The Hammer Head Etch Compensation action performs etch compensation for the SMD pads of BGA boards. The function adds fillets or balls to the corners of the SMD pads to compensate for over-etching.
The results of a sample action are shown in the pictures below.
Before Action:
After Action
A new option was added to the Corner Shape parameter: This option enables creation of square features for etch compensation.
The compensation can be carried out using one of two methods:
*
By changing the SMD pad into a (single) pad with a new shape.
*
By ensuring that the SMD is a rectangle and adding corner features
to the layer.
One of the important parameters to the action is the size of the compensation. This can be given either as a percentage of the SMD width, or as an explicit value.
As can be seen in the lower right corner of the SMD pad in the above examples, the action does not compensate if by doing so it will create a sliver (acid trap) at a particular corner. See the description of the Sliver Spacing parameter for more details.
The action will also maintain a minimal copper spacing requirement between features of different nets. This can be done either by removing a corner or by reducing the size of the compensation. See the description of the Cu. Spacing and the Maintain Cu. Spacing By parameters.
The action provides histograms of the fully compensated, partially compensated and uncompensated SMD pads.
Result attributes according to the following syntax are produced:
Attribute |
Description |
...fully_compensated |
Number of SMD pads in the Fully Compensated SMD Pads category for each layer. |
...removed_corners |
Number of SMD pads in the Compensated With Removed Corners category for each layer |
...size_reduced |
Number of SMD pads in the Compensated With Reduced Size category for each layer |
...not_compensated |
Number of SMD pads in the Uncompensated SMD Pads category for each layer |
fully_compensated |
Total number of SMD pads in the Fully Compensated SMD Pads category for all processed layers. |
removed_corners |
Total number of SMD pads in the Compensated With Removed Corners category for all processed layers. |
size_reduced |
Total number of SMD pads in the Compensated With Reduced Size category for all processed layers |
not_compensated |
Total number of SMD pads in the Uncompensated SMD Pads category for all processed layers |
The actual distance used in sliver spacing corner removal is calculated from the skeleton of the corner to the element in question.
*
Fillet
shapes: the skeleton is the segment from the corner of the SMD pad to the point
of the fillet.
*
Ball shapes:
the skeleton is the segment from the corner of the SMD pad to the point on the
outline of the ball at a 45 degree angle to the corner.
Owing to the nature of the shapes, the Sliver Spacing parameter would generally be larger for fillets than ball shapes.