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Sn-Ag-Cu misch metal lead-free solder with low content of Cu and preparation method thereof

A mixed rare earth, lead-free solder technology, applied in the direction of manufacturing tools, welding equipment, metal processing equipment, etc., can solve the problems of high cost of solder, increase of Ag3Sn intermetallic compounds, increase of cost of solder, etc., and achieve high oxidation resistance. Performance and anti-corrosion performance, improve anti-oxidation ability and wettability, reduce the effect of equipment renovation cost

Active Publication Date: 2010-05-05
上海一远电子科技有限公司
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Among the patents related to lead-free solder, there are many patents related to tin-copper and tin-silver-copper, including multiple alloys, such as the U.S. patent application (publication number: US6325279) for SnAgCuBiIn solder, due to the existence of In, the solder Material cost increased significantly
The currently generally recognized SnAgCu series alloy solder has a U.S. patent application (publication number: US5527628), which contains 3.5-7.7% Ag by weight in the alloy solder; Japanese patent application (publication number: JP5050286A), in the alloy solder Containing 3.0-5.0% Ag by weight; Chinese patent application (publication number: CN1385280A) is a SnAgCuCe alloy solder, the alloy solder contains 2-5% Ag by weight, and the above-mentioned alloy solder contains a higher proportion of Ag, although the performance of this alloy solder is better than that of ordinary SnCu solder, but the price is twice as expensive as that of ordinary SnCu solder, and the cost is higher
[0004] The Sn-3.8Ag0.7Cu alloy brazing filler metal recommended by the European Union and the Sn-3.0Ag-0.5Cu alloy brazing filler metal recommended by Japan, the weight percent content of Ag is not less than 3.0%, the problem that brings thus is: (1) Ag Contribute to the occurrence of electromigration phenomenon, causing bridging short circuit
(2) The increase of Ag in the solder alloy will lead to the increase of Ag3Sn intermetallic compounds. Since the Ag3Sn intermetallic compounds are elongated in the solder structure, it will seriously affect the mechanical properties of the solder and joints and reduce the reliability of the joints.
(3) The cost rises. Due to the large amount of Ag used in the SnAgCu solder, the current price of Ag has risen sharply, and if you continue to use the solder containing Ag more than 3.0%, a large amount of Ag will be consumed, which will inevitably lead to higher solder costs. Not suitable for market demand

Method used

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  • Sn-Ag-Cu misch metal lead-free solder with low content of Cu and preparation method thereof
  • Sn-Ag-Cu misch metal lead-free solder with low content of Cu and preparation method thereof

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Experimental program
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Effect test

Embodiment 1

[0030]Add the mixed salt of potassium chloride:potassium oxide=(1~1.7):(0.8~1.3)(weight percent) into the furnace, after melting at 580°C, add 98.79% tin by weight; after the tin is completely melted, 0.2% by weight of Ag and 1.0% by weight of Cu are added to the tin liquid and stirred to form an alloy; at the same time, 0.01% by weight of La-Ce-based mixed rare earths is quickly added to the above alloy liquid and continuously stirred until Until the rare earth is completely melted; keep the temperature at 460°C for 1.5 hours and stir to homogenize the alloy. After cooling, remove the mixed salt of potassium chloride and potassium oxide on the surface after the alloy is solidified, and obtain the tin-silver-copper mixed rare earth lead-free solder with low silver content.

Embodiment 2

[0032] Add the mixed salt of potassium chloride:potassium oxide=(1~1.7):(0.8~1.3)(weight percent) into the furnace, after melting at 580°C, add 98.35% tin by weight; after the tin is completely melted, 0.6% by weight of Ag and 0.8% by weight of Cu are added to the tin liquid and stirred to form an alloy; at the same time, 0.25% by weight of La / Ce-based mixed rare earth is quickly added to the above alloy liquid and continuously stirred until Until the rare earth is completely melted; keep the temperature at 460°C for 1.5 hours and stir to homogenize the alloy. After cooling, remove the mixed salt of potassium chloride and potassium oxide on the surface after the alloy is solidified, and obtain the tin-silver-copper mixed rare earth lead-free solder with low silver content.

Embodiment 3

[0034] Add the mixed salt of potassium chloride:potassium oxide=(1~1.7):(0.8~1.3)(weight percent) into the melting furnace, after melting at 580°C, add 96.6% tin by weight; after the tin is completely melted, 1.5% by weight of Ag and 1.4% by weight of Cu are added to the tin liquid, stirred to form an alloy; at the same time, 0.5% by weight of La / Ce-based mixed rare earth is quickly added to the above alloy liquid, and continuously stirred until Until the rare earth is completely melted; keep the temperature at 460°C for 1.5 hours and stir to homogenize the alloy. After cooling, remove the mixed salt of potassium chloride and potassium oxide on the surface after the alloy is solidified, and obtain the tin-silver-copper mixed rare earth lead-free solder with low silver content.

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Abstract

The invention relates to a Sn-Ag-Cu misch metal lead-free solder with low content of Cu and a preparation method thereof. The method solves the problems of overhigh content of Ag and inferior brazing performance in current lead-free solder. The lead-free solder is composed of the following components by weight percent: 0.1-2.0% of Ag; 0.2%-2.5% of Cu; 0.1%-3.0% of misch metal; and Sn and unavoidable impurity elements as the balance. The preparation method thereof comprises the following steps: A: completely melting the metal Sn; B: adding the metal Ag and Cu into the molten metal of Sn and sufficiently stirring the molten metal to form alloy liquid; and C: adding the misch metal into the alloy liquid fast until the misch metal is completely molten, removing the mixed salt of potassium chloride and potassium oxide on the surface to result in the lead-free solder. The Sn-Ag-Cu misch metal lead-free solder with low content of Cu according to the invention has the advantages of low content of Ag, low cost, excellent brazing performance, etc.

Description

technical field [0001] The invention relates to a lead-free solder and a preparation method thereof, in particular to a tin-silver-copper mixed rare earth lead-free solder with low silver content and a preparation method thereof; it belongs to the field of surface assembly technology in the microelectronics industry. Background technique [0002] Due to the harm of lead to human beings, preventing lead pollution has become an irreversible trend in the world. Two EU directives, namely "Waste Electrical and Electronic Equipment Directive" (WEEE) and "Directive on the Prohibition of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment" (RoHS) have come into force. The promulgation of these environmental protection laws will make China's electronics manufacturing industry face new trade and technical barriers, requiring that power electronic products sold in the European market must be lead-free products, and lead-free solder is used in the field of sur...

Claims

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Application Information

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IPC IPC(8): B23K35/26B23K35/40
Inventor 余洪桂邓勇刘婷罗建吴芝锭
Owner 上海一远电子科技有限公司
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