Thermal conductivity surface-mount adhesives

Adhesives used for screen or stencil printing in surface-mount applications are generally electrically insulative types whose functions are mechanical attachment and thermal dissipation. However, electrically conductive, silver-filled epoxies have been used for many years as ohmic contact adhesives to interconnect bare-chip devices in hybrid microcircuits and are used as solder replacements for surface mounting of components on printed-circuit boards. Regardless of their... 

In the surface mount assembly process, type 11 and type III boards will always require adhesive to mount the SMDs for passage through the solder wave. This is apparent when one envisions components on the bottom side of the substrate with no through hole leads to hold them in place. Adhesives will stay in place after the soldering process and throughout the fife of the substrate and the product, since there is no convenient means for adhesive removal once the solder process is complete. Additionally, adhesives can be used to enhance both thermal and electrical conduction between device features and board features. This means use of an adhesive must consider a number of both physical and chemical characteristics ... 

Z.M. Mo et al.. Thermal Fatigue Cracking of Surface Mount Conductive Adhesive Joints, Solder. Surf. Mt. Technol, Vol 16 (No. 1), 2004, p 48-52... 

Figure 41 Schematic representation of microdevices attached to thick film metallization pads printed on a ceramic carrier in a multichip module carrying both flip chip 1 and surface-mounted 2 components. Enlarged views show the bonding area (a) silver-filled isotropic adhesive with possible irreversible changes due to thermal cycling (b) anisotropic adhesive made of conducting spheres embedded in thermoplastic or...

---