Auatomatic inspection system for IC lead frames and visual inspection method thereof

• US 4,851,902 A
• Filed: 08/05/1987
• Issued: 07/25/1989
• Est. Priority Date: 10/29/1986
• Status: Expired due to Fees

• Current Assignee: Electroplating Engineers Of Japan Limited (Tanaka Holdings Company Limited)
• Original Assignee: Electroplating Engineers Of Japan Limited (Tanaka Holdings Company Limited)
• Inventors: Tezuka, Junichi, Kishi, Takaaki, Murata, Yasuto
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Kostak, Victor R.
• Application Number:
  US07/082,097
• Time in Patent Office: 720 Days
• Field of Search: 358/101, 358/106, 358/107, 209/525, 209/526, 209/577, 382/8
• US Class Current: 348/126
• CPC Class Codes: B07C 5/08 measured electrically or electronically B07C5/10 takes precedence ; sorting according to electric or electromagnetic properties B07C5/344; measuring size in general using electric or magnetic means G01B7/00; testing coins G07D5/00
• CPC Class Codes: B07C 5/10 measured by light-responsive means sorting according to colour B07C5/342
• CPC Class Codes: B07C 5/3416 according to radiation transmissivity, e.g. for light, x-rays, particle radiation detecting hidden objects G01V
• CPC Class Codes: B07C 5/3422 using video scanning devices, e.g. TV-cameras
• CPC Class Codes: G01R 31/304 of printed or hybrid circuits G01R31/305 - G01R31/315 take precedence
• CPC Class Codes: H01L 21/67276 Production flow monitoring, e.g. for increasing throughput program-control systems per se G05B19/00, e.g. total factory control G05B19/418
• CPC Class Codes: H01L 21/67288 Monitoring of warpage, curvature, damage, defects or the like
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

The a system includes a visual inspection unit, a plating thickness inspection unit, and a shape inspection unit, suitably arranged in combination on the inspection line for automatic inspection of stains, flaws, glossiness or deformation in plated IC lead frames. The system can be used by an inventive method to correct errors in positional relation between a reference image and images input from an inspection camera, to obtain a comparison between a reference luminance curve and the individual luminance curves and the correlation between reflectivity and the corresponding area, and to obtain a comparison between the reference correlation and individual correlations to thereby enhance automation and precision in inspection IC lead frames.

Claims

1. An automatic inspection system for IC lead frames, comprising:

an inspection line having an input terminal and comprising a visual inspection unit, a shape inspection unit, a loading unit adapted to transfer one IC lead frame at a time from a pile thereof to said input terminal of the inspection line, and unloading means responsive to signals from said visual inspection unit or said shape inspection unit for taking out accepted or rejected IC lead frames from the inspection line;

said visual inspection unit comprising an illumination means which emits light on a first test IC lead frame which is being inspected at said visual inspection unit, and TV camera adapted to provide a test image indicative of the patterned shape and appearance of said first test IC lead frame out of the light reflected therefrom, and including evaluation means to compare and analyze said test image with a reference image indicative of the patterned shape and appearance of an acceptable IC lead frame and to inspect the patterned shape and appearance of said test IC lead frame; and

said shape inspection unit comprising at least a pair of conductive cases adapted to hold a second test IC lead frame being inspected in said shape inspection unit on both sides and conductive contacts which are provided within and are electrically insulated from both said cases and adapted to be maintained at a small distance from the surface of a reference, acceptably shaped IC lead frame when said acceptably shaped IC lead frame is held by said cases, so that deformation of said second test IC lead frame can be detected by electric connection/disconnection between said second test IC lead frame, said cases and said contacts when said second test IC lead frame is held by said cases or said contacts.

2. An automatic inspection system for IC lead frames having small holes therethrough, comprising:

an inspection line comprising a conveyor having an input end and a discharge end and inspection units in association with said conveyor, a loading unit for loading IC lead frames on said input end of said conveyor;

a taking-out unit for removing rejected products, and an unloading unit on said inspection line;

wherein said loading unit includes a pair of mounting base units on opposite sides of said input end of said conveyor and elevating cylinders which move upwardly stacks of IC lead frames piled up thereon to maintain them at a specific height, and chucking means for picking up the topmost IC lead frame from the stacks on the mounting base units alternately, said chucking means including a pair of chucking mechanisms which can move horizontally and vertically, each said chucking mechanism including chucking claws adapted to hold a respective IC lead frame from both sides;

