Ali Tootoonchi, Jad Rasul -- Motorola Inc

Motorola Bistatix is a radio frequency identification (RFID) tag that utilizes a small RF silicon chip embedded in a carbon ink antenna. Unlike today's passive bar codes, Bistatix can transmit and receive two-way information to help identify, track and route packages remotely. The Bistatix tag is inexpensive and disposable, requiring advanced IC packaging technology and very low cost material and manufacturing processes. The concept of flipping or inverting a silicon chip to be mounted on a paper substrate offers distinct advantages and enables meeting the performance requirements.

The flip chip with screen-printed dielectric layer and conductive bumps is aligned and placed on the substrate with compressive force. A controlled volume of adhesive filler is dispensed between the IC chip and the conductive ink antenna on the paper substrate. The adhesive underfills and cures at room temperature in a few seconds. Advantages for this process are the elimination of additional curing processes and reduction of equipment requirements. Another significant advantage is the capability for adhesive to fill the narrow gap under the chip. This enables a lower bump height and a reduced total IC packaging thickness.

Extensive process development and reliability assessment has been completed to achieve a flip chip on a paper substrate assembly with high throughput and low cost. The flip chip-on-paper process developed utilizes a room temperature cured adhesive. This paper discusses the assembly reliability results for this low cost flip chip on paper technology utilized in the Bistatix tag.