CN101491866B - Low-temperature leadless cored solder alloy and produced solder paste - Google Patents
Low-temperature leadless cored solder alloy and produced solder paste Download PDFInfo
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- CN101491866B CN101491866B CN200810065651.3A CN200810065651A CN101491866B CN 101491866 B CN101491866 B CN 101491866B CN 200810065651 A CN200810065651 A CN 200810065651A CN 101491866 B CN101491866 B CN 101491866B
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Abstract
The invention discloses a low-temperature lead-free soldering paste. As an SMT solder, the low-temperature lead-free brazing solder alloy is improved by adding 0.5 to 3 weight percent of Ag or 0.1 to 1.0 weight percent of Cu into a system which takes Sn-58Bi as a main component. The solder alloy after the improvement improves wetting property and welding spot strength. The soldering paste of solder alloy powder containing the Ag and the Cu can provide good wettability and reliability, meet the requirements of a solder alloy and soldering paste needed by SMT, and is particularly applicable to occasions where the low-temperature application is needed.
Description
Technical field
The present invention relates to a kind of low temperature lead-free solder alloy, relate in particular to a kind of solder(ing) paste made from this solder alloy composition.
background technology
Along with the enhancing of people's environmental consciousness, the Sn-Pb soft soldering alloy that in electronics industry, tradition adopts starts to be replaced by no-lead soft soldering gradually.
In presently used no-lead soft soldering, composition is mainly Sn-Cu, Sn-Ag and Sn-Ag-Cu system.Take these systems as basis, can improve the performance of solder alloy by adding alloying element.For example on Sn-Ag (3.5-6.0%) basis, add micro-Ni to suppress Cu to the diffusion in soldering alloy.Japan Nihon proposes the leadless solder being made up of Sn-(0.3-0.7) Cu-(0.04-0.1) Ni in U.S. Pat 6180055 on the basis with SnCu eutectic composition, element Ni can suppress Cu to the dissolving in fusion welding, reduces the possibility that Cu occurs to the dissolution velocity in molten solder and bridging.
The fusing point of these solder compositions respectively between 217-227 ℃, the Sn-37Pb scolder fusing point (183 ℃) using higher than tradition far away.In use, this just needs wave-soldering tin-soldering temperature is 250-265 ℃, and in reflow process, peak temperature is 240-245 ℃.Particularly, in SMT reflow process, used solder(ing) paste, solder(ing) paste contains and the mixed uniformly solder powder of scaling powder, the solder powder particularly mixing with rosin flux homogeneous.Conventionally, in reflow soldering, by printing or disperseing, solder(ing) paste is provided on printed circuit board (PCB), utilizes the adhesive attraction of solder(ing) paste, the electronic component of chip type is adsorbed temporarily and is connected on printed circuit board (PCB).Therefore,, in reflow soldering, the electronic component that install is exposed under welding temperature equally.The homogeneous heating ability of so high welding temperature to welding equipment and the temperature capacity of components and parts are all huge tests.
Given this, it is US6503338 that the patent No. has been declared by Japanese Senju company, the leadless welding alloy that composition is Sn-8Zn-3Bi, and fusing point is 192-197 ℃, close to the fusing point of Sn-37Pb scolder.But, up to now, still have components and parts still can not bear so high welding temperature, need to use the solder alloy that fusing point is lower.Therefore Sn-Bi brazing filler metal alloy just becomes a kind of selection, and the fusing point of Sn-58Bi eutectic solder is 138 ℃, can meet the requirement of welding temperature.But Bi is a kind of oxidizable alloying element, the scaling powder of Sn-Bi solder alloy is had relatively high expectations, and in welding process, fusion welding is poor along the climbing ability of component's feet and the wettability on pad, the corresponding intensity that also reduces solder joint.
As countermeasure, in order to improve these bad shortcomings of Sn-Bi solder alloy, can wherein add other alloying element in the past and improve its performance.
summary of the invention
The object of the present invention is to provide a kind of low-temperature and lead-free tin soldering cream.
A kind of low-temperature and lead-free tin soldering cream of the present invention, solder(ing) paste includes this low-temperature lead-free cored solder alloy and the solder paste as solder flux, this low-temperature lead-free cored solder alloy is to add alloying element Ag and Cu in existing Sn-Bi solder system, wherein the percentage by weight component of middle Sn, Bi, Ag respectively: Sn accounts for 35-65%, Bi accounts for 35-65%, Ag accounts for 0.2-6%, in the brazing filler metal alloy powder of this low-temperature lead-free cored solder alloy, also contains Cu, and its percentage by weight component is 0.1-3.0%.
