Small Batch PCB Checklist Video: 100 Boards Ready
What This Video Covers
A working prototype only proves the circuit can function. A 100- or 500-piece run proves the same board can be built repeatedly to the same spec. This video walks through four factory-side checks before you leave PCB prototype quantities and enter a small batch.
First, Gerber, drill, and fab notes must be the released revision and must match what you selected on the quote, layer count, outline, and special notes included. Second, critical specs (thickness, copper weight, surface finish, and any controlled stack-up) need to be written, not assumed. Third, impedance, via tenting or plugging, and other process extras belong on the drawing so CAM does not guess. Fourth, board outline, hole positions, connectors, and component height must be checked against the enclosure, not only against the CAD canvas.
These same gaps show up on FR4 PCB builds for industrial control and consumer electronics pilots. Align files, specs, process notes, and mechanical fit before you request an instant PCB quote or a PCB assembly quote.
Key Highlights
- A prototype proves function; a 100–500 piece batch proves the design can be manufactured the same way twice. Do not scale on an unverified Gerber set.
- Layer count, thickness, copper weight, surface finish, impedance, and via treatment must be explicit on the order and drawing. Factories will not infer them from a schematic.
- Check outline, hole positions, connectors, and component clearance against the finished enclosure before releasing a small batch, not after boards arrive.
Why a Working Prototype Is Not a Production Release
Prototype lots are built to learn. CAM engineers often accept tighter exceptions, substitute a close stack-up, or skip process notes that would be mandatory at 100 pieces. That is acceptable when you are validating firmware and bring-up. It is not acceptable when you need 100 identical boards for a pilot customer, a certification lab, or a first OEM shipment.
At small batch, setup cost is still high and scrap is expensive. One mismatched outline, one undocumented impedance pair, or one via treatment conflict can stop the line for an engineering query (EQ) or force a respin of the entire lot. Factories treat 100–500 pieces as production: the released Gerber set, the quote parameters, and the fab drawing are the contract.
Teams moving IoT modules, industrial controllers, or automotive evaluation kits into pilot builds should treat this as a gated release: electrical sign-off, file freeze, spec freeze, mechanical fit, then order.
Check 1 — Final Gerber Files Must Match the Order
The most common small-batch failure is not a process defect. It is a file mismatch. Engineers upload an older Gerber while the quote form lists a newer layer count, a different outline, or a special process that never made it into the RS-274X set. CAM builds from the files, not from the chat history.
Before you click order, confirm:
- Gerber, Excellon drill, and board outline are the same revision as the firmware and BOM you intend to ship.
- Layer names and polarity match the stack-up drawing.
- Fab notes, netlist (if supplied), and pick-and-place / BOM revision are consistent if you are also ordering turnkey PCB assembly.
- Any last-minute pad or keep-out change is in the Gerber, not only in the schematic.
If CAM finds a conflict between the quote form and the files, production pauses for EQ. On a five-piece prototype that delay is annoying. On a 100-piece pilot with a customer date, it is a missed window.
Check 2 — Lock Critical Specs Before CAM Starts
Quote defaults are not a spec. If you leave thickness, copper, or finish blank, the factory will apply a standard 1.6 mm FR-4, 1 oz copper, HASL or ENIG default. That may be fine for a first bring-up board. It is not fine if your enclosure, connector stack height, or current density assumed something else.
Write these on the drawing and on the order:
| Spec | Why it matters at 100 pcs | Typical small-batch default if left blank |
|---|---|---|
| Layer count | Drives stack-up, via span, and cost | Taken from Gerber layer count. Errors here stop CAM |
| Finished thickness | Connector height, card guides, thermal mass | 1.6 mm FR-4 |
| Copper weight | Current, etch factor, impedance | 1 oz outer |
| Surface finish | Fine-pitch solderability, shelf life, gold fingers | HASL or ENIG by factory policy |
| Solder mask / silkscreen | Bridge width, legend readability | Green mask, white legend |
| Special notes | Impedance, plugged vias, extra test | Not applied unless documented |
For 4 layer PCB and 6 layer PCB pilots, also lock Tg (standard vs. high-Tg), copper distribution, and whether impedance coupons are required. Ambiguity here is how two "identical" lots measure differently.
Check 3 — Do Not Leave Manufacturing Details to Assumptions
If a feature is important to function, it must be documented. CAM will not invent impedance targets, via fill, or controlled depth from a schematic screenshot.
Document at minimum:
- Impedance: target ohms, reference layers, and whether a coupon is required.
- Via treatment: tented, opened, plugged, or resin-filled and capped, especially under BGA or near pads.
- Hole types: PTH vs. NPTH, press-fit, and plated slots.
- Test: flying probe vs. fixture, and whether 100% electrical test is required on the small batch.
