Your SMT Line Can Build 280 Boards Daily. You’re Delivering 195. Here’s Why Secondary Operations Are the Hidden Bottleneck and Can Cost Up to £1.6m Lost Revenue
Your primary SMT line places 52,000 components per hour. Your production schedule says you can build 280 boards per day. But you’re consistently delivering only 195 boards.
The bottleneck isn’t your placement capacity. It’s the secondary operations your planning system doesn’t properly account for and it’s costing UK electronics manufacturers between £67,000 and £180,000 annually in lost throughput.
After working with numerous electronics manufacturers, I’ve observed a consistent pattern: production planning focuses intensely on SMT line takt time whilst treating secondary operations as “they’ll sort themselves out.” The result is systematic under-delivery, expediting costs, and capacity utilisation that never matches the spreadsheet predictions.
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What Are Secondary Operations in Electronics Manufacturing?
Before we discuss their impact on takt time, let’s clarify what we mean by “second-ops” in an electronics manufacturing context.
Primary operations are your main SMT assembly processes:
- Solder paste printing
- Component placement (pick-and-place)
- Reflow soldering
- Automated optical inspection (AOI)
Secondary operations are everything else required to complete the product:
- Through-hole component insertion and wave soldering
- Manual soldering of connectors, large components, or awkward parts
- Conformal coating application and curing
- Mechanical assembly (enclosures, brackets, hardware)
- Cable and wire assembly
- Functional testing beyond basic electrical test
- Programming and firmware loading
- Final inspection and packaging
For many electronics products, these secondary operations consume 40-60% of total manufacturing time, but they receive perhaps 10-20% of planning attention.
Understanding Takt Time in Electronics Manufacturing
Takt time is the rate at which you need to complete products to meet customer demand.
It’s calculated simply:
Takt Time = Available Production Time ÷ Customer Demand
If you have 450 minutes of production time per shift and need to deliver 90 boards, your takt time is 5 minutes per board.
In theory, if every operation in your process takes less than 5 minutes, you can meet demand.
In practice, secondary operations routinely violate takt time and most planning systems don’t properly account for this.
The Five Ways Second-Ops Destroy Takt Time
- Sequential Dependency Creating Cascading Delays
Your SMT line completes a board every 3.2 minutes. Excellent and well within your 5-minute takt time.
But that board then requires:
- Through-hole connector soldering: 4 minutes
- Conformal coating application: 2 minutes
- Coating cure time: 45 minutes
- Functional test: 8 minutes
- Enclosure assembly: 6 minutes
Total secondary operations time: 65 minutes (excluding the 45-minute cure, which can run in parallel batches)
Even with batch processing and parallel work, your effective takt time is now dominated by the longest secondary operation not your SMT line speed.
Financial impact: If your planning assumes 3.2-minute takt based on SMT capacity, you’re systematically over-promising delivery by 30-40%. The resulting expediting costs, air freight charges, and customer relationship damage rarely appear in any cost variance report.
- Variable Process Times That Planning Ignores
SMT operations are highly automated with predictable cycle times. Secondary operations especially manual ones vary significantly.
Example: Manual connector soldering
- Experienced operator: 3.5 minutes per board
- New operator: 6.2 minutes per board
- Operator fatigue (hour 7-8 of shift): 5.8 minutes per board
- Complex board variant: 8.1 minutes per board
Your planning system uses: 4.0 minutes (average)
The problem: Averages are useless for takt time calculations. You need to plan to the realistic worst-case within normal variation probably 6.5-7.0 minutes for this operation.
Financial impact: When actual times exceed planned times, you have three bad options:
- Miss delivery commitments (customer penalties, lost future business)
- Authorise overtime at 1.5x rates (margin erosion)
- Hold SMT production to prevent WIP build-up (capacity waste)
All three cost money. None show up as “secondary operations planning failure” in your management accounts.
