WO2001036929A2 - Controle de trous de liaison dans un systeme de controle optique - Google Patents

Controle de trous de liaison dans un systeme de controle optique Download PDF

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Publication number
WO2001036929A2
WO2001036929A2 PCT/US2000/041911 US0041911W WO0136929A2 WO 2001036929 A2 WO2001036929 A2 WO 2001036929A2 US 0041911 W US0041911 W US 0041911W WO 0136929 A2 WO0136929 A2 WO 0136929A2
Authority
WO
WIPO (PCT)
Prior art keywords
diffuser
camera
vias
inspection
light source
Prior art date
Application number
PCT/US2000/041911
Other languages
English (en)
Other versions
WO2001036929A3 (fr
Inventor
Gary E. Frame
Original Assignee
Midas Vision Sysems, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Midas Vision Sysems, Inc. filed Critical Midas Vision Sysems, Inc.
Priority to AU27511/01A priority Critical patent/AU2751101A/en
Publication of WO2001036929A2 publication Critical patent/WO2001036929A2/fr
Publication of WO2001036929A3 publication Critical patent/WO2001036929A3/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/8806—Specially adapted optical and illumination features
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/956—Inspecting patterns on the surface of objects
    • G01N21/95692—Patterns showing hole parts, e.g. honeycomb filtering structures

