Selective Meets The Wave

Over recent years there has been a big push to try and remove wave soldering from the through -hole assembly process. This is not always possible. Common wave associated problems such as bridging between pins and skipped joints etc. inevitably require a high reliance for a re-work function with this mode of operation. Since the speed of a wave solder system, when compared to the alternative processes, is quicker it still has to be considered as a viable process in a modern production line.

Pillarhouse has taken a slightly different approach to this dilemma in an attempt to see how selective can work in partnership with wave to give a fast and, critically, more reliable process. Our Engineers have examined how best the selective process can be used to correct any anomalies, normally associated with the wave process, once product exits this phase of a production line. Working in partnership with Landrex AOI, Pillarhouse has helped develop solutions where product can be inspected after the wave process in order to identify if there are any issues with through-hole solder joints, and in some instances, surface mount components. Upon positive fault detection, the relevant data is relayed from AOI to the selective machine, where the specific joint(s) only are re-worked, and thereby correcting products to acceptable levels. In conducting this procedure, there is every chance that the cycle time can be maintained and yield rates significantly increased.

The Pillarhouse/Landrex approach is to have a number of automated re-work methods that can be implemented in a production environment. Some customers wish to identify, over a number of boards, regular issues from the wave solder system and then the use of selective to always solder these areas whether the board needs requires it or not. Others require a selective soldering system to be in-line with AOI where the AOI passes the information to the selective machine to perform the re-work repair. The board will then continue down the production line. However the most efficient and most popular system is where the selective soldering is in parallel with the AOI machine and linked via shuttle conveyors. The rejected board is shuttled off of the line to the selective system to be re-worked. Then the board is passed back to the line prior to the AOI. This allows the reworked board to be inspected again, ensuring that only quality boards pass down the production line, with the use of only a single inspection system.

Furthermore, the system can be used in a manual, off-line, mode. Where, with the use of a barcode system, the stored inspection information from AOI can be recalled to a hand-load machine and reworked completely offline. Even though we have developed this system with Landrex and they are our preferred partner, the selective soldering software is such that we can take the data from most AOI machines and achieve the same results.