Overview
A supplier says it has room for your PCBA order next week. The factory runs multiple SMT lines, its published capacity looks substantial, and the proposed production date seems reasonable.
Before relying on that date, an OEM buyer needs to establish what the available capacity actually covers.
An open SMT slot may be enough to populate the boards but not to complete the through-hole assembly or functional testing. The production line might also need a changeover that has not yet been allowed for, or the materials may not be ready when the slot opens.
For OEMs comparing PCB assembly suppliers, available production capacity is the capacity that can be assigned to a specific build during the required window, taking into account the product, existing commitments, and the operations needed to finish it.
That makes two questions worth separating: how much production time does the order require, and how much suitable time can the factory actually allocate?
A machine specification cannot answer both.
First, Make Sure Everyone Means the Same Thing by "Finished"
A supplier can give an accurate SMT completion date that still falls short of the customer's requirements.
If the purchase order covers surface-mount assembly only, finishing SMT may be the relevant milestone. For a mixed-technology PCBA requiring through-hole components, programming, functional testing, and final inspection, the job has further to go.
The production plan needs to reflect that difference.
Consider an industrial control board with SMT devices, through-hole connectors, and a dedicated functional test. Its manufacturing workload cannot be represented by the placement cycle alone. A straightforward SMT-only board, on the other hand, shouldn't be held up by THT or specialized test resources it doesn't require.
Before comparing suppliers' capacity figures, the buyer and manufacturer should agree on the product revision, order quantity, required operations, and completion milestone.
Those details may still be evolving during an initial RFQ. OEM teams can discuss the available BOM, Gerber files, panel design, expected quantity, and testing requirements with Shenzhen STHL Technology Co., Ltd. at info@pcba-china.com.
That discussion helps establish the manufacturing scope and any open engineering questions. It does not, by itself, reserve production time.
Check the unit before comparing production rates
An SMT department may count panels processed. Downstream assembly may count individual PCBAs. Quality may report the quantity accepted after the agreed inspections and tests.
Those numbers aren't interchangeable.
A manufacturing panel can contain several boards, and a double-sided assembly may require additional processing passes without producing additional finished units. If the capacity estimate uses panels per hour while the purchase order specifies individual PCBAs, the conversion needs to follow the actual panel layout.
Accepted output also needs a clear definition.
A board requiring authorized repair and retesting may ultimately pass the agreed acceptance criteria, but the additional work still consumes manufacturing resources. Counting every board that leaves reflow as finished output would overlook that workload.
For an order requiring tested PCBAs, the relevant production quantity is the number expected to complete the specified manufacturing and acceptance process-not simply the number placed on the SMT line.
What Do STHL's Published SMT Capacity Figures Actually Measure?
STHL's Technology and manufacturing capability overview lists seven automated SMT production lines equipped with Panasonic NPM-D3 placement machines.
The page quotes a placement-capability figure of up to 84,000 components per hour (CPH) per line. It also presents approximately 14 million placements per day and a monthly board-capacity reference exceeding 300,000 units.
These figures indicate the scale and upper-end capability of STHL's manufacturing resources under favorable operating assumptions. They should not be interpreted as consistently achieved output for every product, or as production time already available to a new customer.
The daily placement figure illustrates the distinction.
Using an assumed average of 1,200 components per board, the published example corresponds to roughly 12,000 board equivalents per day. That calculation describes an illustrative relationship between component placements and board quantity.
It does not establish how many assembled, inspected, and accepted PCBAs from a particular design can be completed in a day.
A control board with a demanding component mix and a dedicated test sequence will have a different workload from a simpler, passive-heavy assembly.
The published figures are useful when evaluating factory scale. They are not a substitute for an estimate based on the actual board.
A placement-machine rating is not the line's finished-board rate
CPH describes component-placement capability under specified equipment conditions. Actual SMT throughput depends on the product and the complete line configuration.
Component count matters, but package types, feeder arrangements, tray-fed devices, vision requirements, placement programs, and machine balance can all affect processing time.
The line also has work to perform beyond placement. Solder paste printing, board handling, reflow, inspection, and material replenishment need to support the intended rate.
For repeat production, actual cycle-time records from the same product are often the most useful starting point.
For a new assembly, the initial estimate may come from an offline placement-program calculation, the proposed line configuration, and experience with comparable products.
Either method can support a preliminary schedule. The important distinction is whether the rate has been demonstrated or remains an engineering estimate.
There is no universal percentage that converts every SMT machine's rated CPH into acceptable PCBAs per hour.
A reasonable capacity assessment uses the actual assembly requirements and applies operating allowances consistently.
For example, if planned changeover time has already been deducted from the available production hours, applying another broad efficiency factor that includes the same changeover loss may count it twice.
The opposite mistake is to start with the highest rated CPH and assume the complete line will sustain that output regardless of the product.
Neither approach gives procurement a reliable basis for comparing delivery options.
