CN1439480A - Oxidation-inhibited lead-free welding materials - Google Patents

Oxidation-inhibited lead-free welding materials Download PDF

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Publication number
CN1439480A
CN1439480A CN 03110895 CN03110895A CN1439480A CN 1439480 A CN1439480 A CN 1439480A CN 03110895 CN03110895 CN 03110895 CN 03110895 A CN03110895 A CN 03110895A CN 1439480 A CN1439480 A CN 1439480A
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solder
lead
free
alloy
oxidation
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CN 03110895
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CN1203960C (en
Inventor
吴建雄
吴建新
马鑫
王凤江
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YICHENGDA INDUSTRIAL Co Ltd SHENZHEN CITY
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YICHENGDA INDUSTRIAL Co Ltd SHENZHEN CITY
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Abstract

A non-lead welding material with antioxidizing power contains Ag (0.5-5 wt.%), Cu (0-2), P (0.01-1), and Sn (rest). It is possible to contain the mixture of La and Ce (0.01-1). Its advantages are excellent properties in solidified texture, mechanical performance and creep fatigue resistance, and high antioxidizing power.

Description

Lead-free solder with oxidation resistance
The technical field is as follows: the invention relates to a solder composition, in particular to a lead-free solder composition.
Background art: currently, the typical solder used in the electronics industry for electronic packaging and assembly is Sn-Pb alloy. Although Sn-Pb alloy has the characteristics of excellent wettability, weldability, electrical conductivity, mechanical property, lower cost andthe like, Pb and Pb-containing substances are toxic and harmful substances which are harmful to human health and pollute the environment. With the increasing development of environmental regulations and the increasing demand for prohibition of lead use, japan, the european union and the united states have successively made their own standards for lead-free solder, in which japanese enterprises have started to use lead-free solders in their products, and the european union has proposed that lead-free solders be used in their entirety in 2008 in the past COST lead-free solder alloy research project. Therefore, there is a need in the electronics industry for a lead-free solder alloy to replace the conventional Sn — Pb solder alloy. Sn-Ag-Cu alloys have good application prospects in the current lead-free solders, and are recommended by the American NEMI (national Electronics Manufacturing initiative), the British DTI (department of Trade and industry), the Soldertec (the Solder technology center) and the like. Based on the Sn-Ag-Cu system, U.S. Pat. No. 4,778,733 proposes a lead-free solder consisting of Sn-Ag (0.05-3%) -Cu (0.7-6%); U.S. patent 5,527,628 describes an alloy having a composition of 93.6Sn-4.7Ag-1.7 Cu; U.S. Pat. No. 5,863,493 shows Sn-Ag (2.0-5.0%) -Cu (0-2.9%) lead-free solders. In addition, U.S. Pat. No. 4,758,407 discloses addition of Ni element based on Sn-Ag (0-5.0%) -Cu (3.0-5.0%); the U.S. Pat. No. 6,179,935 discloses addition of trace elements Ni and Ge based on Sn-Ag (0-4.0%) -Cu (0-2.0%). The Sn-Ag-Cu solder has excellent comprehensive performance, but has poor wettability, coarse alloy structure and uneven distribution. On the other hand, since the content of Sn in the Sn-Ag-Cu based lead-free solder alloy is as high as 90 wt% or more, the amount of metal oxides generated is greatly increased in comparison with the conventional Sn-37Pb solder during use. Although the rare earth element RE is added in the Chinese patent CN1332057A to give the lead-free solder containing the rare earth element, the oxidation resistance of the solder is also reduced due to the existence of a large amount of Sn in the solder.
