TW202247935A - Tin alloy solder paste - Google Patents

Abstract

A tin alloy solder paste is composed of a mixture of an alloy with a high melting point, an alloy with a low melting point, and a flux blended in the mixing ratios of 20~40 wt%: 50~70 wt%: 10~12 wt% respectively. The alloy with a high melting point is a binary alloy selected from the group consisting of Zn-Al, Sn-high Pb, Au-Sn, Ag-B, Sn-Cu, Sn-Ag, Sn-Ni and a combination thereof; the alloy with a low melting point is a tin alloy selected from tin-lead solder paste Sn63Pb37, or lead-free solder SAC305, or lead-free solder SAC305; the flux is composed of rosin and derivatives thereof, thixotropic agents, high-efficiency polymerization inhibitors, activators, and solvent.

Description

Tin-based alloy solder paste

The present invention relates to a solder paste; more specifically, it refers to a tin-based alloy solder paste.

In the reflow soldering process of the connecting materials of integrated circuit electronic components, due to the requirement of multi-level PCB packaging process, multiple reflows of the soldered substrate are involved, and the traditional low-melting point solders will make the soldering after secondary (multiple) reflows The size of the point shrinks and thermal collapse occurs, resulting in displacement of the connecting part of the component. In severe cases, remelting of the solder joint may even cause the problem of missing parts, which directly affects the welding quality.

This phenomenon is easy to occur especially in the process of repeated reflow welding. The root cause is the poor heat resistance of the solder joints and the low melting point of the structure. The current solder, from the perspective of the phase structure of the welded joint, mainly has the following aspects Types: 1. The solder joint is composed of a tin-based alloy matrix plus a thin layer of metal interlayer compound (inter-metallic compound, IMC): the high-temperature reinforcement phase of this type of alloy joint (traditional solder Sn63Pb37, SAC305) is mainly scalloped layered Cu ₆ Sn ₅ , in the process of multiple reflow fusion to form solder joints, it is easy to form coarse inter-metallic compound (IMC) and harmful phase Cu ₃ Sn and increase the brittleness of solder joints. 2. The solder joint is composed of a tin-based alloy matrix plus a dispersed reinforced inter-metallic compound (IMC): this type of alloy joint is composed of a dispersed reinforced phase inter-metallic compound (IMC) to form a skeleton, and the skeleton gap Filled with tin to form a welded joint with good strength and toughness. At present, tin-based alloys are mainly doped with micro-nano elemental particles. Although this method can reduce the welding temperature, the welded joints formed have more pores. 3. The structure of the solder joint is completely transformed into the inter-metallic compound (IMC) of the reinforcement phase: during the reflow soldering process of this type of alloy solder, the scallop-shaped inter-metallic compound (IMC) is first formed, and after a long period of After reflow for a long time, the solder joint will be completely converted into inter-metallic compound (IMC), but the conversion time of inter-metallic compound (IMC) is longer, and the soldering temperature is too high. The inter-metallic compound (IMC) alloy bonding layer is too thick, which greatly reduces the mechanical properties.

In view of this, based on my many years of research and development experience in related fields, I conducted in-depth discussions on the aforementioned deficiencies, and actively sought solutions based on the aforementioned needs. After a long period of hard research and multiple tests, I finally completed the present invention.

The main purpose of the present invention is to provide a kind of soldering material prepared by mixing and doping tin-based alloy and tin alloy containing high-temperature enhancement phase, in order to obtain high-temperature enhancement phase metal interlayer compound (inter-metallic compound, IMC) welded joints, and improve the heat resistance and mechanical properties of welded joints.

In order to achieve the above-mentioned purpose, the tin-based alloy solder paste of the present invention is composed of high melting point alloy, low melting point alloy and flux, and the mixing ratio of the high melting point alloy: low melting point alloy: flux is between 20 ~ 40wt %: 50~70wt%: between 10~12wt%.

The high melting point alloy system consists of zinc aluminum (Zn-Al), tin high lead (Sn-high Pb), gold tin (Au-Sn), silver bismuth (Ag-Bi), tin copper (Sn-Cu), tin One or more of binary alloys of silver (Sn-Ag) and tin tweezers (Sn-Ni), and the melting point of the high melting point alloy system is between 230°C and 500°C.

The low-melting-point alloy system is a tin-based alloy, and the tin-based alloy is any one of tin-lead paste Sn63Pb37 or lead-free solder Sn42Bi58 or lead-free solder SAC305, and the melting point of the low-melting point alloy system is between 138°C and 217°C.

The flux system includes modified rosin and its derivatives, thixotropic agent, high-efficiency polymerization inhibitor, activator and solvent, and the modified rosin and its derivatives account for 40-55% of the whole, and the thixotropic agent accounts for 2~5.5% of the whole, high-efficiency polymerization inhibitors account for 0.1~5% of the whole, activators account for 2.5~16% of the whole, and the rest are solvents.

