Apparatus and method for testing circuit board

• US 6,154,038 A
• Filed: 05/20/1997
• Issued: 11/28/2000
• Est. Priority Date: 09/20/1993
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Ito, Akio, Nakazawa, Kazuhiro, Ozaki, Kazuyuki
• Primary Examiner(s): KARLSEN, ERNEST F
• Application Number:
  US08/859,266
• Time in Patent Office: 1,288 Days
• Field of Search: 324/459, 324/500, 324/501, 324/514, 324/537, 324/750, 324/752, 324/754
• US Class Current: 324/754.23
• CPC Class Codes: G01R 31/309 of printed or hybrid circuits or circuit substrates

Abstract

An apparatus for testing a circuit board has a holder for holding the circuit board, a detector for detecting the electrical characteristics of the circuit board, and a controller for controlling laser plasma switches. The detector has a path forming unit positioned away from the circuit board by a predetermined gap. The path forming unit forms a first conductive path between a position corresponding to a first test pad on a trace of the circuit board and a first power source, as well as a second conductive path between a position corresponding to a second test pad on another trace of the circuit board and a second power source. The controller emits a laser beam to a first space between the first test pad and the first conductive path and another laser beam toward a second space between the second test pad and the second conductive path, to make the first and second spaces conductive. The detector has a sampler connected to one of the first and second conductive paths, to sample electrical characteristic values of the circuit board.

Claims

1. An apparatus for testing a circuit board having wiring patterns and traces with pads, comprising:

a means for holding said circuit board;

a means for detecting the electrical characteristics of said circuit board, having a conductive path between a position corresponding to a first test pad on one of said traces and a first power source as well as a second conductive path between a position corresponding to a second test pad on another of said traces and ground potential;

a means for controlling a first laser plasma switch in a first space between said first test pad and said first conductive path and a second laser plasma switch in a second space between said second test pad and said second conductive path, said first and second laser plasma switches being activated with laser beams to make said first and second spaces conductive;

an electrical characteristic value sampling means included in said electrical characteristics detection means and connected to one of said first and second conductive paths; and

a sealing means for sealing a space between a photoconductive sheet or glass plate and said circuit board, and the sealed space is filled with a pressurized or depressurized air or rare gas,

wherein said laser plasma switch control means makes said first and second spaces conductive, and a predetermined time thereafter, said electrical characteristics detection means drives said sampling means to detect an electrical characteristic value in said conductive paths.

2. An apparatus as claimed in claim 1, wherein said conductive path forming means is made from laser transmission material.

3. An apparatus as claimed in claim 2, wherein said conductive path forming means is made from photoconductive material.

4. An apparatus as claimed in claim 3, wherein said conductive path forming means is made from photoconductive material and has a means for supporting the photoconductive material.

5. An apparatus as claimed in claim 4, wherein said photoconductive material support means has a function of controlling light transmission.

6. An apparatus as claimed in claim 5, wherein said photoconductive material support means is a liquid crystal mask.

7. An apparatus as claimed in claim 6, wherein said photoconductive material support means has a means for controlling patterns to transmit light.

8. An apparatus as claimed in claim 1, wherein said laser plasma switch control means has a means for emitting laser beams and a means for deflecting the laser beams.

9. An apparatus as claimed in claim 3, wherein said electrical characteristics detection means has a means for exciting the photoconductive material.

10. An apparatus as claimed in claim 1, wherein the electrical characteristics detected by said electrical characteristics detection means include resistance, voltages, currents, and insulation resistance.

11. The apparatus of claim 1, wherein said rare gas consists of at least one of argon and neon.

12. The apparatus of claim 1, wherein said sealing means comprises an O-ring.