Why Occurs Rough Unshaped Welding in PCB Assembly
PCB design and manufacture is critical and don’t allowed any mistake.The article will analyses why occurs rough unshaped welding in PCB assembly.
There have many factors lead to rough unshaped welding,like PCB PTH weldability, welding temperature incorrect,solder components incorrect,etc. It’s unfavourable for PCB components running,so we must avoid rough unshaped welding.
PCB PTH weldability
If PCB PTH weldability is not good, it makes weld defect and impact parameter of components, components connects multilayer unstability,lead to whole PCB miss function.
If the welding temperature is overhigh,then the welding material expedite spread and achieve high active lead to surface oxidized immediately between PCB and welding material.then appeared rough unshaped welding.
Welding material is very important constituent part in welding chemistry process,common low smelting point metal Sn-Pb or Sn-Pb-Ag, need strict control impurity rate avoid impurity oxide be dissolved by soldering flux lead to rough unshaped welding.
PCB bow and twist
It’s easy make PCB bow and twist when make assembly, stress changed lead to rough unshaped welding. The main problem is PCB out-of flatness.For large PCB,itself weight drop down can lead to bow and twist.The space should be 0.5mm between component and PCB board edge.
In PCB layout, if the dimension is too big. Although it’s usefull for welding ,but the trace is too long lead to impedance increase,resist noise capability decline,increase cost.If the board dimension is too small lead to heat dissipation drop.It’s unhelpful for welding.the adjoin trace will interfere each other.so need optimize design.The best PCB dimension long/width rate is 4:3. The trace width should be symmetry,avoid big area copper cover.