This view has more or less been completely turned upside down, says Dr. Wadhwa, who is co-editing a special issue of scientific papers on pregnancy and stress to be published in Health Psychology next year.
A wire feeder is used to supply solder. Both lead-tin and silver-tin material can be soldered. Process recipes will differ depending on the alloy composition. For soldering 44-pin chip carriers to a board using soldering preforms, power levels were on the order of 10 Watts and solder times approximately 1 second.
Lead-tin solder layers on copper leads can form copper-tin intermetallic layers; the solder alloy is then locally depleted of tin and form a lead-rich layer. The Sn-Cu intermetallics then can get exposed to oxidation, resulting in impaired solderability.he widespread use of this popular lead-free solder alloy family is based on the reduced melting point of the Sn-Ag-Cu ternary eutectic behavior (217 ËC), which is below the Sn-3.5Ag (wt.%) eutectic of 221 Â°C and the Sn-0.7Cu eutectic of 227 Â°C (recently revised by P. Snugovsky to Sn-0.9Cu).