Issue link: https://iconnect007.uberflip.com/i/1511625
14 PCB007 MAGAZINE I NOVEMBER 2023 camera/sensor is selected. e most common failure is the use of simple cameras in shops with high material mix, and then skipping out on the the detailed camera light settings cali- bration work required for each material. By contrast, the expensive X-ray is not suscepti- ble to this issue at all, for example, and the dual wavelength systems reduce the potential error tremendously for a reasonable price. e deci- sion is one of "pay me now/pay me later" (i.e., CapEx vs. scrap costs). Alignment and Placement Alignment algorithms are typically orthogo- nal or trapezoidal in nature for most machines, though any-point compensation has been available since 2017 from multiple equipment suppliers. Still, the most common method of alignment remains four-corner. On multi-up panels with tight tolerance requirements, the registration is done in the four corners on the sub-panel level to provide improved optimiza- tion. is is oen called local registration. Hack: Drill position compensation for placement error Aer placing laser or mechanical alignment targets in the panel, it is valuable to remeasure the holes and record their size/positions. By doing this, one can identify the error between where the holes were supposed to be placed and where the spindle or laser head actu- ally placed them. Especially, with mechanical holes, this can oen be off by up to one mil or more, especially on the exit side of the panel. By measuring and applying these measured offsets on the subsequent drilling or imaging operations, the placement error can be nulled out, and for a very low OpEx investment, the gain in capability is high. is system works best when 2D codes are used, as offsets can be saved to each 2D code row in the database. 2. Inelastic Process Steps Overall, this family of steps is a necessary evil which must be constantly modeled and controlled. It involves very strong process and product coupled interactions. Some of the potential processes are also incompatible with tight registration tolerances on thinner prod- ucts and need to be completely avoided when- ever possible. Inelastic process steps oen lead to a non-linear error which is not measurable by four-point tooling systems, and oen gets characterized as "random movement" and "swimming" by many shops. Hack: Non-linear analysis for characterization of inelastic processes Four-corner fiducial placement is not capa- ble of detecting non-linear error, and compen- sation algorithms are generally only linear. is is simply because there are not enough points to determine the shape of the individual axis, since each axis only has two points to make the line (i.e., X1, X2, Y1, Y2). What is interesting is that if you add more fiducials (like at the mid- point of each axis, for instance), it is quite com- mon that the non-linear error oen exceeds the linear error on advanced designs (particu- larly with thinner dielectrics). ere are two ways to address this issue. One can move to eight-point or more tooling to characterize the error and do a non-linear best- fit globally (which adds cost), and/or one can analyze the eight points as part of a first arti-