- Hidden Setup Times Between Product Variants
Your SMT line changeovers are tracked religiously. Your secondary operation changeovers? Barely acknowledged.
Consider conformal coating:
Switching from Product A (acrylic coating) to Product B (silicone coating) requires:
- System flush and cleaning: 25 minutes
- Material changeover: 8 minutes
- Test spray and adjustment: 12 minutes
- First article cure and verification: 45 minutes
Total: 90 minutes of non-productive time
If you’re running high-mix production with frequent product changes, these secondary operation setups accumulate quickly but they’re rarely factored into takt time calculations or capacity planning.
Financial impact: A conformal coating operation running 6 product changes per day loses 540 minutes (9 hours) to changeovers. At £85/hour absorbed cost, that’s £765 daily in capacity that your planning spreadsheet assumes is productive time.
- Quality Escapes Requiring Rework
SMT defects are typically caught immediately by AOI. Secondary operation defects? Often discovered much later, sometimes at final test or even by the customer.
Common secondary operation defects:
- Insufficient or excessive conformal coating coverage
- Cold solder joints on manual through-hole work
- Mechanical assembly errors (wrong hardware, cross-threaded fasteners)
- Incomplete or incorrect programming
- Damaged connectors during cable assembly
The takt time impact: A board that fails final test must cycle back through rework, which:
- Removes it from the current production batch (disrupting flow)
- Consumes additional secondary operation capacity (typically 2-3x the original time due to disassembly/reassembly)
- Creates scheduling chaos as rework competes with new production for resources
Example calculation:
If 4% of boards require secondary operation rework, and rework takes 2.5x the original time:
- 100 boards produced
- 4 boards need rework at 2.5x time = 10 boards worth of capacity consumed
- Your effective capacity: 90.9 boards (not 100)
- Capacity loss: 9.1%
This 9% capacity loss never appears in your SMT-focused takt time calculations.
- Resource Constraints Creating Artificial Bottlenecks
Your SMT line runs lights-out with minimal operator intervention. Your secondary operations? Labour-intensive.
Typical scenario:
You have capacity to build 240 boards per day through SMT. But you only have:
- 2 operators trained on through-hole soldering (capacity: 180 boards/day)
- 1 functional test station (capacity: 160 boards/day)
- 3 mechanical assembly workers (capacity: 210 boards/day)
Your true capacity: 160 boards per day (limited by functional test)
Yet your production schedule, based on SMT takt time, promises 240 boards. The 80-board shortfall creates:
- Constant expediting and priority changes
- WIP build-up between SMT and test
- Overtime costs
- Delivery delays
Financial impact: If you’re billing for 240 boards but delivering 160, you’re not just missing revenue. You’re paying overtime to partially close the gap, accumulating WIP carrying costs, and damaging customer relationships.
The Real Cost of Ignoring Secondary Operations in Takt Time Planning
Let’s model a realistic scenario for a mid-sized UK electronics manufacturer:
Production target based on SMT takt time: 1,200 boards/week
Actual delivery constrained by secondary ops: 850 boards/week
Shortfall: 350 boards/week = 18,200 boards/year
Lost revenue: 18,200 boards × £85 average selling price = £1,547,000 annually
But it’s worse than just lost revenue:
Additional costs incurred:
- Overtime to partially recover shortfall: £67,000/year
- Expediting and air freight: £34,000/year
- WIP carrying costs (excess inventory sitting between operations): £28,000/year
- Customer penalty clauses for late delivery: £18,000/year
Total financial impact: £1,694,000 in lost revenue and avoidable costs
For a manufacturer with £8-10M annual revenue, this represents 17-21% of total turnover disappearing due to secondary operations planning failure.
How to Properly Account for Second-Ops in Takt Time Planning
Step 1: Map Your Complete Value Stream
Don’t stop your process map at reflow. Document every secondary operation including:
- Standard time for each operation
- Setup/changeover time between variants
- Quality yield/defect rates
- Resource requirements (labour, equipment, floor space)
Step 2: Calculate Effective Takt Time by Bottleneck
Identify your true constraint. It’s probably not your SMT line.
