Contact Resistance of Flip-Chip Joints in Wearable Electronic Textiles
Abstract
Flip-chip bonding to a Cu lead frame transferred to a fabric was achieved by use of a non-conducting adhesive. Average contact resistance of the flip-chip joints was evaluated on variation of the Cu and Sn thickness of Cu/Sn bumps of size 150 × 220 μm2. The total thickness of the Cu/Sn bumps was fixed at 15 μm. The average contact resistance of the flip-chip joints on the fabric was 5.4-10.8 mΩ, depending on the Sn thickness of the Cu/Sn bumps; this was lower than for flip-chip joints on a rigid Si substrate (15.6-26.5 mΩ). The average contact resistance of flip-chip joints on the fabric decreased from 10.8 mΩ to 5.5 mΩ when the chip-bump configuration was changed from 15- μm-thick Sn to 7- μm-thick Cu/8- μm-thick Sn. The contact resistance of flip-chip joints bonded with the 7- μm-thick Cu/8- μm-thick Sn bumps remained below 10 mΩ for up to 750 h in the 85°C/85% relative humidity test and even decreased to below 4 mΩ in the storage test at 125°C for up to 1000 h.
- Publication:
-
Journal of Electronic Materials
- Pub Date:
- December 2014
- DOI:
- 10.1007/s11664-014-3431-8
- Bibcode:
- 2014JEMat..43.4464C
- Keywords:
-
- Wearable electronics;
- electronic textile;
- flip-chip;
- contact resistance;
- fabric