Proper Use of the C3
The C3 was designed and developed as a non-destructive process monitor tool for the electronics industry. It remains the only tester on the market that indicates whether a specific, critical area of a PCBA is clean. The C3 quickly provides feedback as to whether potentially detrimental residues, frequently from manufacturing processes, are present.
Not for Material Screening
The C3 was not designed as a material screening tool. Foresite occasionally hears of clients utilizing the C3 for this purpose. It must be understood that unreacted flux will commonly give a Fail reading by the C3. This would also occur utilizing ion chromatography (IC) analysis, whereby unreacted flux residues show up in large concentrations as ionic and organic residues.
What to Do
Ideally, if a contract manufacturer obtains a Fail reading with the C3 on an SMT area where a new paste was utilized, the CM should first look at if their equipment is properly optimized.
Clean C3 results should be achievable with any appropriate solder paste on the market, if the manufacturer’s recommended parameters are followed. Foresite does not recommend using the C3 system as part of a material selection protocol, as poor C3 results are typically indicative of processing issues and not improper material selection.
Conclusion
With proper material selection, application, and processing, good C3 results should be achievable with virtually any solder paste. Therefore, Foresite does not recommend the use of C3 results as a factor for material selection on new or existing product lines.