The invention content is as follows: the invention provides a lead-free solder with oxidation resistance, which solves the problem of low oxidation resistance of the existing lead-free solder. The lead-free solder comprises the following chemical components in percentage by weight: ag0.5-5, Cu0-2, P0.001-1 and Sn in balance. La and Ce mixed rare earth RE accounting for 0.01-1% of the weight of the solder can be added into the solder. The lead-free solder alloy according to the present invention does not use highly toxic lead in tin and lead which are basic compositions of solder, and has superior solderability to conventional solders. The function and the optimum content of each additive element in the present invention are described in detail below: the Ag can form Sn-Ag eutectic (Sn-3.5Ag, 221 ℃) with the Sn matrix to reduce the melting point of the solder and improve the mechanical property of the solder, and particularly, the Sn-Ag series solder has excellent creep fatigue resistance compared with the traditional Sn-Pb eutectic. If the amount of Ag added is less than 0.5%, these effects will not be significant. Addition of Ag of 5.0% or more causes a sharp increase in liquidus temperature of the solder alloy, resulting in an increase in soldering temperature and thus the electronic components may suffer thermal damage. The Ag content is preferably 1.0% to 4.0%, more preferably 3.0% to 4.0%. The addition of Cu can form ternary eutectic among Sn-Ag-Cu so as to reduce the melting point of the solder. The Cu element can also improve the wettability of the Sn-Ag solder. The existence of Cu element can also improve the strength of the solder to make up the defect of insufficient strength of Sn-Ag solder. The Sn-Ag-Cu eutectic solder also has higher strength. Also, when electroniccomponents are soldered to a printed circuit board to which copper foil leads are applied by means of dip soldering in a molten solder pot, Cu present in the molten solder pot has an additional effect of suppressing diffusion of copper in the copper foil leads into the molten solder pot. The copper content is preferably 0.1% to 2.0%, more preferably 0.1% to 1.0%. Since the present invention contains a large amount of tin (up to 90% or more) instead of lead, the amount of metal oxide generated on the surface of the molten solder in the solder pot is increased in practical use. Therefore, the addition of 0.001% -1% of the element P can effectively prevent the oxidation of the solder alloy, because of the skin effect of the element P, a very thin film is formed on the upper surface of the molten solder alloy in the solder pot, and by the oxidation reaction occurring on the solder surface:
direct contact of the solder alloy with the surrounding air may be hindered. On the other hand, the presence of the elements Ag and Cu in the solder also promotes this skin effect of P, thereby preventing further oxidation of the solder surface. If the amount of the element P added is less than 0.001%, such an oxidation preventing effect is not significant, and the addition of 1% or more of the element P deteriorates the solderability of the solder alloy. When P is addedThe P content in the alloy is preferably 0.005% to 0.5%, more preferably 0.005% to 0.1%. In the invention, a proper amount of rare earth element RE is also added to improve the structure of the solder, because the RE element can beSo as to promote the nucleation of the solder in the solidification process and play a role in homogenizing the deterioration of the solder structure, thereby improving the mechanical property of the solder alloy. The addition of RE can also significantly improve the creep fatigue resistance of the solder. If the RE content is less than 0.01%, the effect is not remarkable, and addition of more than 1% of RE results in deterioration of solder properties and an increase in melting point. When RE is added, the RE content in the alloy is preferably 0.05% to 0.5%. The solder of the present invention does not contain Pb due to the above-described effects of the respective components, and exhibits excellent characteristics in terms of solidification structure, mechanical properties, and creep fatigue resistance of the solder, as compared with conventional Sn-Ag-Cu solder alloys. The lead-free solder of the present invention having the above composition can be obtained by conventional smelting, i.e., Sn, Ag, Cu are supplied as metal raw materials, and RE and element P are required to be obtained by adding them in the form of an intermediate alloy, heating and stirring in a crucible, and casting. The solder alloy can be processed into the forms of solder bars, solder rods, solder wires, solder balls, solder paste and the like by the traditional process, thereby meeting the requirements of solder alloy for PCB assembly, SMT microelectronic surface packaging, surface mounting and the like. The invention aims to provide a lead-free solder alloy, which