THT assembly: PTH board assembly service, from prototype to production

When a project requires connectors, terminals, relays, transformers or power components that must withstand vibration, mechanical loads and thermal cycling, THT assembly remains a very solid engineering choice. At CTA Electronics we handle it every day, often on mixed-technology boards where the fine-pitch section is SMT and the “robust” section is PTH board assembly.

In this guide you’ll find how we manage outsourced PTH assembly, what we actually check, and which information we need to bring your product into production in a stable, repeatable way.

Why choose PTH board assembly

PTH (through-hole) is not a “second-best” solution. It’s the right answer when you need:

• high mechanical strength (connectors, interfaces, wiring, terminals)
• power handling and higher currents
• bulky components or thermally “demanding” parts
• reliability in harsh environments: vibration, shock, temperature swings

In other words: if your board has to work in the field and not just in the lab, PTH often makes the difference.

How we run THT assembly without surprises

The point isn’t just soldering. The point is delivering a repeatable, traceable board that’s ready to be integrated into your product. That’s why our THT assembly flow is built to prevent errors before they reach the bench.

1) Technical validation and industrialisation (DFM/DFT)

Before production starts, we perform an operational technical check on:

• BOM and part codes (equivalents and alternatives, if requested)
• manufacturing and assembly files, revisions and variants
• polarity, orientation, heights and mechanical constraints
• accessibility for inspection and testing (test points, critical areas)

This phase drastically reduces typical issues: wrong parts, inconsistent footprints, untestable boards, unexpected rework.

2) PTH component insertion: precision and repeatability

Through-hole insertion can be straightforward — or full of pitfalls. We address it with:

• polarity checks and lot identification
• height control and proper seating to avoid stress on pins
• special care for mechanical parts (connectors and terminals) that require perfect positioning for final assembly

The goal is always the same: a “clean” board, stable and consistent from batch to batch.

3) PTH soldering: we choose the method for the board, not by habit

In a serious outsourced PTH assembly service, soldering isn’t “one-size-fits-all”. It depends on geometry, density, sensitive components and volumes.

• Wave soldering when it’s the most efficient and safe option for the design.
• Selective soldering when the board is mixed-technology or when certain areas must not go through wave.
• Hand soldering for complex points, special connectors, controlled rework or small batches.

What matters is long-term joint quality: proper wetting, no bridges, adequate hole fill, and no unnecessary thermal stress on components.

4) Quality checks: visual, documented, consistent

In PTH board assembly, defects are “visible” — but only if you look for them methodically. We apply structured checks and shared acceptance criteria, focusing on:

• critical PTH joints (connectors, power, mechanical components)
• bridges, cold joints, insufficient wetting
• orientation and polarity
• lifted or stressed components

When needed, we add extra controls based on the application and field risk.

5) Testing: from the board to the product

If you’re choosing a partner, you know the difference isn’t simply “assembling” a board. It’s delivering a board that works — and stays stable over time.

Depending on your project, we can support:

• electrical or functional tests (when procedures and fixtures are available)
• targeted checks on critical points (power rails, connectors, key signals)
• traceability management for lots and variants (useful for quality control and after-sales support)

If you already have a test plan, we implement it with you. If you don’t, we help you set one up in a practical way.

Materials management: labour-only or full service

Every company has a different supply chain. That’s why we work flexibly:

• labour-only: you supply components and PCBs, we handle THT/PTH assembly and the agreed checks
• full service: if you prefer, we can also support the operational management of job materials under shared rules (specs, equivalents, lots)

The rule is simple: less ambiguity in, fewer production issues.

What we need to start your outsourced PTH assembly

To start quickly and cleanly, it helps to have:

• Gerber files and BOM with clear part codes
• assembly files, polarity notes, variants
• quantities and batch forecast (even indicative)
• special requirements: coating, washing, packaging, markings, traceability
• test information (test spec, jigs, procedures, criteria)

If something is missing, it’s not a problem: we flag it immediately and resolve it before it becomes a production stop.

When to choose CTA Electronics for THT assembly

We’re the right partner if you’re looking for:

• a supplier that manages PTH board assembly with an industrial approach
• support on mixed SMT + PTH boards
• a clear process, with controls, traceability and technical communication
• a partner able to move from prototype to series production while maintaining consistent quality

For any information, you can contact us via the chat in the bottom right or through the contact page.

Frequently asked questions about THT assembly

If you’d like to jump straight to the full overview of our service, visit the dedicated PCB assembly page.