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Laser soldering of flip-chips

2005; Elsevier BV; Volume: 44; Issue: 2 Linguagem: Inglês

10.1016/j.optlaseng.2005.03.002

1873-0302

Krisztián Kordás, Andrea Edit Pap, Géza Tóth, Marko Pudas, Jussi Jääskeläinen, A. Uusimäki, Jouko Vähäkangas,

3D IC and TSV technologies

Abstract A novel process for laser soldering of flip-chips on transparent printed circuit board assemblies is presented. The experiments were carried out on silver test patterns printed on glass wafers using a roller-type gravure offset printing method. The contact pads, where the bumps of the flip-chips are positioned, were covered with a thin layer of additional solder paste. The aligned samples (solder pad—solder paste—chip bump) were illuminated through the glass substrate using an Ar + laser beam ( λ = 488 nm , P = 0.6 – 3.0 W , d = 100 μ m at 1/e) to heat the printed pad and melt the solder paste, thus forming a joint between the printed pad and the chip bump. The heat-affected zone was modeled using computer-assisted finite element method. The solder joint cross-sections were analyzed using optical and electron microscopy as well as energy dispersive X-ray element analyses. The laser-soldered joints were of good mechanical and electrical quality and the process proved to be suitable for manufacturing customized circuit prototypes.