Definitions

  • This invention relates to optical inspection systems .
  • Optical inspection systems are used to inspect objects such as printed circuit boards.
  • Such systems generally include a camera and a light source to illuminate the printed circuit board.
  • the camera is used to produce a video signal that is processed to determine whether the printed circuit board passes or fails an inspection.
  • Such systems may include a telecentric lens.
  • the telecentric lens is disposed between the camera and the assembly, and is as wide as the light source.
  • an optical inspection apparatus includes a platform for holding a device under inspection and a light source disposed to illuminate a backside portion of the device.
  • the inspection apparatus also includes a camera disposed over a front side portion of the device to receive optical energy that penetrates through the device and a diffuser disposed over a front side portion of the device, said diffuser producing an image on a bottom surface of said diffuser, for processing by the camera.
  • the apparatus is arranged such that the image is of features of the device produced from light that penetrates the device.
  • the apparatus can be used to inspect vias in printed circuit boards, ceramic substrates or substrates having an array of vias with the vias having a high aspect ratio.
  • the apparatus can use a collimated light source.
  • the diffuser can be a ground glass plate or a sheet of plastic having an etched surface.
  • the apparatus can also include a processor to process a video signal from the camera to determine whether the device passes an inspection.
  • a method for optically inspecting a substrate having a via includes arranging a diffuser between a platform for holding a substrate under inspection, illuminating a backside portion of the substrate with a light source and producing an image on a bottom surface of said diffuser, for processing by a camera disposed over the front side of the substrate in response to received optical energy that penetrates through the substrate.
  • FIG. 1 is a block diagram of a machine inspection system including a diffuser placed over a device under inspection.
  • FIG. 2 is a diagrammatical view of the system of
  • FIG. 3 is a plan view of a printed circuit board having vias that are inspected by the system of FIG. 1.
  • FIG. 3A is a cross-sectional view taken along lines 3A-3A of FIG. 3.
  • FIG. 4 is a plan view of a diffuser disposed over the PC board of FIG. 3.
  • FIG. 4A is a cross-sectional view taken along lines 4A-4A of FIG. 4.
  • FIG. 5 is a blown up view of a portion of FIG.
  • FIG. 5A is a blown up view of a portion of FIG. 4A.
  • FIG. 6 is a flow chart depicting a process to examine vias in the system of FIG. 1.
  • the machine inspection system 10 includes a camera 12 that is disposed above a platform 14.
  • the platform 14 is supported by a stand 15.
  • the platform 14 holds an assembly 30 including a device to undergo an inspection such as a printed circuit board 32 (PCB) and a diffuser 36 disposed on a surface of the printed circuit board 32.
  • the diffuser 36 is further described in conjunction with FIG. 2.
  • the system 10 also includes a light source 16 disposed under the platform 14 so that the light is incident on a surface of the assembly 30 that is opposite to the surface of the assembly 30 having the diffuser 36.
  • the inspection system 10 can be used to inspect ceramic substrates, or any other material. It is especially useful on boards that contain an array of vias where the vias have a high aspect ratio, i.e., depth to width of e.g., 3-5 or more.
  • Platform 14 engages the assembly 30 on its side, as shown. Other arrangements can be used as long as it does not obstruct light from entering the vias from underneath the PC board.
  • the light source 16 is disposed under the platform 14 such that light rays 16a are incident on the bottom surface of the board 32, and shine through the vias in board 32 and the diffuser as light rays 16b that are intercepted by camera 12.
  • the camera 12 produces a video signal that is fed to processor 18.
  • the video signal is used in the processor 18 to process the video signal into an image signal.
  • the image can be displayed on display device 20 and information from the video signal or image can be used to inspect the assembly by various techniques such as design rule, pixel counting or template matching as disclosed, for example in U.S.
  • the camera 12 has a field of view that is larger than the diameter of the lens.
  • the camera includes lens 12a that is part of an optical system and the detector 12b.
  • a large field of view is provided by using a detector 12b with a large number of detector elements e.g., 2,048 elements, 4,096 elements or 8,192 elements. Each element may represent a predefined area e.g., .001 inches or .002 inches. Thus, a 8,192 element detector would have a 8.192 or 16.384 inch field of view.
  • Such a detector 12b provides a larger field of view to make the inspection process faster.
  • the process is faster because there is less motion i.e., scans of the camera 12 across the device to be inspected, as illustrated by the three phantom positions shown for the camera 12 in FIG. 1. While a larger field of view provided by a camera having a larger number of elements is desirable to make inspections faster, there are some problems associated with this arrangement, in particular, when examining vias. Large fields of view progressively exacerbate these problems when compared to smaller fields of view. As cameras with higher fields of view are used, vias on the periphery of the field of view can appear to be deformed because of the way that light is captured by the camera.
  • This field of view problem becomes especially important with high aspect ratio vias, e.g., those vias that have a depth substantially greater than their width (e.g., 5-20 or more aspect ratios) .
  • the only light that comes through the vias travels in a straight line parallel to the via axis.
  • the light coming from vias at the periphery of the board will not hit the lens 12a in the camera since it is relatively small.
  • the lens 12a of the camera is typically 1 inch in diameter.
  • the light from vias at the edges of the board will not hit the lens and thus via will not be seen by the camera.
  • some printed circuit boards may also have vias that are large.
  • light can come in at a wider range of angles. That makes the intensity of the light appear brighter at the center of the large vias because more light gets into the wider via since the light comes in from a wider range of angles.
  • printed circuit board 32 includes a plurality of vias, e.g., three vias 33a-33c, drilled or otherwise disposed through the board 32.
  • via 33a is disposed towards the periphery of the board 32; whereas, via 33b is disposed towards the center of board 32.
  • Via 33c is not further referenced since it is shown in the subsequent cross- sectional views of the remaining figures.
  • camera 12 as shown in FIG. 1, has a large field of view and a relatively high magnification, the light that enters the camera through via 33a disposed at the periphery of the field can be distorted making the via 33a appear as an oval when in fact it is completely round.
  • Via 33a may appear partially plugged because of the way that light is captured by the camera from the via 33a.
  • the via 33a may have a high aspect ratio i.e., the board may be ten or more times as thick as the width of the via 33a. The smaller the via 33a, the less likely that light through the via 33a will hit the lens and the more likely it is that the via 33a can be mistaken as a malformed or plugged via by the inspection process in processor 18.
  • a second problem occurs with simple backlighting of the image.
  • the use of non-collimated light produces a hot spot in the center of the image.
  • This nonuniform light intensity over the surface of the holes may also cause the machine inspection processing 18 to interpret that occurrence as a malformed via.
  • the assembly 30 includes the diffuser disposed over the PC board 32.
  • diffuser 36 examples include a ground glass plate and a sheet of plastic film such as Mylar which is etched on one surface and is commercially available at drafting supply stores. Other examples are possible.
  • the diffuser 36 serves to diffuse light coming through the vias 33a-33c and project the light as an image at the bottom of the diffuser e.g., glass plate or Mylar film.
  • the plate can have any reasonable thickness, e.g., 0.1 to 0.5 inches or other thickness and the sheet of plastic can be one to several e.g., 10 or so mils thick.
  • the diffuser 36 produces an image 37 on the bottom surface thereof that can be seen from the top surface.
  • the image 37 is provided without the concomitant distortion that is seen by the camera 12 when light simply travels through the via towards the camera 12.
  • Ground glass produces the image 37 on one surface so that it can be viewed from the other surface.
  • the Mylar embodiment has a very small amount of surface roughness on one side that gives the Mylar a hazy appearance. This has the same characteristics as ground glass. Mylar is a thinner and less expensive and is available in larger quantities.
  • the diffuser 36 provides an imaging plane above the board. All of the light that passes through the vias is incident on the imaging plane and actually produces the image 37 on the diffusing surface that is free of distortion. For ground glass or Mylar the image 37 is produce on the bottom of the diffuser 36 while the camera captures the image 37 through the glass or Mylar at the top surface. The image 37 captured in this manner is free of the restrictions caused by the angle of the light.
  • the field of view restriction is not present in the projected image 37 on the image plane.
  • the backlighting source 16 is preferably a collimated source 16'.
  • source 16 could be a non-collimated light source that has a collimating lens 17 disposed thereover or other arrangements.
  • the collimated source 16' produces light rays that are parallel to each other, such that all light enters the vias at the same angle and is collected on the ground glass or etched surface at the same intensity for any size hole.
  • the process 60 includes disposing 62 a diffuser 36 over a top surface of the device under inspection such as the printed circuit board having vias.
  • Light preferably from a collimated light source, is directed towards the backside of the device and passes through the vias and through the diffuser 36 disposed on the device under inspection.
  • the light that travels through the vias forms an image on the bottom surface of the diffuser.
  • the image is captured by the camera 12.
  • the camera 12 receives this image from the bottom portion of the diffuser and processes the image using conventional techniques such that the image can be compared to a template or other vision recognition process to determine whether the vias which represent the image correspond to properly drilled holes.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

