Why Stainless Steel (Still) Rules Solder Paste Stencils
OSH expands production to include stainless steel stencils.
After working almost exclusively with polyimide solder paste stencils, OSH is expanding to manufacture stainless steel stencils. Here's a glance at why.
With the growing number of SMDs (surface mount devices) and the decline in the availability of through-hole parts, more and more electronic hobbyists, designers, and inventors are using surface mount components.
As the name implies, SMDs are soldered directly to the surface of printed circuit boards with no mounting holes and, while they can be soldered by hand, a better technique requires accurate placement of solder paste to the pads, parts placement, and subsequent reflow soldering in an oven.
Currently, the best way to accurately dispense solder paste is through the use of a stencil, and OSH Stencils pioneered the production of polyimide stencils that are economical enough for low-volume production. For more information about using stencils for PCB construction, see this article.
Although polyimide stencils are great for many projects, they do have a lifespan of a few dozen uses, and they can easily be damaged by careless handling. The gold standard for solder paste stencils is actually a "steel" standard — stainless steel, that is. They are more durable and more precise than polyimide, but the price has put them out of the reach of hobbyists and other low-volume users until now.
OSH Stencils has just added a stainless steel line to their product offerings.
A small .004" thick stainless steel stencil with precision laser-cut apertures.
For a closer look at how polyimide and stainless steel stencils compare, check out this write-up (PDF).
Inside the Stencil-Making Process
Brent, founder and owner of OSH Stencils, says, "We've always been driven to maintain the highest quality product, for the lowest possible price, and to fulfill orders in 24 hours or less. This expansion follows that same philosophy we used for polyimide and enables us to bring the same customer expectations and experience to the stainless steel market."
To that end, OSH has invested in state-of-the-art equipment as typified by their new LPKF G 6080 laser cutter shown below. The entire unit is on the left and a closeup of the cutting deck is on the right.
Although it's not obvious in the photos, the G 6080 is a beast, weighing in at over 4,400 pounds. It is the standard by which all stencil lasers are judged, and is a heavyweight in performance as well as size. The G 6080 is capable of cutting 51,200 apertures per hour in materials up to 1 millimeter thick. Its laser repetition rate is up to 45 kHz with axial precision and repeatability of +/- 2 µm. Its right-angle precision is 4 angular seconds, and it can make cuts as small as 0.00078 inches.
Despite strides made in polyimide stencils, despite their popularity and affordability, stainless steel stencils remain highly sought after. OSH's choice to expand its offerings and manufacturing operations is a testament to stainless steel's ubiquitous appeal.