3.3 SAMA5D24/BGA256 Custom Test Board
This custom board is designed solely for testing multiple MPU+SDRAM configurations. It features five individual sets of SAMA5D24 MPU paired with 2xDDR3L-SDRAM, 2xDDR2-SDRAM, 2xLPDDR1-SDRAM, 2xLPDDR2-SDRAM and 1xLPDDR3-SDRAM devices. Each set has its own power management integrated circuit (PMIC).
The layer stack-up is shown in the following figure and table. Since all five sets are on the same board, they share the same stack-up.
Note the use of blind vias. Considering the very fine 0.4 mm ball pitch of the SAMA5D24, microvias in MPU pads were used. Large through-hole vias were not used in the fan-out of the MPU.
| Layer Name | Type | Material | Thickness [mm] | Thickness [mil] | Dielectric Material | Dielectric Constant |
|---|---|---|---|---|---|---|
| Top Overlay | Overlay | – | – | – | – | – |
| Top Solder | Solder Mask/Coverlay | Surface Material | 0.02 | 0.79 | Solder Resist | 3.5 |
| TOP | Signal | Copper | 0.035 | 1.38 | – | – |
| Dielectric1 | Dielectric | Prepreg | 0.105 | 4.13 | FR-4 | 4.5 |
| GND02 | Signal | Copper | 0.018 | 0.71 | – | – |
| Dielectric2 | Dielectric | Core | 0.13 | 5.12 | FR-4 | 4.5 |
| ART03 | Signal | Copper | 0.018 | 0.71 | – | – |
| Dielectric3 | Dielectric | Prepreg | 0.105 | 4.13 | FR-4 | 4.5 |
| ART04 | Signal | Copper | 0.018 | 0.71 | – | – |
| Dielectric4 | Dielectric | Core | 0.13 | 5.12 | FR-4 | 4.5 |
| PWR05 | Signal | Copper | 0.018 | 0.71 | – | – |
| Dielectric5 | Dielectric | Prepreg | 0.105 | 4.13 | FR-4 | 4.5 |
| ART06 | Signal | Copper | 0.018 | 0.71 | – | – |
| Dielectric6 | Dielectric | Core | 0.13 | 5.12 | FR-4 | 4.5 |
| GND07 | Signal | Copper | 0.018 | 0.71 | – | – |
| Dielectric7 | Dielectric | Prepreg | 0.105 | 4.13 | FR-4 | 4.5 |
| BOTTOM | Signal | Copper | 0.035 | 1.38 | – | – |
| Bottom Solder | Solder Mask/Coverlay | Surface Material | 0.02 | 0.79 | Solder Resist | 3.5 |
| Bottom Overlay | Overlay | – | – | – | – | – |