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Is Conductive Epoxy a Low-Temperature Alternative to Lead-Free Solder?

Conductive epoxy is a common material choice for bonding components, especially if the assembly process is temperature-sensitive. Tin-based solder paste or preforms with flux are preferred Pb-free bonding materials; however, conductive epoxies arguably provide advantages over these traditional solder assembly materials. 

 

It has been my experience that these advantages are perceived in the absence of an awareness of the full solder assembly materials product offering. Specialty solders can provide the same advantages as conductive epoxies and then some.   

Some claimed advantages to conductive epoxies include:

·         RoHS-compliance

·         Ease of assembly

·         No-clean

·         Low cure temperatures

 

Low-temperature solders such as 58Bi42Sn and 52In48Sn are specialty low-temperature solders which have these same properties including processing temperatures below 150ºC. Both of the referenced alloys are Pb-free, can-be used with no-clean fluxes and are assembled using the traditional solder assembly techniques.

 

It would seem a toss-up between whether to use a conductive epoxy or specialty solder to assemble temperature-sensitive components except that there are additional advantages to a soldered assembly as compared with an epoxy-assembly. These include:

 

·         Thermal cycling reliability

·         Solder material consistency

·         Reworkability

·         Thermal Conductivity