Advanced Packaging Technology Conference Proceedings


WHEN ARE CONDUCTIVE ADHESIVES AN ALTERNATIVE TO SOLDERS?

Author: Dr. Ken Gilleo
Company: Cookson Electronics
Date Published: 6/12/2001   Conference: Advanced Packaging Technology


Abstract: Our industry continues to heat up, sputter and often smolder with Lead-Free (L-F) issues. The good news is that there are plenty of L-F alloys. That’s also the bad news. Substantial data is available on lead-free systems this year. The challenge has been answered but the answer is the challenge! A quick study of the “new” solders lets the impartial observer conclude: (1) no drop-in replacement has been found, (2) L-F solders are reliable and (3) higher processing temperatures are almost certain.

The pending L-F “Temperature Tax” is causing concern over damage to laminates, packages and some semiconductors. Will high temperature processing be a cost penalty for using L-F solders? Will BGAs require extra drying procedures, will PCBs degrade and will optoelectronic components fail? The new CPUs with low-k polymers and emerging organic electronics could possibly have problems. What products will fail 240 to 260 degrees C soldering? And let’s not forget high-density stacked die packages, MEMS (MicroElectroMechanical System) and MOEMS (MicroOpticalElectroMechanical System) devices that can be heat-limited.

Conductive adhesives have provided a good solution for temperature-limited assembly for decades. These time-tested polymers can be processed like solder using the same equipment. The good news is that the assembly temperature is 130o to 150 degrees C. But are adhesives really viable even though used for SMT assembly in medical products and aircraft where reliability is a must? Your business phone, ink jet printer and laptop’s display flip chip drivers were probably adhesively bonded. This paper will compare Polymer Solders to Lead-Free solders to show limitations and advantages. Guidelines for designs and applications will be provided. Finally, possible solutions to adhesive deficiencies for suggest, particularly in the mechanical strength area.

Keywords: conductive adhesives, silver, lead-free, low-temperature, solderless, epoxy, degradation.



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