A favorite topic of everyone - hehehehehe!

Measles do not usually appear along the edge, but next to or between holes
that have been soldered.

Do you have resin starvation or crazing or haloing along the edge.

Microsections will tell you where the separations are that are causing the
white areas.  That would be helpful to know in determining what you have.

If you are a board shop and are seeing this phenomena, it could be the
presence of moisture that is present on older lots, but not newer lots -
depending on storage.

When you say the "measles" are prepreg dependent - that points more
to the moisture condition.  Measles are usually found close to the surface
of a board and not on the internal prepreg layers.  Or are you using foil
outer layers and the laminate between layers 1/2 is made of prepreg?

Susan Mansilla
 Robisan Lab

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