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The reason and solution of SMT cold welding

283 Published by FASTPCBA 8月 23,2018

The reason and solution of SMT cold welding

In the welding defects of SMT, cold welding appears less, but the hazard is great, because it affects the long-term stability of the product, and the problem of electrical connectivity often appears in the hands of customers.The phenomenon of cold welding of SMT is mainly reflected by the cracks or gaps in the solder surface or interior of welding pads and components.This crack and notch does not affect the online testing of the product, and the electrical connection is normal after SMT processing.However, in the hands of customers, due to the influence of uncontrollable factors, such as continuous use, overcurrent or overpressure, and harsh service environment, cracks or gaps are amplified and broken, thus causing undesirable products.

SMT

SMT

SMT cold welding

The principle and cause of SMT cold welding is that during the welding process, the furnace temperature curve of backflow welding (generally backflow welding) is not reasonable, resulting in the extremely rapid rise of temperature or extremely rapid decline, solder paste from paste to liquid state, then from liquid state to solid state process, solder paste tension is not uniform, resulting in cold welding phenomenon.It’s like a sword that breaks when it’s not hardened properly.To avoid SMT cold welding, we need to set the temperature curve of reflow welding correctly to ensure the temperature rise and fall steadily and avoid sudden rise and sudden drop.

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