Products that operate in high-temperature environments usually need a solder that melts above the reflow temperature of the standard solders used in wave soldering and surface mount technology (SMT), such as eutectic tin-lead (63Sn/37Pb), and standard SAC-type alloys. The reflow temperatures for these solders may range from 200-240°C.
Solders melting at >230°C: Many common high-temperature solder alloys contain lead (Pb), but there are many Pb-free options also available. Antimony (Sb)-based solders are commonly used in applications that need melting points just above the standard solder reflow process range. Examples include MEMS microphones and gyroscopes. Indalloy 259 (90Sn 10Sb) and Indalloy 133 (95Sn 5Sb) are two of the more common alloys.
Solders melting at >260°C: Die-attach and similar packaging applications that must conform to JEDEC/IPC J-STD-020 require a solder alloy that melts at greater than 260-265°C. In these devices, Indalloy 151 (92.5Pb/5Sn/2.5Ag) and Indalloy 163 (95.5Pb/2Sn/2.5Ag) are the most common lead-based solder alloys. Gold-based alloys such as Indalloy 182 (80Au 20Sn) and Indalloy 183 (88Au 12Ge) are commonly used in applications such as step-soldering in RF packages, hermetic sealing, aerospace, and medical. These gold-based alloys have a high tensile strength, superior thermal fatigue resistance, and exceptional thermal conductivity, as well as resistance to corrosion and oxidation.
Lead (Pb)-containing and Pb-free solders have been used for many years for wafer and substrate-bumping applications. Most recently, these solders have been replaced by Sn-based Pb-free solders; however, the majority of cutting-edge applications, such as copper pillar/microbump, have moved to a low-silver plated solder. Additionally, some very fine pitch temperature-sensitive applications now use pure indium or indium-silver-plated bumps.
The selection of Pb-free and lead-based alloys for power semiconductor applications is large, and their usage is likely to continue into the future. However, some long-standing lead-free alloys and some novel high-melting Pb-free solder paste technologies are in use in specific applications.
|Lower Tj IGBT usage||96.5||3.5||221°C||Eutectic|
|Also known as "J-alloy"||65||25||10||233°C||Eutectic|
|Commonly used in step-soldering processes||95||5||237°C||240°C|
|Highest Sb content possible in standard Sn/Sb wire||91.5||8.5||241°C||248°C|
|Commonly used in step-soldering processes||90||10||243°C||257°C|
|Highest melting standard Sn/Sb alloy||86||14|
|Very poor solder-ability||11||89||262°C||360°C|
|Very high tensile strength and thermal / electrical conductivities||20||80||280°C||Eutectic|
|Usable for very high Tj die-attach such as SiC||88||12||356°C||Eutectic|
Products available for high-temperature soldering include:
- Die Attach Solders
- Braze Alloys
- Gold Solders
- Solder Preforms
- Solder Paste
- Solder Ribbon/Foil
- Solder Wire
If you are not sure what solder you might need, we also offer Solder Research Kits that allow you to test several different solder fluxes to determine which one will work best in your application. If you need help in this selection, please contact one of our Technical Support Engineers.
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