In order to allow a more detailed understanding of the purpose, function, features and structure of the present invention, the preferred embodiments are described below with accompanying drawings.

First, please refer to Figure 1 to Figure 6 together.

Fig. 1 is a schematic diagram of the tin-based alloy solder paste of the present invention, Fig. 2 is a schematic diagram of the metal interlayer compound (inter-metallic compound, IMC) precipitated by the high melting point alloy of the present invention, and Fig. 3 is a schematic diagram of the structural transformation of the reflow soldering process of the present invention ( 1), Fig. 4 is a schematic diagram of the organizational transformation of the reflow soldering process of the present invention (2), Fig. 5 is a schematic diagram of the organizational transformation of the reflow soldering process of the present invention (3), and Fig. 6 is a schematic diagram of the organizational transformation of the reflow soldering process of the present invention (4) .

The tin-based alloy solder paste 1 of the present invention contains a high melting point alloy 11. Composed of low melting point alloy 12 and flux 13, and the mixing ratio of the high melting point alloy 11:low melting point alloy 12:flux 13 is between 20~40wt%: 50~70wt%: 10~12wt%.

The high melting point alloy 11 is selected from zinc-aluminum (Zn-Al), tin-high lead (Sn-high Pb), gold-tin (Au-Sn), silver-bismuth (Ag-Bi), tin-copper (Sn-Cu), One or more of the binary alloys of tin-silver (Sn-Ag) and tin-tweezers (Sn-Ni) are made into powder particles through a powder mill, and the melting point of the high melting point alloy 11 is between 230°C~ 500°C.

The low-melting-point alloy 12 is a tin-based alloy, which is any one of tin-lead paste Sn63Pb37, lead-free solder Sn42Bi58 or lead-free solder SAC305, and the melting point of the low-melting-point alloy 12 is between 138°C and 217°C.

The flux 13 contains modified rosin and its derivatives, thixotropic agent, high-efficiency polymerization inhibitor, activator and solvent, and the modified rosin and its derivatives account for 40-55% of the whole, and the thixotropic agent Accounting for 2~5.5% of the whole, high-efficiency polymerization inhibitors account for 0.1~5% of the whole, activators account for 2.5~16% of the whole, and the rest are solvents. In addition, the detailed components of the flux are super-grade hydrogenated rosin, 18 acid acyl Amine, ethylene bis stearic acid amide, N,N-diethylhydroxylamine (DEHA), sebacic acid, malic acid, fluorocarbon surfactant FSN100, diethanolamine and diethylene glycol monoethyl ether, and the special grade Hydrogenated rosin accounts for 50-55% of the whole, 18-acid amide accounts for 1-2% of the whole, ethylene bis-stearamide accounts for 1-3% of the whole, N,N-diethylhydroxylamine (DEHA) Accounting for 1~3% of the whole, sebacic acid accounts for 1~3% of the whole, malic acid accounts for 2~5% of the whole, fluorocarbon surfactant FSN100 accounts for 0.1~1% of the whole, diethanolamine accounts for 0.1~ 1%, the rest is diethylene glycol monoethyl ether.

The detailed description of the embodiments of the present invention and related drawings for reference is as follows:

When the present invention is applied between two substrates 3 for reflow soldering, a layer of metal interlayer compound (inter-metallic compound, IMC) 2 will be formed between the substrate 3 and the present invention, and due to the high melting point alloy 11 Contains a large amount of ready-made inter-metallic compound (IMC) 2 particles, when the high-melting point alloy 11 and low-melting point alloy 12 alloy powders are fused to form solder joints 4, and the inter-metallic compound (inter-metallic compound) compound, IMC)2 particles are distributed and interconnected in the whole solder joint, forming a network skeleton with Cu ₆ Sn ₅ , Ag ₃ Sn, Ni ₃ Sn ₄ as the main reinforcing phase, and the gap between the skeletons will be filled with tin To reduce the generation rate of internal pores 5.

Then, in order to detect whether the present invention can achieve the desired effect after reflow soldering, the present invention is reflow soldered with tin and commercially available solder paste SAC305 and tested, and the results are shown in the following table (1): control group Shear strength (MPa) porosity Humidity Density (g/cm ³ ) 300°C Tensile Strength (MPa) tin+copper 28 8% level 4 8.28 28 SAC305+copper 48 10% level 2 7.46 30 control group Shear strength (MPa) porosity Humidity Density (g/cm ³ ) 300°C Tensile Strength (MPa) this invention 50 5% level 2 7.3 32 The present invention (copper accounts for more than 11WT%) 53 2% level 2 7.38 34 The present invention (silver accounts for more than 11WT%) 58 3% level 2 7.42 35 The present invention (tweezers account for more than 11WT%) 61 2.2% level 2 7.48 33 Table I)

First, in terms of overall shear strength after reflow soldering, the shear strength of the present invention is significantly better than the combination of tin and copper, and the shear strength of the present invention is also slightly better than the combination of SAC305 and copper.