For each operation, calculate:
- Available time per shift
- Demand rate
- Required takt time
- Actual capable takt time (including setup losses, defects, variation)
Your effective takt time is determined by your slowest operation, not your fastest.
Step 3: Design for Takt Time Balance
If secondary operations limit throughput, you have several options:
Option A: Add secondary operation capacity
- Additional test stations, coating equipment, or trained operators
- Capital investment, but directly addresses constraint
Option B: Reduce secondary operation time
- Design changes to eliminate manual steps
- Improved tooling/fixtures to speed operations
- Better training to reduce variation
Option C: Redesign production flow
- Batch secondary operations to reduce setup frequency
- Create dedicated cells for high-volume products
- Implement parallel processing where possible
Step 4: Synchronise Planning Systems
Your production scheduling must reflect secondary operation constraints, not just SMT capacity.
Implement:
- Finite capacity scheduling that includes all operations
- Visible WIP limits between operations
- Pull signals from secondary operations to SMT (don’t push boards into bottlenecks)
Step 5: Cost Secondary Operations Accurately
Stop allocating secondary operation costs as general overhead. Create activity-based cost pools for:
- Manual through-hole soldering (cost per joint or per board)
- Conformal coating (cost per board by coating type)
- Functional testing (cost per test by complexity)
- Mechanical assembly (cost per assembly step)
This reveals which products consume disproportionate secondary operation resources critical for pricing decisions.
The ROI of Getting This Right
Example: Addressing a functional test bottleneck
Current state:
- 1 test station, 160 boards/day capacity
- SMT can produce 240 boards/day
- Constraint: 80 boards/day shortfall
Investment option: Add second test station
- Capital cost: £45,000
- Installation and validation: £8,000
- Training: £3,000
- Total investment: £56,000
Financial return:
- Additional capacity: 80 boards/day = 20,800 boards/year
- Revenue recovery: 20,800 × £85 = £1,768,000
- Contribution margin (assume 35%): £618,800
- Less: Additional variable costs (test consumables, operator): £78,000
- Net annual benefit: £540,800
ROI: 866% in year one
Payback period: 5.4 weeks
Unfortunately, many manufacturers delay this investment for years because their planning systems don’t make the secondary operation constraint visible.
Conclusion: Takt Time Is Only as Fast as Your Slowest Operation
Electronics manufacturers obsess over SMT line speed because it’s visible, measurable, and impressive. Meanwhile, secondary operations quietly limit actual throughput by 30-40% and planning systems pretend it isn’t happening.
The result is usually systematic over-promising, constant expediting, margin erosion through overtime, and capacity investments in the wrong places.
Proper takt time planning must account for your entire value stream especially the manual, variable, often-overlooked secondary operations that actually determine your delivery capability.
Your SMT line’s takt time doesn’t matter if your functional test station can only handle 160 boards when you promised 240.
Ready to identify where secondary operations are limiting your throughput? I help UK electronics manufacturers implement value stream mapping and activity-based costing that reveals true capacity constraints and supports data-driven improvement investment.
Let’s discuss how proper cost architecture and capacity analysis can transform your delivery performance and profitability.
Contact me today to schedule a value stream assessment.
Written by Yesim Tilley Founder of Skynet Accounting
Follow me on LinkedIn: www.linkedin.com/in/skynet-yesim-tilley
About the Author: I specialise in management accounting for UK electronics manufacturers, helping businesses implement costing and capacity planning systems that reflect production reality. My focus is on manufacturers where standard planning approaches systematically fail to capture operational constraints particularly in high-mix, complex assembly environments with significant secondary operations.
What’s your biggest frustration with production planning accuracy? Let’s discuss how better visibility into secondary operation economics can improve both delivery performance and financial results.
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