![]() On another board, with no ground plane, there are thermal vias to copper on the bottom side, and we've had over a thousand devices soldered. It's not in volume production (yet), so just a few dozen devices soldered so far. I'm not sure what they did, I guess they used plenty of preheat, but the soldering was fine. I asked them if they had any trouble, and they said no trouble at all. I was worried that the assembly house might have trouble with the soldering, but the boards came back looking great. I recently did some designs with thermal vias under the thermal pads the thermal vias went to copper on the bottom side and in some cases also to the ground plane layer, with no thermal relief. Short of manually laying it out, is there any way to apply clearance rules to polygons on non-signal layers? I've also tried copying it from the bottom layer and pasting to the solder mask without repouring, but the primitives stay on the bottom copper layer until you repour it. I've tried naming the polygon, and giving it a net and making clearance rules for those but nothing seems to work. I know it's unlikely with a 1mm gap, but I've got other locations with the same problem with 0.2mm gap. With no mask there, the solder could bridge over to the via and cause much bigger problems. Since the bottom solder is not an electrical layer, the rules don't apply to it, and the poly goes right over the vias in the HV tracks (see attached image). The problem is I don't want solder mask on this heatsink, so I copied the poly and pasted onto the bottom solder layer. This works fine - creates a nice neat cutout around them. I want to make the poly as big as possible, so instead of manually stepping around the traces in question I just gave them a 1mm clearance rule. Next to it I've got a couple of high voltage traces that I want to keep well clear of the heatsink polygon. Reflow affords positioning parts on either side enabling increased density and component varieties.I've got a component which requires a fairly hefty heatsink pour on the bottom layer. Reflow solders components solely using solder paste before oven heating while wave relies on flowing pumped solder contacting bottom board surfaces only. Table: Troubleshooting suggestions for common solder reflow defects FQA What is the key difference between reflow soldering and wave soldering? Paste storage conditions, paste formulation Print process controls, placement inspection Paste contamination, oxides, insufficient heat Table: Comparison of leading thermal methods for actuating solder reflow processīy methodically tracing symptoms backwards through process stages, defects point closer towards relevant mechanisms enabling corrective actions – part art, part science. Precision impossible with external sources Limited heat capacity challenges extreme thermal densitiesĬan induce secondary placement shifts around target zones Approachīalance of cost and capability for general useĮxcellent uniformity ideal for chips and large boards In all cases, monitoring temperature exposure of paste above liquidus and time about solidus thresholds while carefully managing ramp differentials proves vital to gain sound assemblies. Supplemental zone targeted high energy lasers sharpen profiles in confined regions of interest with precision impossible through external heating that might disturb neighboring locales helpful for chip scale or embedded joining requirements. ![]() Pick-and-place machines allowed positioning SMD parts precisely but operators still manually touched soldering irons or dual-flow machines to tack devices before additional oven passes, slowing throughput with substantial labor costs associated. Tedious glue or securing was required to temporarily hold tiny or multi-terminal parts in place. Reflow transformed electronics assembly by reducing manual effort and enabling reliable attachment of complex components like fine-pitched integrated circuits or bottom-terminated devices unachievable by hand: Wave Soldering OriginsĮarly surface mount techniques like wave soldering passed boards over flowing pumped solder, but only worked for one-sided components with bottom contacts. Why is it important to smooth heating zone ramps during reflow?.How does the pick-and-place process know accurate component locations?. ![]()
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