New flip chip technology utilizing non-conductive adhesive adapted for high volume chip card module production

So far, the chip-on-board (COB) has been established as the most cost-effective technique for the mass production of chip cards. Considering this, one may be surprised to know that a flip chip process was preferred to COB for a new generation of smart cards using a flex substrate. Even more surprising is the fact that the flip chip technique uses a non-conductive adhesive. It is still difficult for any flip chip process to complete with COB for such a low cost application. Also, the time needed to cure the adhesive during bonding reduces throughput dramatically. To combat these challenges, an alternative solution to the standard flip chip process using gold stud-bumps and a non-conductive paste was recently developed: it involves separating the chip bonding and curing steps. This promising technique requires specific bonding equipment where the substrate are presented in a reel-to-reel configuration and the entire process is completed within a single line. Advanced packaging equipment has been customized for this purpose. After the adhesive is dispensed, the chips are picked up and placed onto the substrate. They are then transferred to a curing station where the adhesive of several bond positions is cured at the same time. In the last step the parts are tested electrically, and the non-functioning ones are marked. This paper explains the competition between COF and FCOF techniques applied to mass production of low cost chip cards, in addition to explaining why using an NCP-based flip chip process is particularly well-suited for this type of production. We then briefly describe the bonding equipment to run this FCOF process to cost-effectively mass produce chip cards.