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Research Papers

Ball Grid Array Interconnection Properties of Solderable Polymer–Solder Composites With Low-Melting-Point Alloy Fillers

[+] Author and Article Information
Byung-Seung Yim

Department of Mechanical Engineering,
Kangwon National University,
Gangwon-do 25913, South Korea

Young-Eui Shin

School of Mechanical Engineering,
Chung-Ang University,
Seoul 156-756, South Korea
e-mail: shinyoun@cau.ac.kr

Jong-Min Kim

School of Mechanical Engineering,
Chung-Ang University,
Seoul 156-756, South Korea
e-mail: 0326kjm@cau.ac.kr

1Corresponding authors.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received January 25, 2017; final manuscript received September 24, 2017; published online October 13, 2017. Assoc. Editor: Kaushik Mysore.

J. Electron. Packag 139(4), 041007 (Oct 13, 2017) (9 pages) Paper No: EP-17-1007; doi: 10.1115/1.4038028 History: Received January 25, 2017; Revised September 24, 2017

In this work, a novel ball grid array (BGA) interconnection process has been developed using solderable polymer–solder composites (SPCs) with low-melting-point alloy (LMPA) fillers to enhance the processability of the conventional capillary underfill technique and to overcome the limitations of the no-flow underfill technique. To confirm the feasibility of the proposed technique, a BGA interconnection test was performed using four types of SPCs with a different LMPA concentration (from 0 to 5 vol %). After the BGA interconnection process, the interconnection characteristics, such as morphology of conduction path and electrical properties of the BGA assemblies, were inspected and compared. The results indicated that BGA assemblies using SPC without LMPA fillers showed weak conduction path formation, including open circuit (solder bump loss) or short circuit formation because of the expansion of air voids within the interconnection area due to the relatively high reflow peak temperature. Meanwhile, assemblies using SPC with 3 vol % LMPAs showed stable metallurgical interconnection formation and electrical resistance due to the relatively low-reflow peak temperature and favorable selective wetting behavior of molten LMPAs for the solder bumps and Cu metallizations.

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References

Figures

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Fig. 1

Schematic of BGA interconnection process using (a) conventional capillary flow underfill technique, (b) traditional no-flow underfill technique, and (c) novel BGA interconnection technique using solderable polymer–solder composites proposed in this study

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Fig. 2

Configuration of the BGA package and the PCB for the BGA interconnection test

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Fig. 3

Schematic of the solder ball wetting test procedure using formulated polymer composite. (a) Test board cleaning and solder ball mount, (b) polymer composite application, (c) reflow, and (d) cross-sectional inspection.

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Fig. 4

Schematic of solder powder wetting test procedure using SPCs. (a) Test board cleaning, (b) SPC mount on the test board using squeegee method, (c) reflow, and (d) test completion and inspection.

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Fig. 5

Schematic of BGA interconnection test using SPCs. (a) Mask alignment on the cleaned PCB, (b) SPC mount on the PCB using squeegee method, (c) BGA mount and reflow, and (d) completion of BGA interconnection.

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Fig. 6

Dynamic DSC analysis results for the formulated polymer composite and two types of solder materials, including Sn–58Bi and Sn–3Ag–0.5Cu

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Fig. 7

Temperature profile for the BGA interconnection process using SPCs

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Fig. 8

Wetting morphology of an LMPA solder ball in polymer composite (a) without reductant and (b) with reductant

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Fig. 9

Wetting and coalescence behaviors of an LMPA filler on the Cu pattern. (a) Initial condition, (b) beginning of melting, flow, coalescence, and wetting behaviors, (c) curing completion, and (d) cross-sectional inspection result.

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Fig. 10

Morphologies of BGA assemblies on the PCB using SPCs with different LMPA contents of (a) 0 vol %, (b) 1 vol %, (c) 3 vol %, and (d) 5 vol %

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Fig. 11

X-ray photographs of the BGA assemblies using SPCs with different LMPA contents of (a) 0 vol %, (b) 1 vol %, (c) 3 vol %, and (d) 5 vol %

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Fig. 12

Morphologies of the conduction path between BGA package and PCB metallization using SPCs with different LMPA contents of (a) 0 vol %, (b) 1 vol %, (c) 3 vol %, and (d) 5 vol %

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Fig. 13

Electrical resistance of the BGA assemblies

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Fig. 14

The interfacial microstructure of the BGA joint using SPC with an LMPA content of 3 vol %. (a) Microstructure of the BGA joint, (b) interfacial microstructure between Cu metallization of the PCB and LMPA, (c) between the solder bump and LMPA, and (d) microstructure of the Sn-rich phase region between the solder bump and LMPA.

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