The effect of Ni thickness on mechanical strength of Pb-free BGA spheres on selectively plated Ni/Au finish

Eu Poh Leng, Min Ding, Joah Rayos, Ibrahim Ahmad, Azman Jalar @ Jalil, Cui Cheng Qiang

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

As the world is changing to Pb-free solder per EU ROHS Directive, the higher reflow temperature requirement for Pb-free solder has demanded better substrate metal trace to solder mask adhesion to prevent delamination problem. Hence, selective Ni/Au plating process becomes more appealing in the fabrication of substrates to support Pb-free Semiconductor BGA product packaging. However, the set back of selective plating substrate is weaker Pb-free solder joint that leads to higher brittle fracture rate induced by shocking/knocking activities during assembly, test and shipping. In this work, Tape BGA (TBGA) substrates with 3 different Ni thicknesses (range from 2 to 10um) were built and attached with Sn3.8Ag0.7Cu Pb-free spheres. Mechanical tests were performed on 2 different levels to examine the strength of the solder joint. On solder joint level, cold ball pull (CBP) and ball shear were used to evaluate the adhesion strength of individual solder joint at Time Zero, after 6 times multiple reflow, and after 168 hours of high temperature storage. The brittle fracture failure rate from this test is believed to have correlation to the missing ball rate in the field. On package level, the tray drop test and packing drop test were conducted to provide a close resemblance to real handling and shipping conditions. Cross-sectioning and SEM investigation were carried out to obtain information on the morphology of intermetallic layer as well as solder mask opening profile. Based on this study, it is determined that the thickness of the Ni needs to be over a certain value (∼5.5um for Tape BGA) to achieve optimum mechanical strength. By increasing the Ni thickness, the mechanical strength of the thicker Ni solder joint is expected to increase by at least 15% as shown in CBP result, with 3 to 4 times higher resistance against brittle fracture during handling and shipping as demonstrated by tray and packing drop-till-fail test result using center pedestal support trays.

Original languageEnglish
Title of host publicationProceedings of the IEEE/CPMT International Electronics Manufacturing Technology (IEMT) Symposium
Pages225-232
Number of pages8
DOIs
Publication statusPublished - 2007
Event32nd IEEE International Electronics Manufacturing Technology Symposium, IEMT - San Jose, CA
Duration: 3 Oct 20075 Oct 2007

Other

Other32nd IEEE International Electronics Manufacturing Technology Symposium, IEMT
CitySan Jose, CA
Period3/10/075/10/07

Fingerprint

Soldering alloys
Strength of materials
Brittle fracture
Freight transportation
Substrates
Plating
Tapes
Masks
Bond strength (materials)
Delamination
Intermetallics
Packaging
Adhesion
Semiconductor materials
Fabrication
Temperature
Scanning electron microscopy
Lead-free solders

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

Cite this

Leng, E. P., Ding, M., Rayos, J., Ahmad, I., Jalar @ Jalil, A., & Qiang, C. C. (2007). The effect of Ni thickness on mechanical strength of Pb-free BGA spheres on selectively plated Ni/Au finish. In Proceedings of the IEEE/CPMT International Electronics Manufacturing Technology (IEMT) Symposium (pp. 225-232). [4417068] https://doi.org/10.1109/IEMT.2007.4417068

The effect of Ni thickness on mechanical strength of Pb-free BGA spheres on selectively plated Ni/Au finish. / Leng, Eu Poh; Ding, Min; Rayos, Joah; Ahmad, Ibrahim; Jalar @ Jalil, Azman; Qiang, Cui Cheng.

Proceedings of the IEEE/CPMT International Electronics Manufacturing Technology (IEMT) Symposium. 2007. p. 225-232 4417068.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Leng, EP, Ding, M, Rayos, J, Ahmad, I, Jalar @ Jalil, A & Qiang, CC 2007, The effect of Ni thickness on mechanical strength of Pb-free BGA spheres on selectively plated Ni/Au finish. in Proceedings of the IEEE/CPMT International Electronics Manufacturing Technology (IEMT) Symposium., 4417068, pp. 225-232, 32nd IEEE International Electronics Manufacturing Technology Symposium, IEMT, San Jose, CA, 3/10/07. https://doi.org/10.1109/IEMT.2007.4417068
Leng EP, Ding M, Rayos J, Ahmad I, Jalar @ Jalil A, Qiang CC. The effect of Ni thickness on mechanical strength of Pb-free BGA spheres on selectively plated Ni/Au finish. In Proceedings of the IEEE/CPMT International Electronics Manufacturing Technology (IEMT) Symposium. 2007. p. 225-232. 4417068 https://doi.org/10.1109/IEMT.2007.4417068
Leng, Eu Poh ; Ding, Min ; Rayos, Joah ; Ahmad, Ibrahim ; Jalar @ Jalil, Azman ; Qiang, Cui Cheng. / The effect of Ni thickness on mechanical strength of Pb-free BGA spheres on selectively plated Ni/Au finish. Proceedings of the IEEE/CPMT International Electronics Manufacturing Technology (IEMT) Symposium. 2007. pp. 225-232
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abstract = "As the world is changing to Pb-free solder per EU ROHS Directive, the higher reflow temperature requirement for Pb-free solder has demanded better substrate metal trace to solder mask adhesion to prevent delamination problem. Hence, selective Ni/Au plating process becomes more appealing in the fabrication of substrates to support Pb-free Semiconductor BGA product packaging. However, the set back of selective plating substrate is weaker Pb-free solder joint that leads to higher brittle fracture rate induced by shocking/knocking activities during assembly, test and shipping. In this work, Tape BGA (TBGA) substrates with 3 different Ni thicknesses (range from 2 to 10um) were built and attached with Sn3.8Ag0.7Cu Pb-free spheres. Mechanical tests were performed on 2 different levels to examine the strength of the solder joint. On solder joint level, cold ball pull (CBP) and ball shear were used to evaluate the adhesion strength of individual solder joint at Time Zero, after 6 times multiple reflow, and after 168 hours of high temperature storage. The brittle fracture failure rate from this test is believed to have correlation to the missing ball rate in the field. On package level, the tray drop test and packing drop test were conducted to provide a close resemblance to real handling and shipping conditions. Cross-sectioning and SEM investigation were carried out to obtain information on the morphology of intermetallic layer as well as solder mask opening profile. Based on this study, it is determined that the thickness of the Ni needs to be over a certain value (∼5.5um for Tape BGA) to achieve optimum mechanical strength. By increasing the Ni thickness, the mechanical strength of the thicker Ni solder joint is expected to increase by at least 15{\%} as shown in CBP result, with 3 to 4 times higher resistance against brittle fracture during handling and shipping as demonstrated by tray and packing drop-till-fail test result using center pedestal support trays.",
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