Method and apparatus for circuit board continuity test, tool for continuity test, and recording medium

• US 6,825,673 B1
• Filed: 05/23/2002
• Issued: 11/30/2004
• Est. Priority Date: 05/19/2000
• Status: Expired due to Fees

• Current Assignee: OHT (Shanghai), Inc. (V Technology Co., Ltd.)
• Original Assignee: OHT (Shanghai), Inc. (V Technology Co., Ltd.)
• Inventors: Yamaoka, Shuji
• Primary Examiner(s): Deb, Anjan
• Assistant Examiner(s): Benson, Walter
• Application Number:
  US10/030,104
• Time in Patent Office: 922 Days
• Field of Search: 324/511, 324/527, 324/528, 324/632, 324/633, 324/655, 324/668, 324/682, 324/686, 324/537
• US Class Current: 324/537
• CPC Class Codes: G01R 31/2805 Bare printed circuit boards
• 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
• CPC Class Codes: G01R 31/312 by capacitive methods

Abstract

The present invention provides an apparatus and method for inspecting electrical continuity of a circuit board, capable of decreasing the impedance in a current path as an inspection object to achieve enhanced SN ratio. A coupling capacitance is formed at one of terminals of a pattern wire on a board as an inspection object in a non-contact manner, and an inductance (450) and a lead wire are connected to this capacitance. An AC inspection signal is applied to the other terminal through the lead wire in a contact manner. A resonance circuit is defined by the capacitance, inductance and pattern wire, and thereby an output signal can be detected with lowering the impedance.

Claims

1. A continuity inspection apparatus for inspecting electrical continuity between first and second terminals of a pattern wire formed on a board, said continuity inspection apparatus comprising:

capacitive coupling means to be capacitively coupled with said first terminal in a non-contact manner to provide a coupling capacitance therebetween;

an inductive element connected to said capacitive coupling means to form a resonance circuit in conjunction with the capacitance yielded by said capacitive coupling means in order to inspect said electrical continuity under a low resistance;

a first lead wire connected to said inductive element;

probe means connected to a second lead wire and to be contacted with said second terminal;

signal inputting means for inputting an inspection signal including an AC component into one of said first and second lead wires; and

signal detecting means for detecting an output of said inspection signal at the other of said first and second lead wires.

2. A continuity inspection apparatus as defined in claim 1, wherein said probe means includes a probe connected to said second lead wire, said probe connected directly and detachably to said second terminal in the form of a resistance.

3. A continuity inspection apparatus as defined in either one of claim 1 or 2, wherein said inspection signal is an AC signal.

4. A continuity inspection apparatus as defined in either one of claim 1 or 2, wherein said inspection signal is a pulse signal.

5. A continuity inspection apparatus as defined in claim 1, wherein said board includes a plurality of pattern wires formed thereon, said pattern wires each having first and second terminal groups, wherein said continuity inspection apparatus further includes selecting means for selecting said first terminal from said first terminal group to connect said selected first terminal to said inductive element.

6. A continuity inspection apparatus as defined in claim 5, wherein said selecting means is a multiplexer circuit including a plurality of analog switches.

7. A continuity inspection apparatus as defined in claim 6, wherein said multiplexer further includes a switch for grounding an output of said terminal which is not selected.

8. A continuity inspection apparatus as defined in claim 1, wherein said board includes a plurality of pattern wires formed thereon, said pattern wires each having first and second terminal groups, wherein said continuity inspection apparatus further includes selecting means for selecting said second terminal from said second terminal group to connect said selected second terminal to said second lead wire.

9. A continuity inspection apparatus as defined in claim 8, wherein said selecting means is a multiplexer circuit including a plurality of analog switches.

10. A continuity inspection apparatus as defined in claim 9, wherein said multiplexer further includes a switch for grounding an output of said terminal which is not selected.

18. A continuity inspection apparatus as defined in any one of claim 1 or 2, which further includes means for changing the frequency of said inspection signal.

21. A continuity inspection apparatus as defined in claim 1 or 20, wherein said low resistance ranges from about 10Ω

to about 100Ω

.

11. A continuity inspection method for inspecting electrical continuity between first and second terminals of a pattern wire formed on a board, said continuity inspection method comprising steps of:

positioning a given electrode close to said first terminal to form a coupling capacitance, and connecting a given inductive element to said electrode, followed by connecting a first lead wire to said inductive element and connecting a second lead wire to said second terminal, so as to form a resonance circuit by said first lead wire, inductive element, electrode, coupling capacitance, first terminal, pattern wire, second terminal and second lead wire in order to inspect said electrical continuity under a low resistance;

applying an inspection signal including an AC component to one of said first and second lead wires; and

detecting an output of said inspection signal at the other of said first and second lead wires.

12. A continuity inspection method as defined in claim 11, wherein said inspection signal is an AC signal.

13. A continuity inspection method as defined in claim 11, wherein said inspection signal is a pulse signal.

14. A continuity inspection method as defined in claim 11, which further includes steps of:

forming a plurality of pattern wires on said board, said pattern wires each having first and second terminal groups; and

selecting said first terminal from said first terminal group to connect said selected first terminal to said inductive element.

15. A continuity inspection method as defined in claim 11, which further includes step of:

previous to said step of applying an inspection signal, determining a resonance frequency for a pattern wire between first and second terminals of a given reference board by applying an inspection signal to said reference board while changing the frequency of said inspection signal; and

in said step of applying an inspection signal, applying said inspection signal to one of said first and second lead wires with using said determined resonance frequency as a frequency thereof.

16. A continuity inspection method as defined in claim 11, which further includes step of:

in said step of determining a resonance frequency, changing the frequency of said inspection signal for said reference board within a given range having a center frequency defined by a standard frequency determined based on the constant of said inductive element.

17. A continuity inspection method as defined in claim 11, which further includes step of:

in said step of applying an inspecting signal, changing the frequency of said inspection signal for said board as an inspection object within a given range having a center frequency defined by the frequency determined in said step of determining a resonance frequency.

19. A computer-readable record medium storing thereon a computer program which achieves a continuity inspection method as defined in either one of claim 11.

22. A continuity inspection method as defined in claim 11, wherein said low resistance ranges from about 10Ω

to about 100Ω

.

20. A continuity inspection apparatus for inspecting electrical continuity between first and second terminals of a pattern wire formed densely on a board, said continuity inspection apparatus comprising:

a sensor electrode having a dimensional size so as to provide a coupling capacitance falling within the range of 50 fF to 1 pF with said pattern wire;

an inductive element connected in parallel or series with said sensor electrode, to form a resonance circuit said inductive element having a constant ranging from 20 mH to 25 μ

H in order to inspect said electrical continuity under a low resistance; and

an oscillator oscillating at a reference frequency falling within the rang of 5 MHz to 10 MHz, said oscillator being adapted to change the frequency thereof in a given range from said reference frequency.