Browse Prior Art Database

Liquid Crystal-Based Test Head

IP.com Disclosure Number: IPCOM000101185D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Begasse, P: AUTHOR [+3]

Abstract

Disclosed is a device to test printed circuit boards (PCBs) and interconnection ceramic substrates combining liquid crystal imaging technics with a high-density composite electrical interface.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 76% of the total text.

Liquid Crystal-Based Test Head

       Disclosed is a device to test printed circuit boards
(PCBs) and interconnection ceramic  substrates combining liquid
crystal imaging technics with a high-density composite electrical
interface.

      A) GENERIC TEST HEAD STRUCTURE: The principle is to transfer
the electrical states of the surface of the device under test to a
liquid crystal display (see B) through a vertical interface (see C)

      B) LIQUID CRYSTAL DISPLAY: The imaging is based on the
electro-optical effect on liquid crystals (LCs) which are confined in
a display-like device providing a good LC orientation, a rigid
flatness to control the LC thickness and the electrical polarization
of the LC molecules.

      C) VERTICAL INTERFACE: The vertical interface combines a high
connection density (compatible with the device to test), a high
lateral resistivity, a low vertical resistivity and some flexibility
(to achieve a good electrical contact on non-regular surfaces).

      Depending on the device, two interfaces are proposed:
      - For PCBs testing: commercially available elastomers with 100
um pitch.
- For Ceramic Substrate (see figure): carbon fibers coated with
polymer and elastomer with 10 um pitch.

      The figure shows a carbon fiber test head checking a ceramic
substrate with the following reference numbers:
       1. Liquid crystal display
       2. Conductive layer
       3. Polymer or Solgel coating
    ...