Injection moulding integration of a red VCSEL illuminator module for a hologram reader sensor

Kimmo Keränen, Toni Saastamoinen, Jukka-Tapani Mäkinen, Mikko Silvennoinen, Ilpo Mustonen, Pasi Vahimaa, Timo Jääskeläinen, Ari Lento, Anneli Ojapalo, Marcus Schorpp, Pekka Hoskio, Pentti Karioja

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

    12 Citations (Scopus)

    Abstract

    A red VCSEL illuminator module demonstrator was manufactured by injection moulding integration. A red VCSEL chip was first attached to a simple FR4 substrate, which contains bonding pads and conducting wires for the VCSEL chip attachment and electrical driving. The substrate was then placed as an insert in an injection mould. The VCSEL chip shielding and optics formation was made in a one-step injection moulding process. The used optical thermoplastic in the processing was polycarbonate (PC). The pursued optical function of the single spherical surface attained in the moulding was to collimate the emitted red light (&lgr;=664.5 nm) from the VCSEL chip. The main critical issue related to the manufacturing of the illuminator module in the injection moulding process was the durability of bonding wire contacts. A single 25 &mgr;m diameter gold wire was used in wire bonding in order to create the upper contact to the chip. The lower contact was processed by attaching the chip to the substrate using conductive epoxy. A test series of 20 modules using FR4 substrate materials were produced. The number of fully operative modules was 12 resulting total module yield of 60%. The main reason for a non-operative module was loosening of the bonding wire during the injection moulding process. The bonding wire durability in the moulding process can be improved by using glob-top shielding of the VCSEL device before injection moulding and using a lower holding pressure in the injection moulding process. A diamond turned insert was used in the mould in order to create a high quality lens surface on the top of the VCSEL chip. The tower average length after one iteration round by mould modification was 8.676 &mgr;m, so the measured value was on average 20 &mgr;m larger than nominal value. The measured RMS roughness of the processed lens surface was 5 ... 7 nm and the radius -3.23 ... 3.83 mm. The radius of the lens and the length of the tower varied depending of the used process parameters. The manufactured illumination module can be integrated with a CMOS image matrix sensor in order to form a compact hologram reader system. The injection moulding integration principle seems to be very promising method to manufacture intelligently integrated and cost-effective optoelectronic products according to experience with this demonstrator.
    Original languageEnglish
    Title of host publicationOptical Sensing Technology and Applications
    PublisherInternational Society for Optics and Photonics SPIE
    DOIs
    Publication statusPublished - 2007
    MoE publication typeA4 Article in a conference publication
    EventInternational Congress on Optics and Optoelectronics: Optical Sensing Technology and Applications - Prague, Czech Republic
    Duration: 16 Apr 200718 Apr 2007

    Publication series

    SeriesProceedings of SPIE
    Volume6585

    Conference

    ConferenceInternational Congress on Optics and Optoelectronics
    Country/TerritoryCzech Republic
    CityPrague
    Period16/04/0718/04/07

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