Reworkable Underfill
Characteristics
- Low temp. snap cure -- 500μm layer of the material takes only 1 second to gel at over 70 degrees
- Excellent reworkability allows for the easy wiping of the resin residue left on PCB.
- Excellent electrical insulation
- Excellent storage stability at 5~10°c
- Excellent endurance for mechanical stress (bending stress)
- Elastic urethane protects solder interconnects from drop shocks.
- Allows for the use of various thermal treatment system
(example: radio frequent dielectric heating system ultra sonic heating system)
Reworkability
Reworkability
Urethane based underfill, 991 series, eliminates the stressful process of taking the underfilled CSP off and cleaning the material residue off of the PCB. The underfill chemically dissolves after a heat treatment and allows for an easy wiping of little residue left on the PCB, which makes it possible for engineers to analyze a defect device and also to save expensive PCBs.
See rework steps of underfilled CSP
Endurance for bending stress
Sunstar's urethane underfills possess excellent bending stress endurance that is often required by mobile electronics.
Drop Shock test
Elastic rubber like urethane property has excellent shock absorbing characteristics and extends the fatigue life of CSP solder joints.
Physical property
| Property | 991 | 991M | 992 | 991D | other | |
|---|---|---|---|---|---|---|
| cure condition | 80°c×10min 100°c×7min 120°c×3min |
80°c×10min 100°c×7min 120°c×3min |
80°c×10min 100°c×7min 120°c×3min |
80°c×10min 100°c×7min 120°c×3min |
||
| Dissolution temp.(°c) | 200°c | 230°c ＊for Sn-Ag-Cu |
200°c | 200°c | TMA | |
| viscosity (mPa · s) | 5400 | 5000 | 8360 | 27000 | BH type 20°c | |
| vis. ratio | 1.00 | 1.00 | 1.08 | 2.0 | 2/20rpm(23°c) | |
| Specific gravity | 1.08 | 1.07 | 1.08 | 1.08 | 20°c | |
| Gelation (second) | 7 | 7 | 7 | 5 | 80°c/200 μm | |
| Degree of hardness | 85 | 84 | 95 | 95 | JISA type JISK-6301 | |
| DumbbellM 50 (N/mm 2) |
2.6 | 2.3 | 8.3 | 7.4 | (20°c) JIS-K6301 | |
| rupture strength (N/mm 2) |
4.1 | 5.4 | 10.8 | 10.5 | ||
| elongation/ ruptuure (%) | 180 | 190 | 230 | 200 | ||
| CTE （ppm/c） |
α1 | 68 | 67 | 62 | 65 | TMA |
| α2 | 197 | 197 | 190 | 192 | ||
| Tg(°c) | -85 | -85 | -85 | -80 | TMA | |
| volume resistance (Ω cm) | 1.2×1012 | 2.2×1013 | 1.5×1013 | 2.1×1013 | (20°c) JIS-K6911 | |
| insulation resistence (Ω cm ) 85c × 85 % |
3.0×109 | 3.0×109 | 1.2×1010 | 2.0×1010 | JIS2 IR 100v |
|
| dielectric constant (ε) | 4.00 | 3.70 | 3.86 | 3.79 | JIS-K6911
1MHz 20°c |
|
| dielectric dissipation factor (tan δ) |
0.034 | 0.043 | 0.050 | 0.037 | ||
| adhesion (N/mm2) | 7.0 | 7.9 | 10.9 | 9.5 | FR-4 | |
| Water absorption (%) | 0.85 | 0.95 | 1.10 | 1.00 | Boiling test 2hr | |
| Storage stability (10°c) | 6 months | 3 months | 4 months | 3 months | 10°c | |
