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Low-silver lead-free solder alloy for brazing and preparation method of low-silver lead-free solder alloy

A lead-free solder and alloy technology is applied in the preparation of the solder alloy and the field of low-silver lead-free solder alloy for brazing, which can solve the problem of uneven structure and composition, increase in preparation cost, decrease in hardness and strength of solder, etc. question

Pending Publication Date: 2021-06-04
陕西工业职业技术学院
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] Brazing technology is widely used in the field of electronic packaging, which can realize the interconnection between electronic packaging devices and materials. The existing technology has developed a variety of lead-free solders through alloying, particle strengthening and other methods and has become the main microelectronic interconnection technology. Connecting materials, Sn, Ag, Cu, Bi, and Ni elemental metals are used in the preparation process of SACBN solder. The melting points of elemental metals Ag, Cu, and Ni are much higher than those of Sn and Bi. During the preparation process, Sn and Bi melt, but Ag , Cu and Ni may not melt, resulting in uneven composition; at the same time, the density difference between the various components is large, and long-term heat preservation will cause gravity segregation; and the higher silver content will lead to more Ag3Sn metal inside the solder Intercompounds are formed, and the impact resistance of brazed joints decreases. More importantly, the higher silver content increases the cost of the solder, but if the silver content in the solder decreases, the Ag3Sn compound formed inside it will decrease, and the solder will have a lower silver content. Hardness, strength, etc. have all decreased, and its reliability has decreased significantly under high-temperature service aging conditions. At the same time, the decrease in silver content also makes its melting point, wettability and other welding properties worse
The existing brazing material preparation method has high Ag content, which increases the preparation cost, and the brazing material used for brazing is easy to oxidize, the uniformity of the composition is poor during salt bath brazing, the creep resistance is poor, and the application limitations are high, which is not conducive to large-scale use

Method used

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preparation example Construction

[0020] Another kind of technical solution adopted in the present invention is: a kind of preparation method of low-silver lead-free solder alloy for brazing, concrete steps are as follows:

[0021] Step 1. Take respectively Sn particles, Bi particles, Sn3.5Ag master alloys, SnCu0.7 master alloys, and SnNi0.5 master alloys with a purity of 99.99%. The above components meet the following conditions by mass percentage: the mass percentage of Sn The mass fraction of Ag is 96%-97%, the mass fraction of Ag is 0.7%-0.8%, the mass fraction of Cu is 0.5%-0.55%, the mass fraction of Bi is 1.60%-2.5%, and the mass fraction of Ni is 0.05%-0.1 %, the sum of the above components is 100%;

[0022] In step 1, the surfaces of Sn particles, Bi particles, Sn3.5Ag master alloy, SnCu0.7 master alloy and SnNi0.5 master alloy are preliminarily cleaned.

[0023] Step 2, preparing NaCl and KCl liquid eutectic salt;

[0024] The specific preparation method of step 2 is: mix NaCl and KCl according to ...

Embodiment 1

[0029] Step 1, respectively weigh Sn particles, Bi particles, Sn3.5Ag master alloy, SnCu0.7 master alloy, SnNi0.5 master alloy with a purity of 99.99%; the above components meet the following conditions by mass percentage: 96.65% Sn, 0.80% Ag, 0.50% Cu, 2.00% Bi, 0.05% Ni.

[0030] Step 2. Mix NaCl and KCl according to the molar ratio of 1:1, weigh 200g and mix evenly, put the evenly mixed NaCl and KCl mixture into a crucible and heat it to 650°C, keep it warm for 0.5h, and melt to form a liquid eutectic salt .

[0031] Step 3. Add the Sn particles, Sn3.5Ag master alloy, SnCu0.7 master alloy, Bi particles and SnNi0.5 master alloy weighed in step 1 to the liquid eutectic salt melted in step 2, and stir until the metal All were melted to obtain a melt.

[0032] Step 4. Insulate the melt obtained in step 3. During the heat preservation process, ultrasonic vibration treatment is performed on the melt. The frequency of ultrasonic vibration is 80KHz and the amplitude is 5 μm. Ult...

Embodiment 2

[0035] Step 1, respectively weigh Sn particles, Bi particles, Sn3.5Ag master alloy, SnCu0.7 master alloy, SnNi0.5 master alloy with a purity of 99.99%; the above components meet the following conditions by mass percentage: 96.15% Sn, 0.85% Ag, 0.51% Cu, 2.47% Bi, 0.02% Ni.

[0036] Step 2. Mix NaCl and KCl according to the molar ratio of 0.9:1, weigh 200g and mix evenly, put the evenly mixed NaCl and KCl mixture into a crucible and heat it to 660°C, keep it warm for 0.6h, and melt to form a liquid eutectic salt .

[0037] Step 3. Add the Sn particles, Sn3.5Ag master alloy, SnCu0.7 master alloy, Bi particles and SnNi0.5 master alloy weighed in step 1 to the liquid eutectic salt melted in step 2, and stir until the metal All were melted to obtain a melt.

[0038] Step 4. Insulate the melt obtained in step 3. During the heat preservation process, the melt is subjected to ultrasonic vibration treatment for 30 minutes. The frequency of ultrasonic vibration is 80KHz and the amplit...

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Abstract

The invention discloses a low-silver lead-free solder alloy for brazing. The raw materials of the alloy comprise the following components of, in percentage by mass, 96%-97% of Sn, 0.8%-0.85% of Ag, 0.5%-0.55% of Cu, 1.60%-2.5% of Bi and 0.05%-0.1% of Ni, and the sum of the components is 100%. The alloy has the characteristics of oxidation resistance, good structure uniformity and excellent creep resistance, and the preparation method of the alloy is simple, easy and convenient to operate and can be used for batch production.

Description

technical field [0001] The invention belongs to the technical field of non-ferrous alloys, in particular to a low-silver lead-free solder alloy for brazing, and also relates to a preparation method of the solder alloy. Background technique [0002] Brazing technology is widely used in the field of electronic packaging, which can realize the interconnection between electronic packaging devices and materials. The existing technology has developed a variety of lead-free solders through alloying, particle strengthening and other methods and has become the main microelectronic interconnection technology. Connecting materials, Sn, Ag, Cu, Bi, and Ni elemental metals are used in the preparation process of SACBN solder. The melting points of elemental metals Ag, Cu, and Ni are much higher than those of Sn and Bi. During the preparation process, Sn and Bi melt, but Ag , Cu and Ni may not melt, resulting in uneven composition; at the same time, the density difference between the vario...

Claims

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Application Information

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IPC IPC(8): B23K35/26B23K35/40
CPCB23K35/262B23K35/40
Inventor 王一龙徐广胜张战英刘振华
Owner 陕西工业职业技术学院
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