KR20100001761A - Sn-ag-cu solder compositions with addition of bi and manufacturing methods thereof - Google Patents

Abstract

Soldering materials for electronic components are disclosed that enable more reliable bonding. The present invention provides a Sn-Ag-Cu-Bi-based solder composed of a mixture of Sn-Ag-Cu-based alloy powder and Sn-Bi alloy powder. According to the present invention, it is possible to provide a more reliable bonding material by controlling the melt phenomenon to suppress the Manhattan phenomenon.

Description

Sn-Ag-Cu-based solder containing Ti and a method for manufacturing the same {Sn-Ag-Cu solder compositions with addition of Bi And Manufacturing Methods

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to solders suitable for use as a joining material for wiring in electronic devices, and more particularly, to solders for suppressing occurrence of Manhattan phenomenon during soldering and a method of manufacturing the same.

In general, soldering serves to bond the metal by melting the solder, and uses a metal having a lower melting temperature than the metal to be joined.

Solder is roughly classified into solder that is melted at a temperature lower than the melting temperature (327 ° C.) of lead (Pb) and light solder having a melting temperature of approximately 450 ° C. or more.

The lead solder is melted at low temperature and is easy to solder. It has a low melting point of lead (Pb) and tin (Sn). On the other hand, as for brazing, brass (main) copper (Cu), zinc (Zn), and lead (Pb) are the main components, and silver (Ag), which is improved in fluidity by adding silver, is used.

Low melting point solders have been widely used as bonding materials for electronic components due to their low melting point. However, lead is a metal that does not decompose, and once it is ingested in the human body, it is not released and accumulates. In particular, it may cause deterioration of intelligence in children and contaminate the soil by waste of lead when left outside. Problem occurs.

Accordingly, the soldering manufacturer is devoted to the development of lead-free solder that is not added lead (Pb), a typical composition is Sn-Ag-Cu-based solder.

For example, US Pat. No. 5,393,489 discloses lead-free alloys composed of Sn 93.5-94.0 wt%, Ag 2.5-3.0 wt%, Bi 1.0-2.0 wt%, Sb 1.0-2.0 wt%, Cu 1.0 wt%. . In addition, Korean Patent Registration No. 10-333401 has 0.5-5.0 wt% of copper (Cu), 0.5-3.5 wt% of silver (Ag), 4.0-10.0 wt% of bismuth (Bi), and 0.0001 of phosphorus (P). Lead-free alloy for soldering, characterized in that -3.0% by weight, the remainder is composed of tin (Sn), Korean Patent Registration No. 10-0509509 is a copper (Cu) 0.01 ~ 3.0% by weight, silver (Ag ) Is 0.001% to 1.0% by weight, indium (P) is 0.001% to 3.0% by weight, bismuth (Bi) is 0.001% to 3.0% by weight, and the remainder is disclosed a solder composed of tin (Sn). In addition, Korean Patent Registration No. 10-0756072 discloses 0.2 to 2.5% by weight of silver (Ag), 0.1 to 2.0% by weight of copper (Cu), 0.001 to 0.1% by weight of nickel (Ni), and 0.001 to phosphorus (P). A lead-free alloy for soldering is disclosed in which 0.5 wt%, bismuth (Bi) is 0.01 to 0.08 wt%, and the remainder is made of tin (Sn).

As described above, Bi is used for Sn-Ag-Cu-based soldering. Bi has a melting point of about 273 ° C., which has a lower melting point than lead, and thus, bismuth has an excellent effect on lowering the melting point of the solder alloy composition when added. It is known that the wettability of. In addition, it is known that the tin (Sn) matrix has characteristics that are not found in other alloy systems in which a large amount of bismuth is dissolved, and has brittle brittleness properties, and it is known that the soldering reliability of the solder is reduced when a large amount is added. have.

Manhattan phenomenon is mentioned as a factor of such a joining reliability fall.

1 is a photograph for explaining the Manhattan phenomenon. Referring to FIG. 1, electronic components joined by solder on a substrate may be distorted from the electrode position of the substrate, or may be severely bonded upright by combining only one side of the electronic component, which is called a Manhattan phenomenon. The reason is known to be due to various reasons, such as a temperature difference of a board | substrate, the nonuniformity of solder print quantity, and the variation of the bonding force of solder. Especially in the case of Sn-Ag-Cu containing excessive Bi, such a phenomenon occurs frequently.

In order to solve the above problems of the prior art, an object of the present invention is to provide a bismuth-containing solder having a high bonding reliability.

