Most pick and place SMT systems perform admirably. Some are faster than others and some have more features than others. However, the SMT process has one common theme regardless of board complexity, volumes, or pick a place and machines. Solder paste deposition is the key to success and the biggest culprit in failure, where 75% of defects originate. Solder paste deposition begins with stencil design and requires a precise understanding of the geometric relationship between the part and the pads on the PCB, taking into consideration any complicating and altering factors to standard processes such as via holes, ground planes, solder mask, or surrounding parts. These are then factored into the calculations for aperture shape, aperture opening, and stencil thickness to optimize volume of solder paste at each location. Additionally, different screen printers, even from the same manufacturer and different models, will have different relationships with the same stencil For that reason, we have standardized our screen printing process across all six of our lines with the same make and model screen printing technology. This virtually eliminates the variability between machines and allows us to run any product on any line with confidence. The same is true for the reflow process. If the profile varies, so too can the results. Since this is the second leading cause of solder defects we have reduced this variability in the same way, by standardizing reflow technology across all six lines with the same ovens to maintain perfect repeatability in the reflow process, providing confidence and flexibility.
We focus on leading edge technology products and these products have limited through hole parts. However, most products do have some through hole parts, and the optimum process for soldering through hole parts in a pre-dominant SMT environment is selective wave solder.
Our three selective wave solder systems are smart systems with stored profiles, temperature sensors, vision, and a controlled Nitrogen atmosphere, providing close to perfect wetting and barrel fill in even the most challenging of designs, results not possible with conventional wave solder.
Control of MSD
Most EMS companies have some level of control for moisture sensitive device exposure. In line with our operating principles we have augmented the level of control of these devices to provide a higher level of confidence by locating dry boxes throughout the facility. These are temperature and humidity controlled cabinets where the parts are staged next to the point of consumption prior to actual assembly. This dramatically reduces the possibility of accidental over exposure.