The brazing filler metal alloy powder of above-mentioned low-temperature lead-free cored solder alloy contains Sn, Bi, Ag and the Cu in its amount of powder, and the percentage by weight component that this Sn, Bi, Ag and Cu are is 88-91%.
Above-mentioned Sn-58Bi is brazing filler metal alloy powder, and with Sn-3.5Ag brazing filler metal alloy powder and Sn-3.8Ag-0.7Cu brazing filler metal alloy powder take according to Sn-58Bi percentage by weight as 65-90%, Sn-3.5Ag percentage by weight is 8-20%, and the ratio of Sn-3.8Ag-0.7Cu percentage by weight 4-10% is evenly mixed
Leadless solder involved in the present invention does not use the lead of hypertoxicity in as the basic composition of solder, belongs to feature of environmental protection leadless solder.
Leadless solder involved in the present invention, fusing point, between 138-155 ℃, welds needed temperature between 170-195 ℃, well below the Welding Problems of traditional Sn-37Pb and Sn-Cu, Sn-Ag, Sn-Ag-Cu no-lead soft soldering.Requirement to welding equipment heating efficiency and components and parts heat resisting temperature reduces greatly.
Describe each effect and optimum content thereof that adds element in present embodiment below in detail.
Add Bi and can form with Sn binary low melting point eutectic scolder at 58wt.%Bi, 138 ℃ time.Bismuth element is to form the basic of solder alloy with tin element.The preferable range of bi content is 40-60wt.%, and preferred content range is 45-60wt.%.
Add Ag and can improve the wetability of solder alloy, the intensity of solder joint, under the condition existing at 0.2-6.0wt.%Ag, also change indistinctively the fusing point of Sn-Bi solder alloy, thereby do not affect low melting point or the low-temperature characteristics of invented leadless solder.The preferable range of silver content is 0.5-4wt.%, and preferred content range is 0.5-3wt.%.
Add Cu and can further improve the intensity of solder alloy and the intensity of the solder joint that forms.The preferable range of copper content is 0.1-2.0wt.%, and preferred content range is 0.1-1.0wt.%.
The lead-free brazing of the present invention with above-mentioned composition can be smelted by conventional method, and Sn, Bi, Ag, Cu, with raw metal supply, heat and stir in crucible, and casting can obtain brazing filler metal alloy.Brazing filler metal alloy of the present invention can be processed to form by traditional handicraft the form of soldering tin bar, solder bar, solder stick, solder ball and solder(ing) paste etc., thereby can meet the needed brazing filler metal alloys such as PCB assembling, SMT microelectronics surface encapsulation and surface mount, particularly need the occasion of cryogenic applications.
The solder(ing) paste using in SMT is by mixing the manufactures of solder powder and weld-aiding cream.The typical system of weld-aiding cream is abietyl weld-aiding cream, and this abietyl weld-aiding cream is by using rosin as key component, is dissolved in solvent and forms together with other additive for example thixotropic agent, activator.Weld-aiding cream requires to have insulating properties and corrosion resistance highly reliably.There is the solder powder of leadless solder of the present invention of above-mentioned composition except as stated above directly by pure Sn, Bi, Ag, outside Cu metal molten dusts after smelting and makes, provide a kind of preparation method of the solder(ing) paste based on this solder alloy composition below: Sn-3.5Ag or other Sn-Ag composition and Sn-58Bi or other Sn-Bi composition, or Sn-Ag-Cu and Sn-58Bi or other Sn-Bi composition, or Sn-3.5Ag or other Sn-Ag composition, Sn-0.7Cu or other Sn-Cu composition mix in proportion with the solder powder of Sn-58Bi or other Sn-Bi composition, thereby obtain respectively having Sn-Ag-Bi or the Sn-Ag-Cu-Bi solder powder of above-mentioned composition.In this inventive method, the relatively easy patent composition of making and can not invade others of Sn-3.5Ag or other Sn-Ag composition, Sn-0.7Cu or other Sn-Cu composition, Sn-Ag-Cu, Sn-58Bi or other Sn-Bi composition, on market, buying is arrived easily, thereby can make easily the solder(ing) paste of the leadless solder of the present invention with above-mentioned composition.
Accompanying drawing explanation
Fig. 1 is embodiment 1, embodiment 2 and comparative example 1 the wettability equilibrium curve of description soft soldering alloy at 180 ℃;
Fig. 2 is low temperature reflux welding temperature curve;
Fig. 3 is high temperature reflux welding temperature curve;
Fig. 4 is QFP pin pull-off strength test method.
The specific embodiment
According to present embodiment in detail the present invention is described in detail, but the scope of the invention is not to be limited to the embodiment that proposed here.In the following description, the percentage of all about alloying component is all percetage by weight.
