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,
use individual components costing tens of thousands of dollars and themselves can cost half a million or more, are notoriously hard to successfully clean manually and rework, and usually have to be scrapped if faulty. The problem stems from the fact that two different types of solder are used in manufacturer, with melting points of 183°C and 302°C respectively. Improper manual cleaning can change the melting temperature of the solder at the pads, so that when the new component is applied with solder paste, the temperature may not be high enough to form an intermetallic joint, and a dry joint could result at those connections.
In addition, many Package on Package chips cannot be confidently cleaned with manual methods due to the threat of melting the bottom package. One highly advanced component, the Invensas BVA POP—which promises a fourfold increase in memory and processing speed—holds the solder balls on with fishhook shaped connectors 50 microns wide and 90 microns high, barely visible to the unaided eye and spaced at .2 mm intervals. Suffice to say that manual cleaning is not an option for this innovation.
Read more about automated contactless cleaning – or scavenging – as a safe, efficient and effective method of cleaning BGAs with small components.