Next, regarding the porosity produced after reflow soldering, the porosity produced by the present invention is obviously lower than the combination of tin plus copper and SAC305 plus copper.

Next, in terms of overall wettability after reflow soldering, the combination of the present invention and SAC305 with copper has the same level of wettability, and the combination of the present invention with SAC305 with copper is superior to tin in terms of wettability Combination with copper.

Furthermore, in terms of the overall density after reflow soldering, the density of the present invention is lower than that of the combination of tin and copper, and compared with the combination of SAC305 and copper, the density of the present invention is slightly higher except that the tweezers account for more than 11WT%. Except for the combination of SAC305 and copper, the density of other combinations is lower than that of SAC305 and copper.

Finally, in terms of the tensile strength of solder joints at a temperature of 300° C. after reflow soldering, the tensile strength of the present invention is significantly better than the combination of tin plus copper and SAC305 plus copper.

Therefore, the present invention has excellent advancement and practicability among similar products. At the same time, after checking the technical data and documents about this type of structure at home and abroad, it is true that no identical or similar structure exists before the application of this case. Therefore, this case Should have met the patent requirements of "creativity", "suitability for industrial utilization" and "progressiveness", the application should be filed in accordance with the law.

Only, what is described above is only a preferred embodiment of the present invention, and all other equivalent structural changes made by applying the description of the present invention and the scope of the patent application should be included in the scope of the patent application of the present invention.

1: Tin-based alloy solder paste 11: high melting point alloy 12: low melting point alloy 13: Flux 2: Metal interlayer compound (inter-metallic compound, IMC) 3: Substrate 4: solder joints 5: stomata

Fig. 1: schematic diagram of tin-based alloy solder paste of the present invention; Figure 2: Schematic diagram of the metal interlayer compound (inter-metallic compound, IMC) precipitated by the refractory alloy of the present invention; Figure 3: Schematic diagram of organizational transformation in the reflow soldering process of the present invention (1); Figure 4: Schematic diagram of organizational transformation in the reflow soldering process of the present invention (2); Figure 5: Schematic diagram of organizational transformation in the reflow soldering process of the present invention (3); Figure 6: Schematic diagram of structure transformation in the reflow soldering process of the present invention (4).

none.

1: Tin-based alloy solder paste

11: high melting point alloy

12: Low melting point alloy

13: Flux

Claims (3)

A tin-based alloy solder paste is composed of a high melting point alloy, a low melting point alloy and flux, and the mixing ratio of the high melting point alloy: low melting point alloy: flux is between 20~40wt%: 50~70wt%: Between 10 and 12wt%; The high melting point alloy system is selected from zinc aluminum (Zn-Al), tin high lead (Sn-high Pb), gold tin (Au-Sn), silver bismuth (Ag-Bi), tin copper (Sn-Cu), tin One or more of binary alloys of silver (Sn-Ag) and tin tweezers (Sn-Ni), and the melting point of the high melting point alloy system is between 230°C and 500°C; The low-melting-point alloy system is a tin-based alloy, and the tin-based alloy is any one of tin-lead paste Sn63Pb37 or lead-free solder Sn42Bi58 or lead-free solder SAC305, and the melting point of the low-melting point alloy system is between 138°C and 217°C; The flux system includes modified rosin and its derivatives, thixotropic agent, high-efficiency polymerization inhibitor, activator and solvent, and the modified rosin and its derivatives account for 40-55% of the whole, and the thixotropic agent accounts for 2~5.5% of the whole, high-efficiency polymerization inhibitors account for 0.1~5% of the whole, activators account for 2.5~16% of the whole, and the rest are solvents. The tin-based alloy solder paste according to claim 1, wherein the high melting point alloy is made into powder particles by a powder making machine. The tin-based alloy solder paste as described in claim item 1, wherein the detailed composition of the flux is extra-grade hydrogenated rosin, 18-acid amide, ethylene bis-stearyl amide, N,N-diethylhydroxylamine ( DEHA), sebacic acid, malic acid, fluorocarbon surfactant FSN100, diethanolamine and diethylene glycol monoethyl ether, and the special-grade hydrogenated rosin accounts for 50-55% of the whole, and 18-acid amide accounts for 1-2% of the whole , Ethylene bis stearic acid amide accounts for 1~3% of the whole, N,N-diethylhydroxylamine (DEHA) accounts for 1~3% of the whole, sebacic acid accounts for 1~3% of the whole, malic acid It accounts for 2~5% of the whole, fluorocarbon surfactant FSN100 accounts for 0.1~1% of the whole, diethanolamine accounts for 0.1~1% of the whole, and the rest is diethylene glycol monoethyl ether.

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