Solder-paste printing, pick-and-place, reflow, AOI, ICT, the five-station SMT line is the backbone of every modern LED fixture. What each station does, and what the inspection report should show.
Four ideas to carry into the next specification conversation you have.
Components sit on the PCB surface, not through holes. Faster, denser, automatable, and unforgiving of paste defects.
Industry data: ~64% of SMT failures start at the stencil. Volume, alignment, and shape of the deposit decide the joint.
Preheat → soak → reflow peak → cooldown. The curve is tuned to the paste alloy (SAC305 ≈ 245 °C peak). Wrong curve = cold joints or chip damage.
Automated Optical Inspection scans every board at high resolution. Missing parts, tombstones, solder bridges, flagged before the board ever ships.
Cycle time per station typical for fine-pitch LED boards. Your numbers depend on board size and pick count.
| Station | What happens | Typical QA gate |
|---|---|---|
| Solder paste print | Stencil deposits paste pads | SPI volume ±10% |
| Pick & place | Robot places resistors, LEDs, ICs | Vision: rotation < 5° |
| Reflow oven | Heat profile melts paste, forms joints | Thermocouple log on every batch |
| AOI | Camera inspects every joint | Zero criticals, ≤ 50 ppm minor |
| ICT / Flying probe | Electrical test of net continuity | 100% test or AQL 0.65 |
| Functional test | Power on, measure light output | Lumen ±5%, CCT ±100 K |
Specification figures are only worth as much as their source. Here is the document behind each number on this page, and an honest label where no published document sets it.
SAC305 (Sn96.5 / Ag3.0 / Cu0.5) has a liquidus near 217 to 220 °C under J-STD-006. Standard practice is a peak 20 to 30 °C above liquidus, and J-STD-020 classifies lead-free components for peaks in the 235 to 260 °C band by package size and thickness. 245 °C sits mid-band. IPC-7530 covers how the profile is developed and logged.
IPC-7527 governs solder paste printing, but it does not publish a single ±10% figure. Acceptance windows are set per assembly and are commonly far wider, on the order of 50 to 150% of nominal aperture volume. ±10% is a tighter in-house control limit, not a published limit. Read it as the target the process is aimed at, not a clause you can cite back to us.
IPC-A-610 does govern component rotation, but it expresses acceptance as side and end overhang measured against land and lead width, not as an angle. IPC-9850 is how placement machines characterise and report accuracy, typically to fractions of a degree at 3 sigma. Under 5° is a shop-floor reject screen restated in plain language, not a clause you will find in either document.
IPC-7095 sets void-area criteria for ball grid arrays measured on an X-ray projection, and 25% by area is the widely applied accept limit, with larger voids pushing a joint into evaluate-or-reject. IPC-A-610 carries the matching workmanship acceptance class.
LM-79 is the measurement method for flux, chromaticity and CCT, not a tolerance. ANSI C78.377 defines the chromaticity bins a product is sold against, and those bins are considerably wider than ±100 K. Published flux tolerance practice sits nearer ±10% of rated. ±5% and ±100 K are internal line targets, deliberately tighter than the published bins.
Every document referenced anywhere on this page, with the issuing body and what it actually governs here. Nothing on this page cites a standard it does not use.
Standards register last reviewed 10 August 2026. Standard titles are given as published by IPC, JEDEC, IES, ANSI and ISO; refer to the current revision of each document for exact clauses.
Five differences that explain price gaps between LED boards.
A pre-reflow SPI station scans every printed pad in 3D. Volume, height, area, alignment, out-of-spec deposits are flagged and the board reprinted. Without SPI, defects only appear at AOI, where rework is 5-10× more expensive.
Nitrogen-atmosphere reflow displaces oxygen during melt. Solder joints come out brighter, with less oxidation, fewer voids in the joint. Mandatory for high-reliability LED applications (transit, marine, medical).
Ball-grid arrays and high-current MOSFETs have joints under the body, invisible to AOI. X-ray inspection looks through the part to verify void content < 25% and joint geometry. We use this on every driver board.
LEDs and ICs ship in moisture-barrier bags with humidity indicators. Once opened, the floor-life clock runs. Premium lines store opened reels in dry cabinets at < 5% RH. Cheap lines do not, and the LEDs pop during reflow.
A modern SMT line records reel ID, operator, machine, reflow profile and AOI image for every board. Years later, a field failure can be traced to a single lot of capacitors. Insist on traceability in your contract.
Our SMT line in Dammam runs SPI, nitrogen reflow, full AOI and 100% functional test on every fixture leaving the plant.
A 10-slide explainer, ready to post straight to LinkedIn as an image carousel. Same content, faster reading.
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