The 7-step journey
Every custom PCBA — whether it's a 4-layer IoT board or a 12-layer AI accelerator — goes through the same 7 steps. Skip one and you'll regret it.
- Schematic capture
Block-level design → component selection → schematic entry in KiCad / Altium / EasyEDA. The schematic is the contract — every downstream step assumes it's correct.
- PCB layout & stackup
Place components → route traces → define stackup (4-layer is the default; 2-layer is for simple stuff; 6+ layer for high-speed). DFM-aware EDA tools (KiCad with check, Altium with active BOM) catch 80% of issues here.
- Gerber review
Export Gerbers + drill files + pick-and-place + BOM. Your EMS partner reviews this BEFORE ordering components. This step catches the 20% DFM issues that EDA tools miss (copper balance, mask slivers, fiducials).
- BOM sourcing
Critical components (the ones that go obsolete or have long lead times) get sourced first. We typically use 2-3 distributors per critical part to avoid single-source risk.
- Stencil & solder paste
Laser-cut stainless stencils for SMT. Paste deposited via squeegee or jet printer. Thickness is 0.1-0.15mm for fine-pitch QFN/BGA; 0.15-0.2mm for standard components.
- SMT assembly
Pick-and-place → reflow (typically 240-260°C peak for lead-free SAC305) → AOI inspection → selective solder for through-hole. Yamaha YSM20 / YSM10 pick-and-place machines give us ±25μm placement accuracy.
- Test & ICT
Automated optical inspection (AOI) → in-circuit test (ICT) → functional test → burn-in. AOI catches 90% of defects; ICT catches the rest. Without ICT, you'll ship dead-on-arrival boards.
Total time from schematic to first article: 10-15 days with a competent EMS partner. With supply chain issues: 4-8 weeks.
The 6 mistakes that delay prototypes by weeks
1. Components chosen without checking availability
You designed around the STM32H747. We can source it — in 16 weeks. Or you could use the STM32H750, which is in stock everywhere.
Fix: Before schematic freeze, check distributor stock (Digi-Key, Mouser, LCSC) for 10k+ quantity on every line item. Better: ask your EMS to do this for you as part of the BOM review.
2. No fiducials on the board
Pick-and-place machines need reference points. Without fiducials, you get a board that "looks placed" but is actually 0.5mm off — which means your BGA balls aren't aligned with the pads.
Fix: Add 3 fiducials (1 panel-level, 2 board-level) in opposite corners. Cost: 2 minutes in the layout tool. Saves: thousands of defective boards.
3. Wrong footprint
You picked a 0402 resistor footprint from the library. Your actual part is a 0603. The pick-and-place can't tell the difference — it just follows the Gerber. You get a board full of 0402 pads with 0603 parts on top. Open circuits everywhere.
Fix: Generate footprints from the part datasheet, not from a generic library. Better: use parts with verified footprints from JLCPCB / PCBWay libraries (they've already done this for thousands of parts).
4. No thermal relief on large copper pours
Your board has a big ground pour. During reflow, the thermal mass is enormous. Small parts solder fine but large BGAs don't reach reflow temperature. Result: cold joints.
Fix: Add 0.3-0.5mm thermal relief spokes around pads connected to large copper pours. Standard practice — your EMS will catch this in DFM if you miss it.
5. Silkscreen on pads
You put a logo on the PCB. It happens to be over a BGA pad. The silkscreen ink lifts during reflow, contaminates solder, and you get a BGA with 30% non-wets.
Fix: Keep silkscreen 0.2mm away from any exposed pad. Almost every EDA tool has a "silkscreen clearance" check — turn it on.
6. Not budgeting for the coverlay / solder mask color
You specified green solder mask. The fab has 3-day lead time. If you want black or red, it's 7-10 days. If you want matte black, it's 2 weeks. Production timelines slip when this isn't planned.
Fix: Stick with green for prototypes (fastest). Decide on cosmetic colors during EVT, not DVT.
The cost breakdown (for a typical IoT board)
| Line item | EVT (50 pcs) | DVT (500 pcs) | PVT (5,000 pcs) |
|---|---|---|---|
| NRE (one-time) | $3,500 | $1,500 | $500 |
| PCB fab (4-layer, 50x70mm) | $8.50/board | $3.20/board | $1.80/board |
| Components (BOM) | $14.20/board | $9.80/board | $6.50/board |
| SMT assembly | $6.00/board | $2.40/board | $1.50/board |
| Test & inspection | $2.50/board | $1.20/board | $0.80/board |
| Total per board | ~$31.20 | ~$16.60 | ~$10.60 |
Plus $1-3/board for packaging (anti-static bag + box + foam). Plus your enclosure, manual, accessory kit, etc.
What we do differently
We've assembled 200+ custom PCBAs in the last 5 years. Here's what saves our customers the most time:
- Free DFM review on any design. Send us your Gerbers + BOM before you commit.
- Pre-buy critical components for you while your design is in DFM review. Saves 4-8 weeks.
- First-article samples in 10 days (vs industry-standard 3-4 weeks).
- AOI + flying probe test on every board. No dead-on-arrival.
- In-house conformal coating & potting for IP-rated products.
Send your project to [email protected]. Free DFM review, no commitment.