PCB Assembly FAQs

Expert Answers for Buyers & Engineers - HCJMPCBA

Q1: What is PCB Assembly (PCBA)?

Answer: PCB Assembly (PCBA) is the process of mounting electronic components (surface-mount/SMT or through-hole/THT) onto a bare PCB to form a functional electronic circuit. The core workflow follows 5 key steps:

Q2: What’s the Difference Between SMT and Through-Hole Assembly? How to Choose?

Answer: The choice depends on component type, application requirements, and production volume. Below is a detailed comparison:

Comparison Aspect	SMT Assembly	Through-Hole Assembly
Component Type	Small, lightweight (01005~50mm×50mm), surface-mount pads (e.g., resistors, ICs)	Larger, high-power (e.g., connectors, electrolytic capacitors), through-hole pins
Placement Method	Automated pick-and-place machines (speed: up to 50,000 components/hour)	Manual insertion or automated equipment + wave soldering
Key Advantages	High component density, low cost for mass production, compact design	Strong mechanical stability, high current-carrying capacity, durable for vibration
Ideal Applications	Consumer electronics (smartphones, routers), 5G modules, compact devices	Industrial control, automotive electronics, aerospace equipment

How to Choose:

Use SMT for miniaturized, high-volume designs (e.g., 10,000+ units) to save space and cost.
Use through-hole for power components or connectors requiring mechanical strength (e.g., automotive wiring harnesses).
Hybrid assembly (SMT + through-hole) is common for complex devices (e.g., industrial PLCs).

Q3: What Files Are Required for PCBA? What Format Standards Must Be Followed?

Answer: Three mandatory files are required to ensure error-free production; optional documents help optimize processes:

File Type	Format	Mandatory Content	Accuracy Requirement
Gerber Files	RS-274X (Extended Gerber)	Copper layers (top/bottom/inner), solder mask, silkscreen, board outline, solder paste layers	3.6 coordinate format (3 integers + 6 decimals), consistent units (mm recommended)
BOM (Bill of Materials)	Excel (.xls/.xlsx) or CSV	Reference designator (R1, C2), MPN, package, quantity, polarity, tolerance	Part number matching rate 100%, no duplicate reference designators
Centroid File	XYRS (X/Y coordinates, rotation, side)	Reference designator, X/Y coordinates, rotation angle (0–360°), board side (Top/Bottom)	±0.02mm coordinate accuracy, rotation error ≤1°

Optional Documents:

Assembly drawings (highlight critical requirements: component height limits, thermal pads).
Test point lists (for functional testing) and physical samples (for prototype validation).

Q4: How to Avoid File-Related Delays in Production?

Answer: Follow these 4 actionable steps:

Use HCJMPCBA’s free DFM (Design for Manufacturability) check tool (available on our portal) to validate files within 6 hours—we’ll flag missing layers, incorrect units, or incompatible formats.
Follow naming conventions: e.g., “ProjectName_TopCopper.gtl” “ProjectName_BOM.xlsx” (avoid special characters).
Double-check for common errors:
- Gerber files: Ensure no missing solder mask/silkscreen layers.
- BOM: Verify polarity for diodes/ICs (mark “+/-” or “Pin 1”).
- Centroid file: Align coordinates with Gerber (use the same origin point).
Submit files 24 hours before production to allow for revisions (if needed).

Q5: What Factors Affect PCBA Cost? How to Reduce Costs Without Sacrificing Quality?

Answer:

Key Cost Drivers:

Cost Factor	Impact on Cost	Example
Order Volume	Setup fee ($8–$12) is fixed; bulk orders reduce per-unit cost	10pcs: $5/piece; 1000pcs: $1.2/piece
Component Complexity	01005 components cost 20% more than 0402; fine-pitch BGA adds $0.005–$0.01 per joint	200 joints with 01005 components: $0.4; with 0402: $0.32
Testing Requirements	FCT (Functional Test) costs 2–3x more than AOI	AOI: $0.5/piece; FCT: $1.5/piece

Cost-Saving Strategies (How to Reduce Costs):

