Printed circuit board (PCB) assembly is the process of soldering electronic components onto a PCB. It is one of the most expensive steps in electronics manufacturing, so determining the assembly cost and finding ways to reduce it is crucial for managing product budgets. This guide will examine the key factors that influence PCB assembly pricing and provide tips to lower costs without sacrificing quality.
Factors That Determine PCB Assembly Cost
The main elements that impact the cost of assembling a PCB include:
Component Count and Complexity
The number of components to be mounted on the board is directly proportional to assembly time and cost. More complex components like BGAs or tiny passives also increase cost.
Board Size and Layers
Larger PCB sizes require longer assembly times. Multilayer boards often need more complex assembly equipment too.
Soldering Process
The soldering technology used – wave, reflow, selective, manual – greatly affects automation levels and throughput.
Testing Requirements
Testing steps like ICT, flying probe, AOI, X-ray increase time and cost but reduce defects.
Location of Assembly
Labor rates, facility costs and overhead vary based on country/region of assembly.
Production Volume
High volumes benefit from economies of scale and better machine utilization.
Board Design
Ease of assembly and testability designed into the board can reduce manufacturing costs.
We will now examine each of these factors in more detail and how design, component selection and manufacturing decisions can optimize PCB assembly costs.
How Component Factors Impact Cost
Component Count
The number of parts to be mounted on a PCB has the greatest influence on assembly pricing. More components means longer assembly time, which translates directly to higher cost. Assemblers generally estimate cost based on component count ranges:
| Component Count Range | Relative Cost |
|---|---|
| <50 | Low |
| 50-300 | Medium |
| >300 | High |
For example, boards with 250 components may be 2-3 times the cost to assemble versus boards with 50 components.
To reduce cost, be disciplined about justifying every component on your bill of materials (BOM). Consider cost reduction redesigns to eliminate unnecessary parts.
Component Size and Pitch
Tiny surface mount devices (SMDs) or those with very fine pitch lead spacing require more sophisticated pick-and-place machines and skilled operators, increasing assembly cost. Larger components are faster to process.
Compare the cost impact of these example component sizes:
| Component | Size/Pitch | Relative Cost |
|---|---|---|
| 0402 resistor | 0.4 x 0.2mm | High |
| SOIC-14 package | 6.5 x 5.2mm | Low |
| BGA package | 15 x 15mm, 0.8mm pitch | Medium |
When possible, choose chip components no smaller than 0603 or 0805 packages. Avoid ultra-fine pitch ICs < 0.4mm pitch if not essential.
BGA and Other Complex Components
Components that require special processing like ball grid arrays (BGAs), connectors, or shields can increase assembly cost. The soldering process required is more complex and rework or repair of these components is also expensive.
Minimize use of BGAs to reduce assembly pricing. Consider alternate high density component options like QFN packages where possible.
Connectors and Odd Shapes
Connectors, switches, buttons, and other odd-shaped components often require manual assembly steps, driving up cost. Designs that rely heavily on these specialty components can suffer cost and lead time impacts.
Reduce unnecessary connectors to lower cost. Consolidate multiple connectors into unified designs when feasible.
Component Height Variations
Mixed surface mount technology combining tall components like connectors or capacitors with low-profile SMDs make assembly more difficult. The soldering process must accommodate parts with varying standoff height.
Matching component heights within ~0.5mm helps streamline assembly. Separating tall and short components into different board areas also simplifies assembly process optimization.
How Board Factors Impact Cost
Board Area Size
PCB sizes under 20 sq. in. (130 cm2) are considered low cost. Boards over 50 sq. in. (320 cm2) or especially above 100 sq. in. (650 cm2) dramatically raise assembly pricing.
Larger area sizes mean longer process times for solder paste printing, component placement, reflow soldering, cleaning, inspection, etc. Large boards may also require equipment upgrades to accommodate their dimensions.
Downsizing PCB area has perhaps the greatest impact to reduce assembly costs. Carefully analyze board layouts and component placement to minimize area whenever possible.
Board Layer Count
Multilayer boards typically cost more than double layer boards to assemble:
| Layer Count | Relative Cost |
|---|---|
| Double layer | Low |
| 4-6 layers | Medium |
| 8+ layers | High |
Via-in-pad designs required for multilayer boards complicate assembly. And soldering defects are harder to detect on inner layers.
