Method for testing a partially constructed electronic circuit

• US 5,561,381 A
• Filed: 01/08/1993
• Issued: 10/01/1996
• Est. Priority Date: 12/13/1989
• Status: Expired due to Term

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Wisnieff, Robert L., Jenkins, Leslie C.
• Primary Examiner(s): Regan, Maura K.
• Application Number:
  US08/002,293
• Time in Patent Office: 1,362 Days
• Field of Search: 324/158 R, 324/158 T, 324/158 D, 324/618, 324/537, 324/770, 359/80
• US Class Current: 324/678
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G01R 31/2621 for testing field effect transistors, i.e. FET's

Abstract

A sense circuit for detecting charge on a TFT/LCD cell capacitor, which comprises a first, integrating circuit attached to the TFT/LCD cell capacitor through a data line, wherein the data line is connected to the cell capacitance through a thin film transistor is disclosed. The thin film transistor including a gate, a drain and a source, wherein the source is connected to the cell capacitor and the drain is connected to the data line. A first, gate supply voltage adapted to drive the gate of the thin film transistor. And a reset circuit adapted to reset the integrating circuit. This embodiment may further include a source for charging said cell capacitor prior to measuring the charge. Further, a method of testing a partially constructed electronic circuit, for example the cell of an LCD, prior to installation of the backplate is also disclosed. The partial circuit comprising an array of contact electrodes, for example cell pad electrodes and an array of address electrodes, for example gate electrodes. The address electrodes being electrically connected to the contact electrodes. The method comprising the steps of providing the partial circuit with a test electrode, for example an adjacent data electrode extending alongside but spaced from at least a first contact electrode; and measuring the capacitance between the first contact electrode and the test electrode.

Claims

1. A method of testing a partially constructed electronic circuit, said partial circuit being combinable with a remainder circuit to form a complete circuit, said partial circuit comprising an array of contact electrodes and an array of switch activating electrodes for activating switches on said electronic circuit, said contact electrodes being electrically connectable to the remainder circuit, said activating electrodes being electrically connected to the contact electrodes, said method comprising the steps of:

providing on the partial circuit a test electrode extending alongside but spaced from at least a first contact electrode; and

measuring the capacitance between the first contact electrode and the test electrode;

wherein;

each contact electrode comprises an electrode pad of a liquid crystal display cell which is partially constructed and one of said switches, each switch having first and second inputs and an output, said first input being electrically connected to one activating electrode associated with the contact electrode, said second input being electrically connected to another activating electrode associated with the contact electrode and said output being electrically connected to the electrode pad; and

the measuring step comprises;

energizing the activating electrodes associated with the contact electrode so as to store electric charge on the electrode pad when the electronic circuit is partially constructed; and

measuring the electric charge stored on the electrode pad by integrating current flowing between said contact electrode and said test electrode over a period of time.

2. A method as claimed in claim 1, wherein:

the electrode pad is electrically connected to and addressable by energizing a unique pair of activating electrodes associated with that contact electrode; and

the step of measuring comprises measuring the capacitance between the first contact electrode and an activating electrode which is not electrically connected to or associated with the first contact electrode.

3. A method as claimed in claim 2, further comprising the steps of:

separately measuring the capacitance between each contact electrode and an activating electrode which is not electrically connected to or associated with the contact electrode.

4. The method of claim 1, wherein said test electrode is grounded.

5. The method of claim 1, wherein said electronic circuit includes a thin film transistor array for a liquid crystal display without a backplate.