Design Optimization:
- Panelize small PCBs (≤50×100mm) into 250×250mm panels to share setup fees (e.g., 6×10cm PCBs per panel = 60% cost reduction per unit).
- Avoid blind/buried vias (add $0.1–$0.3 per via) and use standard vias (0.3mm diameter).
Component Selection:
- Use domestic alternatives (e.g., Chinese MLCCs vs. Japanese) for non-critical applications (30% cost reduction).
- Choose in-stock components (HCJMPCBA’s 40k+ inventory) to avoid sourcing delays and premium fees.
Process Simplification:
- Use automated SMT instead of manual assembly (30% labor cost reduction).
- Skip FCT for prototypes; use AOI + flying probe tests (covers 99% of defects).

Q6: What Is the Typical Lead Time for PCBA? How to Handle Rush Orders?

Answer:

Standard Lead Time:

Order Type	Quantity	Lead Time	Included Services
Prototype	1–50pcs	3–5 days	PCB fabrication + SMT assembly + AOI/X-ray inspection
Mass Production	500–10,000pcs	7–12 days	Full QC (SPI + AOI + FCT) + packaging + global shipping

Rush Service (24–48h Delivery):

Eligibility: Prototypes (1–50pcs) with complete, error-free files and in-stock components.
Cost: 30–50% premium on standard pricing (varies by order size).
How to Qualify:
1. Submit files via our “Rush Order” portal (www.hcjm-pcba.com/RFQ).
2. Confirm component availability with our sales team (24/7 support).
3. Accept simplified testing (AOI + flying probe instead of FCT).

Q7: What Are HCJMPCBA’s SMT Assembly Capabilities? (Precision, Component Range)

Answer: Our state-of-the-art equipment supports high-precision and high-volume production:

Capability	Technical Specification	Application Scenario
Placement Accuracy	±0.01mm (high-precision machines: Fuji NXT III) / ±0.025mm (high-speed machines: Yamaha YSM40R)	Fine-pitch BGA (0.4mm pitch), QFN packages
Component Range	SMT: 01005 (0.4mm×0.2mm) to 50mm×50mm; through-hole: wire diameter 0.4–2.0mm	Consumer electronics, industrial control, automotive
贴装 Speed	Up to 50,000 components/hour (high-speed lines) / 30,000 components/hour (high-precision lines)	Mass production (e.g., 100k+ units/month)

Q8: What Soldering Processes Are Used? What Are the Key Parameters for Reliability?

Answer: We use two core soldering processes, optimized for different component types:

Process	Equipment	Key Parameters	Quality Standard
Reflow Soldering (SMT)	Heller 1809EXL (8 温区)	Peak temperature: 245±5°C; preheat: 150–180°C (60s); nitrogen purity: 99.99%	IPC-J-STD-001 Class II/III
Wave Soldering (Through-Hole)	ERSA Versaflow 3/45	Wave temperature: 255±5°C; preheat: 150–180°C; flux residue: <0.1mg/in²	IPC-J-STD-001 Class II

How to Ensure Soldering Reliability:

Use lead-free solder paste (Sn96.5Ag3.0Cu0.5) compliant with RoHS 2.0.
For high-reliability applications (e.g., aerospace), use nitrogen reflow to reduce oxidation.
Conduct SPI (Solder Paste Inspection) to ensure paste thickness (0.10–0.15mm) and uniformity.

Q9: What Quality Control (QC) Processes Are in Place for PCBA?

Answer: We follow a 4-stage QC workflow to ensure 99.8% first-pass yield:

QC Stage	Inspection Method	Key Checkpoints	Acceptance Criteria
Incoming Material Inspection	Visual inspection + solderability test	PCB warpage, component oxidation, BOM matching	PCB warpage ≤0.75%, component solderability ≥95%
In-Process Inspection	SPI (solder paste) + AOI (placement)	Paste thickness, component alignment, polarity	Paste thickness variation ±10%, 0 polarity errors
Post-Soldering Inspection	AOI + X-ray (BGA/QFN)	Soldering defects (voids, bridging), hidden joints	BGA voids ≤25% (IPC-7095), 0 critical defects
Final Testing	ICT (continuity) + FCT (functionality)	Electrical continuity, functional performance	100% continuity, functional yield ≥99.5%

Q10: What Are Common PCBA Defects? How to Prevent & Resolve Them?

