Replacement of SAC305 Solder for SN100C Lead Free Solder?



We are an EMS.

Production desires to change the solder paste for the back end (touch up) and go from SAC 305 to SN100C. Their arguments are:

• Much less expensive.
• Dwell is greater,.
• Less flux deposits.
• The resin does not change color.
• Welding is brighter.
• Same tin as for the wave process.
• We use less liquid flux and paste, causes a reduction in wash operations.
• The production staff much prefers working with the SN100C than SAC305.

These arguments are not supported by documented experiences.

Fifty percent of our production is for critical products (utilities, medical). The other half of our production is for various other clients.

What should we do? They ask our department (Quality Dpt.) to comment on this.

The opinion of my boss is not to change for homologated products (PPAP, etc.), and for others we could use their suggestion.

I’m personally not very much in favor of deploying two types of pasted to the back end because of other problems that this can result.

What would you do at my place?




Fully vaccinated are you?
Hi Les. Sorry no one has replied. I'm not sure if we have any solder experts here. I will say I agree that two different methods for different types of customers is a gaping opportunity for error.

A quick "Bump". My Thanks in advance to anyone who can help with this one.
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