Scope, Test samples/preparation – A P Products Meritec SMT Products Using Lead-Free Solder User Manual
Page 3
Meritec • 1359 West Jackson Street • Painesville • Ohio • 44077 • USA
3
Scope
To determine acceptable methods and materials for mounting Meritec’s SMT products
using lead-free processes. The findings will form the basis by which Meritec can assist it’s
customers in making this crucial changeover.
After reviewing the current product line, it was decided that Meritec’s SOP Sockets
represented the biggest challenge. Of these, we chose to test the TSOP and the PSOP
types as follows:
1...To mount Pb-free Meritec SOP sockets using a Pb-free printed circuit board and
process. Establish maximum, target, and minimum time/temperature profiles from which a
recommendation can be made for Meritec’s customers.
• Maximum time/temperature profile is one that results in a successful wetting and flow of
the solder on the contacts, but begins to show deleterious effects on the plastic of the
socket components.
• Target time/temperature will be the profile that confirms good solder characteristics and
causes no damage to the plastic of the socket.
• Minimum time/temperature profile is one that results in marginal wetting and flow of the
solder alloy on any one contact of the socket. The solder joint will take on characteristics
consistent with what’s known as a “cold” solder joint.
2...Mounting of Pb-free Meritec SOP sockets will also be done using a 63/37 solder alloy
and the currently recommended profile. This will be done to establish a backwards
compatibility of the new plating with a 63/37 lead bearing solder.
Test Samples/Preparation
• Sockets...Two sockets were chosen for inclusion in this test:
Meritec P/N
Size/Type
980020-56-P1
56TSOP
980021-44-P1
44PSOP
• Printed Circuit Board...A test Board (Meritec P/N 600440-02) was manufactured with
four pad patterns for each of the two sockets being tested. Further, the pad patterns
were arranged in a way that would maximize infrared “shadowing”. This was done to
emulate a worst case reflow soldering scenario. Immersion silver was chosen as a pcb
finish for the Pb-free tests and Sn63/Pb37 HASL for the backwards compatibility tests.
• Solder Paste...AIM Solder Product Number NC254/SAC305 was used for Pb-free
testing and has an alloy composition of Sn96.5/Ag3.0/Cu0.5 with a no-clean flux
chemistry. Backwards compatibility testing was done using an Indium Corporation of
America Product Number NC-SMQ92J, which is a no-clean Sn63/Pb37 solder paste.