资料介绍
This application note is intended to inform and assist
the customers of Microchip Technology Inc. with
Surface Mount Devices (SMD’s). The process of
packaging a semiconductor in plastic brings to pass a
somewhat unlikely marriage of different materials. In
order to minimize potential adverse effects of surface
mount solder techniques, it is worthwhile to understand
the interaction of the package materials during the time
they are subjected to thermal stress. Understanding
both the limits of thermal stressing that SMD’s can
withstand and how those stresses interact to produce
failures are crucial to successfully maintaining
reliability in the finished product. A recommended
Infrared (IR) solder profile is provided as a reference
later.
The electronics industry has moved to smaller and
thinner surface mount packaging in the progress
toward miniaturization of circuits. This trend has
necessitated the use of lower profile and smaller
footprint packages. There has been an increase in
reliability problems corresponding with the shrinking
size of plastic SMD’s. These problems manifest
themselves in such ways as moisture sensitivity,
cracked packages, open bond wires and intermittent
continuity failures. Problems of this type are not
present in the devices prior to assembly onto printed
circuit boards but are the result of thermally induced
stressing to the part during assembly or any rework
such as desoldering. AN598
Plastic Packaging and the Effects of Surface Mount Soldering Techniques
The heat from soldering causes a buildup of additional
Author: John Barber stresses within the device that were not present from
Surface Mount Technology Team the manufacturing process. Board level solder
processes, such as IR reow and Vapor phase reow,
are well-known areas where temperatures can reach
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