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.
High-Temperature Technical Documents
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Safety Data Sheets
High-Temperature Blog Posts
Today's Indium Mailbag question asks about the storage of indium-contained solder paste at a temperture well below the recommended temperature of -20.
What is the ideal time-above liquidus during solder reflow? Too long or too short can cause dewetting and charring, or not allow the intermetallic formation to wet.
The second stage of a reflow profile activates the flux in the solder paste and prepares the solder for reflow. This can be a critical stage to avoid defects such as tombstoning, voiding, graping, and non-wetting.
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