Understanding SMT Stencils and Squeegee Blades

One of the most common ways to apply solder paste to an SMT stencil printer is with a squeegee blade. In this article, we’re going to look at how to use a squeegee blade properly to do this.

The other common way to apply solder paste to an SMT stencil printer is with enclosed head printing. Both are viable options, but we often find that the squeegee blade is the best option for most people. So if you want to know a bit more about squeegee blades, you’re in the right place.

With squeegee blade printing, you’ll be able to control parameters effectively—things like blade angle and downward pressure can be easily adjusted, making it a versatile way to use SMT stencil printers.

But for this, you will need the right type of squeegee blades, and high quality ones if possible. Your blades must be flexible enough to consistently deliver the right volume of paste for printing works.

Different types of squeegee blades

There are basically two main types of squeegee blades: metal squeegees and rubber squeegees. Rubber squeegees can also be referred to as polyurethane squeegees.

Metal squeegees

If you’re operating your SMT stencil printer at lower pressures, metal squeegee blades are often the best option as opposed to rubber squeegees. Metal squeegees don’t scoop paste from apertures and don’t wear out as easily as rubber variants, but they do have some limitations for certain printing jobs.

Another benefit of metal squeegees is that they don’t need sharpening like rubber ones do. Metal squeegees have become more popular in recent years as components have become higher quality.

There are a range of different metal squeegee blade thicknesses available. These are most commonly made from stainless steel. One of the most popular standard sizes for a metal squeegee is 0.150mm and is made with a single thickness edge.

These can be made with a recessed edge with a base of 0.300mm and tapered down to an edge of 0.150mm.

Many metal squeegee blades are single thickness and are manufactured with a laser cutting process for extra precision. These are ideal for jobs that have a mix of components and give a wide pressure window as well as robust sturdiness and minimal degradation in quality.

You can also get mobile edge metal squeegee blades, which can be more adaptable than single thickness blades and an adjustable profile without reducing on the quality of the print. They can also help create a cleaner finished print.

Printing with squeegee blades

To print well with squeegee blades you need to be aware of the angle, speed and pressure of the blade and printer setup. You need enough downward force to properly travel across the stencil and make sure paste is applied properly.

The speed is also important to properly print to the desired outcome, as well as the pressure. Different printing jobs will have different requirements for these parameters, but there are some general guidelines you might want to follow, like a pressure of 0.5-1kg per 50mm and a speed of around 25 mm per second.

Keeping your squeegee blades in good condition

Keeping your squeegee blades in good condition is important, and they always need to be maintained properly to sustain good function. Any damage to your squeegee blades can inhibit performance and lead to poor quality prints.

This means that you should check all blades thoroughly before and after use, you can use an automated cleaning system if necessary. Make sure you address any issues as soon as possible, which is why checks after a print are important (rather than before use). Solder paste and residue should be removed thoroughly. A reliable and repeatable process is important, so any damaged blades should be fixed as soon as possible.

Consulting the manufacturer of your squeegee blades could also be a good idea, so you have a general estimation of how long the blades are expected to last and stay in good condition.

When using stainless steel squeegee blades, you must be even more careful when handling. Any type of squeegee blade should be inspected thoroughly even when new and made sure they are in good shape before installing. Flaws you might want to keep a lookout for include dents and nicks.

If you operate stencil printers, you should stop any process that is not printing properly or wiping correctly. These issues could be an indication that the printer is not set up properly and could lead to more damage to components. Test prints can be useful to help spot issues as well, and a proper print should produce a smooth surface without puddles or streaks.

Keeping your components in good working order at all times is important, but so is making sure you’ve got high quality squeegee blades from the best manufacturers. This will help ensure better quality prints and make sure your tools last longer.

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