SAC305 Lead-Free Reflow Soldering in China
1 resources tagged with "Sac305"
SAC305 (Sn96.5/Ag3.0/Cu0.5) is the standard lead-free solder alloy for RoHS-compliant PCB assembly in China, with a melting point around 217–220°C versus 183°C for leaded Sn63Pb37. That higher peak reflow temperature — typically 240–250°C — narrows the process window and makes profile control and J-STD-020 moisture-sensitivity handling more critical. The common failure when a factory runs a sloppy SAC305 profile is cold joints, head-in-pillow defects on BGAs, and tombstoning on small passives.
Sourcing SAC305 assembly means confirming the factory uses a validated reflow profile and bakes moisture-sensitive parts per their MSL rating. The pitfall is a factory reusing a leaded profile for lead-free work, which under-heats joints and causes intermittent field failures.
Wiki (1)
FAQ
Why is SAC305 harder to reflow than leaded solder?
SAC305 melts near 217°C versus 183°C for Sn63Pb37, so peak reflow runs 240–250°C. The tighter window and higher temperature raise the risk of cold joints, tombstoning, and BGA defects if the profile isn't dialed in.
What should I check on a lead-free assembly line?
Ask for the reflow profile (zone temps and ramp rates), confirm it matches SAC305 not a leaded recipe, and verify moisture-sensitive parts are baked and handled per their J-STD-020 MSL rating before reflow.
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