Martin König

The challenge of ultra thin chip assembly

Because of their low height, the low assembly topography and their mechanical flexibility, ultra thin chips (about 20 /spl mu/m) offer a wide field of possible applications. During the last years, the Fraunhofer-Institute for Reliability and Microintegration has successfully investigated in production, handling and assembly processes for such thin ICs. The chip handling and assembly processes had to be adopted to the very thin material, beginning with the development of special dicing by thinning process. A new pick and place process using thermal releasable tapes has been developed. For the chip assembly and contacting various methods depending on the application are available. This includes face up or face down variations. The complete process chain from wafer processing up to the assembled ultra thin IC together with some application examples are discussed in this paper.

Micro-contact printing of OTFT on polymer foils

In the emerging field of large area electronics polymer foil substrates play a key role in large area and flexible electronic, illumination and display systems. Compared to silicon, however, coatings on polymer substrates and in particular foils are challenging to pattern on a scale below 10 µm due to surface roughness and surface defects caused by industrial manufacturing processes.

Fast flip chip assembly for reel-to-reel manufacturing

For low-cost applications like smart labels, a mounting technology, which allows high throughput is necessary. Therefore, such products are fabricated reel-to-reel on flexible substrates. With this technology, cheap substrate materials can be used and substrate handling is reduced to a minimum, but to achieve fast production cycles it is important to establish rapid and efficient mounting technologies. Flip chip assembly using anisotropic conductive adhesive (ACA) offers an inexpensive method interconnecting many contacts simultaneously, but mounting speed is limited by the fact that a defined pressure has to be maintained during curing. For chips with only a few contacts, alternative methods which allow higher throughput are investigated.

A New Method of Flip Chip Assembly Using a Light Silver Filled Glue

Automated and cost-efficient manufacturing processes are of paramount importance for low-cost mass products. One for a bottle neck of the manufacturing transponder is the present chip assembly. ICs are assembled by flip chip adhesive technology using anisotropic or non-conductive adhesives. Simultaneous, both pressure and temperature are required, meaning a high process engineering complexity for mass products. An adhesive, lightly filled with Ag, is used in the proposed new development. Pressure is required but momentarily during placing the chip. For curing only temperature is used. Contact resistance in the range of mOhm and insulation resistance between neighboring bond pads of >20 MOhm were realised and proved by test chips