1.3.2. Via Capture Pad Layout and Dimension
The size and layout of via capture pads affect the amount of space available for escape routing. In general, you can lay out via capture pads in the following two ways:
- In-line with the surface land pads
- Diagonal to the surface land pads
The decision to place the via capture pads diagonally or in-line with the surface land pads is based on the following factors:
- Diameter of the via capture pad
- Stringer length
- Clearance between via capture pad and surface land pad
Use the Placement of Via Capture Pad for 1.00-mm Flip-Chip BGA NSMD Land Pads figure and the Formula for Via Layouts for 1.00-mm Flip-Chip BGA NSMD Land Pads table to guide the layout of 1.00-mm pitch BGA packages using NSMD land pads.
If your PCB design guidelines do not conform to either equation in the following table, contact Intel® Premier Support for further assistance.
Layout | Formula |
---|---|
In-line | a + c + d <= 0.53 mm |
Diagonally | a + c + d <= 0.94 mm |
Note that the Formula for Via Layouts for 1.00-mm Flip-Chip BGA NSMD Land Pads table shows that you can place a larger via capture pad diagonally than in-line with the surface land pads.
Use the Placement of Via Capture Pad for 0.80-mm UBGA (BT Substrate) NSMD Land Pads figure and the Formula for Via Layouts for 0.80-mm UBGA (BT Substrate) NSMD Land Pads table to guide the layout of 0.80-mm pitch UBGA packages using NSMD land pads.
If your PCB design guidelines do not conform to either equation in the following table, contact Intel® Premier Support for further assistance.
Layout | Formula |
---|---|
In-line | a + c + d <= 0.46 mm |
Diagonally | a + c + d <= 0.68 mm |
Note that the Formula for Via Layouts for 0.80-mm UBGA (BT Substrate) NSMD Land Pads table shows that you can place a larger via capture pad diagonally than in-line with the surface land pads.
For 0.5-mm pitch, Altera® recommends you to use microvia technology of 0.10-mm via drill in the pad, and route trace in the inner layers.
For 0.4-mm pitch, Altera® recommends you to use microvia technology of 0.10-mm via drill in the pad, and route trace in the inner layers.
Via capture pad size also affects how many traces can be routed on a PCB. The Typical and Premium Via Capture Pad Sizes for a 1.00-mm Flip-Chip BGA figure shows sample layouts of typical and premium via capture pads. The typical layout shows a via capture pad size of 0.660 mm, a via size of 0.254 mm, and an inner space and trace of 0.102 mm. With this layout, only one trace can be routed between the vias. If more traces are required, you must reduce the via capture pad size or the space and trace size.
The premium layout shows a via capture pad size of 0.508 mm, a via size of 0.203 mm, and an inner space and trace of 0.076 mm. This layout provides enough space to route two traces between the vias.
The following table lists the typical and premium layout specifications for a 1.00 mm Flip-Chip BGA used by most PCB vendors.
Specification | Typical (mm) | Premium (mm) PCB Thickness >1.5 mm | Premium (mm) PCB Thickness <= 1.5 mm |
---|---|---|---|
Trace and space width | 0.1/0.1 | 0.076/0.076 | 0.076/0.076 |
Drilled hole diameter | 0.305 | 0.254 | 0.150 |
Finished via diameter | 0.254 | 0.203 | 0.100 |
Via capture pad | 0.660 | 0.508 | 0.275 |
Aspect ratio | 7:1 | 10:1 | 10:1 |
The Typical and Premium Via Capture Pad Sizes for a 0.80-mm UBGA (BT Substrate) figure shows sample layouts of typical and premium via capture pads. The typical layout shows a via capture pad size of 0.495 mm, a via size of 0.254 mm, and an inner space and trace of 0.102 mm. With this layout, only one trace can be routed between the vias. If more traces are required, you must reduce the via capture pad size or the space and trace size.
The premium layout shows a via capture pad size of 0.419 mm, a via size of 0.165 mm, and an inner space and trace of 0.076 mm. This layout provides enough space to route two traces between the vias.
The following table lists the typical and premium layout specifications for a 0.80 mm UBGA (BT Substrate) used by most PCB vendors.
Specification | Typical (mm) | Premium (mm) PCB Thickness >1.5 mm | Premium (mm) PCB Thickness <= 1.5 mm |
---|---|---|---|
Trace and space width | 0.1/0.1 | 0.076/0.076 | 0.076/0.076 |
Drilled hole diameter | 0.381 | 0.330 | 0.254 |
Finished via diameter | 0.254 | 0.165 | 0.127 |
Via capture pad | 0.495 | 0.419 | 0.381 |
Aspect ratio | 8:1 | 25:1 | 12:1 |
The Typical Via Capture Pad Size for a 0.50-mm MBGA figure shows sample layout of typical via capture pad. The typical layout shows a via capture pad size of 0.25 mm, a via size of 0.10 mm, and an inner space and trace of 0.068 mm.
The following table lists the typical layout specifications for a 0.50-mm MBGA used by most PCB vendors.
Specification | Typical (mm) |
---|---|
Trace and space width | 0.086 |
Finished via diameter | 0.10 |
Via capture pad | 0.25 |
The Typical Via Capture Pad Size for a 0.40-mm VBGA (also known as WLCSP) figure shows sample layout of typical via capture pad. The typical layout shows a via capture pad size of 0.25 mm and a via size of 0.10 mm. For the 0.40-mm pitch, there is not enough space to route trace in the component layer, because the minimum trace width is 0.075 mm and the minimum gap between the trace and pad is 0.086 mm.
For detailed information on drill sizes, via sizes, space and trace sizes, or via capture pad sizes, contact your PCB vendor directly.