Stencils and Masks

This page provides design advice and technical information, useful when designing stencils or masks.

• Most cost effective process
• Fast turnaround
• Pricing not determined by amount of detail
• No burrs
• Stress free
• Flat parts
• Complex detail 
• Cheap tooling
• Consistent reproduction

Chemically etched stencils are the workhorses of the stencil world. They are the most cost effective and offer a fast turnaround. Most notably manufactured from stainless steel, they are manufactured by coating the metal foil with resist, exposing an image onto both sides with a pin-registered phototool and then etching the foil from both sides simultaneously using a dual sided process. Since the process is dual sided, the apertures, or openings, are created as the etchant works through the metal not only from the top and bottom but also horizontally.

Pricing is driven by the size of the metal foil. The amount of apertures and holes does not impact the price at all, as all detail is etched simultaneously. Whereas laser-cutting, the alternative method of manufacture is priced according to the number of apertures and holes – the more there are, the more costly it is.

The graphic tooling charge is typically £95. This is a one off cost, subject to the artwork remaining unchanged. The photo-tool will reproduce exactly the same parts every time. Chemical milling is renowned for being a stress free method of manufacture, producing flat parts that are burr free. 

Features

Metal 

We hold a wide range of sheet metal; types and thicknesses in stock. Typically, we hold .025mm thick to 1.5mm thick metal. We stock many types of metal, the most popular ones are stainless steel, mild steel, carbon steel, brass, copper, phos bronze and aluminium.

Aspect Ratio

One point to bear in mind is the aspect ratio. In simple terms, the ratio limits the smallest aperture opening that can be etched, in terms of the metal thickness at hand. Typically, for chemically etched parts, the aspect ratio is defined as 1 to 1. However, the minimum detail currently achievable, with consistency is .1mm, even in metal that is thinner than .1mm in thickness.

Trapezoidal Definition (surface mount stencils)

Apertures can be produced with trapezoidal definition. This is where the squeegee side opening is slightly smaller than the required size on the release side. Therefore, wall shape is similar to an upturned bucket, thereby promoting improved paste release.

Pricing

Perhaps one of the most important features of using chemical milling as a process of manufacture, is that the number of holes and apertures, or amount of detail does not impact the price. All detail is manufactured simultaneously. Price is determined largely by the size of the part and the thickness of the metal.

Tolerances

We manufacture to a minimum working tolerance of + and – 10% of metal thickness or + and - .025mm, whichever is greater. Therefore in .25mm thick metal, the tolerance would be + and - .025mm. Positional tolerances are fixed at + and - .025mm.

Half Etch Detail

It is possible to create half etched fiducials and title block nomenclature. 

Fiducials – for alignment by printers with vision systems, can be half etched and infilled with a black-epoxy paint. This provides an instantly recognisable contrast for the vision system to locate against a glossy metal background. 

Title blocks containing part numbers, creations dates and other relevant information, can also be half etched into the parts for identification purposes. 

Plating

Evaporation masks become be-spattered with whatever material is being deposited. Cleaning the masks to remove this residue will wear the mask over time, rendering it useless. By plating Evaporation masks in either Gold or Rhodium, we can extend the life span of the masks. Both gold and Rhodium can withstand the acids used in post-deposition cleaning and therefore protect the substrate metal. Studies show that by using this method, the masks can withstand the cleaning process for up to 10 times longer than traditional masks.

To find out more about the Photo Etching Process please either contact us on 01480 226699, or take “The Process Tour” on our website