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Impact of PCB Manufacturing, Design, and Material to PCB Warpage
This paper will use high temperature warpage metrology to evaluate the impact that PCB manufacturing, design, and material has on BGA and panel area PCB warpage.
Technical Paper
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Authored By:
H. Fu
iNEMI
A. Caputo, S.R. Aravamudhan
Intel Corporation
N. Hubble, C. Olson
Akrometrix
M. Huang, A. Hsieh
Wistron Corporation
J.W. Cai, Y. Li, D. Li
Shengyi Technology
P. Vernhes, B. Feit, P.L. Toussaint
Insidix
CC. Chang, L.L. Qin, C.Y. Hsu
Unimicron
C. Lin
HannStar Board Corporation
Summary
Customer demands for smaller form factor electronic devices are driving the use of thinner electronic components and thinner printed circuit boards (PCB) in the assembly process. The use of thinner components and thinner multi-up panel PCBs (≤ 1 mm) has led to PCB warpage issues in the surface mount (SMT) assembly process, which in turn impacts the PCB assembly yield. PCBs with excessive warpage impact paste print quality in the print process, and solder joint formation during reflow soldering leading to SMT assembly defects. Lack of industry standard for PCB warpage at reflow temperature further compounds the PCB warpage risk to SMT assembly yield. This paper will use high temperature warpage metrology to evaluate the impact that PCB manufacturing, design, and material has on ball grid arrays (BGA) and panel area PCB warpage by varying the PCB post processing (Bake vs. No-Bake), panel location (corner vs. center), PCB thickness (0.8 mm vs. 0.6 mm), Material (Mid Tg vs. High Tg), and processing (i.e. lamination at condition A vs. B).
Conclusions
As PCB designs become smaller and more compact to meet current industry trends, PCB thickness will shrink, thus resulting in greater PCB warpage during the SMT process. The key finding from this DOE is that PCB manufacturing and processing (i.e. press/lamination) has the greatest impact on PCB warpage, with thinner PCBs showing greater variability in coplanarity (i.e. Vendor A) vs. thicker PCBs (0.8 mm). However, PCB processing can reduce the variability in coplanarity between thinner (0.6 mm) vs. thicker (0.8 mm) PCBs as was observed with vendor B. Based on the findings of this work, it is believed that PCB post processing (i.e. post processing bake), material, and shipping panel location within the manufacturing panel have less impact on PCB warpage.
Initially Published in the SMTA Proceedings
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Comments
Symmetrical stack ups and copper distribution is key to maintaining flatness. See IPC-2221 section 5.2.4 and IPC-2222 4.2.2
Gerry Partida, Summit Interconnect
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