IPC-A-600 Laminate Conditions Explained: Measling, Crazing, Blistering and More
Nov 07, 2026
Laminate conditions are some of the most argued-about findings in bare board inspection. Measling, crazing, blistering and weave exposure can look similar at a glance, but they mean different things and are judged differently.
Here's a plain-language guide for anyone inspecting printed boards to IPC-A-600.
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ElectroSpec’s IPC-A-600 CIS certification covers laminate integrity and the rest of Revision M across 4 module exams.
Why Laminate Conditions Matter
A printed board's laminate is the insulating structure that holds the copper. Conditions inside it can reduce electrical spacing, trap moisture or grow under heat. Some are cosmetic. Others are early signs of a reliability problem.
IPC-A-600 gives the criteria for telling them apart, by product class.
Measling
Measling shows up as small white spots or "crosses" below the surface, at the points where the glass weave fibers intersect. The fibers have separated from the resin at those intersections.
It is often linked to thermal stress, for example during soldering. Whether it is acceptable depends on how much there is, where it is and the product class.
Crazing
Crazing is also a separation of glass fibers from the resin, but it appears as connected white spots or lines rather than isolated crosses. It is often associated with mechanical stress such as drilling or routing.
The key question is whether it reduces spacing between conductors below the minimum.
Blistering
A blister is a local swelling and separation, either between layers of the base material or between the laminate and the copper. Blisters are judged with the same concern as delamination, because they are a physical separation inside the board.
Delamination
Delamination is a larger separation between layers of the base material, or between the base material and the copper. It is one of the more serious laminate conditions, because it can spread under heat and reduce insulation.
Acceptance depends on its size, its position relative to conductors and the board edge, whether it reduces spacing, and the product class.
Weave Texture vs. Weave Exposure
These two are often confused.
- Weave texture means the glass weave pattern is visible because the surface resin is thin, but the fibers are still fully covered. It is generally cosmetic.
- Weave exposure means the resin no longer completely covers the glass fibers. Exposed fibers can affect spacing and moisture resistance, so weave exposure is judged against the standard's criteria rather than treated as cosmetic.
Haloing
Haloing is a light-colored area around a hole or machined edge, caused by mechanical damage to the laminate. It is judged mainly by how far it extends toward the nearest conductor.
How to Inspect Laminate Conditions Well
- Use the right magnification and lighting. Many laminate conditions are invisible without them.
- Identify the condition correctly before judging it. Measling and crazing are judged differently from delamination.
- Measure, don't guess. Spacing and distance to conductors decide many of these calls.
- Confirm the product class on the drawing first.
- Use the illustrations and photos in IPC-A-600, which show target, acceptable and defect conditions side by side.
Frequently Asked Questions
Is measling always a defect?
No. It depends on extent, location and product class.
Is the IPC-A-600 exam open book?
Yes. IPC-A-600 CIS is 4 open-book module exams, so you will use the standard to look up criteria like these during the exam.
