Mixed Assembly Services – SMT and Through-Hole PCB Assembly
SMT and Through-Hole Components on the Same PCB
Plenty of commercial electronic products just can’t be built well with one component technology on its own.
High-density ICs and tiny passives are made for surface mount, while connectors, transformers, switches, relays and anything carrying a mechanical load often need the muscle of through-hole construction.
At PCB Company, we’re a UK-based manufacturer offering mixed PCB assembly that brings SMT and THT components together on the same board.
We take on prototypes, quick-turn builds, high-mix low-volume work and full production quantities for businesses right across the UK and Europe.
By pulling PCB fabrication, component sourcing, surface-mount assembly, through-hole assembly, inspection, testing and rework under one roof, we help OEMs and engineering teams cut down the procurement headache and keep a tighter grip on their builds.
What Is Mixed-Technology PCB Assembly?
Meeting and Exceeding Industry Standards
Mixed assembly — you’ll also hear it called hybrid PCB assembly, or simply SMT and THT assembly — puts both surface-mount devices and through-hole components on a single board.
You’d reach for it when a product needs the compact layout and slick automated placement of SMT, but also the mechanical strength, power handling or package availability that through-hole parts bring to the table.
A typical mixed-technology board might carry:
- Fine-pitch integrated circuits
- Ball Grid Arrays and QFNs
- Small surface-mount passives
- Through-hole connectors and terminal blocks
- Relays and transformers
- Large capacitors
- Power components
- Switches, displays or user controls
- Customer-specific modules
- Pre-programmed devices
- Components on one side or both
Mixed assembly fits nicely into industrial controls, power electronics, communications gear, automotive systems, medical devices, instrumentation and aerospace assemblies.
Design for Mixed-Technology Manufacturability
Mixed assemblies gain a lot from an early engineering review. Small layout calls can quietly push up production time, defect risk and unit cost.
Design habits worth adopting:
- Keeping access clear around through-hole joints
- Marking polarity and pin one clearly
- Leaving clearance between tall THT parts and SMT devices
- Keeping test points reachable after final assembly
- Allowing for connector and enclosure tolerances
- Spelling out which component substitutions are acceptable
- Flagging moisture-sensitive devices
- Flagging temperature-limited components
- Supplying complete centroid data
- Supplying clear assembly drawings
- Matching finished hole sizes to component leads
- Checking heavy copper around solder joints
- Managing thermal mass across the layout
Our team can bring DFM, DFA and DFT input to help turn a working circuit into an assembly you can build the same way, batch after batch.
Why Mixed PCB Assembly Requires Careful Planning
A mixed board isn’t just an SMT assembly with a few extra parts stuck on afterwards.
The build sequence has to take account of soldering processes, component temperature limits, access, clearances, board support and the ever-present risk of disturbing parts that are already down.
Things we keep in mind:
- Which components go on and get soldered first
- Whether parts sit on one side or both
- How much heat each stage puts into the board
- Component body height
- Room to work around the larger parts
- Access to through-hole solder joints
- Whether the solder alloy and PCB surface finish get along
- Moisture-sensitive component handling
- Inspection access under and around components
- Test-point access once everything’s assembled
- Connectors lining up with the enclosure
More often than not, SMT placement and reflow are done before the through-hole stage. But the right order always comes from the actual component mix, the PCB layout and what the product needs — not a fixed rule.
Our engineering support covers Design for Manufacturability, Design for Assembly and Design for Test review, which helps flag production risks before you’ve bought components or sent boards into assembly.
Mixed SMT and THT Assembly Options
We keep the commercial side flexible so it fits how you buy and how your supply chain works.
Full Turnkey Mixed Assembly
We look after PCB manufacture, component procurement, SMT assembly, through-hole PCB assembly, inspection and agreed testing. You deal with one supplier instead of trying to line up a separate PCB fabricator, component distributor, SMT house and through-hole contractor.
Partial Turnkey Assembly
You hand over selected components, specialist devices or controlled stock, and we source the rest and finish the mixed-technology build. Handy for customer-specific parts, programmed devices and anything already sitting in your inventory.
Consignment Assembly
You supply the boards and the component kit; we carry out the agreed SMT, THT, inspection and testing. A good fit when you’ve already got the stock, you’re tied to approved vendors, or the components are yours.
Prototype and Quick-Turn Assembly
Prototype mixed builds have a habit of surfacing issues that CAD alone won’t show you — connector alignment, component access, the assembly sequence, testability. With no standard minimum order, we’re happy to support early engineering builds as well as repeat production.
Our Mixed Assembly Workflow
Manufacturing Data Review:
We work through the Gerber files, bill of materials, centroid data, assembly drawings and any project instructions.
Unclear references, polarity markings, substitutions or special-process needs are best sorted before the job’s released to production.
On denser boards, the review also takes in fine-pitch packages, BGA requirements, pad geometry and how the SMT and through-hole features relate to one another.
Component Sourcing and Verification:
For full and partial turnkey projects, we source components against the approved BOM.
Parts you supply can drop into the same build too, once we’ve reviewed the kit, checked the identification and confirmed quantities.
Accurate manufacturer part numbers really matter here. A connector that’s a slightly different size, or an alternative package, might be electrically identical yet still won’t fit the PCB, the enclosure or the assembly process.
