Bare Board Cleanliness
The cleanliness of a completed PCB is crucial because a contaminated
circuit board deteriorates
insulation resistance and dielectric strength.
IPC-5704 provides industry guidance on cleanliness testing for both
product acceptance and process control,
equipment and chemistries.
"The cleanliness of a printed board can directly impact the effectiveness
or quality of an assembled
printed board," explains John Perry, IPC
technical project manager. "Residues increase the risk of
can electrically impede a printed board's function, so having acceptance
criteria for various
levels of testing as well as direction on how many
samples should be tested is extremely important."
C-7000 for Unpopulated Circuit Boards
The cleanliness provisions for IPC-5704 have been adapted from Delphi's C-7000. A bare board specification based on ion chromatography, C-7000 has been successfully used for 10-15 years and is consistent with recommended cleanliness levels from CSL/Foresite, PAL, and Rockwell Collins.
Like the industry standard Ionograph, Ion Chromatography measures total ionic contamination. However, and unlike an Ionograph, Ion Chromatography provides a breakdown of the levels of each individual component of ionic contamination.
Process Solutions for High-Reliability Applications
Providing solutions for Printed Circuit Boards with High-Reliability Applications
means accommodating the enhanced specification required. As a result, we employed a multi-step process adjustment to ensure bare board cleanliness.
A primary contributor to high ionic contamination levels is the flux used in the HASL process, which can become entrapped in soldermask pores.
To close these pores, Saturn installed a UV oven in line with our soldermask developing and baking line. The UV "bumping" completes the soldermask cross-linking process to close the pores--ensuring the flux remains free on the PCB surface and no longer entrapped within the soldermask.
Custom Post-HASL Cleaning Line...On Steroids!
Saturn designed and built a custom post-HASL cleaning line for the sole purpose of removing the flux from the board's surface.
Simply put, it's an industry-standard post-cleaner on steroids.
Comparison Chart Provides Breakdown...Even if Industry Doesn't
Below is a chart comparing the industry-standard to Saturn's custom-built post-HASL cleaner.