Vacuum effect on the void formation of the molded underfill process in flip chip packaging

Xue Ru Guo, Wen Bin Young

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


The flip chip packaging technology uses solder bumps for the electrical connection between the chip and substrate. A two-step procedure is usually used for the flip chip packaging. In the process, underfill material is filled into the gap between the chip and substrate by the capillary force. After that, epoxy molding compound (EMC) is used to overmold the entire assembly in a mold cavity through the process of the transfer molding. On the other hand, the molded underfill (MUF) process performs the packaging at a single step. In the MUF process, the EMC material fills the mold cavity with preplaced flip chip assembly, and finishes the underfill and overmold at the same time. In this study, experiments were performed to study the mechanism of the void formation in MUF. The effect of vacuum on the void formation was investigated. It was found that high quality of vacuum was necessary in order to eliminate the air pocket enclosed during the filling process. For different materials, the required vacuum quality may be different and it is well below the perfect vacuum.

Original languageEnglish
Pages (from-to)613-622
Number of pages10
JournalMicroelectronics Reliability
Issue number3-4
Publication statusPublished - 2015 Feb 1

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Safety, Risk, Reliability and Quality
  • Surfaces, Coatings and Films
  • Electrical and Electronic Engineering


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