AN2036 Datasheet, PDF (1/7 Pages) STMicroelectronics – Solderability Tests

AN2036
APPLICATION NOTE
Solderability Tests
Lead-free devices, from STMicroelectronics, are warranted to pass the solderability tests, and to form a
reliable solder joint with the base material of the circuit board, using Leaded (Sn-Pb) solder or Lead-free
(Sn-Ag-Cu) solder. This document describes the context of this assertion.
ST Lead-free devices conform to the ECOPACK^® 7191395 specification from ST. This, in turn, complies
with the European directive on Restrictions on Hazardous Substances (RoHS) 2002/95/EU, and with the
IPC/JEDEC 020 standard for resistance to soldering heat and soldering process.
These devices have to be solderable with both Leaded materials and processes, and with Lead-free ma-
terials and processes. With a composition close to the ternary eutectic composition (Table 1.), the Tin-
Silver-Copper (Sn-Ag-Cu) alloy is considered as the standard lead-free material. Only Tin-Bismuth coated
devices are not tested in Tin-Lead solder. This is because the Tin-Bismuth coating is not recommended
for mixing with Tin-Lead solder, for board mounting, due to a reliability risk on the solder joints.
Table 1. Solder Composition for Solderability Tests
Solder
Composition
Tin
Lead-free
Silver
Copper
SnPb
Tin
Lead
Range (% weight)
94.6 to 96.6
3.0 to 4.3
0.4 to 1.1
60 to 64
36 to 40
There are two kinds of tests that are applied to evaluate such ability of a surface to be wetted:
■ Dip and Look
■ Wetting Balance
Both tests are well known, and applied, worldwide. However, different methods are often used (such as
MIL standard 883-2003, JEDEC J-STD-002, JESD22-B102 and IEC 60749-21). The ones chosen by ST
are intended to cover the ones that are in most widespread use by our customers.
In these tests, the packages are “aged”, in order to test the solderability under the worst conditions and to
warrant at least 2 years of storage with no significant degradation of solderability.
November 2004
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