Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
1998-09-25
2001-08-21
Boudreau, Leo (Department: 2621)
Image analysis
Applications
Manufacturing or product inspection
C382S147000, C382S154000, C250S559340
Reexamination Certificate
active
06278797
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for inspecting a substrate or circuit board on which is arranged two-dimensionally a plurality of terminal pads or contact pads (herein referred to as lands) for electrical connection with a chip or another circuit board (circuit board provided with lands being herein referred to as “land-attached circuit board”).
2. Description of the Related Art
In recent years, there is an increasing tendency that integrated circuit chips, such as microprocessor chips and computer chips are becoming higher in the density of integration and rapidly increasing in the number of input/output terminals. Such a chip is connected to a printed circuit board such as a motherboard by way of a flip-chip connecting board. The number of lands formed on the front surface of the connecting board is several hundreds at the minimum and several thousands at the maximum. Further, on the rear surface of the connecting board are formed a number of lands which correspond in position to the respective lands of a matching printed circuit board for connecting the connecting board to the printed circuit board by means of solder balls, etc. In this connection, if the lands formed on the substrate are, for example, not in place or not uniform in the height level of the surface thereof due to waviness, warping, bending, etc., there arises a problem in that a defective connection may possibly occur to cause a malfunction of an integrated circuit, so strict inspection of the lands is necessitated.
Heretofore known as the most popular inspecting technique for inspecting the formed condition of each land of such a land-attached circuit board, is an inspection technique of picking up a rear surface side image of the board by means of a CCD camera or the like and making a judgement on whether the formed condition of each land is good or not, on the basis of the picked-up image. However, such an inspection technique based on the picked-up image has a disadvantage in that it can never obtain information on land surface height distribution though it can carry out inspection of the position, area, etc. of the land with ease. In this connection, it is considered to first carry out measurement of land area or other dimensions on the basis of the picked-up image and then carry out inspection of height distribution by using a known laser height measurement technique such as a knife edge technique and confocal technique. However, such inspection and measurement require a laser height measurement apparatus and an inspection apparatus for inspection on the basis of a picked-up image, respectively and separately, thus resulting in an increased cost of the apparatus. Further, by the known laser height measurement technique, it takes several seconds to measure the surface height level of one land (hereinafter referred to as land height level). Thus, in case of the board having a great number of lands, it takes a time ranging from several tens of minutes to several hours to measure the heights of all the lands on one circuit board, so it is actually impossible to carry out 100% inspection of mass-produced circuit boards.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided a novel and improved apparatus for inspecting a circuit board with a plurality of lands disposed on one side of a circuit board substrate two-dimensionally, which side has at a place other than a place provided with the lands an exposed portion constituting a background surface which is different in reflectance from a surface of each of the lands. The apparatus comprises a measurement system which includes:
a beam source for supplying an inspection beam onto an inspection surface of the circuit board, the inspection surface including a surface region where the lands are disposed;
a beam receiving section for receiving a reflected beam resulting from the inspection beam and reflected from the inspection surface, and producing a detection output which varies according to a reflected beam brightness and a reflected beam received position at the beam receiving section;
beam scanning means for scanning the beam within the inspection surface two-dimensionally;
height level information preparing means for preparing height level information which is information on height level at respective positions within the inspection surface, on the basis of the detection output reflecting the reflected beam received position at the beam receiving section; and
reflected beam brightness information preparing means for preparing reflected beam brightness information which is information on the reflected beam brightness at respective positions on the inspection surface.
The apparatus further comprises:
land existing region fixing means for fixing, within the inspection surface, land existing regions where the respective lands exist, on the basis of the difference in the reflected beam brightness represented by the reflected beam brightness information, between the background surface and the surface of each of the lands;
inspection information preparing means for preparing inspection information including land height level information which is information relating to surface height levels of the respective lands, on the basis of the height level information at respective positions within the land existing regions fixed by the land existing region fixing means; and
inspection information output means for outputting the inspection information prepared by the inspection information preparing means.
An object to be inspected by the present invention is a circuit board which has an exposed side surface between lands (i.e., background surface), which exposed side surface is different in reflectance with respect to an inspection beam from a surface of each land. Specifically, a substrate for the circuit board is made of a resinous material such as a high polymer material, a ceramic material or the like. A surface portion of the land is constituted by a metallic layer such as a gold-plated layer. Thus, the surface of the land constitutes a high reflectance region, whereas the background surface portion made of a resinous material such as a high polymer material constitutes a low reflectance region.
In the above described inspection apparatus, the beam such as a laser beam is scanned two-dimensionally on the inspection surface of the circuit board with the lands while allowing its reflected beam from the inspection surface to be received by the beam receiving section. The beam receiving section is formed by a device, such as a position sensitive detector (PSD), which is capable of producing an output which varies according to the reflected beam brightness and reflected beam received position (which reflects the height level of the reflection surface). On the basis of the output of the beam receiving section, the reflected beam brightness information and height level information at respective positions on the inspection surface are prepared. From the reflected beam brightness information at the respective positions, the existing region of each of the lands on the inspection surface can be fixed. From the height level information at the respective positions within the thus fixed land existing region, the land height level can be fixed. That is, by the use of a single inspection apparatus, it becomes possible to detect the information on the land existing region, and the size, area, formed position, etc. of the land. Further, inspection of height levels of a number of lands can be carried out rapidly by two-dimensional scanning of an inspection beam.
In the meantime, in case the circuit board substrate is made of a high polymer material or a ceramic material whose outer surface is lower in reflectance with respect to the inspection beam than the surface of each land (i.e., low reflectance material), the land existing region fixing means can fix the land existing regions by regarding the regions which enable detection of a reflected beam brightness level equal to or hig
Kotagiri Akira
Matsubara Yoichi
Nagasaki Masato
Tsunekawa Tomoyoshi
Boudreau Leo
Foley & Lardner
NGK Spark Plug Co. Ltd.
Werner Brian P.
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