Solder paste printer

01

Check stencil apertures before choosing settings

An Elektor article on stencil design explains that paste must release from the aperture walls as the stencil lifts, which depends on two ratios: area ratio, the aperture opening area divided by the area of its walls, and aspect ratio, aperture width divided by stencil thickness. Citing IPC-7525, it recommends an area ratio of 0.66 and an aspect ratio of 1.5, and notes stepped stencils of varying thickness for boards mixing BGAs, QFPs and small chips. [1]

Editorial calculation: for a round aperture of diameter D in a stencil of thickness T, area ÷ wall area = (πD²/4) ÷ (πDT) = D ÷ 4T. A 0.25 mm aperture gives 0.25 ÷ (4 × 0.10) ≈ 0.63 in a 0.10 mm stencil, below 0.66, and 0.25 ÷ (4 × 0.08) ≈ 0.78 in a 0.08 mm stencil. [1]

Indium's data sheet for a lead-free paste adds aperture guidance: reduce discrete-component apertures by 10–20% to cut mid-chip solder beads, reduce fine-pitch apertures at 20 mil pitch and finer by an amount it calls process-dependent (“5–15% is common”), and prefer electroformed or laser-cut and electropolished stencils. [2]

Give the supplier the board sizes, thickness and warpage, panel and fiducial layout, stencil frame size, smallest aperture and stencil thickness, paste type, required accuracy, cycle time, line direction and conveyor height.

02

Set squeegee, speed and machine accuracy

The Indium paste data sheet recommends a paste bead of about 20–25 mm diameter, 25–150 mm/s print speed, squeegee pressure of 0.018–0.027 kg per mm of blade, metal blades at about 60°, separation speed of 5–20 mm/s, an under-stencil wipe starting once every 5 prints, and stencil life above 8 hours at 30–60% RH and 22–28 °C. [2]

Editorial calculation: with a 300 mm blade, 0.018–0.027 kg/mm × 300 mm ≈ 5.4–8.1 kg of squeegee load. NeoDen's ND450 lists 0.5–10 kg printing pressure and 200–450 mm blades, so that window fits within its range. [2] [3]

Machine figures are stated by makers: NeoDen's ND450 lists ±0.025 mm printing accuracy and repeatability, 1–100 mm/s printing speed, 0.1–30 mm/s separation speed, 12–18 s cycle time, PCBs from 50 × 50 mm to 450 × 350 mm and 0.4–4 mm thick, 0.6–0.7 MPa air and 350 kg; HTGD quotes ±25 µm at 6σ with Cpk ≥ 2.0 for an automatic printer. [3] [4] Ask how accuracy is measured.

03

Manual, semi-automatic and in-line automatic printers

NeoDen and HTGD list manual, semi-automatic and fully automatic solder paste printers, some sold within complete SMT lines. [3] [4]

NeoDen lists automatic printers within full SMT lines; HTGD lists automatic vision printers and SPI; iTech lists frameless and fully automatic printers; Hayawin lists manual, semi-automatic and fully automatic printers; Mingrui, GS-SMT, CNSMT, Moje and I.C.T list printers alongside pick-and-place machines and reflow ovens. [3] [4]

04

Vision, squeegee head, clamps, board support, cleaner and conveyor

Each row names what to fix in the order for that part; frame size, board thickness and conveyor direction come from your line.

05

Board size, speed, accuracy and room conditions for the quotation

Board, stencil and line data come from your process. Where NeoDen, HTGD or the Indium paste sheet publishes a value, it is shown as an example in the middle column.

06

Send the board, stencil and line data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Boards: [size range; thickness; warpage; panel; fiducials]
Stencil: [frame size; thickness; smallest aperture; stepped or not]
Paste: [type; maker's print window]
Accuracy: [alignment and repeatability; test method]
Line: [cycle time; conveyor direction and height; SPI link]
Cleaning: [dry, wet, vacuum wipe]
Utilities: [power; air]

See manufacturer records Send an enquiry through CNFX