Never heard of "special finger marker stickers" for checking wave parallelism.
We assume that you're talking board-to-wave parallelism. We use a Durostone fixture with a thermalcouple [TC] in each far corner of the fixture (flush to the bottom of the fixture, exposed to the wave) to measure the time lag between corner 1 and corner 2, for the purpose of establishing coplanarity of the wave to the board. There should not be a significant time difference between the temperature spike indicated on TC1 and TC2 when they: * Hit the pot. * Leave the pot.
A company that makes fancy-schmancy wave measuringerometers found that: * Many wave soldering machines lack good paralellism. * A significant jump in unparallelism-caused defects occurs when the side-to-side difference in dwell is over 0.2 seconds.
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