PCB procurement FAQ: how many layers, FR4 vs high-Tg vs Rogers materials, controlled impedance requirements, copper weight selection, ENIG vs HASL surface finish, Gerber file checklist, and typical lead times.
1. How many layers does my PCB need?
Layer count depends on signal density, impedance requirements, and component complexity.
| Layers | Typical Application | Notes |
|---|---|---|
| 1–2 | Simple consumer electronics, LED boards | Lowest cost |
| 4 | MCU-based designs, moderate signal density | Most common for industrial boards |
| 6–8 | FPGA boards, DDR memory, high-speed digital | Controlled impedance recommended |
| 10+ | Complex FPGA, backplanes, RF/digital mixed | Higher cost, longer lead time |
Key principle: Add layers when signal integrity demands it, not just to simplify routing. Each additional layer adds cost and lead time.
2. What PCB material should I choose?
| Material | Tg | Best For | Relative Cost |
|---|---|---|---|
| FR-4 Standard | 130–140°C | Consumer, low-layer-count boards | 1× |
| FR-4 High-Tg | 170–180°C | Industrial, automotive, lead-free | 1.2× |
| Rogers 4350B | 280°C | RF/microwave, antenna boards | 3–5× |
| Polyimide | 250°C+ | Flex boards, high-temp aerospace | 2–3× |
For most industrial and telecom applications: High-Tg FR-4 is the sweet spot — handles lead-free reflow temperatures and costs only 20% more than standard.
3. What is controlled impedance and when do I need it?
Controlled impedance means the PCB trace width, spacing, and dielectric thickness are precisely specified to achieve a target impedance (typically 50Ω single-ended or 100Ω differential).
You need controlled impedance when:
Your design uses high-speed serial interfaces (USB 3.0, PCIe, SATA, HDMI, Ethernet 1G+)
You're routing DDR memory (50–60Ω)
You're designing RF circuits (50Ω)
Your signal rise time is fast enough that traces behave as transmission lines
What to specify to your PCB supplier:
Target impedance and tolerance (e.g., "50Ω ±10%")
Which layers need impedance control
Your stackup reference (or ask them to propose one)
4. What copper thickness do I need?
| Copper Weight | Thickness | Used For |
|---|---|---|
| 0.5 oz | 17.5 μm | Fine-pitch BGA, high-density boards |
| 1 oz | 35 μm | Standard — most digital and mixed-signal boards |
| 2 oz | 70 μm | Power supply boards, high-current traces |
| 3 oz+ | 105+ μm | Motor controllers, power converters |
Rule of thumb: Signal layers — 1 oz standard. Power planes — 1–2 oz depending on current. If your board carries >10A, calculate trace width vs. temperature rise and consider 2 oz or thicker.
5. What surface finish should I choose?
| Finish | Shelf Life | Best For | Notes |
|---|---|---|---|
| HASL (Lead) | 12 months | Prototyping, low-cost | Not RoHS |
| HASL (Lead-Free) | 12 months | RoHS prototypes | Uneven surface, not ideal for fine-pitch |
| ENIG | 12 months | Fine-pitch BGA, gold wire bonding | Flat surface, excellent shelf life |
| OSP | 6 months | High-volume consumer | Short shelf life, low cost |
| Immersion Silver | 6–12 months | RF, high-speed digital | Good for signal integrity |
| Immersion Tin | 6 months | Press-fit connectors | Risk of tin whiskers |
ENIG is the safest default for industrial, telecom, and medical boards — flat surface for fine-pitch components, long shelf life, and RoHS compliant.
6. What files do I need to send for PCB fabrication?
Minimum required:
Gerber files (RS-274X or X2 format) — one per layer
NC drill file (Excellon format)
Fabrication drawing or readme.txt
Recommended additional files:
IPC-356 netlist (for bare-board electrical test)
Stackup specification
Controlled impedance requirements
Material specification (if deviating from standard FR-4)
Board outline drawing with dimensions
7. What are typical lead times?
| Type | Layers | Standard | Quick-Turn |
|---|---|---|---|
| Prototype | 2–4 | 5–7 days | 24–48 hours |
| Prototype | 6–8 | 7–10 days | 3–5 days |
| Production | 2–4 | 2–3 weeks | 1 week |
| Production | 6–8 | 3–4 weeks | 1.5–2 weeks |
Lead times vary by factory capacity and order volume. Contact us for current estimates.
8. Can ADD Components help with PCB sourcing?
Yes. While our core business is semiconductor and optical module distribution, we partner with qualified PCB fabrication facilities and can arrange bare-board procurement as part of a PCBA project. This means you get components + boards + assembly managed through a single point of contact.
Contact us with your Gerber files and BOM for a combined quotation.
Last updated on July 06, 2026