LOW MELTING TEMPERATURE COMPLIANT SOLDERS
Low melting temperature compliant solders are disclosed. In one particular exemplary embodiment, a low melting temperature compliant solder alloy comprises from about 91.5% to about 97.998% by weight tin, from about 0.001% to about 3.5% by weight silver, from about 0.0% to about 1.0% by weight copper, and from about 2.001% to about 4.0% by weight indium.
Latest Indium Corporation of America Patents:
- Technique for increasing the compliance of tin-indium solders
- Technique for increasing the compliance of lead-free solders containing silver
- Method for fabricating large dimension bonds using reactive multilayer joining
- Technique for forming a thermally conductive interface with patterned metal foil
- MATERIALS HAVING INCREASED MOBILITY AFTER HEATING
This patent application claims priority to U.S. Provisional Patent Application No. 60/720,039, filed Sep. 26, 2005, which is hereby incorporated by reference herein in its entirety.
FIELD OF THE DISCLOSUREThe present disclosure relates generally to solder compositions and, more particularly, to low melting temperature compliant solders.
BACKGROUND OF THE DISCLOSUREAs feature sizes of semiconductor devices continue to shrink, low dielectric constant (low K) materials are more frequently employed to replace conventional insulators (e.g., silicon oxide) in the manufacturing of semiconductor devices. Currently, carbon-doped silicon oxide (SiOC) (K˜2.5-3) is the industry's primary choice for a low K material in the manufacturing of semiconductor devices.
Carbon-doped silicon oxide (SiOC) typically comprises numerous air pockets to improve low K performance. However, these air pockets make this low K material very brittle and susceptible to fracture. Consequently, during electronic packaging and assembly processes, this low K material is known to crack due to stresses generated during soldering processes. In particular, solder paste reflow processes require reflow temperatures approximately 20-30° C. above the liquidus temperatures of solder alloys. For example, for a conventional Sn63Pb37 solder paste, the reflow temperature is typically around 210-230° C. However, the recent conversion to Sn—Ag—Cu lead free solder alloys has resulted in a great increase in reflow temperatures to typically around 235-260° C. The liquidus temperatures and yield strengths of some of these Sn—Ag—Cu lead free solder alloys is summarized in the table of
Due to the higher liquidus temperatures (>218° C.) of the Sn—Ag—Cu lead free solder alloys and mismatches in coefficients of thermal expansion between these Sn—Ag—Cu lead free solder alloys and low K materials, high stresses develop in low K materials during cooling from high temperature reflow processes and thus cause cracking and failures in the low K materials. In light of the above, solder alloys with lower melting temperatures are required.
In addition to the requirement for solder alloys with low liquidus temperatures, the ability of a solder to deform to accommodate possible stresses or impact loading is critical to the reliability of electronic devices employing low k materials. In general, solders with low yield strengths are softer and easier to deform so as to relieve stresses. Common low melting temperature solder alloys presently consist mainly of generic 91Sn9Zn solder alloy and patented Sn—Ag—In and Sn—Ag—Cu—In solder alloys. However, in comparison with Sn—Ag—Cu solder alloys, these common low melting temperature solder alloys are at least 50% greater in yield strength and rigidity. A brief summary of these common low melting temperature solder alloys is provided in the table of
As shown in
In view of the foregoing, it would be desirable to provide low melting temperature compliant solders which overcome the above-described inadequacies and shortcomings.
SUMMARY OF THE DISCLOSURELow melting temperature compliant solders are disclosed. In one particular exemplary embodiment, a low melting temperature compliant solder alloy comprises from about 91.5% to about 97.998% by weight tin, from about 0.001% to about 3.5% by weight silver, from about 0.0% to about 1.0% by weight copper, and from about 2.001% to about 4.0% by weight indium.
In accordance with other aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy may comprise at most about 3.0% by weight indium.
In accordance with further aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy may comprise at most about 2.5% by weight indium.
In accordance with still further aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy may further comprise traces of impurities.
In accordance with still further aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy does not comprise traces of impurities.
