Prevent Solder Bridging During Pcb Board Assembly
Solder bridging is a significant problem during pcb board assembly that can lead to costly defects such as shorts and electrolytic corrosion. It typically occurs when extra solder connects two points on the printed circuit board that shouldn’t be connected. This issue can be caused by a variety of factors, including excessive solder paste, incorrect reflow profiles, and component leads that are too long in relation to their pads. To prevent solder bridges, it’s important to follow best practices for pcb fabrication and assembly.
Solder bridges can occur when liquid solder flows between components’ pins and pads, forming an electrical short. This can cause the device to malfunction or even fail entirely. Solder bridges can be prevented by using the right tools and following proper procedures when assembling PCBs. It is also essential to use flux-resistant materials and observe safety precautions while working with volatile substances.
The most common cause of solder bridges is excess solder paste applied to the PCB. This can be due to several factors, such as the amount of solder paste used, stencil thickness, and pad size. The amount of solder paste required is dependent on the components’ placement, which determines the location and size of the pads and stencil apertures. If the pads are close together, a smaller stencil aperture should be used so that there is not too much solder paste deposited.
How to Prevent Solder Bridging During Pcb Board Assembly
Moreover, a solder mask dam should be placed between SMT pads to act as an isolation wall and prevent spillovers. This can be facilitated by using a solder mask aperture with the correct dimensions for the pads. Besides, it is also essential to use the correct lead length for through-hole components. The length should be proportional to the size and thickness of the PCB, component mass and size, and type of soldering.
It is also important to use the appropriate reflow profile for the particular pcb assembly technology and components. Having the correct temperature profiles and dwell times will ensure that the melted solder is fully reflown during the reflow process. It will also ensure that the solder is well-wetted on the components’ leads and PCB pads, reducing the likelihood of solder bridges.
Another reason why solder bridges may occur is the improper application of the solder mask. If the PCB’s solder mask is too thick, it will cover up part of the pads and result in uneven paste deposit. The solder paste should be applied evenly, which can be achieved by using the right stencil thickness and by ensuring that the pads are sized appropriately.
Lastly, PCB manufacturers should utilize fiducial markers or precisely defined alignment indicators in their pcb layout designs. These markers allow the CM to place the components accurately in terms of orientation and alignment with their pads, which reduces the likelihood of solder bridges. Moreover, these markings can be used to highlight regions that require special attention during the reflow process. In addition to that, they can help the CM to identify and remove any contaminants from the surface of the PCB.