A snap-in capacitor should be released only after its exact series drawing, PCB footprint, polarity, seating, vent path, and first-article fit have all been verified. Manufacturer examples show that terminal count, pitch, hole diameter, and lead length are not universal. The safest OEM process uses the supplier drawing as the controlling document, checks the bare board against it, and records the physical result before production.
Key Takeaways
Six checks before release
Match the exact series drawing, not a generic snap-in footprint.
Verify pitch, hole diameter, terminal count, and polarity on the bare PCB.
Seat the body flush when the manufacturer requires it.
Do not force a terminal into a mismatched footprint.
Keep pressure-relief paths and underside copper clear.
Approve production only after a documented first-article inspection.
Why the exact series drawing must control the PCB footprint
Snap-in describes a family, not one universal layout
Nichicon's terminal guide illustrates several configurations. Its ET three-pin snap-in form is shown for 22 mm to 35 mm case diameters and uses two electrical holes of 2.0 +/- 0.1 mm on a 10.0 +/- 0.1 mm spacing, plus a 2.5 mm support hole. The same guide shows four-pin EF and EG layouts for 35 mm and 40 mm cases with 22.5 +/- 0.1 mm spacing and four 2.0 +/- 0.1 mm holes. A five-pin EJ straight-terminal form for 40 mm cases instead shows 25.0 +/- 0.1 mm spacing. These examples alone rule out a single generic library footprint.
TDK's B43544 drawing provides another concrete reference: two mounting holes of 2.0 +/- 0.1 mm separated by 10.0 +/- 0.1 mm. Its standard terminal length is 6.3 +/- 1 mm, with a shorter version also available. Those numbers are useful evidence, but only for that documented series and option. A purchasing substitute must be checked against the released board and drawing rather than assumed compatible.
| Published example | Footprint detail | Case / terminal note | OEM action |
|---|---|---|---|
| Nichicon ET | 10.0 +/- 0.1 mm; 2 x 2.0 +/- 0.1 mm | 3-pin snap-in, dia. 22-35 mm | Include support-hole geometry |
| Nichicon EF / EG | 22.5 +/- 0.1 mm; 4 x 2.0 +/- 0.1 mm | 4-pin, dia. 35-40 mm | Confirm terminal length option |
| Nichicon EJ | 25.0 +/- 0.1 mm; 5 x 2.0 +/- 0.1 mm | 5-pin straight, dia. 40 mm | Do not substitute a 4-pin library part |
| TDK B43544 | 10.0 +/- 0.1 mm; 2 x 2.0 +/- 0.1 mm | 6.3 +/- 1 mm standard terminal | Check the ordered terminal variant |
How to verify mounting before production
Inspect the bare board before inserting a capacitor
Start with a 1:1 footprint print or a measured first board. Confirm hole center spacing, drill size after plating, non-electrical support holes, polarity marks, courtyard, and keep-out zones. Then compare each point with the exact manufacturer drawing and the supplier's confirmed terminal option. The inspection record should name the drawing revision and part number. This prevents an apparently similar capacitor from entering production against an older footprint.
Polarity deserves an independent check. Nichicon's terminal guide identifies the negative terminal by mesh marking. The board legend, assembly drawing, inspection camera, and operator instruction should all agree with the delivered part orientation. A mechanical fit alone cannot prove correct polarity.
Insert without forcing and confirm the specified seating
Nippon Chemi-Con instructs that terminal spacing must equal the PCB hole spacing before installation. It also states that a snap-in capacitor should be inserted and pressed until the body is settled flush on the board, without standing off. Nichicon similarly says applicable snap-in can types should be installed tightly to the board with no gap. If the body will not seat with controlled hand force, stop and inspect the footprint, plating, bent terminals, and ordered option. Forcing the part can deform terminals or the can and hide a board error.
Mounting equipment must not apply force beyond the product specification. Chemi-Con specifically warns against excessive mechanical force during picking, placement, positioning, or lead cutting. Treat feeder setup, gripper pressure, insertion travel, and board support as validated process parameters, not operator preference.
Vent paths, copper keep-outs, and first-article approval
Keep the safety function unobstructed
For aluminum electrolytic capacitors with a pressure-relief vent, the board and enclosure must leave a safe path. Chemi-Con's general guidance gives minimum clearance examples of 3 mm for 18-35 mm case diameters and 5 mm for 40 mm and larger cases. It also says not to place wiring over the vent. If the vent faces the board, provide a ventilation hole beneath it. Around the seal side, copper should remain at least 1 mm away, preferably 2 mm or more, and double-sided boards should avoid unnecessary vias or patterns under the capacitor.
These clearances complement, rather than replace, the exact product drawing. Record enclosure distance, nearby heat sources, underside copper, and ventilation openings during layout review. For a deeper review, use LORIDA's electrolytic capacitor vent-clearance checklist.
Make the first article a release gate
Inspect at least the part number, capacitance and voltage marking, polarity, terminal pattern, hole fit, seating, can condition, vent clearance, and solder result. Photograph the top and underside, record any insertion force concern, and retain the board revision. If a series or terminal option changes, repeat the fit check. Browse LORIDA's aluminum electrolytic capacitor range and send the drawing through the engineering inquiry page.
Frequently Asked Questions
Is 10 mm the standard pitch for every snap-in capacitor?
No, 10 mm is a common example, not a universal snap-in standard. The cited TDK B43544 and Nichicon ET drawings use a 10.0 +/- 0.1 mm spacing for two electrical holes. Nichicon's other documented terminal styles show 22.5 +/- 0.1 mm and 25.0 +/- 0.1 mm patterns with four or five holes. Case size, series, terminal count, and ordered option determine the required footprint. Build the PCB library from the exact released drawing and recheck any proposed substitute before approval.
Should a snap-in capacitor sit flush on the PCB?
Yes, when the manufacturer's guidance for that construction calls for flush seating. Chemi-Con says snap-in terminals should be inserted and the body pressed down until it is settled flush, without standing off. Nichicon also states that applicable snap-in can types should be installed tightly with no gap. Do not close a gap by applying excessive force. A persistent stand-off may indicate wrong pitch, undersized finished holes, bent terminals, or a different terminal variant.
Can support pins be connected electrically?
Only terminals identified as electrical by the exact series drawing should enter the circuit. Multi-pin snap-in layouts may include mechanical support or blank positions, and their geometry varies. Copying a generic symbol can connect a support feature incorrectly or omit a required hole. Map every pin from the manufacturer drawing into the schematic symbol, footprint, polarity legend, and inspection plan, then verify continuity on the first article before release.
What should an OEM send for a snap-in fit review?
Send the exact capacitor part number, supplier drawing, PCB footprint, board thickness, finished hole sizes, polarity orientation, enclosure section, and first-article plan. Include the expected mounting process, solder method, nearby heat sources, vent clearance, vibration environment, and any approved alternates. Photographs or a 3D section help reveal interference and seating problems. This package lets the supplier review electrical ratings and mechanical fit together instead of treating capacitance and voltage as the whole specification.
Need a snap-in capacitor footprint review?
Send the part number, board drawing, and enclosure section
LORIDA can help organize the electrical and mechanical inputs for supplier confirmation and first-article validation.
Sources
Manufacturer documents used for the numeric examples
Last Updated: September 30, 2026. Published manufacturer dimensions are examples for the cited series and documents; confirm the current drawing for the exact ordered part.
