At our new assembly facility in Markham, Ontario, Bittele Electronics performs X-Ray inspection on all assembly orders that contain BGA, LGA, or any other leadless package types. Our Nordson Dage Quadra 3 X-Ray Machine is top-of-the-line and it is used to complete the process. It has extremely high resolution for images, 5 times clearer than other standard X-Ray inspection machines (down to 1 micron). It can also be used for troubleshooting, being capable of helping to determine the root cause for defects such as insufficient solder paste, skewed part placement, or even improper reflow profile.
The process to start the X-Ray machine begins with warming up the machine. This takes about 3 to 5 minutes. The next step is setting the board clearance height and then loading the board(s) into the machine. The fully rotational camera can then be used to view the board from different angles. The image of the board is loaded onto the computer and from there the inspection begins. The proper wattage is selected based on the complexity of the parts and the number of special parts (BGAs, QFNs, etc.). The higher the power, the higher the resolution. The operator will check every solder joint and pad to make sure that the solder voids do not exceed an acceptable limit. For BGAs and LGAs, there may not be any solder voids present that are greater than 25% of the total area. For QFNs, this percentage must be less than 30%. For any parts with heatsinks (usually on some QFNs and fine pitch parts), the void zone must not be any larger than 50% as outlined in IPC standards. This is seen when observing the parts, the solder is shown as darkened areas on the screen. Voids show up as light areas (or “bubbles”) of space where solder is not present. So long as these voids remain under their specified percentages for all pads on all parts present on the board, it will pass its inspection. Any board the fails the inspection may be subject to rework.