Design with cheaper double layer boards where possible. Minimize layer count for low volume or cost-sensitive projects.
Fine Pitch Components
Assembling boards with many ultra-fine pitch components under 0.4 or 0.5mm requires specialized assembly processes that increase cost:
- High precision pick-and-place machines
- Advanced optical inspection
- Special X-ray inspection
- Tight process control for reflow parameters
Coarser component pitches above 0.65mm can use standard lower-cost assembly lines. Avoid using extreme pitch ICs unless absolutely required.
High Component Density
PCBs with dense component placement and routing require smaller solder pads, finer solder paste printing, higher accuracy pick-and-place machines, and more advanced inspection. This forces use of more expensive assembly techniques.
If possible, increase spacing between components and enlarge pad geometries to simplify assembly requirements. Watch component-to-component spacing on both sides of board.
Flexible or Rigid-Flex PCBs
Assembling PCBs built with flexible circuit substrates adds cost and complexity versus standard rigid boards. Special carrier plates and clamping may be needed during assembly to control warpage. And many flex/rigid-flex boards require manual assembly steps.
Avoid flexible boards unless bending or flexing is functionally required. Carefully design rigid sections on rigid-flex boards to maximize use of pick-and-place assembly.
High Temperature Materials
Assembling boards that use polyimide, ceramic, and other high temperature materials requires process adjustments from standard FR-4 epoxy boards. Special soldering profiles may be needed to ensure materials are not overheated. And inspection requirements are tighter.
Utilize standard FR-4 materials wherever possible. Reserve high temperature boards only for environments exceeding FR-4 ratings to control cost.
How Assembly Process Impacts Cost
Soldering Method
The approach used to solder components influences equipment utilization, quality, and throughput:
| Method | Description | Relative Cost |
|---|---|---|
| Wave soldering | Board passes over flowing wave of solder | Low |
| Reflow soldering | Solder paste reflowed in oven | Medium |
| Selective soldering | Mini-wave targeted at joints | Medium |
| Manual soldering | Hand soldering all joints | High |
Simpler methods like wave soldering provide the most cost-effective assembly. But component parameters often dictate use of more advanced reflow or selective techniques.
Inspection and Testing
Testing steps are added to assembly lines to screen defects but increase total cost:
| Testing Method | Usage | Relative Cost |
|---|---|---|
| AOI | Automated optical inspection | Medium |
| ICT | In-circuit test | High |
| Flying probe | Electrical continuity checking | High |
| X-Ray | Detects hidden solder defects | High |
Determine minimum testing needed to meet quality levels for your product and application. Balance cost versus risk of escapes reaching field.
Conformal Coating
Applying protective acrylic or urethane coating adds an extra production step with increased costs. Adds ~10-20% to assembly pricing.
Only use conformal coating when environmental protection is truly required since bare boards are cheaper. Consider selective coating of sensitive areas only to reduce costs.
Cable and Wire Harness Assembly
Integrating external cables or wire harnesses with the PCB subassembly increases complexity and cost. Manual wiring steps are often required.
Simplify cabling requirements if possible. Consider modular cable designs that allow field connections to minimize wiring done during production assembly.
Box and Enclosure Assembly
Populating PCBs into plastic or metal enclosures requires additional process steps and tools versus bare board assembly. Automated assembly is limited.
Defer high-cost box build steps until later stages of production to keep initial assembly costs down. Consider purchasing pre-assembled enclosures from specialist suppliers where feasible.
How Location Impacts PCB Assembly Pricing
Country and geographic region are major cost factors, mainly due to differences in labor rates:
| Location | Typical Hourly Labor Rate Range |
|---|---|
| United States | $40 – $150 per hour |
| Canada | $35 – $85 per hour |
| Western Europe | $30 – $50 per hour |
| Eastern Europe | $15 – $35 per hour |
| China | $10 – $25 per hour |
| Southeast Asia | $6 – $15 per hour |
Labor represents 50%+ of total assembly cost. So lower wage regions can provide dramatic savings. However, also consider hidden costs like shipping, travel, communications, quality, IP protection, etc.