L'invention concerne un appareil de contrôle optique. Cet appareil comprend un plateau pour supporter un dispositif contrôlé et une source de lumière est prévue pour éclairer une partie arrière du dispositif. Cet appareil de contrôle comprend également une caméra placée sur une partie latérale avant du dispositif pour recevoir l'énergie optique qui pénètre par le dispositif et un diffuseur également placé sur une partie latérale avant du dispositif. La source d'éclairage fournit une image sur une surface de fond du diffuseur en vue de son traitement par la caméra.
PCT/US2000/041911 1999-11-05 2000-11-06 Controle de trous de liaison dans un systeme de controle optique WO2001036929A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU27511/01A AU2751101A (en) 1999-11-05 2000-11-06 Via inspection in optical inspection system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US43488599A 1999-11-05 1999-11-05
US09/434,885 1999-11-05

Publications (2)

Publication Number Publication Date
WO2001036929A2 true WO2001036929A2 (fr) 2001-05-25
WO2001036929A3 WO2001036929A3 (fr) 2001-12-06

Family

ID=23726097

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2000/041911 WO2001036929A2 (fr) 1999-11-05 2000-11-06 Controle de trous de liaison dans un systeme de controle optique

Country Status (3)

Country Link
AU (1) AU2751101A (fr)
TW (1) TW466337B (fr)
WO (1) WO2001036929A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111795954A (zh) * 2020-09-09 2020-10-20 苏州鼎纳自动化技术有限公司 一种透光度精密检测机构

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4560273A (en) * 1982-11-30 1985-12-24 Fujitsu Limited Method and apparatus for inspecting plated through holes in printed circuit boards
US4655349A (en) * 1984-12-27 1987-04-07 Brockway, Inc. System for automatically inspecting transparent containers for sidewall and dimensional defects
US4818617A (en) * 1986-08-14 1989-04-04 Stock Larry A Method and material for checking drilled printed circuit boards
US4843231A (en) * 1986-07-28 1989-06-27 Saint-Gobain Cinematique Et Controle Apparatus for the inspection of transparent materials utilizing a diffusing screen
US5301012A (en) * 1992-10-30 1994-04-05 International Business Machines Corporation Optical technique for rapid inspection of via underetch and contamination

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4560273A (en) * 1982-11-30 1985-12-24 Fujitsu Limited Method and apparatus for inspecting plated through holes in printed circuit boards
US4655349A (en) * 1984-12-27 1987-04-07 Brockway, Inc. System for automatically inspecting transparent containers for sidewall and dimensional defects
US4843231A (en) * 1986-07-28 1989-06-27 Saint-Gobain Cinematique Et Controle Apparatus for the inspection of transparent materials utilizing a diffusing screen
US4818617A (en) * 1986-08-14 1989-04-04 Stock Larry A Method and material for checking drilled printed circuit boards
US5301012A (en) * 1992-10-30 1994-04-05 International Business Machines Corporation Optical technique for rapid inspection of via underetch and contamination

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111795954A (zh) * 2020-09-09 2020-10-20 苏州鼎纳自动化技术有限公司 一种透光度精密检测机构

Also Published As

Publication number Publication date
TW466337B (en) 2001-12-01
AU2751101A (en) 2001-05-30
WO2001036929A3 (fr) 2001-12-06

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