wherein at least one of said inspection units is a visual inspection unit comprising a TV camera adapted to provide a test image out of the light reflected from a first test IC lead frame which is being inspected at said one visual inspection unit, and evaluation means for comparing and analyzing the test image with a reference image indicative of the patterned shape and appearance of an acceptable IC lead frame to detect the appearance of the first test IC lead frame, said visual inspection unit including pinch rollers adapted to intermittently feed each IC lead frame to said visual inspection unit, and a positioning mechanism adapted to precisely position each IC lead frame in said visual inspection unit, said positioning mechanism comprising positioning pins and means for moving said positioning pins from underneath the test IC lead frame into said small holes of the first rest IC lead frame;

wherein at least one said inspection units is a plating thickness inspection unit of the non-destructive type the adapted to measure the plating thickness of the IC lead frame, and including measuring means for irradiating radio-active rays onto a second test IC lead frame undergoing inspection at said plating thickness inspection unit and measuring back-scattering thereof;

wherein said rejected-product-taking-out unit comprises first taking-out means for removing IC lead frames rejected on account of appearance from said conveyor line and secnd taking-out means for removing IC lead frames rejected on account of plating thickness from said conveyor line, said first and second taking-out means each including a chucking mechanism which can move horizontally and vertically and having chucking jaws adapted to hold an IC lead frame on both sides, and being operable to remove IC lead frames from the inspection line with said chucking mechanisms when the IC lead frames are rejected by either visual inspection or plating thickness inspection, said first and second taking-out means being responsive to signals from either the visual inspection unit or the plating thickness inspection unit; and

wherein said unloading unit comprises an unloading device adapted to remove accepted IC lead frames from said conveyor and being further adapted to take out accepted IC lead frames which arrive on said conveyor and pile them in lots on both sides of said conveyor, and a packaging device which wraps said lots of accepted IC lead frames with rust-resistant paper.

3. A visual inspection method for IC lead frames comprising the steps of:

providing a reference correlation of reflectivity versus area for a model-plated IC lead frame;

measuring reflectivities of the light reflected from respective surfaces of a test IC lead frame depending on the conditions thereof and simultaneously measuring the area size of the object area corresponding to the reflectivity to obtain a test correlation therebetween for said test IC lead frame; and

comparing said reference correlation and said test correlation for determining plating defects, distribution of plating film thickness and dimensions of said test IC lead frame.

4. An automatic inspection system for IC lead frames, comprising:

an inspection line having an input end and a discharge end, and comprising first and second visual inspection units;

a loading unit for transferring IC lead frames, one at a time, from a pile of said IC lead frames onto said input end of said inspection line;

an unloading unit for separately removing (1) accepted IC lead frames and (2) rejected IC lead frames, from the said discharge end of said inspection line in response to signals from said first visual inspection unit or said second visual inspection unit, said first visual inspection unit comprising first illumination means for directing light onto a surface of an IC lead frame undergoing inspection at said first visual inspection unit, a first TV camera for viewing said surface of said IC lead frame undergoing inspection and providing a first, electronic test image indicative of the pattern on said surface, and a first image inspection device for comparing said first test image from said surface with a first electronic reference image indicative of the pattern on an acceptable IC lead frame, and discriminating between IC lead frames having acceptable patterns and IC lead frames having defective patterns;

said second visual inspection unit comprising a second illumination means for directing light onto a surface of an IC lead frame undergoing inspection at said second visual inspection unit, a second TV camera for viewing said surface of said IC lead frame undergoing inspection at said second visual inspection unit and providing a second electronic test image indicative of the appearance of said surface, and a second image inspection device for comparing said second test image with a second electronic reference image indicative of the appearance of the surface of an acceptable IC lead frame, and discriminating between IC lead frames having an acceptable appearance and IC lead frames having a defective appearance.

5. The automatic inspection unit for IC lead frames as claimed in claim 4 in which said first and second visual inspection units each include a first polarizing filter which passes only one directional light and is arranged between said light source and said test IC lead frame, and a second polarizing filter which passes only one directional light perpendicular to the light passing through the first filter and is arranged between said test IC lead frame and said TV camera.

6. The automatic inspection system for IC lead frames claimed in claim 4 in which said loading unit includes chucking units comprising chucking claws and chucking mechanisms, said chucking claws comprising a pair of holder plates which are positioned above the pile of IC lead frames, at least one pair of claw members suspended from said holder plates by plate springs so that said claw members oppose each other, said chucking mechanism including a transporting means for causing said holder plates to approach each other to engage and hold the edges of the topmost IC lead frame with the opposing surfaces thereof, so that the topmost IC lead frame can be taken out separately.

