Reduce the stencil aperture dimensions by 10%.Ensure on point pressure and accuracy for component placement.Proper attention should be given to the alignment of stencil apertures to pads unless you are using an automatic printer alignment.An appropriate reflow profile is also very important.Typically, 90% metal is, or at least should be used for a stencil printing solder paste application. This ratio would slump if we use this for a fine pitch surface mount printing. For example, usually dispensable solder paste has a metal content of 85-87% metal. In other words, no slumping of the solder paste. An appropriate application requires an appropriate solder paste metal to flux weight ratio.Too much of component placement pressure can squeeze paste out of pads. Placement inaccuracy can further narrow the gap between pads, hence, escalating the chance of bridging.The extended soak will input more heat to the paste and result in paste hot slump phenomenon. Part contact with solder paste may skew the deposit making the solder paste to bridge. If the pre-heat area has an excessively slow of a ramp rate it can account for bridging.The profile can be broken down into four zones – the preheat, soak, reflow, and cool-down zones. Along with that, it wets the surfaces being joined together, and finally, solidify the solder to form a strong metallurgical bond. We know the purpose of the reflow process is to melt the powder particles in the solder paste. The reflow profile may likewise add to bridging.High temperatures and moistness can likewise prompt solder paste slump. An incorrect solder paste metal to flux weight proportion causes a slump.Solder paste cold slump can likewise prompt bridging.This may happen when the stencil aperture to pad proportion is excessively high. ![]() Too much deposition of solder paste can likewise cause bridging.The print arrangement, or stencil arrangement to the PCB pad configuration, can be somewhat off. A variety of reasons can account for bridging however, the most widely recognized reason is an issue in the solder paste printing process.These shorts result in a malfunction of the circuit. Solder bridging is solder across the two conductors that should not be electrically connected, and which cause electrical shorts. Surface Mount Technology Troubleshooting #1 Solder-bridging or electrical bridging
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |