Silver nanoporous sheet for solid-state die attach in power device packaging

Reliability of Ag Nanoporous Bonding Joint for High Temperature Die Attach under Temperature Cycling

“…The bonding layer re ections showed somewhat different contrasts, regardless of the number of temperature cycles. In the case of the as-bonded condition, the white area observed seemed to be due to the porous part of the Ag layer, as previously reported 11) . Before 1000 cycles, there was no clear evidence of Ag layer delamination.…”

“…The shear strength of the as-bonded Ag NPB joint is approximately 22 MPa. This is almost the same as the shear strength of Ag NPB with an ENIG nished Cu disk 11) , and that of a Pb-5Sn die attach 5) . There was no signi cant change in the average value the shear test results up to 1500 cycles compared with the as-bonded results.…”

“…The thickness and ligament size of the Ag nanoporous sheet ( Fig. 1(a)) were approximately 90-100 μm and 110 nm, respectively 11) .…”

“…As an effort to eliminate the Pb containing solders in high temperature electronics, numerous alternative Pb-free bonding techniques that could be used for high temperature die attach have been reported, including high melting temperature solders, such as Au- 4) , Bi- 5) , and Zn-based 6) solders; transient liquid phase bonding 7) , and Ag sintering methods using a nanoparticle [8][9][10] or Ag nanoporous sheet 11,12) . Among these, in our previous research, we successfully demonstrated a novel die attach method using a Ag nanoporous sheet, called Ag nanoporous bonding (NPB), without the aid of the any organic substance.…”

“…It is a potential candidate for a high temperature die attach technique. However, its long-term reliability under severe environments was not estimated 11,12) . Temperature cycling tests are generally performed to examine the durability of electronic device joints under the thermal stress induced by a coef cient of thermal expansion (CTE) mismatch.…”