7. An automatic inspection unit for IC lead frames having small holes therethrough, comprising:

an inspection line comprising a conveyor having an input end and a discharge end and inspection unit means in association with said conveyor;

a loading unit for transferring IC lead frames onto said input end of said conveyor, said loading unit comprising a pair of mounting base units on opposite sides of said conveyor, each of said mounting base units being adapted to support a stack of IC lead frames and having an elevating cylinder coupled thereto for raising said mounting base unit to maintain the uppermost IC lead frame of the stack at a selected position with respect to said conveyor, said loading unit comprising chucking means having chucking claws for picking up the uppermost IC lead frame of each of said stacks alternately and depositing it on said input end of said conveyor;

said inspection unit means comprising a visual inspection unit comprising illumination means for directing light onto a surface of an IC lead frame undergoing inspection at said visual inspection unit, a TV camera for viewing the surface of said IC lead frame undergoing inspection and providing an electronic test image so that the appearance of said surface can be compared and analyzed and accepted IC lead frames having acceptable patterns can be differentiated from rejected IC lead frames having defective patterns, pinch rollers for intermittently feeding IC lead frames to said visual inspection unit, positioning pins receivable in the holes of an IC lead frame undergoing inspection at said visual inspection unit to precisely position said IC lead frame with respect to said TV camera;

a first discharge unit for taking out rejected IC lead frames in response to signals from said inspection unit means; and

an unloading unit for taking out accepted IC lead frames in response to signals from said inspection unit means, said unloading unit comprising means for forming stacks of accepted IC lead frames on both sides of said conveyor, and a packaging device for wrapping stacks comprising a selected number of accepted lead frames in anti-rust paper.

8. The automatic inspection unit for IC lead frames as claimed in claim 7 in which said visual inspection unit includes a first polarizing filter, which passes only one directional light is arranged between said light source and the IC lead frame, and a second polarizing filter, which passes only one directional light perpendicular to the above light passing through the first filter, is arranged between said test IC lead frame and said TV camera.

9. The automatic inspection system for IC lead frames claimed in claim 7 in which in that said loading unit includes chucking units comprising chucking claws and chucking mechanisms, said chucking claws comprising a pair of holder plates which are positioned above the pile of IC lead frames, at least one pair of claw members suspended from said holder plates by plate springs so that said claw members oppose each other, said chucking mechanism including a transporting means for causing said holder plates to approach each other to engage and hold the edges of the topmost IC lead frame with the opposing surfaces thereof, so that the topmost IC lead frame can be taken out separately.

10. A visual inspection method for elongated, test, IC lead frames, each IC lead frame being comprised of a plurality of IC portions, which portions are connected in side-by-side relation along the lengthwise extent of said lead frame, each IC portion including an island member and an inner lead, which comprises the steps of:

storing an electronic reference image indicative of the pattern of the surface of a reference IC portion of an acceptable reference IC lead frame which reference IC portion is precisely positioned with respect to an inspection TV camera at an inspection station, said positioning being based on measurements made at plural positioning points on the surface of said reference IC portion;

intermittently sequentially unidirectionally advancing IC lead frames in said lengthwise direction along a conveyor through said inspection station so that said IC portions are presented for inspection at said station in succession;

at said inspection station, viewing with said TV camera the surface of the test IC portion undergoing inspection and providing an electronic test image indicative of the pattern of said surface of said test IC portion, comparing said test image with said reference image and, if the portions of said test image corresponding to said positioning points do not match those of said reference image, adjusting said test image so that the portions thereof corresponding to said positioning points on the surface of said test IC portion match the portions of said reference image corresponding to the positioning points on the surface of said reference IC portion, feeding back to said conveyor information of the mistmatch between said test image and said reference image and adjusting the operation of said conveyor in order to remove the mismatch between said test image and said reference image.

11. A visual inspection method for inspecting the plating of an IC lead frame, comprising the steps of:

providing the reference luminance curve for a model-plated IC lead frame;

providing the test luminance curve for a test IC lead frame;

electrically processing at least one of said luminance curves to eliminate from said curves the effect of the differences of the gloss of the platings on the model-plated IC lead frames and the test IC lead frame; and

comparing said curves to determine whether said test IC lead frame exhibits a plating defect.