Through-Hole (DIP) Assembly

What surface mount cannot carry goes to through-hole and secondary soldering. The insertion stations sit next to the SMT lines: boards come off reflow and go straight into insertion, are soldered by the method the board calls for, then cleaned, inspected and coated in the same building. The board does not leave the site between reflow and final inspection.

When through-hole is the right choice

• Power supplies, adapters and LED drivers carrying large electrolytics, inductors and transformers.
• Industrial control and instrumentation boards with many terminals, sockets and relays, where joints see vibration.
• Connectors, switches and terminal blocks that will be mated and unmated repeatedly in service.
• Aluminium and heavy-copper boards where the thermal mass of the joint is high.
• Mixed-technology boards: SMT on one side with through-hole on the other, or double-sided SMT plus secondary soldering.

Wave and selective soldering

Conventional through-hole boards run over the wave with a pallet masking anything that must not see solder. One pass does the whole board, which keeps it the cheaper method on insertion-heavy volume work. Pot temperature, conveyor speed, preheat and flux volume are set from board thickness and copper weight, proved on a test board, and released for volume only after the first article passes.

Where a board is densely populated, or surface-mount parts on the solder side rule out a full wave, we use selective soldering and solder only the joints named. Heat stays local, which is safer for neighbouring SMT parts and plastic bodies. The two methods can be split across zones of one board. The routing is decided at engineering review and written into the process sheet, not improvised at the machine.

Hand soldering and fixtures

Odd-form parts, expensive devices and anything fitted after the main soldering step are done by hand. Locating fixtures and clamps are made from your drawing first, so insertion height, orientation and spacing come out the same on every board. Iron temperature, tip type and dwell time per joint are written into the work instruction, and stations are checked and logged at the start of each shift, so the result does not depend on who is on the bench.

Hand-soldered joints are inspected one by one for fillet formation, wetting, bridging and icicles, under magnification where the part warrants it. Rework has its own station, with BGA and IR rework equipment. Reworked boards go back through inspection and the number of rework cycles on that board is recorded.

ESD control and process discipline

The floor is temperature and humidity controlled and ESD-controlled. Benches carry grounded mats, operators wear wrist straps and ESD coats, and irons and instruments are checked for grounding and tip temperature on a schedule. Material moves by batch with a route card attached to the work order. Insertion, soldering and inspection are each signed off, so a board can be traced back to its operator, its equipment and its material batch.

Conformal coating

Boards going into humid, dusty or corrosive environments can be conformal coated, by brush, spray or selective dispensing depending on the layout. Connectors, sockets, test points and heatsink faces are masked with fixtures or tape before coating, and cure time follows the material datasheet. After cure the film is checked for even coverage, pooling, bubbles and missed areas. Name the coating material and thickness you want on the RFQ, mark the keep-out areas on the assembly drawing, and the masking will be built to them.

Capability

Soldering methods	Wave soldering, selective soldering, hand soldering
Board formats	Pure through-hole, single-sided SMT plus through-hole, double-sided SMT with secondary soldering
Board types	FR-4, aluminium (MCPCB), ceramic, Rogers, flex, rigid-flex
Fixtures	Locating fixtures, wave pallets and masking fixtures, made in-house for your board
Rework	BGA rework and IR rework at a dedicated station
Surface protection	Conformal coating by brush, spray or selective dispensing, with masked keep-out areas and controlled cure
Solder alloy	SAC305 lead-free as standard; tin-lead where you specify it.
Inspection and test	Visual inspection, AOI, X-ray, ICT, flying probe, FCT
Workmanship	Boards are built to the IPC-A-610 acceptance class you specify
Workshop	Temperature and humidity controlled, ESD-controlled floor