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TECHNICAL PAPERS

Evaluation of Smear and Its Effect on the Mechanical Integrity of Plated Through Hole-Inner Plane Interface in Thick Printed Wiring Boards

[+] Author and Article Information
R. Venkatraman

LSI Logic Corporation, 3140 Alfred Street, Santa Clara, CA 95054

K. Ramakrishna

Digital DNA Laboratories, Semiconductor Products Sector, Motorola, Inc., Austin, TX 78712

K. Knadle, W. T. Chen, G. C. Haddon

Microelectronics Division, IBM Corporation, Endicott, NY 13760-8000

J. Electron. Packag 123(1), 6-15 (Jul 01, 2000) (10 pages) doi:10.1115/1.1326437 History: Received July 01, 2000
Copyright © 2001 by ASME
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References

Figures

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Schematic showing the stitch pattern connecting PTHs in tested samples
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Schematic showing the geometry of resin-filled areas around unconnected copper power planes
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Determination of percentage smear in PTH - inner plane connections
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A typical plot of peel load versus peel length. The arrows correspond to resin rich areas along the cross-section of the sample. Each of the peaks was found to correspond to a glass bundle attached to the PTH along its length. The overall graph appears to increase with peel length due to the nonuniformity in the sectioning explained in the text.
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A peel test in progress
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Schematic of cross section of PTH peel specimen. The distance “x” was not uniform through the length of the sample and was measured accurately for comparison purposes.
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Backscattered SEM image of a copper inner plane: (a) before hole clean and (b) after hole clean. The smear coverage seen in (a) was the worst case of coverage seen.
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Plot showing the effect of desmearing on the adhesion of the PTH barrel copper to the resin rich areas. Clearly, the hole clean operation enhances the adhesion.
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Birefringence patterns from (a) drilled hole with high drill hits and (b) with low drill hits
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Estimated drill temperature as a function of birefringence ring thickness calculated using Eq. (1). The contact time and the position along the cross section of the board corresponded to the location where the B-ring measurement was taken.
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Optical micrographs of coupons failed in ATC testing. The barrel cracks are indicated by arrows. Note that the cracks in the barrel lie at the interface between the resin rich areas and the glass bundles.
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PTH barrel failure locations after ATC. There are 18 PTHs in the sample. The shaded areas indicate the glass bundle areas and the white areas indicate the pure resin areas measured experimentally. Each failure location is indicated by a solid square. Note that most of the failures lie close to the border between the glass bundle and resin rich areas.
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Variation of equivalent plastic strain, εe, along the PTH without and with inner plane connections for a ΔT of 102°C
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Variation of equivalent plastic strain, εe, along the PTH/dielectric interface in the clearance hole region for cases without and with inner plane connections for a ΔT of 102°C
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Variation of normal (peel) stress, σrr, along the PTH/dielectric (and IP) interface in the clearance hole region for cases without and with inner plane connections for a ΔT of 102°C
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Variation of shear stress, σrz, along the PTH/dielectric (and IP) interface in the clearance hole region for cases without and with inner plane connections for a ΔT of 102°C
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Variation of shear stress, σrz, along the PTH/IP interface for interior and external IP connections for a ΔT of 102°C

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