Voltage injector and detector using pixel array for printed circuit board testing

• US 7,355,385 B2
• Filed: 07/28/2005
• Issued: 04/08/2008
• Est. Priority Date: 07/28/2005
• Status: Expired due to Fees

• Current Assignee: Varex Imaging Corporation
• Original Assignee: Varian Medical Systems Incorporated (Siemens AG)
• Inventors: Zentai, George
• Primary Examiner(s): PATEL, PARESH H
• Application Number:
  US11/192,849
• Publication Number:
  US 20070024272A1
• Time in Patent Office: 985 Days
• Field of Search: None
• US Class Current: 324/763.01
• CPC Class Codes: G01R 31/2812 Checking for open circuits or shorts, e.g. solder bridges; Testing conductivity, resistivity or impedance of connections G01R31/66

Abstract

One embodiment includes an injector pixel array having injector pixels each coupled to the bottom surface of a conductive material having a directional electrical conductivity only in a direction corresponding to a path between the bottom surface and top surface of the conductive material. Each injector pixel includes a semiconductor based switch coupled to a charge or voltage driver to inject a charge or voltage into each injector pixel. Embodiments, also include a detector pixel array having detector pixels each coupled to the bottom surface of the directionally conductive material. Each detector pixel includes a semiconductor based switch coupled to a charge or voltage storage capacitor to detect a charge or voltage at each detector pixel.

Claims

1. An apparatus, comprising:

a conductive material having a first surface and a second surface, the conductive material having a directional electrical conductivity in directions from the second surface to the first surface, and in directions from the first surface to the second surface;

an injector pixel array having a plurality of injector pixels, each injector pixel coupled to the second surface of the conductive material and having a semiconductor based electronically addressable switch coupled to a driver to inject a charge or a voltage into each injector pixel.

2. The apparatus of claim 1, wherein the switch is an electronically activated switch;

and wherein the driver is one of a charge injector, a voltage injector, a pulse addresser, and an excitation pulse generator.

3. The apparatus of claim 1, wherein each injector pixel comprises an electronically addressable thin film transistor (TFT) or an electronically addressable complementary metal oxide semiconductor (CMOS) switch coupled between an injector electrode and a TFT or a CMOS driver amplifier.

4. The apparatus of claim 1, further comprising:

a detector pixel array having a plurality of detector pixels, each detector pixel coupled to the second surface of the conductive material and having a thin film transistor (TFT) or a complementary metal oxide semiconductor (CMOS) detector capacitor coupled to a TFT or CMOS switch coupled to detect a charge or a voltage at each detector pixel.

5. The apparatus of claim 4, wherein an electrostatic charge corresponding to a voltage injected by a driver through a trace on a printed circuit board (PCB) and electrically coupled to the first surface may be detected from the trace by a detector pixel, wherein the injection pixel is the same pixel as the detector pixel.

6. The apparatus of claim 4, wherein the injector pixels are the same as the detector pixels and the apparatus is an electrostatic imager to test an electronically adressed testing pattern of traces of a PCB by injecting charges or voltages into the traces using the injector pixels and detecting the injected charges or voltages using the detector pixels.

7. The apparatus according to claim 6, further comprising:

a tri-state enable driver circuit at each pixel to disconnect the driver from the pixel during detection.

9. The apparatus of claim 4, wherein an electrostatic charge or a voltage injected by a driver through a first trace on a first side of a printed circuit board (PCB) and electrically coupled to the first surface may be detected by a detector pixel from a second trace on a second side of the PCB coupled to the first trace by at least one conductive via through the PCB.

10. The apparatus of claim 4, wherein the apparatus is a first apparatus, the first surface is electrically coupled to a first trace on a first side of a printed circuit board (PCB) having a conductive via connecting the metal trace to a second trace on a second side of the PCB, and

further comprising a second apparatus similar to the first apparatus, having a first surface electrically coupled to the second trace to detect a signal injected by the first apparatus.

11. The apparatus of claim 4, wherein the injector pixel array is part of a first device coupled to a controller and the detector pixel array is a part of a different second device coupled to the controller.

12. The apparatus of claim 4, further comprising:

a controller to apply a plurality of test voltages to an only electronically addressed charge pattern of a plurality of conductive traces of a PCB using a plurality of drivers, and to check an only electronically addressed readout pattern from a plurality of detector pixels at a plurality of locations associated with the conductive traces, wherein the readout pattern comprises a plurality of readout voltages corresponding to the plurality of applied voltages.

13. The apparatus of claim 1, wherein the conductive material is configured to conduct electricity only in directions corresponding to a path between a contact point on the second surface and a contact point on the first surface.

14. The apparatus of claim 1, wherein the conductive material comprises:

a layer of electrically insulating material having a plurality of disconnected conductive fibers extending from the second surface to the first surface.

15. The apparatus of claim 14, wherein the insulating material is one of silicon and a hardened epoxy, other soft insulating material and the conductive fibers are carbon fibers, metal ferromagnetic fibers, or semiconductor fibers.

16. The apparatus of claim 14, wherein the conductive fibers are electrically coupled to a trace of a PCB disposed over the injector pixel.

17. The apparatus of claim 1, wherein the conductive material comprises:

a thickness between 10 E-6 meters and 2000 E-6 meters in thickness.

8. The apparatus of 6, further comprising:

a switch to switch between connecting and disconnecting the driver from the pixel.

18. An apparatus, comprising:

a conductive material having a first surface and a second surface, the conductive material having a directional electrical conductivity in directions from the second surface to the first surface, and in directions from the first surface to the second surface;

an injector pixel array having a plurality of injector pixels, each injector pixel coupled to the second surface of the conductive material and having a semiconductor based switch coupled to a driver to inject a charge or a voltage into each injector pixel, wherein the semiconductor based switch of each injector pixel is part of an electronically addressed pattern.

19. The apparatus of claim 18, wherein the apparatus is an electrostatic imager to test an electronically addressed testing pattern of traces of a PCB by electronically addressing a switch of each injector pixels to form the pattern.

20. The apparatus of claim 18, wherein each injector pixel comprises an electronically addressable thin film transistor (TFT) or an electronically addressable complementary metal oxide semiconductor (CMOS) switch coupled between an injector electrode and a TFT or a CMOS driver amplifier.

21. The apparatus of claim 18, further comprising:

a detector pixel array having a plurality of detector pixels, each detector pixel coupled to the second surface of the conductive material and having a thin film transistor (TFT) or a complementary metal oxide semiconductor (CMOS) detector capacitor coupled to a TFT or CMOS switch coupled to detect a charge or a voltage at each detector pixel.