Multilayer varistors (MLVs)
Radio frequency series
5
Conductive adhesion
Attaching surface-mounted devices (SMDs) with electrically conductive adhesives is a commer-
cially attractive method of component connection to supplement or even replace conventional sol-
dering methods.
Electrically conductive adhesives consist of a non-conductive plastic (epoxy resin, polyimide or
silicon) in which electrically conductive metal particles (gold, silver, palladium, nickel, etc) are em-
bedded. Electrical conduction is effected by contact between the metal particles.
Adhesion is particularly suitable for meeting the demands of hybrid technology. The adhesives
can be deposited ready for production requirements by screen printing, stamping or by dis-
pensers. As shown in the following table, conductive adhesion involves two work operations fewer
than soldering.
Reflow soldering
Screen-print solder paste
Mount SMD
Wave soldering
Apply glue dot
Mount SMD
Cure glue
Conductive adhesion
Screen-print conductive adhesive
Mount SMD
Predry solder paste
Reflow soldering
Wash
Cure adhesive
Wave soldering
Wash
Inspect
Inspect
Inspect
A further advantage of adhesion is that the components are subjected to virtually no temperature
shock at all. The curing temperatures of the adhesives are between 120 °C and 180 °C, typical
curing times are between 30 minutes and one hour.
The bending strength of glued chips is, in comparison with that of soldered chips, higher by a fac-
tor of at least 2, as is to be expected due to the elasticity of the glued joints.
The lower conductivity of conductive adhesive may lead to higher contact resistance and thus re-
sult in electrical data different to those of soldered components. Users must pay special attention
to this in RF applications.
Please read Cautions and warnings and
Important notes at the end of this document.
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EPCOS [ EPCOS ]