Optimizing Designs to Reduce Assembly Costs
Simple choices in PCB layout and component selection can help streamline assembly and lower cost:
- Use larger 1206 or 0805 SMT packages instead of tiny 0402 or 0201 when feasible
- Increase spacing between components to at least 8-10 mils or 0.20mm
- Avoid ultra-fine pitch ICs under 0.4mm. Use 0.5mm+ pitch packages.
- Minimize tall parts adjacent to low-profile SMDs to reduce height variations
- Utilize uniform component sizes/shapes instead of mixed specs
- Maximize use of double-sided assembly instead of multilayer via-in-pad
- Consolidate connectors into standardized super-connectors
- Reduce overall PCB size and avoid over-large boards > 100 sq. in. whenever possible
- Clearly separate and segregate SMT and through-hole component regions
- Include board-level test points, fiducials, and other DFT features
- Apply solder mask cleanly without webbing between fine pitch pads
These simple design-for-assembly tips ensure your board can be manufactured without specialized assembly processes that increase cost.
Strategies to Reduce PCB Assembly Costs
In summary, here are the top tactics that can help minimize total assembly expenses:
- Simplify designs – reduce parts counts, avoid complex components like BGAs, minimize cabling or connectors unless essential
- Consolidate components – substitute multiple simple parts with integrated multipurpose ICs whenever possible
- Standardize – use common footprints, uniform heights, consistent placements across all boards
- Utilize cost-effective components – avoid exotic small or ultra-fine pitch packages, go with mainstream SMT specs
- Design for assembly – allow generous spacing, avoid mixed technology, design for easy inspection
- Minimize PCB footprint – critically evaluate all board dimensions to reduce size and layers
- Standardize test requirements – balance defect detection versus cost, avoid unnecessary testing
- Assess geographic options – use locations with optimal labor rates and infrastructure
- Work with assembly experts – seek guidance from your EMS provider during design process
PCB Assembly Cost Estimation Tools
Several free online calculators can provide ballpark assembly quotes based on key parameters:
- PCB Assembly Quote Calculator
- MCL PCBA Cost Estimator
- PCB Assembly Cost Estimator
- PCBA Cost Estimator
- PCB Price Calculator
These self-service tools generate budgetary pricing in seconds. But consult directly with assembly partners for detailed quotes on production projects.
Getting Accurate Assembly Quotes
Follow this process when requesting PCB assembly quotes:
1. Send full manufacturing files – Gerbers, BOM, placement files, assembly drawings
2. Define order details – quantity, lead time, target cost, quality expectations
3. Select assembly provider – shot for 2-3 quotes from reputable EMS companies
4. Review detailed proposal – analyze pricing breakdowns, projected savings
5. Confirm final pricing – negotiate if needed, lock-in contract
Leverage assembly experts as early as possible in the design stage to optimize decisions for low cost and high quality.
FQA about PCB Assembly Costs
What is the typical cost per assembled board?
Assembly prices range widely from $5 to $50+ per board depending on complexity, order volume, and geography. Simpler boards in mid to high volumes can reach $2 to $10.
What percentage of total product cost is assembly?
PCB assembly accounts for 30-60% of total product cost for many electronics. The lowest BOM component costs may only represent 10% of product price.
Can automated assembly reduce labor costs?
Yes, use of advanced pick-and-place and soldering automation can reduce labor content for higher volume assemblies. But equipment costs are high.
When does it make sense to use manual assembly?
For quick-turn prototyping or very low volume, manual assembly may cost less than programming automation equipment. Even simple boards can cost over $1000+ in setup fees.
How much does test and inspection impact assembly costs?
Testing can add 10-30% onto baseline assembly costs. Balance requirements versus budget and production goals.
Conclusion
Determining PCB assembly costs and minimizing expenses takes careful analysis across all aspects of component selection, board design, manufacturing processes, geographic location, and product lifecycle needs. Simple double-sided boards with mainstream SMT components in mid to high volumes generally yield the most cost-effective assembly. Seeking early guidance from EMS assembly partners can help designers optimize all decisions for reduced manufacturing costs without sacrificing quality or reliability.