An Opening on the PMC Calendar Is Only the Beginning
Even a sound production-rate estimate does not tell the buyer when the factory can run the job.
The production planning and material control (PMC) team also has to account for existing customer commitments, tentative orders, maintenance, available operators, shared resources, and the setup work needed between products.
A production calendar might show enough unused hours over a week. Those hours still have to fit the proposed manufacturing run.
Why scattered gaps can be harder to use than one continuous slot
Imagine the planning calendar contains several short openings between existing jobs.
Their combined duration may exceed the estimated processing time for the new order. But using those gaps could involve repeated line clearance, feeder preparation, setup verification, and material handling.
For a repeat assembly with compatible tooling already prepared, splitting the run may be perfectly practical.
A newly introduced board with a substantially different setup may be better suited to a longer, uninterrupted window.
The question is not whether fragmented time is always inefficient. It is whether the proposed arrangement allows enough usable production time after the necessary preparation.
A smaller but workable slot can be more valuable than a larger collection of hours that cannot accommodate the job.
Changeover time is determined by the job, not a fixed allowance
STHL's PMC team does not apply one universal changeover duration to every PCBA order.
The actual setup work depends on the product being introduced and the configuration of the line. A change may involve a different stencil, feeder preparation, program verification, tooling adjustments, line clearance, and first-article checks.
An established repeat product with a compatible setup may require relatively little preparation. Switching to a new assembly with a different component mix can involve considerably more work.
How often those changeovers occur is another decision.
Order quantities, batch sizes, requested delivery dates, product mix, and existing commitments influence whether jobs can be grouped into longer production runs or scheduled in smaller batches.
A high-mix production schedule may involve more frequent changeovers because customers require different products in smaller quantities. That is not necessarily poor planning.
What matters is whether the proposed production window accounts for the setup work and allows the order to be completed under the agreed conditions.
A fixed changeover-time promise is less useful than a schedule built around the actual product and production requirements.
The available line may not be suitable for the board
There is also a compatibility question.
SMT lines are not always interchangeable. PCB dimensions, panel design, component packages, feeder availability, placement capabilities, tooling, board handling, and inspection arrangements affect which resources can run a particular assembly.
A line may be technically capable of processing the board but require preparation that has not been included in the original estimate.
Some supporting equipment may also be shared. An idle placement machine is not much help if a required setup resource is committed elsewhere.
For a routine RFQ, the OEM does not need a feeder-by-feeder setup report. The supplier should nevertheless be able to establish that the capacity estimate is based on equipment suitable for the actual assembly.
This becomes especially important when a manufacturer proposes running one order across two SMT lines.
Parallel production can increase output, but both lines need suitable programs, feeder arrangements, materials, personnel, and the required production verification. The downstream process also has to keep up.
If two SMT lines feed one constrained test operation, the extra populated boards may simply wait longer for testing.
The relevant improvement is how many acceptable PCBAs can complete the required manufacturing route by the customer's date.
SMT Can Finish on Time While the Order Is Still Waiting
For mixed-technology assemblies, the operations after reflow deserve their own place in the capacity review.
STHL's published equipment configuration includes two THT assembly lines and an upper-end theoretical insertion-capacity reference of up to 500,000 insertion points per day.
That figure describes insertion activity under the relevant assumptions. It does not represent a fixed daily quantity of finished PCBAs.
A board with a few through-hole connectors has a different workload from one containing numerous relays, transformers, or other components requiring extensive insertion and soldering work.
The actual THT processing time depends on the component mix, insertion method, soldering process, fixtures, available operators, and setup requirements.
Wave soldering and selective soldering should not be assigned the same generic processing rate without considering the board and manufacturing route.
For an SMT-only assembly, THT availability may be irrelevant. For a mixed-technology order, the THT schedule can determine whether the final quantity is ready when required.
Functional test capacity is more than a workstation count
STHL's Technology page also lists two testing lines and 50 stations.
That gives buyers an indication of the factory's testing infrastructure. It does not mean 50 independent FCT setups are available for any particular product.
Functional testing may depend on a dedicated fixture, approved firmware, test software, interface cables, programmable loads, or shared measurement instruments.
A workstation can be physically unoccupied while the fixture or equipment required for the customer's board is in use elsewhere.
The complete test cycle matters, too.
Connecting and loading the board, applying power, executing the test, recording results, and unloading the assembly can take longer than the automated test sequence alone.
Multiple fixtures may not deliver proportional throughput if they share instruments, operate sequentially, or depend on the same operator.
When functional verification is part of the purchase order, the relevant Testing and Inspection resources need to be assessed against the actual test requirements.
Not every PCBA requires ICT, FCT, burn-in, or every other inspection method the factory can provide. Only the operations included in the agreed manufacturing and test scope belong in the order's capacity calculation.
A bottleneck also has to be available at the right time
The slowest operation can limit sustained production throughput. But the completion date of a specific order depends on more than the lowest hourly rate.
