Will It Close? Checking Component Heights Against Your Enclosure Before Manufacturing

A production team finds that a regulator inductor pushes against the lid of a PC/ABS case. The board outline fits, but the component is 7.1 millimeters high and internal clearance above the board is 5.9 millimeters; the problem is height, not footprint overlap.

The team was building a new 24 V sensor node for a conveyor line. The manufacturing engineer asked the electrical and mechanical designers to check the complete stack before the next case order. The guide below follows the review they used on the new board.

The manufacturing engineer used the cracked case as a go/no-go gauge for every new lid revision.

1. Start with the tallest real part

The node used a STM32G071KBT6, MAX3485 RS-485 transceiver, protected 24 V input, two temperature-sensor connectors, and a 5 V buck regulator. The regulator needed a 6.8-millimeter inductor. The four-layer board measured 72 by 48 millimeters and mounted on four M3 standoffs inside a 96 by 66 by 30 millimeter PC/ABS case.

The mechanical engineer checked the manufacturer drawings for the inductor, connectors, and electrolytic capacitor. He recorded the component height from the PCB surface, not from the case floor. The regulator's 7.1-millimeter inductor became the controlling part. The screw heads, solder fillets, and connector latches also needed space above the board.

The Flux agent kept the selected component models with the circuit and PCB. The electrical engineer reviewed the inductor's datasheet and confirmed the package dimensions. He updated the BOM and checked the board layout before passing the assembly to the manufacturing engineer. The component-height data gave the mechanical review a real value to compare against the lid.

2. Add the mounting stack below the board

The manufacturing engineer imported the case STEP model and the board outline. The enclosure floor had four M3 brass inserts, each 4 millimeters high. The PCB sat on 3-millimeter standoffs and was 1.6 millimeters thick, so its component surface started 8.6 millimeters above the floor. A 1.2-millimeter wall and a 1-millimeter silicone gasket reduced the usable cavity beneath the lid.

The mechanical engineer measured the internal height at the board center and above each corner. The lid had a shallow rib over the regulator area. The minimum opening was 14.5 millimeters from the case floor. Subtracting the 8.6-millimeter stack of inserts, standoffs, and board left 5.9 millimeters above the component surface. The 7.1-millimeter inductor was 1.2 millimeters too tall, and the connector latch also reached the rib.

The X-ray 3D view made the conflict clear. The inductor and the connector latch both touched the lid rib even though the board outline fit the case. The mechanical engineer moved the rib 3 millimeters toward the edge and added a 2-millimeter relief pocket, which gave the inductor 0.8 millimeters of margin. The lid retained 1.2 millimeters of wall thickness above that area.

3. Check the whole cover, not one section

The mechanical engineer inspected the board in several cross-sections. The tall inductor sat below the relieved area. The M3 screw heads stayed inside their bosses. The side connectors cleared the wall openings, and the cable plugs could be removed without lifting the PCB.

The team checked the closed enclosure in 3D and X-ray view. It looked at the board corners, standoffs, gasket, latch, screw bosses, and cable exits. The review also included a 1-millimeter expansion pad above the regulator region. The pad contacted the case rib for heat transfer without pressing directly on the inductor.

The manufacturing engineer asked the electrical engineer to model the connector's mated plug rather than only the PCB header. The plug body required 8 millimeters for its latch release. The new case relief created 10 millimeters, so a technician could unplug it with the board installed. The design kept 2.5 millimeters between the plug and the case wall.

Three requests from the height review

Place the STM32G071KBT6, MAX3485, 24 V regulator, and 7.1-millimeter inductor on the 72 by 48 millimeter board. Preserve the four M3 holes and flag any component taller than the case cavity.

Import the 96 by 66 by 30 millimeter PC/ABS case and its lid. Check the full board-to-lid stack, including 4-millimeter inserts, 3-millimeter standoffs, the 1.6-millimeter board thickness, screw heads, connector latches, and the silicone gasket.

Show the assembled sensor node in X-ray view. Keep 1 millimeter above the regulator for the thermal pad, clear the connector plug by 2.5 millimeters, and add a relief where the lid rib crosses the inductor.

4. Release only after the printed first article closes

The electrical engineer and the mechanical engineer completed the board and enclosure review in three hours. They checked the tallest component, connector bodies, screw heads, standoff height, gasket, lid rib, and thermal pad in one project. The Flux agent maintained the BOM and component models as the electrical engineer changed the connector. The manufacturing engineer approved the enclosure after comparing the first printed lid with the assembly view.

The new case used the same external size as the old one, but the internal geometry changed where the inductor and connector latch needed space. The team printed one SLA lid and one PA12 body before ordering the production-intent PC/ABS case batch. The first physical assembly closed without force, and the thermal pad touched the case rib.

The earlier forty-case loss had come from treating a board outline as a complete fit check. The manufacturing engineer's review used the component models, mounting stack, screw heads, connector plugs, gasket, and cover geometry together. The X-ray view showed hidden conflicts before fabrication, and the first article confirmed the printed model against real parts.

A component-height checklist

• Measure the tallest part from the PCB surface using its manufacturer drawing.
• Add standoffs, inserts, board thickness, screw heads, gasket, and lid features to the stack.
• Include mated connectors and latch-release space, not only board footprints.
• Check multiple enclosure sections in 3D and X-ray views.
• Review thermal pads and case ribs without loading fragile components.
• Print one case and test a complete assembly before ordering the batch.

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