Implementation of Low Power Diode Laser for Soldering by FPC (Fibre Push Connection) Method

摘要

Due to the increasing miniaturization and complexity of integrated circuits, the corresponding packages require higher lead counts and reduced pitches. For the reduced contact geometries new packaging and chip interconnection technologies are necessary. TAB is a suitable technology for chips with high lead counts [1]. The usually applied gang bonding technique is limited by the planarity and alignment tolerances of the thermode [2]. The application of lasers is an alternative.rnThe implementation and the reproducibility of the laser connection technology in the micro electronics depend on following aspects:rn1. good thermal contact between the two partsrn2. high convertibility of the laser energy into thermal energy.rnThe FPC (fibre push connection) is a suitable laser connection method [8]. The FPC system offers several solutions with regard to the mentioned problems. This system enables the laser beam being transported by glass fibre to the contact parts. The end piece of the fibre serves at the same time as push unit. With this system an optimal thermal coupling between the two connection parts can be achieved. The advantage of this system, in contrary to other laser connection applications, is that the attenuation heat of the fibre end surface is additionally at the disposal for the connection. A higher translation of laser energy into the thermal energy improves the use of laser energy.rnBecause a part of laser energy at the end surface of the fibre is transformed into thermal energy, a reproducible connection even of a contact material with high reflectionrnproperties, such as gold, is possible with FPC, independent from the quality absorption of the used material.rnA temperature controlled unit gives a guaranty for reproducibility of the interconnection and avoids the thermal damages of the connecting parts. The reproducibility of different metallizations and the reliability of the connection with a pitch below 100 urn will be presented as well as further possible applications of this system[8].