| Summary: | 碩士 === 國立交通大學 === 工學院碩士在職專班半導體材料與製程設備組 === 99 === The trend of electronic products toward high performance, compact size, and lightweight requires an interconnection technology of high density such as a flip chip package. Flip-chip bonding is a method for mounting integrated circuit chips onto a substrate using very small protruding electrodes called bumps. In electronic packaging, solder bumps serve for signal propagation, electrical conduction, mechanical support and heat dissipation. After 2016, the alternative Pb-free solders must be adopted to replace traditional Pb-Sn solders without major changes in manufacturing process or significant investments. Sn-Ag alloy is thought to be a promising material for fabricating bumps with better connection reliability.
Eelectroplating is a superior batch formation technique of bumps and is widely used in practical applications due to low cost and high throughput. However, Sn-Ag alloy
electroplating is a complicated process as the process involves the simultaneous deposition of thousands of solder bumps and complicated metal and additive reactions. In metal alloy electroplating process, the local current density and each bump quality may be influenced not only by mass-transport conditions but also by the charge-transfer kinetics at the metal-electrolyte interface.
In this thesis, the effects of rotation speed, bath temperature and ionic concentration on the surface morphology, deposition rate, chemical composition, and texture of Sn-Ag alloys were investigated by scanning electron microscope, energy dispersive X-ray, four-point-probe and X-ray diffraction. The purpose is to explore how to well control Ag content in the Sn-Ag deposits and obtain near-eutectic Sn-Ag bumps.
In mass transfer dominant region, increasing ion replenishment will decrease polarization and then increase Sn-Ag grain size and surface roughness. However, in pure mass transfer region, increasing ion replenishment will decrease ion depletion and surface aggregation and then decrease Sn-Ag grain size and surface roughness. Increasing mass transfer effect or Ag ion concentration will increase Ag% of Sn-Ag deposits whereas increasing applied voltage will decrease it. And a proposed equivalent circuit was setup in this study.
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