Prevent Solder Bridging During PCB Assembly

With component package sizes continuing to shrink, it’s important to keep a close eye on the manufacturing process to ensure that the board is assembled without soldering issues. One of the most common problems that can arise is solder bridging, which occurs when two pads, pins or traces that should be connected form an unintended connection via a bridge of solder. Fortunately, this is an issue that can be easily prevented with proper design and assembly processes.

Solder paste with the wrong viscosity. Using the right type of paste for your specific application is essential to avoid this problem. For example, thicker viscosity pastes can spread excessively and lead to bridging, while thinner types can flow too quickly and leave gaps that create the potential for bridges. Stencils must be cleaned and maintained frequently to avoid contamination and oxidation, which can affect the quality of printing and the reliability of the resulting printed circuit board.

Implement regular inspection processes using Automated Optical Inspection (AOI) systems to detect and address tombstoning early in the assembly process. Continuously monitor and adjust the assembly process parameters based on feedback and inspection results to maintain optimal conditions. By addressing these aspects comprehensively, manufacturers can significantly reduce the occurrence of tombstoning, leading to higher quality and more reliable PCB assemblies.

 

How to Prevent Solder Bridging During PCB Assembly

Excessive solder paste application. A number of factors can affect how much solder is applied to a pad, including the stencil design and its alignment. Using smaller aperture sizes in the stencils can reduce this risk by controlling the amount of paste that is deposited onto the pads. Rounding the edges of the holes in the stencils can also help prevent bridging by promoting better paste release and less spread.

Long lead lengths. Using through-hole components with leads that are too long can increase the chance of soldering bridges, especially if the pads and the leads have different temperatures. In order to avoid this, the reflow profile and dwell time must be adjusted accordingly in order to match the needs of the pcb assembly us and the components.

Poor component placement. The positioning of components on the PCB can have a significant impact on the formation of solder bridges, and it’s important to use a pick-and-place machine with the right level of accuracy in order to ensure that all the parts are properly aligned. Moreover, using fiducial marks – which are precisely designed markers that can be placed on the PCB to help automated machines locate it and accurately place its components – can also reduce this risk.

When working with an EMS partner, make sure they have sufficient experience and are willing to discuss their processes in detail. Ask about their stencil design, inspection protocols and other factors that can influence the occurrence of solder bridges. A little diligence in preventing these issues can save you thousands of pounds worth of rework costs later on down the line.

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