In accordance with additional aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy may further comprise from about 0.01% to about 3.0% by weight at least one dopant selected from the group consisting of zinc (Zn), nickel (Ni), iron (Fe), cobalt (Co), germanium (Ge), phosphorus (P), aluminum (Al), antimony (Sb), cadmium (Cd), tellurium (Te), bismuth (Bi), platinum (Pt), rare earth elements, and combinations thereof to improve oxidation resistance and increase physical properties and thermal fatigue resistance.
In accordance with still additional aspects of this particular exemplary embodiment, the rare earth elements may be selected from the group consisting of cerium (Ce), lanthanum (La), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), actinium (Ac), thorium (Th), protactinium (Pa), and combinations thereof.
In another particular exemplary embodiment, a low melting temperature compliant solder alloy comprises from about 89.7% to about 94.499% by weight tin, from about 3.5% to about 6.0% by weight silver, from about 0.0% to about 0.3% by weight copper, and from about 2.001% to about 4.0% by weight indium.
In accordance with other aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy may comprise at most about 3.0% by weight indium.
In accordance with further aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy may comprise at most about 2.5% by weight indium.
In accordance with still further aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy may further comprise traces of impurities.
In accordance with still further aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy does not comprise traces of impurities.
In accordance with additional aspects of this particular exemplary embodiment, the low melting temperature compliant solder alloy may further comprise from about 0.01% to about 3.0% by weight at least one dopant selected from the group consisting of zinc (Zn), nickel (Ni), iron (Fe), cobalt (Co), germanium (Ge), phosphorus (P), aluminum (Al), antimony (Sb), cadmium (Cd), tellurium (Te), bismuth (Bi), platinum (Pt), rare earth elements, and combinations thereof to improve oxidation resistance and increase physical properties and thermal fatigue resistance.
In accordance with still additional aspects of this particular exemplary embodiment, the rare earth elements may be selected from the group consisting of cerium (Ce), lanthanum (La), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), actinium (Ac), thorium (Th), protactinium (Pa), and combinations thereof.
The present disclosure will now be described in more detail with reference to exemplary embodiments thereof as shown in the accompanying drawings. While the present disclosure is described below with reference to exemplary embodiments, it should be understood that the present disclosure is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein, and with respect to which the present disclosure may be of significant utility.
BRIEF DESCRIPTION OF THE DRAWINGSIn order to facilitate a fuller understanding of the present disclosure, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the present disclosure, but are intended to be exemplary only.
Referring to
However, adding indium (In) to the standard Sn—Ag—Cu (SAC) alloys also results in a rapid increase of the yield strength due to solution hardening, and high strength Sn—Ag—Cu—In alloys may cause high stresses and unacceptable high defects. Thus, it would be beneficial to determine compositional ranges for Sn—Ag—Cu—In alloys that result in low liquidus temperatures, low yield strength, and low rigidity. Indeed, the present disclosure is directed to Sn—Ag—Cu—In alloy compositions exhibiting low liquidus temperatures, low yield strength, and low rigidity. Such Sn—Ag—Cu—In alloy compositions include Ag(0.001-3.5)%, Cu(0-1)%, In(2.001-4)%, balanced with Sn, and Ag(3.5-6)%, Cu(0-0.3)%, In(2.001-4)%, balanced with Sn. These Sn—Ag—Cu—In alloy compositions were derived through a series of multiple experimentations as exemplified below.
EXAMPLE 1 The liquidus temperatures and yield strengths of indium (In) added Sn-1Ag-0.5Cu alloy compositions with respect to the concentration of indium (In) are shown in the table of
The liquidus temperatures and yield strengths of indium (In) added Sn-2Ag-0.5Cu alloy compositions with respect to the concentration of indium (In) are shown in the table of
The yield strengths of the resultant alloy compositions remained about constant as the concentration of indium (In) increased up to 2.5%. However, when the concentration of indium (In) exceeded 2.5%, the yield strengths increased as the concentration of indium (In) increased.
