There are various reasons for the short circuit between the solder joints of the circuit board formed during the soldering process with solder paste
, which can be mainly divided into three categories: one is the reason of the solder paste itself; the other is the reason of the incoming circuit board ; The third is the influence of welding process. Solder paste manufacturers can analyze the reasons for these defects one by one:
1. The incoming material of the circuit board causes bridging. Due to the uneven surface during the production process of the circuit board, the pads on which the electronic components are mounted are not on the same plane. When the stainless steel mesh is used to cover the circuit board, the steel mesh and the circuit The tightness between the boards is not enough, resulting in a gap between the two, and the solder paste flows into the gap between the two during the process of scraping the solder paste on the stainless steel mesh. The lead-free solder paste that enters the gap is in the reflow process will result in bridging. In the event of such poor soldering caused by incoming circuit boards, solder paste manufacturers suggest that the solder mask between the pads can be removed, which will greatly reduce the poor solder paste bridging caused by the uneven surface of the circuit board. Due to the bridging caused by the flatness of the circuit board, the solder paste manufacturer recommends that the electronics factory negotiate with the manufacturer of the circuit board material, which can be improved through the production process of the circuit board.
2. In the design of stainless steel mesh, the size of the openings of the solder joints on the mesh during the design of the stainless steel mesh, the lead-free solder paste manufacturer recommends that the opening size should be slightly smaller than the size of the pads, only the size of the solder paste slumping on the steel mesh is smaller than The size of the solder joints on the circuit board can make up for the poor bridge connection caused by the gap between the openings of the stainless steel mesh circuit board. These two differentiated sizes can improve the bridging caused by the poor sealing of the circuit board and the stainless steel mesh. Solder paste manufacturers have found in practice that reducing the size of the openings of the solder joints of the stainless steel mesh will greatly improve the solder paste printing and sealing, resulting in poor short circuit between the two solder joints. It is recommended that electronic manufacturers can follow the above view. Carry out the opening design of the stainless steel mesh.
3. If the back of the stainless steel mesh is contaminated, if the stainless steel mesh is contaminated with lead-free solder paste, the contaminated position will be coated on the circuit board during the printing process, causing the circuit board to be contaminated where the solder paste should not be printed. A small amount of solder paste, the melting of the solder paste at these locations during the over-reflow soldering process will cause a connected line to form between the two solder joints on the circuit board, resulting in bridging. The lead-free solder paste manufacturer suggests that if this kind of problem occurs, it should be stopped to check whether the gap between the stainless steel mesh and the circuit board is reasonable? You can appropriately increase the pressure of the solder paste printing squeegee, increase the frequency of wiping the back of the stainless steel mesh, or directly replace the reagents used for scrubbing.