Characterization of Bulk and Thin Film Fracture in Electronic Packaging

[+] Author and Article Information
Vijay Subramanian

Intel Corporation,
5000 West Chandler Boulevard,
Mail Stop CH5-157,
Chandler, AZ 85226
e-mail: vijay.subramanian@intel.com

Kyle Yazzie, Tsgereda Alazar, Bharat Penmecha, Pilin Liu, Yiqun Bai, Pramod Malatkar

Intel Corporation,
5000 West Chandler Boulevard,
Mail Stop CH5-157,
Chandler, AZ 85226

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received January 26, 2017; final manuscript received May 2, 2017; published online June 12, 2017. Assoc. Editor: S. Ravi Annapragada.

J. Electron. Packag 139(2), 020912 (Jun 12, 2017) (7 pages) Paper No: EP-17-1010; doi: 10.1115/1.4036661 History: Received January 26, 2017; Revised May 02, 2017

As semiconductor packaging technologies continue to scale, it drives the use of existing and new materials in thin layer form factors. Increasing packaging complexity implies that materials in thin layers are subject to nontrivial loading conditions, which may exceed the toughness of the material, leading to cracks. It is important to ensure that the reliability of these low-cost materials is at par or better than currently used materials. This in turn leads to significant efforts in the area of material characterization at the lab level to speed up the development process. Methods for testing and characterizing fracture-induced failures in various material systems in electronic packaging are investigated in this paper. The learnings from different test methods are compared and discussed here. More specifically, different fracture characterization techniques on (a) freestanding “thin” solder-resist films and (b) filled “bulk” epoxy materials such as underfills and epoxy mold compounds are investigated. For thin films, learnings from different test methods for measuring fracture toughness, namely, uniaxial tension (with and without an edge precrack) and membrane penetration tests, are discussed. Reasonably good agreement is found between the various thin film toughness test methods; however, ease of sample preparation, fixture, and adaptability to environmental testing will be discussed. In the case of filled epoxy resin systems, the single-edge-notched bending (SENB) technique is utilized to obtain the fracture toughness of underfills and mold compounds with filler materials. Learnings on different methods of creating precracks in SENB samples are also investigated and presented.

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Fig. 1

Simplified schematic shows the typical constituents of a flip-chip package

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Fig. 2

Typical images of (a) notch created by a diamond blade band saw and precracks created using razor blade (b) and laser milling (c)

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Fig. 3

Drop hammer jig for precracking notched samples using a sharp razor blade

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Fig. 4

Membrane penetration test setup

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Fig. 5

Thin film tensile dog bone and SENT sample geometries

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Fig. 6

Comparison of KIc values of underfill materials with different filler loading percentages and precracking techniques

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Fig. 7

KIc values of polycarbonate samples with blunt (no precrack), razor blade created precrack, and UV laser precrack

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Fig. 8

Normalized failure loads for four different types of solder-resist films and under different clamping conditions

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Fig. 9

Stress distribution in the film during membrane penetration test, as obtained from FE modeling. Inset shows the principal stress distribution in the solder-resist film underneath the loading pin.

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Fig. 10

Dependence of peak (failure) load on film thickness

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Fig. 11

Normalized failure load values adjusted for film thickness variation between the four films

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Fig. 12

Effect of thermal aging is shown for two types of solder-resist films

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Fig. 13

Tensile failure load distribution for solder-resist films A and C

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Fig. 14

Normalized KC values of solder-resist films A and C




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