- Panelization: customer panel vs. factory panel, V-score vs. tab-route, and edge clearance for connectors.
These notes prevent the classic EQ loop: files show open vias, the form says "tented," solder mask is generated one way, and the lot cannot start. That loop is cheap at prototype quantity and expensive at 100 pieces plus stencil and SMT setup.
If the small batch is assembled, add paste-layer review and SMT stencil aperture notes so fabrication and assembly are not working from two different assumptions.
Check 4 — Fit the Real Product, Not Only the Layout
Electrical DRC does not check the plastic. Before releasing 100 boards, overlay the finished board (or a dimensioned 3D step) on the enclosure, gasket, and cable stack.
Verify:
- Outline and corner radii vs. the housing pocket, including plating and routing tolerance.
- Mounting hole positions and finished hole size vs. standoffs and screws.
- Connector and USB/DC jack protrusion vs. the bezel.
- Tall parts (electrolytics, inductors, shields) vs. lid and potting.
- Keep-outs for antennas, batteries, and heat sinks.
A prototype that sat on a bench with flying wires can pass every electrical test and still fail incoming inspection when the batch arrives and the USB port sits 0.8 mm behind the opening. That is a mechanical respin, not a fab defect.
Prototype vs. Small Batch vs. Mass Production
| Stage | Typical qty | Primary goal | What must be frozen | Common failure if you skip the checklist |
|---|---|---|---|---|
| Prototype | 1–10 | Prove the circuit | Enough to build once | Acceptable file sloppiness |
| Small batch / pilot | 50–500 | Prove repeatability | Files, specs, process notes, mechanical fit | EQ hold, mixed revisions, enclosure miss |
| Mass production | 1,000+ | Yield and unit cost | Full DFM, panel, test fixture, AVL | Cost and yield only after the above is stable |
Use PCB mass production rules only after the pilot lot matches the drawing. Do not jump from a five-piece hand-assembled board to 5,000 without a documented 100-piece intermediate.
Pre-Order Checklist for 100–500 Piece Runs
- Frozen Gerber + drill + outline + fab drawing, same revision as BOM.
- Layer count, thickness, copper, finish, and mask/legend written on the order.
- Impedance, via treatment, and special processes written, not implied.
- Enclosure overlay signed off (holes, connectors, height).
- If assembling: BOM revision, polarity notes, and stencil strategy agreed.
- Quote parameters match the files; then submit the online PCB quote.
A prototype proves the design can work. A small batch proves you can make it again. Align files, specs, manufacturing requirements, and product fit before you scale.
FAQ
Q1: Is 100 pieces still a prototype or already production?
A1: For the factory it is production. CAM, process cards, and electrical test follow the released files. Treat 100–500 as a pilot production lot: freeze revision, specs, and mechanical fit. Prototype exceptions (temporary stack-up, missing via notes) should already be closed.
Q2: What happens if my Gerber revision does not match the quote form?
A2: CAM stops and issues an EQ. Production does not start until you confirm which revision and which spec wins. On a 100-piece lot that delay also idles panel planning and, if ordered together, SMT programming.
Q3: Which specs most often get left blank on small-batch FR-4 orders?
A3: Finished thickness, copper weight, surface finish, via tenting vs. opening, and impedance targets. Defaults will be applied. If your enclosure or SI budget assumed something else, the lot will be electrically "correct" to the files and mechanically or RF-wrong to the product.
Q4: Should I panelize 100 boards myself or let the factory panelize?
A4: Unless you already have an approved customer panel with tooling holes, fiducials, and rail width that match the assembler, factory panelization is usually safer for a first 100-piece run. Self-panels with tight mouse-bites or connectors on the score line are a frequent yield hit at this quantity.
Q5: When should I add SMT assembly to the same 100-piece order?
A5: When the PCB revision is frozen and the BOM is purchasable. Ordering bare boards first is still valid if you expect a mechanical tweak. If both are frozen, a combined PCBA quote avoids a second setup and keeps fabrication notes aligned with paste and via treatment.
Your prototype worked.
But is it ready for a small batch?
Before you order 100 or 500 PCBs, check these four things.
First, your files.
Make sure your Gerber files are the final version—and that they match your order specifications.
Second, your critical specs.
Layer count, board thickness, copper weight, surface finish, and any special requirements should all be clearly defined.
Third, your manufacturing details.
Things like impedance control, via treatment, or special processes shouldn't be left to assumptions. If it's important to your design, make sure it's clearly documented.
And fourth, the actual product.
Check your board dimensions, hole positions, connectors, and component clearance against the final enclosure—not just the PCB layout.
A prototype proves that your design can work.
A small batch proves that you're ready to make it repeatedly.
So before scaling up, make sure your files, specs, manufacturing requirements, and product fit are all aligned.
Got a design ready? Claim your $60 new-user coupon and get your quote from the factory.
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