Embodiment 1, leadless solder is by 58%Bi, 1%Ag, and remainder is 41%Sn composition.
Embodiment 3,75% the spherical powder based on Sn-58Bi leadless welding alloy, 15% the spherical powder based on Sn-3.5Ag leadless welding alloy are thoroughly mixed to prepare solder(ing) paste with 10% the weld-aiding cream based on rosin, described solder(ing) paste has 48.33%Bi, 0.583%Ag, remainder is the soldering alloy composition of 51.087%Sn composition, and solder powder proportion in solder(ing) paste is 90%.Described weld-aiding cream is based on following composition, belong to typical abietyl system: 45% Foral, 45% propylene glycol monomethyl ether, 2% diphenylguanidine HBr, 5% modified hydrogenated castor oil, 1% malonic acid, 2% dibromo butene glycol, dissolve making completely through heating and obtain, weld-aiding cream proportion in solder(ing) paste is 10%.
Comparative example 1, leadless solder is by 58%Bi, and remainder is 42%Sn.
Comparative example 2, thoroughly mixes to prepare solder(ing) paste by 90% the spherical powder based on Sn-58Bi leadless welding alloy with 10% the weld-aiding cream based on rosin.Described weld-aiding cream is based on following composition, belong to typical abietyl system: 45% Foral, 45% propylene glycol monomethyl ether, 2% diphenylguanidine HBr, 5% modified hydrogenated castor oil, 1% malonic acid, 2% dibromo butene glycol, dissolve making completely through heating and obtain.
(1) wetting test
According to the 4th part " the wettability test method based on wettability equilibrium method and contact angle method " in the JIS Z3198 of Japanese Industrial Standards " lead-free solder test method " to embodiment 1 and 2 and the leadless solder that obtains of comparative example 1 adopt wettability equilibrium instrument to carry out wetability test.Testing substrates is Cu plate, adopts active abietyl scaling powder, and test result is shown in Fig. 1.
In wettability equilibrium curve, the time that intersects of curve and abscissa represents the wetting time of soft soldering alloy, the maximum wetting power characterized of it and curve goes out the wettability of soft soldering alloy, wetting time is shorter, wetting power is larger, shows that the wetability of soft soldering alloy is better.Wetting time and the wetting power of embodiment 1 described solder alloy are respectively 0.751s and 3.53mN, and wetting time and the wetting power of embodiment 2 described solder alloys are respectively 0.673s and 3.47mN.Wetting time and the wetting power of comparative example 1 described solder alloy are respectively 0.797s and 2.73mN.Embodiment 1 and 2 has shorter wetting time and the wetting power of Geng Gao compared with comparative example 1, has reflected that the more traditional Sn-58Bi solder alloy of solder alloy described in the invention has better wetability.
(2) thermal reflow profile
By embodiment 3 and 4 and the solder(ing) paste that obtains of comparative example 2 and 3 by serigraphy on pcb board, the upper corresponding pad of PCB is the standard QFP pad that 208 pins, spacing are 0.4mm, then stick QFP components and parts, cross reflow soldering and weld also slowdown monitoring circuit plate surface thermal reflow profile, realize the temperature curve of good welding and see Fig. 2 and Fig. 3.The Sn-Bi base solder(ing) paste that embodiment 3, embodiment 4 and comparative example 2 obtain is at the temperature described in Fig. 2, and solder alloy melts, and has realized the good welding between QFP components and parts and pcb board pad.And the Sn-Ag-Cu base leadless soldering tin paste that comparative example 3 obtains need to could be realized molten solder under temperature curve that Fig. 3 describes.The peak temperature of Fig. 2 and thermal reflow profile that Fig. 3 describes is respectively 180-190 ℃ and 245 ℃.Illustrate that soft soldering alloy described in the invention is a kind of solder alloy, its Peak temperature is less than 200 ℃, and the welding temperature of more conventional Sn-Ag-Cu leadless welding alloy is low approximately 50 ℃.Therefore, adopt the heating efficiency of solder alloy described in the invention to welding equipment and the heat-resisting requirement of components and parts greatly to reduce.
(3) pull-off strength of solder joint that solder alloy forms
According to the 6th part in the JISZ3198 of Japanese Industrial Standards " lead-free solder test method " " the miter angle pull-off test method of QFP lead solder-joint " to embodiment 3 and 4 and the no-lead soft soldering solder(ing) paste that obtains of comparative example 2 after above-mentioned reflow soldering, the printed circuit board (PCB) level QFP assembly obtaining is fixed in particular jig, then stretch to measure the intensity of solder joint along miter angle method, as Fig. 4.
