Measling appears as small white spots or crosses beneath the board surface at the intersections of the glass weave, where fibers have separated from the resin, usually through thermal stress or moisture. It is internal and does not spread on its own, so it is often acceptable as long as it does not bridge too much of the spacing between conductors. Crazing is a related condition in which the white marks link up into streaks.
Measling under the power resistors after burn-in, check it against 610 before anyone calls it delam.
Also heard as
- measles
Do not mix it up with
- Delamination: Delamination is a real separation of layers that blisters the board; measling is local fiber separation inside the weave.
Related terms
Delamination
Separation between layers of a board's laminate or between laminate and copper, usually from heat or moisture.
Bake
To heat bare boards or moisture-sensitive parts in an oven to drive out absorbed water before soldering.
IPC class
Reliability class 1, 2 or 3 under IPC standards, setting the acceptance criteria a board is built to.