Types of Solder Stencils: Laser-Cut, Electroformed and Etched

I had covered a lot of stencils in the past, they are awesome tools for an electronics designer. At this point everyone knows they are a simple thin piece of steel which acts as a mask for soldering paste. Once applied we can put the components and heat them. And we have our PCB ready! Too simple. Although there are some steps which we have to look into such as soldering paste thermal profile and heating process of the PCB. If heated in the wrong way components can also be damaged. Today we are not going to talk about any design procedure but about stencil manufacturing. There are a lot of manufacturing companies making different types of stencils. The three most common types of solder stencils are:

1. Laser-Cut Stencils

2. Electroformed Stencils

3. Chemically Etched Stencils

Based on the difference we will make a choice which one is good to go for a particular use.

1. Laser-Cut Solder Stencils

Laser-cut stencils are made by using high-precision lasers (usually Nd : YAG or fiber lasers) to cut apertures into a stainless steel foil. The laser is confined and still gives a surface abnormality at micron level. It gives a rough surface cutting by eyes we can not tell so, but there is limited tapering of walls.  But lasers are the fastest technology available and most used because of its fast turnaround times. Depending upon the wavelength and diameter lasers can go down to 0.3 mm or less. And modern stencils like step-up and step down can also be manufactured. After the laser cutting stencil can be dipped into a nanocoating which helps to smoothen the surface more effectively and remove the adhesion property. If you are just seeking a fast prototyping solution,JLCPCB specializes in laser-cut stencils, providing high-precision, customizable options for prototyping and production, ensuring reliable solder paste printing and fast turnaround times.

2. Electroformed Solder Stencils

Electroformed stencils are produced via electroplating. But these stencils have superior paste release due to smoother and more tapered sidewalls.  A photoresist pattern is applied to a metal (usually nickel) that is deposited through electrochemical growth to form the stencil. They are used for fine pitch and have greater durability. They have consistent aperture wall thickness due to smoother surfaces. By the way, these stencils have higher lead times and are very less common for prototyping due to their prices. Due to their smoothness and accuracy they are used for ultra fine pitch 0.2 mm or smaller.

3. Chemically Etched Solder Stencils

A chemical etching process uses a photoresist and acid or alkaline solution. By removing metal and creating aperture patterns. No need for electric currents and high power lasers, but chemicals also have a limit to etch after that they need to be replaced. Yet they are inexpensive and we have a standard procedure to follow. They are good for low density and large components. This cheap thing comes with a bigger cost of poor edge definition and rough surfaces. Etching causes undercutting and sloped sidewalls which are abnormal in stencil manufacturing. This will cause poor paste release when small apertures come into play. They can be used for hobby purposes.

Performance Comparison:

Selecting the right stencil depends on:

• Pitch size of components
• Volume of production
• Cost constraints
• Complexity of the design
• Paste release needs

Here is a detailed table discussing all these factors.

Conclusion

The performance of your PCB assembly process is closely tied to the type of stencil you select. I covered a detailed description of all the techniques with the problems related to them.

Like the laser-cut stencils offer a reliable, well-rounded solution and suitable for most standard applications. Electroformed stencils provide exceptional precision and paste release, but at a higher cost. On the other hand, chemically etched stencils remain a cost-effective choice for less demanding requirements. Understanding the properties and limitations of each stencil type allows you to select the best solution for your specific PCB design and production needs. If you are seeking laser-cut stencils, JLCPCB is the best choice. JLCPCB focuses on high-quality laser-cut stencils with optional electropolishing and nano-coating, helping engineers achieve consistent solder paste printing and higher assembly yield.