SMT Reflow Fixture: ±0.02 mm Location Case Study
What We Built
These are reflow soldering fixtures for SMT assembly lines. Aluminum alloy base plate with precision locating holes and vacuum relief slots. The plate sits on the conveyor rails and holds the PCB flat through the reflow oven. If the locating holes are off or the plate bows, the PCB does not seat properly and the solder joints come out uneven.
The Problem
The client runs high-volume consumer electronics. Their old fixtures were machined on a CNC router. Locating hole tolerance drifted to ±0.05 mm over batch production, so the plate would not index cleanly on the equipment rails. Flatness was worse—some plates bowed to 0.2 mm after heat cycling. That gap between PCB and fixture caused uneven heat transfer in the reflow zone. We saw cold joints on BGA packages and tombstoning on 0402 passives. They needed a process that could hold ±0.02 mm on 200+ holes per plate and keep overall flatness under 0.1 mm after repeated thermal cycling.
How We Fixed It
We switched to laser micro-cutting for the locating holes and datum edges. The laser cuts the holes directly from the CAD layout, so there is no tool wear accumulating over a batch. For the base plate flatness, we start with stress-relieved aluminum sheet and machine the datum face before any laser work. The vacuum slots and component relief pockets are cut in the same setup to maintain position relative to the locating holes. On larger plates, we laser micro-weld reinforcing ribs to the underside to keep the plate from sagging during oven cycles. Every plate gets CMM checked on three datum holes and a flatness scan across the working surface before it ships.
Numbers That Matter
200+ holes per plate
Post-heat cycle
Drill locate holes
Weld ribs
Product Gallery
PCB Reflow Soldering Fixture (Metal)
PCB Reflow Soldering Fixture (Patterned)
Related Manufacturing Capability
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