Method for Measuring Display Bond Resistances

Patent metadata

Field	Value
Publication number	US-2016202298-A1
Application number	US-201614993711-A
Country	US
Kind code	A1
Filing date	Jan 12, 2016
Priority date	Jan 13, 2015
Publication date	Jul 14, 2016
Grant date	—

Abstract

A display may have a substrate layer to which a display driver integrated circuit and flexible printed circuit are bonded. The display driver integrated circuit may be provided with switches and control circuitry for controlling the operation of the switches during bond resistance measurements. Test equipment may apply currents to pads in the display driver integrated circuit through contacts in the flexible printed circuit while controlling the switching circuitry. Based on these measurements and the measurement of trace resistances in a dummy flexible printed circuit, the test equipment may determine bond resistances for bonds between the display driver integrated circuit and the display substrate and between the flexible printed circuit and the display substrate. Displays may have master and slave display driver integrated circuits that share coarse reference voltages produced by the master from raw power supply voltages.

First claim

What is claimed is:

1 . A display driver integrated circuit, comprising:
display driver circuitry for supplying signals to a display, wherein the display driver circuitry includes control circuitry; a first tristate output buffer coupled to a first pad for supplying a first of the signals to the display; a second tristate output buffer coupled to a second pad for supplying a second of the signals to the display, wherein the first and second tristate buffers are controlled by the display driver circuitry; and a ground; and switching circuitry coupled between the first and second pads and the ground that is controlled by the control circuitry to make bond resistance measurements.

2 . The display driver integrated circuit defined in claim 1 wherein the switching circuitry includes a first switch coupled between the first pad and the second pad.

3 . The display driver integrated circuit defined in claim 2 wherein the switching circuitry includes a second switch coupled between the first pad and the ground.

4 . The display driver integrated circuit defined in claim 3 wherein the switching circuitry includes a third switch coupled between the second pad and the ground.

5 . The display driver integrated circuit defined in claim 4 wherein the first and second bond pads are bonded to the display and wherein the bond resistance measurements include measurements of resistances associated with bonds between the bond pads and the display.

6 . The display driver integrated circuit defined in claim 5 wherein a flexible printed circuit is bonded to the display and wherein the bond resistance measurements include measurements of resistances associated with bonds between the flexible printed circuit and the display.

7 . A method of measuring bond resistances for a display having a display substrate and a display driver integrated circuit, wherein the display driver integrated circuit has first and second pads attached with bonds to corresponding pads on the display substrate, wherein a flexible printed circuit has third and fourth second pads attached with bonds to corresponding pads on the display substrate, wherein the flexible printed circuit has first and second contacts that are coupled respectively to the first and second pads on the display driver integrated circuit through traces in the flexible printed circuit and the third and fourth pads on the flexible printed circuit, and wherein measuring the bond resistances includes measuring bond resistances associated with the bonds for the first and second pads of the display driver integrated circuit and the bonds for the third and fourth pads of the flexible printed circuit, the method comprising:
with test equipment, applying at least a first current to the first contact, wherein the first current flows through the flexible printed circuit, the third and fourth pads, the bonds with which the third and fourth pads of the flexible printed circuit are attached to the display substrate, and the bonds with which the first and second pads of the display driver integrate circuit are attached to the display substrate; and while the first current is applied to the first contact, measuring a first voltage on the first contact with the test equipment.

8 . The method defined in claim 7 further comprising:
measuring a second voltage on the second contact while the first current is applied to the first contact.

9 . The method defined in claim 8 further comprising:
applying a second current to the first contact.

10 . The method defined in claim 9 further comprising:
measuring a third voltage on the first contact while the second current is applied to the first contact.

11 . The method defined in claim 10 further comprising:
measuring a fourth voltage on the second contact while the second current is applied to the first contact.

12 . The method defined in claim 11 further comprising:
determining the bond resistances associated with the bonds for the first and second pads of the display driver integrated circuit and the bonds for the third and fourth pads of the flexible printed circuit based at least partly on the first and second currents and the first, second, third, and fourth voltages.

13 . The method defined in claim 12 further comprising:
coupling the test equipment to a dummy flexible printed circuit; and
measuring a trace resistance for a trace on the dummy flexible printed circuit with the test equipment while the test equipment is coupled to the dummy flexible printed circuit.

14 . The method defined in claim 13 wherein determining the bond resistances associated with the bonds for the first and second pads of the display driver integrated circuit and the bonds for the third and fourth pads of the flexible printed circuit comprises determining the bond resistances associated with the bonds for the first and second pads of the display driver integrated circuit and the bonds for the third and fourth pads of the flexible printed circuit based at least partly on the measured trace resistance.

15 . The method defined in claim 14 wherein a switch is coupled between the first and second pads, the method further comprising:
closing the switch while applying the first current.

16 . The method defined in claim 15 further comprising:
opening the switch during normal operation of the display driver integrated circuit in which signals are supplied from the display driver integrated circuit to pixels in the display.

17 . Apparatus, comprising:
a display having a display substrate; a display driver integrated circuit that is coupled to the display substrate with first bonds and that has switches; a flexible printed circuit that has traces and that is coupled to the display substrate with second bonds; and test equipment that determines resistances for the first and second bonds by applying currents to the flexible printed circuit and measuring voltages while controlling the switches.

18 . The apparatus defined in claim 17 wherein the first bonds comprise solder bonds.

19 . The apparatus defined in claim 18 wherein the second bonds comprise conductive adhesive bonds.

20 . The apparatus defined in claim 19 wherein the test equipment is configured to make flexible printed circuit trace resistance measurements on a dummy flexible printed circuit and wherein the test equipment is configured to determine the resistances for the first and second bonds at least partly based on the trace resistance measurements.

Assignees

• Apple Inc

Inventors

• Brahma Kingsuk
• Stronks David A
• Bae Hopil
• Yao Wei H

Classifications

• G09G3/2096

  Details of the interface to the display terminal specific for a flat panel (suitable for both CRT and flat panel G09G5/006; specific for a CRT G09G1/167) · CPC title

• G09G2320/0223

  Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes · CPC title

• G09G3/006

  Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays (testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309) · CPC title

• G09G3/3607

  for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels (display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127) · CPC title

• G09G3/2092

  Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto (suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165) · CPC title