EXAMPLE 3 The liquidus temperatures and yield strengths of indium (In) added Sn-2.5Ag-0.5Cu alloy compositions with respect to the concentration of indium (In) are shown in the table of
The liquidus temperatures and yield strengths of indium (In) added Sn-3Ag-0.5Cu alloy compositions with respect to the concentration of indium (In) are shown in the table of
The liquidus temperatures and yield strengths of indium (In) added Sn-4Ag-0.2Cu alloy compositions with respect to the concentration of indium (In) are shown in the table of
The yield strengths of the Sn—Ag—Cu—In alloys with respect to the concentration of indium (In) are shown in the graph of
In order to obtain a better understanding of the above results, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were performed on the above mentioned alloys. For example,
In addition, it has been discovered that solution hardening of indium was typically the main mechanism for strengthening Sn—Ag—Cu—In solder alloys. However, in the Sn—Ag—Cu—In compositions of the present disclosure, indium (In) is removed from the solution, thus reducing the solution hardening effect, and instead forms the off-stoichiometric Sn66.6Ag29.4In4 particles, which did not strengthen the alloy as much as the replaced stoichiometric Ag3Sn particles. As a result of the above-mentioned effects, the yield strengths of the presently disclosed indium (In) added Sn—Ag—Cu alloy compositions decrease as the concentration of indium (In) increases (i.e., between (2.001-4)% In).
The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.
Claims
1. A low melting temperature compliant solder alloy consisting essentially of from about 91.5% to about 97.998% by weight tin, from about 0.001% to about 3.5% by weight silver, from about 0.0% to about 1.0% by weight copper, and from about 2.001% to about 4.0% by weight indium.
2. The low melting temperature compliant solder alloy of claim 1, wherein the alloy comprises at most about 3.0% by weight indium.
3. The low melting temperature compliant solder alloy of claim 1, wherein the alloy comprises at most about 2.5% by weight indium.
4. The low melting temperature compliant solder alloy of claim 1, wherein the alloy includes traces of impurities.
5. The low melting temperature compliant solder alloy of claim 1, wherein the alloy does not include traces of impurities.
6. The low melting temperature compliant solder alloy of claim 1, further consisting of from about 0.01% to about 3.0% by weight at least one dopant selected from the group consisting of zinc (Zn), nickel (Ni), iron (Fe), cobalt (Co), germanium (Ge), phosphorus (P), aluminum (Al), antimony (Sb), cadmium (Cd), tellurium (Te), bismuth (Bi), platinum (Pt), rare earth elements, and combinations thereof to improve oxidation resistance and increase physical properties and thermal fatigue resistance.
7. The low melting temperature compliant solder alloy of claim 6, wherein the rare earth elements are selected from the group consisting of cerium (Ce), lanthanum (La), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), actinium (Ac), thorium (Th), protactinium (Pa), and combinations thereof.
8. A low melting temperature compliant solder alloy consisting essentially of from about 89.7% to about 94.499% by weight tin, from about 3.5% to about 6.0% by weight silver, from about 0.0% to about 0.3% by weight copper, and from about 2.001% to about 4.0% by weight indium.
9. The low melting temperature compliant solder alloy of claim 8, wherein the alloy comprises at most about 3.0% by weight indium.
10. The low melting temperature compliant solder alloy of claim 8, wherein the alloy comprises at most about 2.5% by weight indium.
11. The low melting temperature compliant solder alloy of claim 8, wherein the alloy includes traces of impurities.
12. The low melting temperature compliant solder alloy of claim 8, wherein the alloy does not include traces of impurities.
13. The low melting temperature compliant solder alloy of claim 8, further consisting of from about 0.01% to about 3.0% by weight at least one dopant selected from the group consisting of zinc (Zn), nickel (Ni), iron (Fe), cobalt (Co), germanium (Ge), phosphorus (P), aluminum (Al), antimony (Sb), cadmium (Cd), tellurium (Te), bismuth (Bi), platinum (Pt), rare earth elements, and combinations thereof to improve oxidation resistance and increase physical properties and thermal fatigue resistance.
14. The low melting temperature compliant solder alloy of claim 13, wherein the rare earth elements are selected from the group consisting of cerium (Ce), lanthanum (La), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), actinium (Ac), thorium (Th), protactinium (Pa), and combinations thereof.
Type: Application
Filed: Jun 7, 2006
Publication Date: Mar 29, 2007
Applicant: Indium Corporation of America (Utica, NY)
Inventors: Benlih Huang (New Hartford, NY), Hong-Sik Hwang (Clinton, NY), Ning-Cheng Lee (New Hartford, NY)
Application Number: 11/422,782
International Classification: C22C 13/00 (20060101);