Definition of a Stencil Misprint
During production stencil printing, circuit boards are periodically misprinted due to clogged apertures, stencil misalignment, solder paste rheology shifts and other issues. Stencil misprints are defined as:
- A-Side Misprint: Initial print out of alignment with no components previously placed
- B-Side Misprint: A-Side was successfully printed, and components placed and soldered. The subsequent printing process of the B-Side results in the solder paste being out of alignment resulting in a B-Side misprint
Best Practices for Misprint Cleaning
While misprinted board cleaning is commonly done by hand or in an offline stencil washer, we recommend using an existing PCB cleaning process that is used for final assembly cleaning. Production cleaning systems remove both wet solder paste and reflowed flux residues while meeting quality and yield objectives.
Process Note: To capture the wet solder paste, it is highly recommended to use a collection and filtration system that safely captures and contains solder spheres. This prevents the solder spheres from going back into the wash solution and mitigates the risk of redisposition on production assemblies. Additionally, a containment and filtration system will prevent raw solder paste from entering the rinse water stream.
Using a production cleaning machine with an aqueous cleaning solution provides numerous benefits to the assembler such as:
- Recovery and rework of expensive hardware
- Removal of wet solder paste
- Containment of solder spheres
- Removal of reflowed flux residues
- Exceptional rinsing
- Ionically clean assemblies
KYZEN offers advanced solutions for misprint cleaning that are designed to clean all flux types. Below are our top recommended products to help enhance your process.