If you have a bunch of complicated boards that need rework, and you need to remove solder and adhesive, it's a time consuming and risky application. In fact, even the most experienced and technical operators can get into delicate situations when faced with repeating component and pad cleaning over and over.
In addition to PCBs becoming thicker over the years, pad and pitch size have also reduced significantly, with many smartphones and other devices now utilizing pad sizes as small as .25mm millimeters spaced at intervals of .5mm. It is known in the industry that new chips are scheduled for release in the next two to three years that utilize designs calling for pad sizes as small as .15 mm with a .3 mm pitch. With adjacent parts so close together, avoiding hitting them with the wick during manual cleaning—and creating another round of rework—will most likely become impossible for even the most skilled technician.
Further, traditional cleaning methods can be even less effective when it comes to cleaning PCBs incorporating advanced chip technologies. For example, one new technology is providing outstanding improvements in security, making it nearly impossible for criminals to access data stored on the processor. However, due to factors such as differing size pads and uneven solder volumes, manual cleaning can be a significant challenge.
Another technology, Ceramic Ball Grid Array (CBGA), a specialty process used in aerospace, military and other high reliability applications, is another high value case in point. These boards,
That’s why Contactless Solder Cleaning is rapidly replacing manual cleaning in increasingly more rework applications.
The PCB rework process has long consisted of three steps:
- Removal of the inoperative component.
- Cleaning of residual solder from the ball grid assembly (BGA) pads which held the inoperative component in place.
- Replacement with a new component to create a viable PCB.
The first and third steps—removal and replacement—have long been automated, and are completed on rework machines with operator assistance. Cleaning, the middle step—and arguably, the most sensitive and vital step when it comes to reclaiming a damaged board—is often done completely manually by a skilled and experienced technician. The cleaning is performed with hand tools, usually a wicking braid and a soldering iron, using standard or specialized tips. The effectiveness of the operation is highly dependent on the skills of the individual operator. With the emphasis often placed on work throughput, board damage is quite common.
One common scenario in manual cleaning is the destruction of a pad due to sticking, when the heat of the soldering iron momentarily dissipates through the board, causing the delicate pad to stick to the wick and be chipped or lifted off the board entirely when the operator pulls the tool back. Overwhelming, destruction to a pad results in a wasted, scrap board.
Contactless solder cleaning is rapidly replacing manual cleaning in more and more PCB rework applications
Today's manufacturers of printed circuit boards (PCBs) are strongly quality driven, but even among those operations that are able to drive yields near or even above 99%, the huge volumes associated with applications such as smartphones and tablets could still leave them with thousands of boards per week that come off the assembly line damaged and in need of rework.
Since the cost of these PCBs can be well over US$200 each, most manufacturers and OEMs consider it vital to develop an effective process for working to reclaim these boards and minimize scrap PCBs—and the resulting losses—in their operations.
(Off center solder ball in the corners)