PARTNER FOCUS


cold region. Secondly, the Internal ground planes connecting to the barrel act as a heat sink, preventing those pins from ever achieving a high enough temperature to reflow sufficiently. Then, the thermal relief pad design for the ground pins should be considered, as long as the electrical performance of the grounding system is not compromised. The thicker the board, the more difficult it is to achieve adequate barrel fill since the issues mentioned previously are even more pronounced. Circuit solutions solved this problem


predominantly by investing in the Ersa Veraflow selective soldering equipment. This was an addition to their existing wave soldering system which is still being used as back up for certain type of boards. The main benefits that the Ersa selective soldering equipment achieved is:


• The ability to solder in tight component spacing.


• Can soldering pth components close to smt components.


• Controlled heating for thicker boards or where there are ground planes.


• The ability to solder in dense concentration of thru-hole pins particularly with large


connectors that have numerous pins.


• Additionally, the ability by programming to handle unique pin configurations.


• All this is achieved with the selective soldering system that includes infrared


pre-heater, automatic flux dispensing and solder nozzles of varying sizes.


• Another important benefit that selective soldering offers is in its consistency with


solder joints each and every time. By investing in the Ersa Veraflow Selective


Solder machine, Circuit Solutions pushed the boundaries with the issue they had with resolving a problem with the barrel fill for a key customer.


3. Solder paste stencil – ability to print PCB size 590 x 450 mm. As part of the surface mount assembly process, Circuit Solutions uses the Speedprint SP710AVI automatic solder dispenser machine. When running a new job through the process a new unique solder stencil is designed and manufactured for this printed circuit board assembly. The stencil is fitted to a frame on the machine and the first stage is applying solder paste to the bare printed circuit board using the new stencil. The paste being applied by the squeegee blade that spreads the solder paste evenly and accurately onto the bare printed circuit board. Circuit Solutions engineering team along


with the technical support of the stencil manufacturer identifies the solder stencil type pertinent to the design requirements of the printed circuit board assembly. Generally, the solder stencil is made of stainless steel foil and laser etched to produce the required footprint apertures to match the components. Prior to the assembly process, the solder


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stencil mounted on a frame that fits within the body of the Speedprint machine. The system allows the stencils to be quickly interchanged for the next job and when fitted is held flat firmly with equal and


maintainable tension across the whole stencil. The standard size stencil is generally


490mm wide with a squeegee blade of 400mm wide. Circuit Solutions recently had a requirement where the board width was 508mm which was larger than the standard size stencil. Their engineering team obtained the largest frame size for this machine which was 610mm wide. They also had a special stencil manufactured to fit. A squeegee blade 600mm wide was supplied that fitted the new stencil size. The job was manufactured and Circuit Solutions achieved perfect results from this assembly. This another example of pushing the boundaries that had a successful outcome along with a satisfied customer. One further machine that Circuit Solutions


invested in was the Nikon X-ray equipment. This has been instrumental in verifying the quality of any of the examples of pushing the boundaries above. The advancements in miniaturisation of


electronic components has resulted in the footprints of components such as micro bgas and QFNs becoming more complex. The consequence being it pushes the boundaries for the pcb manufacturer and also the pcb assembler. The evolution in the design of electronic components is continually putting the pressure onto contract manufacturers to come up with solutions to these problems.


Circuit Solutions (Cambridge) Ltd www.circuitsolutions.co.uk


OCTOBER 2021 | ELECTRONICS TODAY 19


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