The SMM was specifically designed for integrated circuit test. Numerous electrical and mechanical performance advantages over the life of the contactor make it ideally suited to this application.

The Surface Mount Matrix (SMM) used in ECT contactors is an anisotropic conductive elastomer which allows for a solderless connection to the performance board. The SMM consists of two parts: a silicone rubber base, which provides compliance, and a matrix of conductors embedded in the silicone, which provide the conductive path to the performance board. The SMM was specifically designed for high-volume integrated circuit test and has several features which make it ideal for this application:

• The use of a wire matrix creates a one-dimensional conductive path (Z-axis only) without cross-conducting in the X and Y-axes.
  
• Each signal path through the SMM uses multiple parallel conductors, minimizing inductance and contact resistance.
  
• Both standard and high-density SMM have a thickness of 1.0mm, allowing for a short electrical path. Half-height SMM, with a thickness of 0.5mm, is available for certain very high-frequency applications.
• Angled conductors tip, rather than bend, when the SMM is compressed, minimizing metal fatigue and maximizing mechanical performance and operating life.
• Gold plating of the SMM wire matrix prevents oxidization and optimizes contact integrity.
  
• The SMM does not scrub the performance board or damage it in any way.
  
• The electrical characteristics of the SMM are not given independently, but are dependent upon the contactor style in which it is used. The SMM is one part of a contacting system in any particular ECT contactor.
  
• Standard-Density SMM: 40-micron conductors spaced every 100 microns throughout the elastomer.
  
• High-Density SMM (for fine pitch grid array applications below 0.75mm): 20-micron conductors spaced every 50
  microns throughout the elastomer.
  
• SMM is used in three types of ECT contactors (please refer to the appropriate data sheets for more information).
  These include:
  • µHPC/PL contactors (for QFP, SOIC, LCC, and SSOP type devices)
    
  • µHPC/GA contactors (for BGA, µBGA, CSP, MLF, QFN, LGA and PGA type devices)
    
  • µHPC/DC contactors (for certain low-volume, very high-performance, and engineering characterization applications, for most device types)