Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
2000-05-22
2002-10-01
Le, N. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S754090
Reexamination Certificate
active
06459272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method for inspecting wiring on a circuit board, and more particularly it pertains to such circuit board inspection apparatus and method which inspect for any occurrence of a short-circuit and/or discontinuity of the wirings on the board. The present invention is applicable to inspection of wirings which are formed on various types of boards or substrates, such as printed circuit boards, flexible wiring films or substrates, multi-layer wiring boards, glass substrates for liquid crystal displays and plasma displays, and film carriers for semiconductor packages.
2. Description of Prior Arts
In general, a plurality of wirings are formed on a board in a wiring pattern. A number of wiring inspection apparatuses have already been proposed and marketed which are capable of inspecting whether a wiring pattern is finished as designed. In order to inspect, for example, whether mutually adjacent pair of wirings, sequentially selected from a group of wirings forming the wiring pattern, are short-circuited or not, a conventional wiring inspection apparatus presses a pair of conductive spring probes, electric terminals or the like (representatively referred to as probes) respectively against the selected wirings. A short-circuit condition between the selected pair of wirings is inspected by checking whether a predetermined current flows through the probes as a voltage is applied between the probes.
Such a short-circuit inspection is conducted usually after the wiring pattern is formed on the board by electroplating or other appropriate methods but before electronic parts are mounted on the board.
Immediately after a wiring pattern is formed, all the wiring paths of the wiring pattern are electrically connected to a temporary common wiring which is used for electroplating. Hence, it is not possible to perform a short-circuit inspection described above in this condition. To cope with this problem, a conventional method for wiring inspection employs a step of mechanically insulating the wiring from one another. In more detail, with reference to
FIG. 21
a portion
11
is punched out of a board
1
together with wirings or wiring paths formed thereon to form an elongated opening and to separate the wirings
21
of a wiring pattern
2
, e.g., seven wirings
21
from the common wiring or conductor
3
on the end of one side (i.e., the left-hand side in
FIG. 21
) of the wirings
21
. Thus, the wirings
21
are electrically separated and insulated from one another. In this condition, seven conductive spring probes (
FIG. 21
shows only four probes P
1
through P
4
for the simplicity of illustration) are pressed against ball grids or pads
22
respectively connected with the corresponding wirings
21
and disposed on the opposite surface of the board
1
. Short-circuit inspection is carried out with a voltage being applied to sequentially selected pairs of the probes and electric current is detected therefrom. As to boards which are determined nondefective as a result of the short-circuit inspection, each extra portion of the board
1
is severed along a cutting line
12
(which is denoted at dashed-and-dotted line in FIG.
21
), to finish the circuit board in a final shape.
The conventional short-circuit inspection of the wirings
21
as described above, requires a punching step for separating the wirings
21
from the common wiring
3
and thereby from one another. This additional step increases a cost for producing a printed wiring board. In addition, since it is necessary to ensure a additional area on the board
1
dedicated solely for the punching, an initial board size must be larger than the size of a final printed wiring board, thus even further increasing the production cost of the board. Moreover, recent design requirement for the wiring patterns of printed wiring boards, makes it impossible to leave or form a punch-through portion on the wiring boards as described above.
Thus, it would be an improvement if printed wiring boards could be inspected with the temporary common wiring
3
left unremoved. However, a wiring inspection apparatus or a wiring inspection method to enable such inspection has not been proposed to this date.
It is not only printed wiring boards which require the performance as described above, but glass substrates for liquid crystal displays and plasma displays as well may enjoy the merit of such procedure. That is, as a plurality of transparent electrodes are disposed on a glass substrate, it would be an improvement to inspect a wiring pattern of the group of transparent electrodes with the ends of the transparent electrodes electrically connected to each other.
The above operation also remains true as to film carriers for semiconductor packages. In a semiconductor package of a film carrier type, a plurality of wirings are arranged on a film carrier in conformity with the layout or arrangement of a semiconductor chip. Therefore, it would be an improvement to inspect a wiring pattern of the group of wirings with the ends of the wirings electrically connected to each other.
Further, for the purpose of improved productivity in the manufacturing of wiring boards, wirings are printed or deposited on a plurality of unit boards which are arranged contiguous in a plane one-dimensionally or two-dimensionally and integrated with each other. Where those unit boards are small or flexible, one can easily handle these boards if the boards are integrated into a somewhat large size during the formation of the wirings thereon and the inspection of their wirings. It is therefore effective to manufacture a wiring board with more than one of the unit boards integrated with one another and handled as one block.
FIGS. 22A and 22B
show an example of a plurality of work pieces or unit boards WC (16 pieces in the example in
FIG. 22A
) which are integrated with each other in two dimensional arrangements as a work W. The work pieces will finally be separated from one another into eventually discrete unit pieces or boards, and are respectively incorporated in electric appliances or the like. Wiring processing such as plating, deposition and etching of wirings is performed on the integral work W. In this case, immediately after the wiring process, wiring patterns of the work pieces WC are connected to each other while wirings in each one of the work pieces are connected to each other.
FIG. 22B
shows an example of a circuit pattern formed on each of the work pieces WC.
When such a board or work W is to be inspected by the conventional method as described earlier, inspection is conducted on each of the work pieces WC after they are separated into discrete elements from one another. In the manufacturing, the work pieces are severed from each other and the wirings are separated from each other before the inspection of the wiring, and an integrated circuit chip and other circuit components are thereafter mounted on each work piece. However, the workability of the single work pieces WC is particularly poor when the work pieces WC are small or flexible. If the work pieces could be inspected while they are integrated with one another into a collective or unitary work piece, i.e., the condition just after the wirings are formed, their workability for the inspection will improve, and circuit components may be mounted respectively on the work pieces while they are integral with one another, thereby enhancing workability of the work pieces for the circuit component mounting.
SUMMARY OF THE INVENTION
Accordingly an object of the present invention is to provide a circuit board inspection apparatus which enables inspection of wirings or wiring paths on a circuit board while the wirings are electrically connected with one another on a common terminal.
Another object of the present invention is to provide a method for inspecting wirings or a conductive path on a circuit board while the wirings are electrically connected with one another.
Still another object of the present invention is to provide a ci
Le N.
Nguyen Vincent Q.
Nidec-Read Corporation
Price and Gess
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