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IMPROVED STRENGTH FOR CONDUCTIVE EPOXY SURFACE MOUNT ATTACHMENT

IP.com Disclosure Number: IPCOM000008634D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-28
Document File: 1 page(s) / 54K

Publishing Venue

Motorola

Related People

Robert Carson: AUTHOR [+3]

Abstract

When applying conductive epoxy as a substitute As a solution to both conductive epoxy surface for solder in surface mount assembly (Figure la), mount challenges, a surface mount adhesive is two significant challenges are encountered. The first applied between the substrate pads (Figure 2a). challenge occurs during placement when the con- When the component is placed on the epoxies, the ductive epoxy spreads under small chip components surface mount adhesive prevents shorting under the making shorting possible (Figure lb). The second component as the conductive epoxy is compressed challenge is poor cohesive strength in the conduc- (,Figure 2b). After curing the epoxy system, the tive epoxy that is often lower than needed to perma- component adhesion is substantially improved; nently attach the part; pull testing always creates pull testing often results in cohesive failure in the cohesive failure in the conductive epoxy (Figure I c). substrate (Figure 2~).

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m MOTOROLA Technical Developments

IMPROVED STRENGTH FOR CONDUCTIVE EPOXY SURFACE MOUNT ATTACHMENT

by Robert Carson, Frank Juskey and Chris Keane

  When applying conductive epoxy as a substitute As a solution to both conductive epoxy surface for solder in surface mount assembly (Figure la), mount challenges, a surface mount adhesive is two significant challenges are encountered. The first applied between the substrate pads (Figure 2a). challenge occurs during placement when the con- When the component is placed on the epoxies, the ductive epoxy spreads under small chip components surface mount adhesive prevents shorting under the making shorting possible (Figure lb). The second component as the conductive epoxy is compressed challenge is poor cohesive strength in the conduc- (,Figure 2b). After curing the epoxy system, the tive epoxy that is often lower than needed to perma- component adhesion is substantially improved; nently attach the part; pull testing always creates pull testing often results in cohesive failure in the cohesive failure in the conductive epoxy (Figure I c). substrate (Figure 2~).

Conductive Surface Mount

Adhyive Substrate

Component

b) b)

c)

4

Fig. I Using conductive epoxy as a replace- ment for solder in surface mount assembly:
a) conductive epoxy applied to substrate pads;
b) component placed on the conductive epoxy:
c) typical failure created in pull testing.

Fig. 2 Using a combination of conductive epoxy and surface mount adhesive for surface...