![]() ![]() The SnBiAg alloy system has a melting point of 138☌ which enables a peak reflow temperature between 160 - 170☌. Lead free solders like Tin / indium 52% and tin / bismuth 58% have significantly lower melting points than tin / lead 37% solder. Two metals help to reduce the melting point, indium, and bismuth. Tin/bismuth, tin/indium, or tin/bismuth/silver are the most common “low melting point” solders (150-170° C). Solders generally melt between 90° C and 450° C.The melting point of solder is engineered via selection of the solder blend and the heat resistance power of the particular devices being attached. By using two different reflow temperature pasts, the parts attached in the first step with a higher temperature paste, can be unaffected by the second lower temperature application. That is, some may require components to be attached first, and then additional ones added in a second step. Low temperature pastes can also be used in conjunction with higher temperature ones for applications requiring two-stage assembly. Low-temperature solder pastes that melt at a heat below 180° C are used for such situations, as “typical” pasts generally reflow at 250° C or higher. The exact solder paste reflow temperature is essential to ensure certain components do not excess their maximum temperature rating during assembly. Size, composition, and flux density play significant roles determining the effectiveness of manufacturing process. The purpose of solder paste is to create a stable bond between the plated connection pads on the PCB board and the electronic components being added to form a working electrical circuit. Solder paste is a combination of small metal solder particles and flux used in printed circuit board assembly & manufacturing.
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