Nail Heading
Nail Heading Evaluation
Nail Heading is a phenomenon that occurs in the drilling of multilayer PWB's. The normal copper inner layers are drawn out or extruded by the drill which forms a nail head like shape on the hole wall.
- The inner hole wall is inspected by cross-section, the dopper layer is measured where the nail head is formed. The nail heading value is expressed as a percentage according to the thickness of the inner layer copper as shown in the figure below.
- If the evaluation using stack drilling has been done, all the panels are measured.
- The maximum nailheading points are measured around final hit hit counts.
 |
|
| The inner layer copper thickness is measured from the average position of the "roughed" surface of the copper layer. | Nail Head[%]= b/a x 100 a: Copper layer thickness [µm] b: Nail head width [µm] |
