same manner as in Example 1 except that the solder paste was used in place of (3,5-t-butyl-4-hydroxyphenyl) propionate. Table 1 shows the results.

Comparative Example 1 A solder paste was prepared in the same manner as in Example 1 except that no antioxidant was used, and the results of a test conducted in the same manner as in Example 1 using the obtained solder paste are shown in Table 1.

[0016]

[Table 1]

From the results in Table 1, it can be seen that the solder pastes of Examples 1 and 2, which are combined with an antioxidant,
Although the soldering state is good even when the preheat temperature is 150 ° C., it is particularly excellent when the preheat temperature is 200 ° C., and other performances are inferior to those in Comparative Example 1 in which no antioxidant is used. There is nothing.

[0018]

According to the present invention, since an antioxidant comprising a hindered phenol compound is used in combination, it is possible to prevent the lead-free solder powder and the flux film from being thermally degraded even during high-temperature reflow. Solder paste composition that does not decrease the adhesive property and can avoid heat damage to electronic components that are vulnerable to high temperatures by changing the heat pattern during reflow, thereby obtaining a mounting board with high circuit reliability And a reflow soldering method can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenji Fujimori 16-2 Oyama Sayamagahara, Iruma City, Saitama Prefecture Within Tamra Kaken Co., Ltd. (72) Inventor Satoshi Okumura 16-2 Oyama Sahara, Iruma City, Saitama Prefecture Inside Tamura Kaken Co., Ltd. (72) Inventor Hiroaki Koyahara 16-2 Sayamagahara, Iruma-shi, Saitama F-term inside Tamura Kaken Co., Ltd. 5E319 BB05 BB08 CC33 GG03

Claims (3)

[Claims] 1. A solder paste composition containing a lead-free solder powder, a rosin resin, an activator and a solvent,
A solder paste composition containing an antioxidant comprising a hindered phenol compound. 2. The solder paste composition according to claim 1, wherein the hindered phenol compound has a molecular weight of at least 500. 3. A reflow soldering method for reflow soldering an electronic component to a soldered portion of a printed circuit board using the solder paste composition according to claim 1 or 2.