Solder resist layers

When defining the layer stack in the Physical Editor, it is not possible to define solder resist, or other coating layers. However, these layers can have an effect on the characteristic impedance of tracks on the outer layers of the board.

Coating layers will be considered if they are defined in the file

$red_job/<jobname>/hpe/<version>.mlr

Any coating defined in this file will not be displayed in the layer stack editor but will be taken into account when running field solutions for the design.

.mlr input file format

The syntax is one statement per line in the format:

CoatingTop  <thickness in DSUs> <Permittivity> <Loss Tangent>

or

CoatingBottom  <thickness in DSUs> <Permittivity> <Loss Tangent>

For example:

CoatingTop 1000 4.5 0.015

CoatingBottom 8500 3.8 0.0

Notes:

• The loss tangent is permitted to be zero but must not be omitted.

• The permittivity and loss tangent have no units.

• <thickness in DSUs> is a coating thickness, not a layer thickness, and its value must be greater than zero. This is shown in the figure below.

• It is legal to specify a coating on one side only if required. In this case, the other statement should be omitted.