Experiences in flip chip production of radiation detectors

Satu Savolainen-Pulli (Corresponding Author), Jaakko Salonen, Jorma Salmi, Sami Vähänen

    Research output: Contribution to journalArticleScientificpeer-review

    8 Citations (Scopus)


    Modern imaging devices often require heterogeneous integration of different materials and technologies. Because of yield considerations, material availability, and various technological limitations, an extremely fine pitch is necessary to realize high-resolution images. Thus, there is a need for a hybridization technology that is able to join together readout amplifiers and pixel detectors at a very fine pitch. This paper describes radiation detector flip chip production at VTT. Our flip chip technology utilizes 25-μm diameter tin–lead solder bumps at a 50-μm pitch and is based on flux-free bonding. When preprocessed wafers are used, as is the case here, the total yield is defined only partly by the flip chip process. Wafer preprocessing done by a third-party silicon foundry and the flip chip process create different process defects. Wafer-level yield maps (based on probing) provided by the customer are used to select good readout chips for assembly. Wafer probing is often done outside of a real clean room environment, resulting in particle contamination and/or scratches on the wafers. Factors affecting the total yield of flip chip bonded detectors are discussed, and some yield numbers of the process are given. Ways to improve yield are considered, and finally guidelines for process planning and device design with respect to yield optimization are given.
    Original languageEnglish
    Pages (from-to)314-319
    Number of pages6
    JournalNuclear Instruments and Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
    Issue number1
    Publication statusPublished - 2006
    MoE publication typeA1 Journal article-refereed
    EventInternational Workshop on Semiconductor Pixel Detectors for Particles and Imaging - Bonn, Germany
    Duration: 5 Sept 20058 Sept 2005


    • flip chip
    • solder bump
    • yield
    • pixel detector


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