NDLI: Mechanics of interfacial delamination under hygrothermal stresses during reflow soldering

Content Provider	IEEE Xplore Digital Library
Author	Lin, T.Y. Tay, A.A.O.
Copyright Year	1997
Description	Author affiliation: Development Support, Philips Centre for Manuf. Technol. (Asia Pacific), Singapore (Lin, T.Y.)
Abstract	Inherent voids or defects at the interface between die pad and plastic encapsulant become stress concentration sites when the IC package absorbs moisture or undergoes reflow soldering. If the stress intensity factor at the interfacial voids exceeds the critical fracture toughness of the pad-encapsulant interface, delamination occurs, eventually leading to popcorn cracking. In this paper, the mechanics of interfacial delamination under hygrothermal stress during solder reflow are discussed. A methodology for computation of the resultant total stress intensity factor due to the combined effects of hygro- and thermal stresses is presented. The methodology is then applied to study the effect of prebaking on delamination during solder reflow. To verify the methodology, a series of experiments was conducted in which several plastic IC packages were fabricated with a very small defect at the pad-encapsulant interface and preconditioning at 85/spl deg/C/85% RH for 168 hours. The packages were then prebaked at 150/spl deg/C for varying periods such as 30 minutes, 6.5 hours and 24 hours before being placed in varying high temperature environments in an oven. Oven temperatures ranged from 185/spl deg/C to 200/spl deg/C. The packages were then examined for delaminations by scanning acoustic microscopy. It was found that when the prebaking period was short, delamination occurred. The methodology developed was applied to predict the minimum period of prebaking required to avoid delamination during solder reflow. Good agreement was obtained between predicted and observed values.
Starting Page	163
Ending Page	169
File Size	771845
Page Count	7
File Format	PDF
ISBN	0780341570
DOI	10.1109/EPTC.1997.723904
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1997-10-10
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Delamination Thermal stresses Plastic integrated circuit packaging Ovens Moisture Reflow soldering Lead Thermal factors Temperature distribution Microscopy
Content Type	Text
Resource Type	Article

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