SMT Assembly:
Solder paste goes down, surface-mount parts are placed, and the board runs through the defined soldering stage.
Fine-pitch components call for careful control of paste deposition, placement and the thermal profile.
We handle fine-pitch BGA assembly and offer X-ray inspection for those hidden solder joints when the job calls for it.
Through-Hole Assembly:
Through-hole parts are prepped, inserted and soldered to the build spec.
We keep a close eye on orientation, seating, body height, lead condition and how everything lines up with mating connectors or mechanical interfaces.
Inspection and Testing:
Inspection and test options on offer:
- Automated optical inspection
- Automated X-ray inspection
- 2D and 3D X-ray inspection
- In-circuit testing
- Flying probe testing
- Board-level functional testing
- System-level functional testing
- Engineering rework
- BGA rework and reballing
The right mix comes down to board complexity, quantity, the fault coverage you need and what a failure would cost you in the finished product.
Benefits of Using One Supplier for SMT and THT
Precision Engineering from Concept to Delivery
Splitting a mixed-technology build across several contractors piles on extra handling, transport, scheduling and finger-pointing. And when a fault does show up, it can be a real puzzle working out which supplier or process caused it.
Running it as one coordinated service brings some genuine commercial upsides:
- A single point of contact for the whole PCB asssembly
- Fewer handovers between suppliers
- A defined assembly sequence
- Simpler material control
- Cleaner revision management
- Coordinated inspection and testing
- Easier engineering feedback
- Less handling between processes
- A clearer path from prototype to production
- Quicker turnaround on rework or corrective action
For procurement, that’s less admin and less supplier juggling. For engineers, it’s a direct technical line for sorting out design and production questions.
Mixed Assembly for New and Existing Products
We can support new product introduction, engineering redesigns, repeat builds and long-standing legacy assemblies. That takes in:
1. New designs pairing dense SMT circuitry with rugged connectors
2. Power electronics that mix SMT control devices with through-hole power components
3. Existing products being refreshed with newer surface-mount devices
4. Legacy assemblies that still need through-hole support
5. Prototype boards waiting on a final design revision
6. Products needing approved engineering modifications
Because we’ve got the wider PCB manufacturing side in-house, the board construction and the assembly requirements can be looked at together as one coordinated project.
Working with a UK Assembly Partner — and Serving Europe Too
A good number of our customers come to us after getting burned by long lead times or suppliers overseas they could never quite get hold of. Keeping the work here in the UK tightens that loop — you’re talking to the engineers actually building your boards, in your time zone and in plain English.
Being UK-based helps on the practical front as well:
- Faster turnaround and shorter shipping for customers across England, Scotland, Wales and Northern Ireland
- Straightforward logistics into Europe, with real experience handling cross-border paperwork post-Brexit
- A solid handle on UK and EU compliance, including RoHS and REACH, plus specified non-RoHS work where your application needs it
- Traceability and support robust enough for regulated sectors like aerospace, medical, defence and industrial control
Whether you’re a start-up in Cambridge, an established manufacturer in the Midlands or a design house on the Continent, you get the same joined-up service — from bare board through to a fully tested, inspected assembly.
Why Choose PCB Company?
Customers pick us for mixed assembly when they want:
- SMT and through-hole assembly from one provider
- Prototype, quick-turn and production support
- Full turnkey, partial turnkey or consigned supply
- No standard minimum order quantity
- RoHS-compliant and specified non-RoHS options
- Fine-pitch and BGA assembly capability
- X-ray and AOI inspection
- Electrical and functional test options
- DFM, DFA and DFT engineering support
- PCB fabrication, sourcing, assembly and testing on one project route
- UK-based communication for UK and European customers
What to Send for a Mixed Assembly Quote
Please send over:
- Gerber or ODB++ files
- Bill of materials with approved manufacturer part numbers
- Pick-and-place or centroid data
- Assembly drawings
- PCB quantity and expected batch schedule
- Required lead time
- Solder alloy and compliance requirements
- Details of any free-issued components
- Programming requirements
- Inspection and testing requirements
- Packaging, labelling and traceability instructions
The fuller the data pack, the sharper we can be on cost, lead time and production risk.
Mixed PCB Assembly FAQs
Yes — that’s exactly what mixed-technology assembly is for: boards that use both surface-mount and through-hole packages.
SMT usually goes first, but the right order really depends on the layout, component temperature limits, the soldering process and access.
Yes. We’ve got automated 2D and 3D X-ray inspection for BGA and other fine-pitch components.
Yes. Our consignment and partial turnkey options let you supply some or all of the components.
Yes. With no standard minimum order, prototype and quick-turn mixed builds can be reviewed right alongside production work.
Yes on both. We’re based in the UK with UK project communication, and we regularly supply customers across Europe, sorting the shipping and paperwork as we go.
Request a Mixed Assembly Quote
Planning a board that brings SMT and through-hole components together?
Send your manufacturing data, BOM, quantity and delivery requirements to PCB Company for an engineering-led quote. Work with a UK mixed-technology specialist that serves customers throughout Europe too.
Call 0203 750 0201 or request a quote at www.pcbcompany.co.uk.