Question: We have a through-hole integrated circuit (IC) component that has good wetting when it goes through the wave soldering machine, and the solder climbs pretty far up the lead. It does not appear that it is touching the IC body, but can you tell me what is the IPC requirement for this process?
Answer: Based upon the requirements of IPC-A-610, “Acceptability of Electronic Assemblies”, solder is not allowed to touch the component body. See Section 18.104.22.168 – Supported Holes, Solder Conditions – Touching Through Hole Component Body.
The intent is that the solder can climb up the lead, but not touch the body. When solder touches the body it can destroy the seal where the lead enters the body of the component and this could cause failures in the component by allowing moisture to enter the component and create latent failures at a later point in time.
The same requirements apply to the surface mount component and this is stated as a note beneath all the table in the surface mount section of IPC-A-610. If the solder does touch the body, it reduces or eliminates the stress relief for the lead which can cause component damage and create failures.