Table 1 has provided embodiment 3 and 4 and 45 degree tensile strength test results of the no-lead soft soldering solder(ing) paste that obtains of comparative example 2 QFP pin after reflow soldering.Can find out, the QFP solder joint that the more traditional Sn-58Bi leadless solder of the QFP solder joint forming based on Sn-Ag-Bi leadless solder and based on Sn-Ag-Cu-Bi leadless solder that the present invention describes forms has higher pull-off strength.
The pull-off strength result of table 1 solder alloy
| Solder alloy | Embodiment 3 | |
Comparative example 2 |
| Measured value (gf) | 418.6 | 422.8 | 409.2 |
| 540.8 | 613.9 | 524.1 | |
| 549.1 | 564.8 | 433.2 | |
| 467.7 | 599.2 | 407.1 | |
| 573.1 | 611.8 | 469.8 | |
| 482.1 | 499.9 | 501.1 | |
| 500.1 | 480.2 | 489.6 | |
| 659.8 | 421.7 | 407.1 | |
| 531.4 | 458.3 | 441.6 | |
| 553.3 | 467.7 | 434.3 | |
| 657.7 | 502.0 | 531.4 | |
| 583.6 | 472.3 | 445.8 | |
| Mean value (gf) | 543.1 | 514.0 | 457.8 |
Claims (1)
1. a low-temperature and lead-free tin soldering cream, solder(ing) paste includes this low-temperature lead-free cored solder alloy and the solder paste as solder flux, it is characterized in that, described low-temperature lead-free cored solder alloy is to add alloying element Ag and Cu in existing Sn-Bi solder system, in the brazing filler metal alloy powder of this low-temperature lead-free cored solder alloy, the percentage by weight component of Sn, Bi, Ag and Cu respectively: Bi accounts for 40%, Ag accounts for 0.2%, Cu and accounts for 0.1-1.0%, and surplus is Sn;
Described low-temperature lead-free cored solder alloy by Sn-58Bi brazing filler metal alloy powder, Sn-3.5Ag brazing filler metal alloy powder and Sn-3.8Ag-0.7Cu brazing filler metal alloy powder take according to Sn-58Bi percentage by weight as 65-90%, Sn-3.5Ag percentage by weight is 8-20%, and the ratio of Sn-3.8Ag-0.7Cu percentage by weight 4-10% is evenly mixed.
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Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102909362B (en) * | 2012-10-15 | 2015-11-18 | 江苏博迁新材料有限公司 | Sub-micron solder alloy powder and preparation method thereof |
| JP2014146652A (en) * | 2013-01-28 | 2014-08-14 | Toppan Printing Co Ltd | Wiring board and method of manufacturing the same |
| CN104043911B (en) * | 2014-06-27 | 2017-08-08 | 深圳市汉尔信电子科技有限公司 | A kind of lead-free solder and its welding method for forming uniform formation's solder joint |
| CN104942461A (en) * | 2015-04-14 | 2015-09-30 | 中山市智牛电子有限公司 | Tin paste preparation method |
| CN105880872A (en) * | 2016-06-03 | 2016-08-24 | 广东昭信照明科技有限公司 | Brazing material and preparing method thereof |
| CN105921840B (en) * | 2016-06-03 | 2018-08-14 | 广东昭信照明科技有限公司 | A kind of soldering processes |
| CN106180939A (en) * | 2016-08-05 | 2016-12-07 | 苏州锡友微连电子科技有限公司 | The soldering paste of laser reflow weldering |
| CN106271217A (en) * | 2016-09-23 | 2017-01-04 | 工业和信息化部电子第五研究所华东分所 | A kind of disposable halogen-free scaling powder and low temperature solder stick |
| JP6619387B2 (en) * | 2017-06-08 | 2019-12-11 | 株式会社タムラ製作所 | Lead-free solder alloy |
| CN107088716B (en) * | 2017-07-03 | 2020-01-24 | 中山翰华锡业有限公司 | Environment-friendly low-temperature residue-free solder paste and preparation method thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1282286A (en) * | 1997-12-16 | 2001-01-31 | 株式会社日立制作所 | Pb-free solder-connected structure and electronic device |
| JP2002001573A (en) * | 2000-06-16 | 2002-01-08 | Nippon Handa Kk | Leadless cream solder and bonding method using the same |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1282286A (en) * | 1997-12-16 | 2001-01-31 | 株式会社日立制作所 | Pb-free solder-connected structure and electronic device |
| JP2002001573A (en) * | 2000-06-16 | 2002-01-08 | Nippon Handa Kk | Leadless cream solder and bonding method using the same |
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