When an industrial IoT client approached us with a new device design, they had already completed the schematic, selected components, and built prototypes that worked well in the lab. The product was a battery-powered sensor device with two complex modules—one on each side of the board. Everything checked out on paper. Everything checked out on paper. This real PCBA manufacturing case began with a 50-unit pilot run that would reveal what the lab tests had missed.
Then came the pilot run: 50 units. Then came the pilot run: 50 units. What followed was a real PCBA manufacturing case with three distinct challenges—each requiring a different type of solution.
What followed was a wake-up call that revealed how design decisions made in the lab can fail on the production line. This real PCBA manufacturing case offers practical lessons for any hardware team preparing to scale production. Three specific challenges emerged—each requiring a different type of solution, from PCB layout adjustments to supply chain coordination to process automation.
The pilot run delivered a shocking result: only 70% passed SMT assembly. The remaining 30% failed with BGA-related defects—cold solder joints, insufficient wetting, and open connections.
The root cause: overlapping BGA footprints on opposite sides of the board.
In this real PCBA manufacturing case, the first major issue emerged from the very first production batch. The client’s design placed two BGA-type modules on opposite sides of the PCB, with their ball grid arrays overlapping in the same PCB area. During the first reflow pass (Side A), the board heated and cooled normally. But during the second reflow pass (Side B), the Side A module was subjected to thermal stress again. The cumulative heat exposure—combined with the localized thermal mass concentration from overlapping copper patterns—caused uneven heat distribution. Some pads reached proper reflow temperature while others didn’t, resulting in partial wetting and cold joints.
X-ray inspection of the 70% that passed revealed another alarming pattern: widespread voids in the BGA solder balls. IPC standards (IPC-A-610) specify that any solder ball void exceeding 25% is a defect. Many “passing” units had voids approaching or exceeding this threshold—meaning they would likely fail in the field within months.
Our solution: A two-part approach.
First, we reported the issue immediately to the client with X-ray images and failure analysis data. We recommended relocating the two modules so their BGA footprints no longer overlapped. This would eliminate the thermal concentration issue at the design level.
Second, for the current batch, we redesigned the reflow fixture to include independent positioning structures beneath each module, and used high-temperature tape to secure the modules during the second reflow pass. The tape prevented micro-movement during thermal expansion, reducing stress on the BGA joints.
The result? After implementing these changes, SMT yield improved from 70% to over 95% on reworked boards. In this real PCBA manufacturing case, the lesson was clear: double-sided BGA placement requires careful thermal analysis—if footprints overlap, you’re asking for trouble.
During the quoting phase, the client had provided sample enclosures for us to reference. They hadn’t provided a formal mechanical BOM—just physical samples and some drawings.
Between the sample phase and mass production, the client’s enclosure supplier made several design changes: some screw specifications changed, wire harness lengths were adjusted, and a few mounting hole positions shifted slightly. These were legitimate improvements—but the client forgot to update us.
We only discovered the changes when we received the final enclosure shipment and conducted our incoming quality control (IQC) inspection. The screws didn’t match the original spec. The wire harnesses were different lengths. The mounting holes didn’t align perfectly with our PCBA.
The challenge: The PCBA had already been fabricated and was about to enter SMT assembly. We couldn’t redesign the board. But we also couldn’t assemble the product with mismatched components.
Our solution: Leverage Shenzhen’s supply chain ecosystem. Within 48 hours, our procurement team sourced replacement screws, adjusted wire harnesses from a local supplier, and had custom spacers manufactured to accommodate the new mounting hole positions. All new parts arrived before PCBA assembly was completed—zero production delay.
This real PCBA manufacturing case taught us two things: first, always provide a complete mechanical BOM—not just samples—during the quoting phase. Second, Shenzhen’s supply chain density is a strategic advantage. A 48-hour turnaround on custom parts would have been impossible elsewhere.
The client’s design required potting (encapsulation) of certain components for environmental protection. Their original plan was straightforward: use 3D-printed fixtures to manually dispense potting compound into each device.
The problem: cost and throughput didn’t scale.
Each 3D-printed fixture cost approximately $10 and could be used for only a limited number of units before wear compromised accuracy. The client needed 5,000 units delivered in 4 weeks. At one fixture per unit (or even one per 5-10 units), fixture cost alone would have been $5,000-$10,000—and manual potting would have taken weeks.
Manual potting also introduces inconsistency: different operators apply different amounts, cure times vary, and human error leads to voids or incomplete coverage. Reject rates would have been unacceptably high.
Our solution: Automated overmolding (insert molding) with a dedicated mold.
We proposed a completely different approach: instead of manual potting, use an automated injection molding process similar to overmolding. We sourced a specialized potting factory that could produce a steel mold for $6,000 USD.
The economics were compelling:
The client approved the investment. The mold was manufactured, the process was validated, and all 5,000 units were potted within 3 days. The client was delighted with both quality and speed.
In this real PCBA manufacturing case, the lesson was clear: don’t assume manual processes scale. What works for 50 units is completely different from what works for 5,000 units. Sometimes upfront investment in automation pays for itself in the first batch alone.
1. Double-sided BGA placement requires thermal analysis.
If BGA footprints overlap on opposite sides, you’re creating a thermal concentration zone that will cause uneven reflow and cold joints. Either space them apart or redesign the layout.
2. X-ray inspection reveals problems you can’t see.
Even when boards “pass” functional tests, X-ray may reveal voids that will cause field failures later. IPC standards exist for a reason—don’t ignore them.
3. A mechanical BOM is not optional.
Physical samples are not a substitute for documentation. If your enclosure changes, your manufacturing partner needs to know—immediately.
4. Shenzhen’s supply chain is a competitive advantage.
When problems arise, being able to source replacement parts within 48 hours is a capability that most regions cannot match.
5. Manual processes don’t scale.
3D-printed fixtures and hand-dispensed potting work for prototypes. For volume production, automated processes with proper tooling are faster, cheaper, and more consistent.
Ready to move your PCBA project from prototype to production? We offer free manufacturability reviews for new designs. Send us your files, and we’ll identify potential production risks—including BGA placement issues, BOM gaps, and scaling bottlenecks—before they become problems.
Q: What’s the most common cause of low SMT yield in new designs?
A: In our experience, BGA placement issues—particularly on double-sided boards—are a top cause. Thermal analysis during layout can prevent most of these problems.
Q: How do you handle BOM changes after production has started?
A: We conduct IQC on all incoming materials and immediately flag discrepancies. With Shenzhen’s supply chain, we can often source replacements within 48-72 hours.
Q: What’s the typical cost difference between manual potting and automated overmolding?
A: For volumes above 1,000 units, automated overmolding with a dedicated mold is almost always more cost-effective. The mold pays for itself within the first batch.
Q: Do you offer X-ray inspection for BGA quality control?
A: Yes. We use X-ray inspection for all BGA assemblies and report void rates against IPC-A-610 standards.
