Table 4 Differences in expansion and contraction of the 0.05-mm-thick core board (excluding copper foil).
From: CTE match of copper foil and build-up film/core board in FCBGA substrate reduces warpage
PF7 (H/H oz copper foil) Difference in Expansion and Contraction (ppm, treatment conditions: baking at 150 °C for 2 h) | ||||||||
|---|---|---|---|---|---|---|---|---|
Sample quantity | Position | Item | Longitudinal direction (ppm) | Latitudinal direction (ppm) | ||||
Before (original stacking) | After (new stacking) | Difference (|Before|-|After∣) | Before (original stacking) | After (new stacking) | Difference (|Before|-|After∣) | |||
12 pieces each | Outer layer | Max | − 659 | − 318 | 341 | − 555 | − 255 | 300 |
Min | − 1096 | − 605 | 491 | − 881 | − 575 | 306 | ||
Average | − 810 | − 471 | 339 | − 753 | − 430 | 323 | ||
Max–Min | 436 | 287 | 149 | 326 | 320 | 6 | ||
