What SMT assembly is
Surface-mount technology (SMT) mounts components directly onto pads on the board surface rather than through drilled holes. It allows small parts — 0402 resistors, QFN and BGA packages — and dense layouts on both sides of a board. Nearly every component on a modern PCB is surface-mount.
The three SMT steps
1. Solder-paste stencil
A stainless stencil cut from your board's paste layer deposits a measured amount of solder paste on every pad. Paste volume decides joint quality, which is why we ask for Gerbers with paste layers. We make the stencil, or use one you supply; double-sided boards need one per side.
2. Pick-and-place
Our NeoDen N9 (53 feeder slots) and YY1 (45 feeder slots) pick parts from reels, trays and cut tape and place them using your centroid file. Each unique BOM line occupies a feeder, so the number of unique parts affects setup time as much as the total part count.
3. Reflow and inspection
The populated board passes through a reflow profile that melts the paste into solder joints. Boards are then inspected; through-hole parts follow by hand.
Part types and pricing
| Part type | Examples | Quoted as |
|---|---|---|
| Standard SMT | Passives, SOT-23, SOIC, LEDs | Per placed part |
| Fine-pitch | QFN, TQFP, fine-pitch connectors | Per part, higher rate |
| BGA | Ball-grid-array ICs | Per part |
| Through-hole | Headers, terminals, large capacitors | Per pin, hand soldered |
Setup, stencil and feeder loading are a one-time cost per batch. Current rates are published on the instant quote page.
Files for SMT assembly
- Gerbers including the top and bottom paste layers
- BOM: designator, value, footprint, MPN, quantity
- Pick-and-place / centroid file (.csv, .pos or .txt)
- Optional: an assembly drawing PDF showing polarity and orientation
Not sure your files are complete? Send what you have; we check them before quoting. See also PCB assembly and PCB design.
Frequently asked questions
What is the difference between SMT and through-hole assembly?
SMT parts sit on pads on the board surface and are reflow soldered; through-hole parts have leads inserted through drilled holes and are soldered separately. CktHub does both.
Which pick-and-place machines does CktHub use?
A NeoDen N9 with 53 feeder slots and a NeoDen YY1 with 45 feeder slots, in Pune.
Can you assemble components on both sides of a PCB?
Yes. Double-sided boards are assembled in two passes, with a stencil for each side.
Do you assemble BGA and fine-pitch parts?
Yes. Fine-pitch and BGA parts are quoted per part.