Electronics manufacturing process: a board and its harness from order to dispatch

The stages below follow one typical product: a motor controller board for a ceiling fan maker, shipped with a short six-way wiring harness that connects the board to the motor and the regulator. The board has surface-mount parts on the top side and a few through-hole parts (a relay, a terminal block, two electrolytic capacitors). A plant that builds only boards, or only harnesses, will skip some steps, but the sequence of records is the same.

At each stage the useful question is not only what happens, but what record it leaves. Those records are what the customer asks for when a field failure comes back.

The process at a glance

1. 1Customer orderPart number, revision, quantity and delivery date for the board and harness set.
2. 2BOM and routingThe released BOM revision, alternates and routing are fixed on the work order.
3. 3Material planningEvery BOM line is checked against stock by lot and open purchase orders.
4. 4ProcurementReels, PCBs, wire and terminals are received by supplier lot and inspected.
5. 5Kitting and production orderThe order is released to its work centres and the kit is issued by lot.
6. 6SMT and THT assemblyPaste print, placement, reflow and AOI, then through-hole insertion and soldering.
7. 7Harness cutting and crimpingWire cut and stripped, terminals crimped, crimp height checked, housings loaded.
8. 8In-process inspection and testBoard functional test and harness continuity test, by unit or by batch.
9. 9Final QCThe board and harness set is checked and released, reworked or rejected.
10. 10Finished goodsReleased lots are received into stock against the order.
11. 11DispatchPicked by lot against the order and shipped with a delivery note.

What happens at each stage, and what it records

1. Customer order

The fan maker orders a quantity of controller sets for a delivery date, against its own part number and drawing revision. The record holds the part number and revision, quantity, due date and the customer's order reference, so a later change can be compared with what was first agreed.

2. BOM and routing

The board BOM has a little over a hundred lines: the bare PCB, resistors, capacitors, the microcontroller, a triac, the relay, the terminal block and solder paste. The harness is a sub-assembly with its own BOM: wire by gauge and colour, terminals, a housing and sleeving. The routing lists paste print, placement, reflow, AOI, through-hole insertion, wave or hand soldering, functional test, then cutting, crimping, housing insertion and continuity test for the harness. The revision released to the order is fixed on it, so an ECN next month does not change what this batch was built to. The guide to multi-level BOM management covers the structure.

3. Material planning

Requirements for every line are compared with stock by lot, other orders' allocations, part reels returned from the line and open purchase orders. The placement machine loses some parts during picking, so planners usually add an attrition allowance on small passives. A useful shortage report names the line and the order it will stop, so purchase chases the part that actually holds the kit, not the one that is easiest to order.

4. Procurement and incoming inspection

Reels arrive with the manufacturer's part number, lot or date code on the label. PCBs arrive by supplier lot, wire by spool and terminals by reel. Incoming inspection checks the part number against the approved list, samples where the plan requires, and holds a failed lot. Moisture-sensitive parts such as the microcontroller arrive in sealed bags, and many plants log when a bag is opened and how much floor life remains under their MSL procedure. The record holds the supplier, the lot, the quantity and the inspection result.

5. Kitting and production order release

The order is placed on the SMT line, the through-hole and soldering stations, the test bench and the harness section according to their capacity. Stores pulls the kit and issues each line to the order by lot. From this point every count, test and rework on the order is linked to the component lots inside it. If an approved alternate is used for a short line, the issue records which part went in.

6. SMT and through-hole assembly

Solder paste is printed through a stencil, components are placed, the board passes through the reflow oven and then AOI. After a changeover, the first board is checked against the BOM and drawing before the batch runs. Through-hole parts are then inserted and soldered on a wave, a selective solder machine or by hand. Operators record good boards, rejects with a reason (bridge, missing part, tombstone, wrong polarity) and downtime with a cause, against the operation. AOI calls that turn out to be real faults go to the rework bench, and the board comes back for re-inspection.

7. Harness cutting and crimping

Wire is cut to length and stripped, and terminals are crimped on. At each setup, and at the interval the plan sets, the crimp height is measured against the specification for that terminal and wire gauge, and many plants add a pull test. A crimp out of tolerance holds the batch until quality decides. Crimped leads are loaded into the housing, sleeved and tied on the harness board. The record holds the wire and terminal lots, the counts per station and the crimp readings.

8. In-process inspection and test

Each board goes through functional test: power up, check the speed steps, check the relay switches. Each harness goes through continuity test on a fixture. Results are recorded per unit or per batch, as the test plan requires, with the operator and time. A failed board goes to rework with the fault recorded, and is tested again against the same batch. Catching faults at this stage keeps them out of the set. The article on reducing rejection by inspecting at the operation explains why the stage matters.

9. Final QC and release

Board and harness are put together as a set, and final QC checks a sample against the customer's requirements: visual workmanship, connector fit, labelling. QC records the disposition: release, rework, use as is, or reject, with a name on it. A held lot cannot move to finished goods.

10. Finished goods

Released sets are received into finished goods by lot, against the order. The store shows what is released, what is on hold and what is available against each open order. Sets that are counted but not received by lot are where the trace most often breaks.

11. Packing and dispatch

Lots are picked against the order, packed in ESD-safe packing where the customer requires it, and shipped with a delivery note and invoice. The record shows which lots went on which delivery, which is where any complaint will start.

What to record and control at each stage

Where the process usually breaks

• At kitting, when a short line is discovered only as the kit is pulled.
• At an ECN, when the floor builds to the new revision but the order still shows the old one, or the other way round.
• At the line, when reels move between jobs and the link from component lot to batch is lost.
• At test, when results stay on the tester and never reach the batch.
• At the rework bench, when boards are fixed and passed without the fault or the re-test being recorded.
• At set assembly, when the harness lot is not recorded against the finished set.

How is one lot traced back from dispatch?

Say the fan maker reports controllers failing in the field from one delivery. The trace runs backwards: delivery note to finished lot, finished lot to the board and harness lots inside it, each lot to its operations, operators, test results and rework, and from there to the component lots (the microcontroller reel, the relay lot, the terminal reel) and their suppliers. Forward from a suspect component lot, the same chain shows every other batch and delivery it went into. When every stage left its record on the lot, this is a lookup. When the records are in separate files, it is an investigation.

How FleekERP records each stage

In FleekERP each stage is a step on the work order. The BOM revision is fixed at release, and production planning places the order on work centres against capacity and material readiness. Stores receives and issues by lot, operators record counts, rejects and downtime from their phones, crimp height is recorded at the crimping operation, and QC records test results per unit or per batch with a hold on failure. Coating or overflow SMT can sit on the routing as a vendor operation with its challan, and dispatch picks by lot. Units are tracked by lot, with serial-level genealogy configured per product where it is needed. The electronics industry page shows the same flow from the plant's point of view.

How the process differs by plant type

• Contract PCB assembly: many customers' BOMs on the same lines, frequent changeovers, and often components supplied by the customer, which have to be kept apart from the plant's own stock.
• Own-product electronics: fewer BOMs but deeper ones, with box build and final functional test after board assembly.
• Wiring harness plants: wire and terminal lots, cutting and crimping as the high-volume steps, crimp checks at every setup and continuity test on fixtures.
• Cable assemblies and small batches: many short orders, so setup and changeover time matter more than run rate.