Lead Free Solders

Figure 16 shows the strain amount decrease of acrylic based Sn-58Bi solder ACFs as a function of temperature by adding 0, 5 and 10 wt% of 0.2 μm silica fillers. Both the amount of the thermal expansion and the elastic strain of polymer resin were reduced by adding silica filler. It was known that reducing the thermal expansion strain and the elastic strain as a function of temperatures are good for the joint reliability in T/C test and the good solder joint formation, respectively [35]. Storage modulus of acrylic based Sn-58Bi solder ACFs with addition of 0, 5, and 10 wt% 0.2 μm silica was increased from 0.4 to 0.9 and 1.3 Mpa in Figure 17, respectively.

3.4 T/C reliability

Figure 17.

Figure 18.

75

0–80 MPa and (b) 0–10 MPa ranges.

before and after 1000 cycles reliability test.

with several bonding pressures.

A Review: Solder Joint Cracks at Sn-Bi58 Solder ACFs Joints

DOI: http://dx.doi.org/10.5772/intechopen.83298

Figure 18 were listing the solder joint morphologies by adding 0, 5 and 10 wt% 0.2 μm sized silica filler of acrylic based Sn-58Bi solder ACFs joints before and after T/C reliability for 1000 cycles. Referring to the enhancement of elastic modulus by adding several silica fillers in Figure 17(b), solder joint cracks were completely removed for acrylic based Sn-58Bi solder ACF joints at 200°C TC bonding condition

For acrylic based Sn-58Bi solder ACFs without added silica fillers, total joint failure occurred at the interface between Sn-58Bi solder joints and Cu metal electrode after 1000 cycles T/C reliability test, because initial solder joint cracks have already existed before the T/C reliability test. Although elastic modulus was increased double by adding 5 wt% 0.2 μm silica fillers, a small solder crack still remained and propagated at Sn-58Bi solder joints resulting in unstable joint contact resistance during T/C reliability. Excellent solder joint morphology was obtained after the 1000 cycles T/C reliability, because initial solder joint crack was perfectly

Elastic modulus of acrylic based Sn-58Bi solder ACFs by adding 0, 5, and 10 wt% 0.2 μm silica fillers at (a)

Solder joint morphologies of acrylic based Sn-58Bi solder ACFs added by 0, 5, and 10 wt% 0.2 μm silica filler


#### Table 3.

Storage modulus of acrylic adhesive during cooling process.

#### Figure 15.

Effects of delaying ultrasonic horn lift-up times (0, 1.2, 5.4, 30.2, and 60.3 seconds) on the Sn-58Bi solder ACFs joint morphologies.

Figure 16. Strain of acrylic based Sn-58Bi solder ACFs with added silica fillers as a function of temperatures.