In order to achieve the above technical problem, the present invention provides a Sn-Ag-Cu-Bi-based solder consisting of a mixture of Sn-Ag-Cu-based alloy powder and Sn-Bi alloy powder.

The present invention is particularly useful when the Bi content is excessive, such as at least 10% by weight.

In addition, in the present invention, the Ag content is 0.01 to 3% by weight, and the Cu content is preferably 0.01 to 1% by weight.

According to the present invention, it is possible to control the melting phenomenon in a wide temperature range to suppress sudden melting due to partial non-uniformity of the composition causing the Manhattan phenomenon.

Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the present invention.

The present inventors understand that the above Manhattan phenomenon is caused by sudden melting of the solder. This abrupt melting, combined with local inhomogeneities in the solder composition, can result in Manhattan phenomena. For example, if a sudden melt occurs in either of the solders provided at the two terminals of the electronic component for bonding to the two electrodes of the substrate, the molten solder is subjected to surface tension due to wetting of the terminals and the electrodes. Will be generated. Such surface tension may eventually act as a pulling force on the electronic component, causing the electronic component to twist, stand up, or fall down in its original position.

To this end, the present inventors attempted to solve this problem by controlling the melting phenomenon in the same composition, rather than finding a composition of Sn-Ag-Cu-Bi system suitable for suppressing the suppression of Manhattan phenomenon.

In view of this, the solder of the Sn-Ag-Cu-Bi composition in the present invention is composed of a mixture of Sn-Ag-Cu alloy and Sn-Bi alloy. As such, the present invention can appropriately control the melting phenomenon of Sn-Ag-Cu-Bi by forming a mixture of alloys of two compositions.

2 is a phase diagram of a Bi-Sn system. As can be seen from FIG. 2, the eutectic temperature of Bi-Sn is about 139 ° C., and the eutectic composition is Sn-58Bi. As such, melting of the Bi—Sn alloy begins at very low temperatures around 140 ° C., which is also used as a solder by itself.

3 is a phase diagram showing Sn-Ag-Cu ternary systems centered around Sn-rich regions. In the case of Sn-Ag-Cu (hereinafter referred to as 'SAC') ternary alloy, the liquidus line changes depending on the content of Ag and Cu. For example, in the case of SAC105 (98.5Sn-1Ag-0.5Cu), the liquidus line is about It is 226 ° C, about 222 ° C for SAC205 (97.5Sn-2Ag-0.5Cu), and the liquidus line for SAC305 is about 220 ° C. As such, it can be seen that the liquidus line of the SAC alloy decreases when the Ag and Cu contents increase in the Sn-rich region in the lower left box (Ag about 3.7 wt% or less and Ag 1 wt% or less) of FIG. 3.

For example, when the Ag content is 3 wt% or less and the Cu content is 1 wt% or less, the liquidus line of the SAC is about 218 ° C or more, the Ag content is 1 wt% or less and the Cu content is 1 wt% In the case below, it can be seen that the liquidus line of the SAC is about 224 ° C or more.

From the above phase equilibrium, it can be seen that the liquidus line of the SAC solder having Ag content of 3 wt% or less and Cu content of 1 wt% or less has a difference of about 79 ° C from the melting temperature of the Sn-Bi alloy. In addition, it can be seen that the melting temperature of the liquid line of the SAC solder having an Ag content of 1 wt% or less and the Cu content of 1 wt% or less is approximately 85 ° C.

Such a powdery mixture of SAC alloy and Sn-Bi alloy starts to melt the Sn-Bi alloy below the melting temperature of the total composition at the time of soldering and proceeds to melting of the whole composition gradually. Therefore, the melting phenomenon of the whole composition gradually occurs. As a result, the sudden melting phenomenon causing the Manhattan phenomenon can be suppressed.

In addition, according to the present invention, as the Ag and Cu contents of the SAC alloy decrease, the melting temperature difference of the Bi-Sn alloy becomes larger, so that the melting phenomenon will occur in a wider temperature range.

Hereinafter, exemplary embodiments of the present invention will be described.

Example

Table 1 below shows the final composition of the solder produced in this example.

division ingredient Sn Ag Cu Bi Example 1 96.15 0.285 0.665 2.9 Example 2 93.3 0.27 0.63 5.8 Example 3 81.9 0.21 0.49 17.4 Comparative Example 1 81.9 0.21 0.49 17.4 Comparative Example 2 99.0 0.3 0.7 Comparative Example 3 42 58

Solders having the composition of the above embodiments were each prepared in the following manner.

