Technical Paper

Air Gap Contactor

Prepared by Lam Tuck Hon.

Presented at BiTS Workshop on March 6 – 9, 2011

Introduction

  • The Signal Integrity performance of a Test Contactor is defined as the speed and quality of the signal transmitted and received via Probe Pins in the Test Contactor.
  • These probe pins are further separated as Power, Ground and Signal pins.
  • There are multiple variables that contribute to the electrical performance of the Test Contactors.
  • Enhancing the multiple variables achieves an optimized Electrical Performance.

Basic Requirement

The (Signal Integrity) electrical performance of the Socket/Contactor will depend on:‐

Assign by Customer

  • Pitch
  • Number of GND Probe Pin
  • Number of Signal Probe Pin

Advise By Socket/Pin Maker

  • Diameter of Probe Pin
  • Length of Probe Pin
  • Material of the Socket

Normal Conventional Contactor

Consists of two plates (Top Plate & Bottom Plate) made of Engineered Plastic materials

Technical Challenge

The main challenge in optimizing the electrical performance/SI of a Test Contactor is to have good control of the Signal Path Impedance

The major parts that affect the impedance:‐

  • Pitch to Pitch
  • Diameter of Probe Pin
  • Dielectric Constant of the Material

Pitch to Pitch

  • Assigned By Customer

Diameter of the Probe Pin

  • Machining limitation
  • Limited choices for fine pitch pins

Material

  • Looking for Low Dielectric Constant material

Air Gap Contactor

  • A new feature known as an Internal Air Gap to further improve the control over impedance.
  • By providing an air gap internally in the Test Contactor the Effective Dielectric Constant is further improved.
  • This is because the Air Gap created provides the lowest Dielectric Constant possible and the best Dielectric Loss Tangent value achievable.
  • By reducing the Dielectric Constant this helps in increasing the impedance of the Probe Pin as the impedance is inversely proportional to the Dielectric Constant.
  • Dielectric Constant of Air = 1
  • Dielectric Loss Tangent of Air = 0, Could not be achieved in any known materials.
  • Due to some of the contactor materials being removed, it will make the contactor’s body structure become weak.
  • Cosmoswork software will be used to analyze the Air Gap Contactor structure.

The technical reviews are as below:‐

  • Solving Impedance mismatch issues especially when the impedance is lower than required impedance
  • The Electrical Properties of Air provides the best electrical value ‐ could not be achieved in any materials
  • Signal Pin
    • Improve Insertion Loss
    • Improve Return Loss

Summary

  • Easily improve the Electrical Performance for current socket by adding the internal Air Gap, significantly save cost and time.
  • To maximize the electrical performance of the AG Contactors, one must find out the correct height required to obtain the necessary impedance and thus maximizing the Signal Integrity of the Contactors.