Title:
Development of Conductive Adhesives for Solder Replacement
Development of Conductive Adhesives for Solder Replacement
Author(s)
Wong, C. P.
Lu, Daoqiang
Lu, Daoqiang
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Abstract
With the phasing out of lead-bearing solders, electrically
conductive adhesives (ECAs) have been identified as an
environmentally friendly alternative to tin/lead (Sn/Pb) solders in
electronics packaging applications. Compared to Sn/Pb solders,
conductive adhesive technology offers numerous advantages. However,
this new technology still has reliability limitations. Two critical
limitations are unstable contact resistance on non- noble metals
and poor impact performance. Our previous study proved that galvanic
corrosion is the dominant mechanism for the unstable contact
resistance during elevated temperature and humidity aging.
The ultimate goal of this study is to develop conductive adhesives
with stable contact resistance and desirable impact performance.
In this study, effects of purity of the resins and moisture absorption
on contact resistance are investigated. Several different additives
(oxygen scavengers and corrosion inhibitors) on contact resistance
stability during elevated temperature and humidity aging are
studied, and effective additives are identified based on this study.
Then, several rubber-modified epoxy resins and two synthesized
epoxide-terminated polyurethane resins are introduced into ECA
formulations to determine their effects on impact strength. The loss
factor, tan , of each formulation is measured using a dynamic mechanical
analyzer (DMA) and impact strength is evaluated using
the National Center for Manufacturing Science (NCMS) standard
drop test procedure. Finally, high performance conductive adhesives
are formulated by combining the modified resins and the effective
additives. It is found that 1) purity of the resins and moisture
absorption of the formulation affect the contact resistance stability
of an ECA; 2) the oxygen scavengers and corrosion inhibitors can
delay contact resistance shift; 3) one of the corrosion inhibitors is
very effective in stabilizing the contact resistance; 4) some rubbermodified
epoxy resins and the epoxide-terminated polyurethane
resins can provide the conductive adhesives with superior impact
performance; and 5) conductive adhesives with stable contact resistance
and desirable impact performance are developed.
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Date Issued
2000-12
Extent
122042 bytes
Resource Type
Text
Resource Subtype
Article