is added with mixed rare earth RE (a mixture of La and Ce) and an element P. Because the structure of the Sn-Ag-Cu solder mainly comprises Sn-rich phase and eutectic phase, the addition of RE can inhibit the coarse Sn-rich phase in the alloy solidification structure, namely, the homogenization of the solidification structure is realized through the modification effect on the solidification and crystallization process of the solder, thereby improving the mechanical property and the creep fatigue resistance of the solder alloy; the addition of the element P, the skin effect of the element P in the molten solder pot can reduce the generation amount of metaloxide on the surface of the solder pot and reduce the fraction defective during the welding of the PCB.
The first embodiment is as follows: the lead-free solder of the embodiment comprises the following components in percentage by weight: ag3.5, Cu0.7, P0.01 and the balance Sn.
The second embodiment is as follows: the lead-free solder of the embodiment comprises the following components in percentage by weight: ag3.5, Cu0.7, P0.05 and the balance Sn.
The third concrete implementation mode: the lead-free solder of the embodiment comprises the following components in percentage by weight: ag3.5, Cu0.7, P0.05, RE0.1 and the balance Sn.
The fourth concrete implementation mode: the lead-free solder of the embodiment comprises the following components in percentage by weight: ag3.5, Cu0.7, P0.05, RE0.4 and the balance Sn.
The conventional lead-free solder (containing ag 3.5%, cu 0.7%, sn95.8%) was now compared with the lead-free solders of the first to fourth embodiments described above (see table 1):
table 1 shows the comparison between the embodiment of the present invention and the conventional SnAgCu lead-free solder
Alloy composition (% by weight) Melting Point (. degree.C.) Spreading factor (％)
Sn Ag Cu P RE Solidus line Liquidus line
Implementation mode one 95.79 3.5 0.7 0.01 215 224 81.46
Second embodiment 95.75 3.5 0.7 0.05 215 223 76.59
Third embodiment 95.65 3.5 0.7 0.05 0.1 217 225 77.61
Embodiment IV 95.35 3.5 0.7 0.05 0.4 215 222 83.03
Conventional example 95.8 3.5 0.7 217 218 79.97
In addition, in order to observe the influence of the additive elements P and RE in the conventional Sn-3.5Ag-0.7Cu solder on the wettability of the solder on the surface of the Cu plate, the solder alloys of the above embodiment and conventional example were subjected to wettability tests, and the results are shown in Table 1. It was found that the wettability of the solder was not greatly affected by the addition of small amounts of P and RE, but when the rare earth content was high, the spreading rate of the solder alloy on the surface of the Cu plate was slightly improved as compared with the conventional example solder as in embodiment three. The embodiment of the invention and the conventional example are also subjected to an oxidation resistance test, namely the solder is kept at the temperature of 280 ℃ for 17.5 hours to observe the burning loss rate of the solder, and the specific test result is shown in table 1. It can be seen that the addition of P (embodiment 1 and embodiment 2) to the conventional SnAgCu (comparative example) can significantly enhance the oxidation resistance of the solder, especially when the P content is 0.01%; on the contrary, when the content of P is higher, the oxidation resistance of the solder is lowered, but still higher than that of the conventional example in which the element P is not added. In the case of rare earth addition, P also has a significant effect of enhancing the oxidation resistance of the solder when the rare earth content is low, but when the rare earth content is high, the oxidation resistance of the solder is lower than that of the traditional SnAgCu lead-free solder even when the element P is added.
Table 2 shows the comparison of the oxidation resistance of the embodiment of the present invention and the conventional SnAgCu lead-free solder
Basis weight (g) Residual weight (g) Burning loss (g) Rate of burn out (％) Time of heat preservation (h) Temperature of heat preservation (℃)
Implementation mode one 31.38 31.3124 0.0676 0.215 17.5 280
Second embodiment 31.38 31.1213 0.2587 0.824 17.5 280
Third embodiment 31.38 31.1629 0.2171 0.692 17.5 280
Embodiment IV 31.38 29.3445 2.0355 6.487 17.5 280
Conventional example 31.38 30.7687 0.6113 1.948 17.5 280