First, Example 1 was prepared by mixing 475g of commercially available SAC0307 (99Sn-0.3Ag-0.7Cu) solder and 25g of commercially available Sn-58Bi solder. Here SAC0307 uses Y-SnAg0.3Cu0.7-Q, product name of YAMAISHIKINZOKU CO., LTD., With an average particle diameter of 20-38 microns, and Sn-58Bi has an average particle diameter of 20-45 microns. The product name Y-Sn42Bi58-Q of YAMAISHIKINZOKU CO., LTD was used.

In the same manner, the compositions of Examples 2 and 3 were mixed. In the case of Example 2, the SAC0307 content was prepared by mixing 450g Sn-58Bi content and 50g. In Example 3, the SAC0307 content was prepared by mixing 350g and Sn-58Bi content by 150g.

The flux used at this time was (GLYCOL ETHER SOLVENT 45%, MODIFIED RESIN 50%, THIXOTROPHY AGNET 2%, ACTIVATOR 2.5%, ANTIOXIDENT 0.5%), and the flux content was about 11.0% by weight based on the total weight. It was made.

For comparison with the present invention, Sn-Ag-Cu-Bi alloy powder having the same final composition as in Example 3 was prepared separately (Comparative Example 1). This powder is prepared by melting the metal powder of the above composition and then grinding it. In addition, in order to compare with the present Example, the behavior of the conventional SAC0307 solder and Bi58-Sn solder was analyzed together similarly to Comparative Examples 2 and 3.

Melting temperature of the samples prepared as described above was measured by SP-5000DS SMT-SCOPE of Sanyo Precision Co., Ltd., and wetting force was tested by SP-2 of Malcom Co., Ltd., test method JIS Z 3284-1994 / KS The tensile strength was measured using D 6773, and the tensile strength was measured according to the test method KS D 0000 2006 / RS D 0026 using a bonding strength tester (DT4000) of Richardson Electronics Korea.

Table 2 below shows the measurement results.

division Melting temperature (℃) Wetting Force (mN) Tensile Strength (MPa) Example 1 139-220 1.85 80 Example 2 139-215 2.1 106 Example 3 139-195 1.99 110 Comparative Example 1 195 1.99 110 Comparative Example 2 221 1.7 58 Comparative Example 3 139 1.8 60

First, in the above table it can be seen that the melting temperature of SAC0307 and Bi58-Sn are 221 ° C and 139 ° C, respectively (Comparative Examples 2 and 3). In the case of SAC0307, the melting temperature is slightly different from the liquidus phase in the phase balance. This is presumably due to the fact that SAC0307 contains impurities.

In addition, as compared with Comparative Example 2, it can be seen that the wetting force and the tensile strength increase with the addition of Bi. It can also be seen that the addition of Bi reduces the final melting temperature.

On the other hand, it can be seen from the above table that the melting temperatures of Examples 1 to 3 span a wide temperature range. For Examples 1-3 the melting is starting around 139 ° C. Finally, the melting temperature is reached in accordance with the components of each composition to melt completely.

This has the same final composition as in Example 3 but contrasts with Comparative Example 1, which is not a mixture of different alloy powders. In Comparative Example 1, no melting phenomenon was observed visually until the final melting temperature reached 195 ° C.

Therefore, when the solder is composed of a mixture of different kinds of alloy powders as in the present invention, melting occurs in a wide temperature range, and thus sudden melting due to partial non-uniformity of the composition causing Manhattan phenomenon can be controlled. The present invention has the advantage of being able to control the melting over a wide temperature range, while maintaining the advantages of the mechanical properties obtained by the addition of Bi, in particular by configuring heterogeneous solders of SAC and Bi-Sn. As the content of Ag and Cu in the SAC is further reduced, the range of such controllable melting temperature will be wider.

1 is a photograph for explaining the Manhattan phenomenon.

2 is a Bi-Sn binary system phase diagram.

3 is a Sn-Ag-Cu ternary phase balance diagram.

Claims (3)

Sn-Ag-Cu-Bi system solder which consists of a mixture of Sn-Ag-Cu system alloy powder and Sn-Bi alloy powder. The method of claim 1, The Bi content of the solder, characterized in that more than 10% by weight. The method of claim 1, The Ag content is 0.01 to 3% by weight, the Cu content is a solder, characterized in that 0.01 to 1% by weight.

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