Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1998-06-01
2001-09-11
Cuneo, Kamand (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S261000, C324S756010, C324S765010, C361S777000
Reexamination Certificate
active
06288346
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an assembly inspection system and method for examining the connected or bonded state of electronic parts of BGA (Ball Grid Array) type or CSP (Chip Scale/Size Package) type.
In recent years, in mounting an electronic part such as an LSI package on a substrate or board, a face bonding method is mainly adopted. BGA type electronic parts and CSP type electronic parts are typically face-bonding type electronic parts. Once an electronic part of the BGA type or that of the CSP type has been mounted in position, a soldered state thereof cannot be visually confirmed. In the process of assembling the board mounted with such a BGA type electronic part or a CSP type electronic part into an electronic equipment, there is a case in which it is impossible to decide whether an equipment failure is due to a defective connection of the BGA/CSP type electronic part or due to another cause. Thus, it is necessary to correctly inspect whether the BGA/CSP type electronic part is correctly bonded on the board. For this purpose, there is proposed an inspection system in which through-hole-provided pads are formed on a printed wiring board in correspondence with ball-shaped solder pads formed on a back surface of the BGA/CSP type electronic part, and in which the state of connection between the BGA/CSP type electronic part and the printed wiring board is inspected after the reflow process according to whether the through-hole-provided pads are filled with solder, as disclosed in Laid-Open Japanese Patent Publication No. 9-127178. Also, as disclosed in Laid-Open Japanese Patent Publication No.7-234189, there is proposed an inspection system utilizing a fine connection inspection device using a sensor.
However, in the former of the above two conventional inspection systems, it is necessary to form on the printed wiring board the through-hole-provided pads corresponding to the ball-shaped solder pads on the back surface of the BGA/CSP type electronic part. Thus, the degree of freedom in designing a pattern deteriorates, which prevents a fine pattern design. In the latter of the two conventional inspection systems, it is necessary to introduce an expensive inspection device and thus the manufacturing cost becomes substantially high.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an assembly inspection system and method capable of inspecting a bonded or connected state of an electronic part of the BGA/ CSP type in a short period of time and at a low cost.
The present invention is applied to an assembly of an electronic part of the BGA/CSP type and a board wherein the electronic part has a plurality of solder pads on a surface thereof confronting the board, and the board has a plurality of connection pads to be bonded with the respective solder pads.
According to the present invention, wiring is extended on the board from each of at least two of the plurality of connection pads to thereby form at least two test lands on the board at locations which are not covered with the electronic part when mounted on the board. Then, an electrical path is formed which extends from each of the test lands to another via wiring of the electronic part and the wiring of the board. Then, a state of electrical connection is inspected between the test lands after bonding the electronic part to the board, to thereby inspect the bonded state between the electronic part and the board.
In an embodiment, the solder pads and the connection pads are arrayed in a matrix form, respectively, and the test lands are connected with the connection pads at four corners of the connection pad array, respectively. Preferably, the wiring of one of the electronic part and the board extends between the solder pads located at first two corners on one side of the solder pad array and between the solder pads located at the other, second two corners on the opposite side of the solder pad array. Also, the wiring of the other of the electronic part and the board extends between the connection pad corresponding to the solder pad located at one of the first two corners and the connection pad corresponding to the solder pad located at one of the second two corners confronting the one of the first two corners. With this arrangement, by inspecting the electrical connection condition between the test lands, an accurate inspection of the bonded state between the electronic part and the board is provided. Also, the position where a faulty connection, if any, has occurred, can be easily inspected.
In an embodiment, the board is formed with five or more test lands, four of which are connected with the connection pads at the four corners of the connection pad array, respectively, and the rest is connected with one or more selected among from the connection pads located in positions other than the four corners. With this arrangement, it is possible to inspect the bonded state between the board and each of the solder pads at the four corners of the electronic part.
REFERENCES:
patent: 4812742 (1989-03-01), Abel et al.
patent: 5010447 (1991-04-01), Wallace
patent: 0 571 963 A2 (1999-12-01), None
patent: 62-274632 (1987-11-01), None
patent: 2-147868 (1990-06-01), None
patent: 4-155273 (1992-05-01), None
patent: A-7-234189 (1995-09-01), None
patent: 8-29454 (1996-02-01), None
patent: A-9-127178 (1997-05-01), None
Ojiri Hirofumi
Yasumoto Takashi
Cuneo Kamand
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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