Sheppard Mullin Richter & Hampton LLP
Composite solder alloy preform
Various embodiments of the invention provide laminate composite preform foils for high-temperature Pb-free soldering applications. The laminate composite preform foil is composed of a high-melting, ductile metal or alloy core layer and a low-melting solder coating layer at either side of the core layer. During soldering, the core metal, liquid solder layer, and substrate metals react and consume the low-melting solder phase to form high-melting intermetallic compound phases (IMCs). The resultant solder joint is composed of a ductile core layer sandwiched by the IMCs layers at substrate sides. The joint has a much higher remelt temperature than the original melting temperature of the initial solder alloy coating, allowing subsequent mounting of packaged devices.
Indium Corporation
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Ning-Cheng Weiping
Lee Liu