Claims (6)

1. The lead-free solder with oxidation resistance is characterized by comprising the following chemical components in percentage by weight: ag0.5-5, Cu0-2, P0.001-1 and Sn in balance.
2. The lead-free solder with oxidation resistance according to claim 1, wherein the content of Ag in the solder is 1% to 4% by weight of the solder.
3. The lead-free solder with oxidation resistance as set forth in claim 1, wherein the content of Cn in the solder is 0.1-2% by weight of the solder.
4. The lead-free solder with oxidation resistance according to claim 1, wherein the content of P in the solder is 0.005% -0.5% by weight of the solder.
5. The lead-free solder with oxidation resistance according to claim 1, 2, 3 or 4, characterized in that RE is further added to the solder in an amount of 0.01-1% by weight of the solder.
6. The lead-free solder with oxidation resistance according to claim 1, 2, 3 or 4, characterized in that RE is added to the solder in an amount of 0.05-0.5% by weight of the solder.
CN 03110895 2003-01-15 2003-01-15 Oxidation-inhibited lead-free welding materials Expired - Lifetime CN1203960C (en)

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CN1203960C CN1203960C (en) 2005-06-01

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007014529A1 (en) * 2005-08-02 2007-02-08 Jusheng Ma A low melting point lead-free solder alloy
US7335269B2 (en) 2005-03-30 2008-02-26 Aoki Laboratories Ltd. Pb-free solder alloy compositions comprising essentially Tin(Sn), Silver(Ag), Copper(Cu), and Phosphorus(P)
CN1977368B (en) * 2004-06-01 2010-04-07 千住金属工业株式会社 Soldering method, solder pellet for die bonding, method for manufacturing solder pellet for die bonding and electronic component
AU2006278029B2 (en) * 2005-08-05 2011-11-17 Grillo-Werke Aktiengesellschaft Method for arc or beam brazing/welding of workspieces of identical or different metals or metal alloys with additional materials of Sn base alloys; Sn base alloy wire
CN102581514A (en) * 2012-03-16 2012-07-18 金华市金钟焊接材料有限公司 Silver solder containing phosphorus, stannum and rare earth
CN103028862A (en) * 2011-09-29 2013-04-10 江苏天瑞仪器股份有限公司 Flux and process used for welding six-level rod of mass spectrometer on fixing plate
CN103273217A (en) * 2013-05-29 2013-09-04 哈尔滨工业大学深圳研究生院 Partially-reinforced high-reliability brazing filler metal and preparing method thereof
CN103586600A (en) * 2013-11-12 2014-02-19 宁波市鄞州恒迅电子材料有限公司 Lead-free soldering tin alloying pellet
CN105834611A (en) * 2016-05-04 2016-08-10 中南大学 High-electrical-conductivity and high-reliability Ce-Sn-Ag-Cu solder suitable for electronic packaging
CN113416866A (en) * 2021-06-29 2021-09-21 南京青锐风新材料科技有限公司 Lead-free solder oxidation resistant alloy and production and preparation process thereof
CN114055012A (en) * 2021-11-05 2022-02-18 安徽工业大学 Multi-element copper-based alloy brazing filler metal containing rare earth elements, preparation method and brazing method thereof

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1977368B (en) * 2004-06-01 2010-04-07 千住金属工业株式会社 Soldering method, solder pellet for die bonding, method for manufacturing solder pellet for die bonding and electronic component
US7335269B2 (en) 2005-03-30 2008-02-26 Aoki Laboratories Ltd. Pb-free solder alloy compositions comprising essentially Tin(Sn), Silver(Ag), Copper(Cu), and Phosphorus(P)
WO2007014529A1 (en) * 2005-08-02 2007-02-08 Jusheng Ma A low melting point lead-free solder alloy
AU2006278029B2 (en) * 2005-08-05 2011-11-17 Grillo-Werke Aktiengesellschaft Method for arc or beam brazing/welding of workspieces of identical or different metals or metal alloys with additional materials of Sn base alloys; Sn base alloy wire
CN103028862B (en) * 2011-09-29 2015-08-26 江苏天瑞仪器股份有限公司 For mass spectrometric six grades of bars being welded on solder flux on fixed head and technique
CN103028862A (en) * 2011-09-29 2013-04-10 江苏天瑞仪器股份有限公司 Flux and process used for welding six-level rod of mass spectrometer on fixing plate
CN102581514B (en) * 2012-03-16 2015-06-03 金华市金钟焊接材料有限公司 Silver solder containing phosphorus, stannum and rare earth
CN102581514A (en) * 2012-03-16 2012-07-18 金华市金钟焊接材料有限公司 Silver solder containing phosphorus, stannum and rare earth
CN103273217A (en) * 2013-05-29 2013-09-04 哈尔滨工业大学深圳研究生院 Partially-reinforced high-reliability brazing filler metal and preparing method thereof
CN103273217B (en) * 2013-05-29 2016-01-13 哈尔滨工业大学深圳研究生院 High reliability solder of a kind of local strengthening and preparation method thereof
CN103586600A (en) * 2013-11-12 2014-02-19 宁波市鄞州恒迅电子材料有限公司 Lead-free soldering tin alloying pellet
CN105834611A (en) * 2016-05-04 2016-08-10 中南大学 High-electrical-conductivity and high-reliability Ce-Sn-Ag-Cu solder suitable for electronic packaging
CN113416866A (en) * 2021-06-29 2021-09-21 南京青锐风新材料科技有限公司 Lead-free solder oxidation resistant alloy and production and preparation process thereof
CN114055012A (en) * 2021-11-05 2022-02-18 安徽工业大学 Multi-element copper-based alloy brazing filler metal containing rare earth elements, preparation method and brazing method thereof

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Denomination of invention: Lead free solder with oxidation resistance

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