COMPLICATED BOARD PROGRAMMING FOR AUTOMATED PRINTED SOLDER PASTE INSPECTION WITHOUT CAD DATA FILE

摘要

Specially designed test boards are used to evaluate the solder paste printing and reflow performances by solder paste manufacturers and many large customers. To maximize the efficiency, such test boards usually have thousands of pads, with same type of pads scattered across the board, and lots of pads or even all pads are designed not to be assembled with any components with the purpose not only to reduce the cost, but also to inspect the solder bumps more conveniently. Therefore for such test boards, the component placement CAD data do not cover all pads, and sometimes the board designer may not create a CAD file at all. To evaluate the paste printing performance objectively, the board needs to be inspected by a solder paste inspector (SPI), such as Koh Young, Parmi, CyberOptics, etc, to get the quantitative printing data. When programming a board with a SPI, different types of pads need to be assigned with different names and vice versa. This way the further statistical analysis on the printing data becomes possible. Usually SPI software can do such pad name assignment automatically based on a CAD file. But without a CAD file, assigning thousands of pad names manually is a very challenge task. Here we present our unique technique to program a complicated test board without any CAD data files. We are going to use Koh Young's CEditor software as an example, but the principle should be applicable to any other SPIs if the needed data set can be accessible to the programmer. This technique is not taught in CEditor's user manual. It can be described briefly as "virtual part" approach. That is, first we divide the board to many vicinages, then assign a "virtual part name" in each vicinage to cover all pads by CEditor. After this step the CEditor can export a pad data file which includes not only the virtual part name, but also lots of other information, such as X, Y position, size and shape, etc. With Microsoft Excel we can sort pads based on size and shape information and assign pad names accordingly. For rectangular pads, the rotate angle (horizontal or vertical) can easily be decided by the x, y size values. With those informations the minimum requirement of a CAD file can be met if we just use the virtual part name as "Library Name". So that the modified Excel file can be loaded back to CEditor for the next step programming just like loading a genuine CAD file. Initially the CAD file created that way may not be perfect and some pads may have wrong assignment. During the next step programming, the wrongly assigned pads can be found easily by CEditor and the information obtained can be used to edit the earlier mistakes in the CAD file. Then corrected CAD file can be used to re-do the programming. If more mistakes are found, the CAD file can be edited again. In this way back and forth a few times a perfect CAD file can be produced and therefore a whole board can be programmed completely and perfectly.