SMT might be available early in the week while the required THT or test resources are committed until later.
Each department could have enough aggregate capacity over a longer period without having compatible time slots for the customer's order.
The production plan needs to account for when each required operation can begin, whether activities can overlap, and when the boards can complete the agreed release process.
For a finite order, simply taking the lowest hourly rate across SMT, THT, and FCT is not enough to predict when the finished boards will be ready.
A Production Slot Is Only Useful If the Build Is Ready
A line can have available time while the work order is not ready to enter production.
A critical component may still be in transit. A substitute part may require approval. The PCB revision might not be released, or a necessary stencil or test fixture may still need preparation.
Stock shown as available in an inventory system can also be misleading. Some material may already be allocated to another order, held pending inspection, or unavailable in the condition required for the planned build.
This is where component kitting becomes relevant.
The required components need to match the approved BOM and manufacturing requirements, with appropriate quantities, identification, packaging, and handling conditions.
The sourcing responsibility can differ between turnkey, partial-turnkey, and customer-consigned projects. The production requirement does not: usable material has to be available when the scheduled operation begins.
There are legitimate exceptions.
A manufacturer may reserve future capacity while components are still in transit. Some projects allow approved partial builds or staged material release.
Others require all critical materials and specified engineering approvals before the production run starts.
These decisions depend on the project requirements and the supplier's production controls, not a single rule applied to every order.
Once the BOM, Gerber files, assembly drawings, order quantity, manufacturing scope, and target production window are sufficiently defined, the OEM can submit the PCBA project for manufacturing review and quotation.
That gives the manufacturing team a basis for reviewing the actual workload, material readiness, and resources required to accommodate the order.
What Evidence Makes a Capacity Reply Worth Relying On?
A manufacturer's equipment list establishes installed capability. It does not establish how much of that capability remains available during the customer's requested window.
A historical production record answers a different question. It may demonstrate how a comparable assembly performed, including relevant cycle times and production conditions.
A current PMC assessment addresses the remaining scheduling question: when can suitable resources be allocated to the new order?
Neither record replaces the other.
A strong historical run rate does not prove that the same line is free next week. An opening on the calendar does not prove that an unfamiliar board can be manufactured within the proposed hours.
The supplier needs a reasonable basis for both the workload estimate and the available production window.
That doesn't mean the OEM should demand access to other customers' orders or unrestricted visibility into the factory's planning system.
A suitably redacted schedule, a summarized resource-load assessment, comparable production records, or a clear conditional planning response may be sufficient, depending on the project.
The buyer should be able to establish what was assessed: the product revision, quantity, completion milestone, proposed production period, and any material resource constraints.
Just as important, the response should identify which assumptions remain open.
"Available," "tentative," and "confirmed" are not interchangeable
A preliminary capacity assessment may indicate that the order appears feasible under current conditions.
A tentative allocation identifies a proposed production period, but the supplier's planning rules determine whether that time is protected from reassignment.
A confirmed production arrangement should be understood in the context of the commercial and manufacturing conditions agreed by the parties.
Those terms are not universal ERP status codes.
A purchase order does not automatically mean every material, fixture, program, or engineering approval is ready. Nor must a manufacturer necessarily wait for every component to arrive before reserving future capacity.
The OEM needs to know what the supplier has actually allocated, what is still conditional, and what could change the proposed schedule.
A useful production-capacity reply makes those distinctions clear rather than offering an unconditional date based only on published factory capacity.
When the Order Changes, Recheck the Resources It Affects
A capacity assessment applies to a defined product, quantity, manufacturing route, and production window.
Increasing the quantity may require more production hours or a different batch arrangement. A revised panel design can affect board handling and throughput. A new component package may change feeder preparation or placement requirements.
Additional THT operations, a different soldering route, or a longer functional test can introduce another scheduling constraint.
A delayed critical component can also shift the earliest practical production start.
Those developments call for reviewing the affected parts of the plan.
They do not automatically mean every order must be cancelled and placed at the back of the production queue.
Some engineering revisions have little or no effect on the required equipment, manufacturing route, or available production time. Others may require a substantial change to the resource allocation.
The important question is whether the original production window still supports the work now being requested.
The Capacity That Matters Is the Capacity the Order Can Use
STHL's published SMT, THT, and testing figures provide a useful picture of its manufacturing resources and the range of PCBA production programs the factory is equipped to support.
For an individual OEM order, however, the production decision has to go further.
The actual board, expected quantity, setup requirements, available machine time, material readiness, and downstream operations all need to fit together.
A supplier does not need to disclose every detail of its shop-floor schedule to make a credible capacity assessment.
It should be able to explain what the proposed production window covers, what supports the workload estimate, and which conditions still need to be confirmed.
That is the information an OEM can use when deciding whether a PCBA order is ready to move from quotation into production.