Answer: The most frequent defects (and solutions) are:

Defect Type	Root Cause	Prevention (How to Avoid)	Resolution (How to Fix)
BGA Voids	Flux volatilization, preheat too fast, PCB moisture	Use low-void solder paste; pre-bake PCBs (125°C/4h); extend preheat to 60–90s	Vacuum reflow (10–20 mbar); rework with hot air station
Bridging (Short Circuits)	Excess solder paste, stencil aperture too large	Optimize stencil aperture (80% of pad width); reduce paste thickness	Remove excess solder with 0.2mm soldering iron tip
Polarity Reversal	Incorrect Centroid file, missing polarity marks	Add polarity marks in Gerber; double-check Centroid rotation	Rework with hot air station; replace damaged components

Q11: What Industry Standards Does HCJMPCBA Comply With? How to Ensure Compliance for My Application?

Answer: We meet global standards for key industries; compliance is tailored to your use case:

Industry	Compliance Standards	Special Requirements
Consumer Electronics	RoHS 2.0, CE, FCC	Lead-free components, EMI shielding (if needed)
Medical Devices	ISO 13485, FDA 21 CFR Part 820, IPC-A-610 Class III	Biocompatible materials, 100% FCT testing
Automotive	IATF 16949, AEC-Q100, ISO 16750	Wide temperature range (-40°C to +125°C), vibration resistance
Aerospace	AS9100, MIL-STD-202G	High-reliability components, burn-in testing (125°C/48h)

How to Ensure Compliance:

Inform our sales team of your target industry (e.g., “medical device”) during quoting.
Provide compliance requirements (e.g., “ISO 13485”) and we’ll adjust processes (e.g., Class III inspection).
Request a compliance report (included with bulk orders) with test data and certification copies.

Q12: Can HCJMPCBA Support Customized PCBA for Special Applications (e.g., High-Temp, High-Power)?

Answer: Yes. We specialize in customized solutions for extreme environments:

High-Temperature Applications (e.g., industrial furnaces): Use ceramic substrates (AlN, thermal conductivity ≥170W/m·K) or high-Tg FR4 (Tg≥170°C), operating temperature up to 150°C.
High-Power Applications (e.g., EV controllers): Implement copper pillar heat sinks (thermal resistance ≤0.2°C/W) and thermal vias (2–3 vias/cm²).
High-Frequency Applications (e.g., 5G base stations): Use low-loss substrates (Teflon/PTFE) and impedance control (±5% tolerance).

How to Request Customization:

Share your application requirements (temperature range, power density, frequency) via email.
Provide design files and our engineering team will propose optimized solutions (e.g., substrate selection, thermal management).

Q13: What Is the Order Process for PCBA? How to Track Production Progress?

Answer: The order process is streamlined into 5 steps:

File Submission: Upload Gerber, BOM, and Centroid files via our portal (www.hcjm-pcba.com/upload).
DFM Review: Our engineers complete analysis within 6 hours and provide optimization suggestions.
Quotation Confirmation: Receive a detailed quote (cost breakdown + lead time) and confirm the order.
Production: Track progress in real time via our online system (see screenshot below).
Delivery: Test reports (AOI/X-ray/FCT) are sent with the order; global shipping (DHL/FedEx) is available.

Q14: What After-Sales Support Is Provided? What Is the Warranty Policy?

Answer:

Warranty: 90-day warranty for all PCBA products. We offer free rework/replacement for defects caused by our process (e.g., soldering errors, component misplacement).
Technical Support: 24/7 engineering support for post-delivery issues (e.g., functional failures, defect analysis).
Return Policy: Accept returns within 7 days of delivery for non-customized orders (unused, unmodified).

How to Claim Warranty:

Contact our after-sales team (aftersales@hcjm-pcba.com) with your order number and defect photos/videos.
We’ll conduct a root cause analysis within 48 hours and propose a solution (rework, replacement, or refund).