Issue link: https://iconnect007.uberflip.com/i/1428512
NOVEMBER 2021 I PCB007 MAGAZINE 23 Brandt: All these additional measurement methods are available in our flying probe machines because we have a basic electronic unit—a unit with the same soware and elec- tronic components for all our flying probes. We have this technology for our existing A7a and A8a technology, and with this is our state- of-the-art, latest generation of the direct linear motor drives technologies in the A9. It's also in the A9 automation technology which released this year. is is our newest technology. With these high voltage features for the quality of shorts, we are getting more requests for four- wire measurement options that can recognize thin plating defects in through-holes or latent test measurements where you can detect dish downs, cracks, mouse bites, or the quite new measurement technology—a back drill test where you can detect remaining stripes or par- tial stripes in back drill holds. All these differ- ent measurement methods can be integrated optionally in these flying probe testers. Starkey: When I first encountered your equip- ment, we were looking at low-voltage resis- tance testing: if the resistance exceeded a spe- cific value, or if the resistance was less than the specified value. en we got shorts and opens and when we looked for them with a magnify- ing glass, we could actually see them. But a lot of the defects that you can identify are beyond the capability of the human eye, even with a good magnifying glass. Just going back to the sort of physical measurements, if we look at the mechanical side, what sizes and fixtures are you able to contact accurately and consistently with the flying probe tester? Brandt: e standard or the limit of the stan- dard product line for flying probe means stan- dard A7, A8, or A9 automation; a standard pad size dimension for two wire probe test is around 50 microns. is means two mil. is is a standard for all flying probe machines. When you want to go less than 50 micron in a pad size you need some requirements to do it. en you have to check the parameters. It means you have to keep the machine in a stable envi- ronment, especially for temperature. You have to integrate a glass calibration plate instead of an FR-4 calibration plate. You will take fine pitch probes instead of standard probes. en it depends in which direction you want to go. When you have a PCB test system, like A9 or A9a, then the limit of the technology is some- where in the range of 30- to 35-micron pad size. If you want to go less in smaller pad dimensions in the direction of 20 to 15 microns, then you have to go in the direction of our S technolo- gies—S2 or S3—in the substrate market and package boards. is is a dedicated business, but you never know, sooner or later it will also move from the substrate market. is technol- ogy, this kind of production capability, is also in the standard printed circuit board. We have to prepare for this. Starkey: You mentioned you have to make sure the environment is stable and the calibration is precise. What are the real characteristics of a printed circuit board to consider when you determine accuracy? How intelligent can your positioning systems be? Brandt: We always use an optical alignment system in all our equipment and in most of the flying probes in the market. e opera- tor selects optical scan marks on the top and bottom sides, and with the optical scan marks they're able to compensate for the shrinkage and offset problems. Here you can compensate tolerances from the production in relation to the real data of the board production; I would say at least in the range of ±2-3%. is means for a big board size you can compensate differ- ent alignment of offsets in the range of three to five millimeters all over the board. Only this kind of optical alignment check of the com- plete board will guarantee that you always con- tact in the middle of the test point. is is a must. If you are not hitting the test points, you get an open. Or if you have,