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Conference Paper: Height inspection of wafer bumps without explicit 3D reconstruction

TitleHeight inspection of wafer bumps without explicit 3D reconstruction
Authors
KeywordsBall bumps
Bump height inspection
Homography
Specular surface
Wafer bumps
Issue Date2006
Citation
The 14th Machine Vision Applications in Industrial Inspection Conference, San Jose, CA., 16-17 January 2006. In Proceedings of the SPIE, 2006, v. 6070, p. 27-34 How to Cite?
AbstractThe shrunk dimension of electronic devices leads to more stringent requirement on process control and quality assurance of their fabrication. For instance, direct die-to-die bonding requires placement of solder bumps not on PCB but on the wafer itself. Such wafer solder bumps, which are much miniaturized from the counterparts on PCB, still need to have their heights meet the specification, or else the electrical connection could be compromised, or the dies be crushed, or even the manufacturing equipments be damaged. Yet the tiny size, typically tens of microns in diameter, and the textureless and mirror nature of the bumps pose great challenge to the 3D inspection process. This paper addresses how a large number of such wafer bumps could have their heights massively checked against the specification. We assume ball bumps in this work. We propose a novel inspection measure about the collection of bump heights that possesses these advantages: (1) it is sensitive to global and local disturbances to the bump heights, thus serving the bump height inspection purpose; (2) it is invariant to how individual bumps are locally displaced against one another on the substrate surface, thus enduring 2D displacement error in soldering the bumps onto the wafer substrate; and (3) it is largely invariant to how the wafer itself is globally positioned relative to the imaging system, thus having tolerance to repeatability error in wafer placement. This measure makes use of the mirror nature of the bumps, which used to cause difficulty in traditional inspection methods, to capture images of two planes. One contains the bump peaks and the other corresponds to the substrate. With the homography matrices of these two planes and fundamental matrix of the camera, we synthesize a matrix called Biplanar Disparity Matrix. This matrix can summarize the bumps' heights in a fast and direct way without going through explicit 3D reconstruction. We also present a design of the imaging and illumination setup that allows the measure to be revealed in two images, and how the inspection measure could be estimated from the image data so acquired. Both synthetic and real data experimental results are shown to illustrate the effectiveness of the proposed system. © 2006 SPIE-IS&T.
Persistent Identifierhttp://hdl.handle.net/10722/99459
ISBN
ISSN

 

DC FieldValueLanguage
dc.contributor.authorDong, Men_HK
dc.contributor.authorChung, Ren_HK
dc.contributor.authorZhao, Yen_HK
dc.contributor.authorLam, EYen_HK
dc.date.accessioned2010-09-25T18:31:09Z-
dc.date.available2010-09-25T18:31:09Z-
dc.date.issued2006en_HK
dc.identifier.citationThe 14th Machine Vision Applications in Industrial Inspection Conference, San Jose, CA., 16-17 January 2006. In Proceedings of the SPIE, 2006, v. 6070, p. 27-34en_HK
dc.identifier.isbn978-081946110-0-
dc.identifier.issn0277-786X-
dc.identifier.urihttp://hdl.handle.net/10722/99459-
dc.description.abstractThe shrunk dimension of electronic devices leads to more stringent requirement on process control and quality assurance of their fabrication. For instance, direct die-to-die bonding requires placement of solder bumps not on PCB but on the wafer itself. Such wafer solder bumps, which are much miniaturized from the counterparts on PCB, still need to have their heights meet the specification, or else the electrical connection could be compromised, or the dies be crushed, or even the manufacturing equipments be damaged. Yet the tiny size, typically tens of microns in diameter, and the textureless and mirror nature of the bumps pose great challenge to the 3D inspection process. This paper addresses how a large number of such wafer bumps could have their heights massively checked against the specification. We assume ball bumps in this work. We propose a novel inspection measure about the collection of bump heights that possesses these advantages: (1) it is sensitive to global and local disturbances to the bump heights, thus serving the bump height inspection purpose; (2) it is invariant to how individual bumps are locally displaced against one another on the substrate surface, thus enduring 2D displacement error in soldering the bumps onto the wafer substrate; and (3) it is largely invariant to how the wafer itself is globally positioned relative to the imaging system, thus having tolerance to repeatability error in wafer placement. This measure makes use of the mirror nature of the bumps, which used to cause difficulty in traditional inspection methods, to capture images of two planes. One contains the bump peaks and the other corresponds to the substrate. With the homography matrices of these two planes and fundamental matrix of the camera, we synthesize a matrix called Biplanar Disparity Matrix. This matrix can summarize the bumps' heights in a fast and direct way without going through explicit 3D reconstruction. We also present a design of the imaging and illumination setup that allows the measure to be revealed in two images, and how the inspection measure could be estimated from the image data so acquired. Both synthetic and real data experimental results are shown to illustrate the effectiveness of the proposed system. © 2006 SPIE-IS&T.-
dc.languageengen_HK
dc.relation.ispartofProceedings of SPIE - The International Society for Optical Engineeringen_HK
dc.subjectBall bumps-
dc.subjectBump height inspection-
dc.subjectHomography-
dc.subjectSpecular surface-
dc.subjectWafer bumps-
dc.titleHeight inspection of wafer bumps without explicit 3D reconstructionen_HK
dc.typeConference_Paperen_HK
dc.identifier.emailLam, EY: elam@eee.hku.hken_HK
dc.identifier.authorityLam, EY=rp00131en_HK
dc.identifier.doi10.1117/12.649228-
dc.identifier.scopuseid_2-s2.0-33645676220-
dc.identifier.hkuros117403en_HK
dc.identifier.hkuros126082-
dc.identifier.volume6070en_HK
dc.identifier.spage27en_HK
dc.identifier.epage34en_HK
dc.customcontrol.immutablesml 151002-

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