Free Trials

Download a free trial to find out which Altium software best suits your needs

How to Buy

Contact your local sales office to get started on improving your design environment


Download the latest in PCB design and EDA software

  • Altium Designer

    Complete Environment for Schematic + Layout

  • CircuitStudio

    Entry Level, Professional PCB Design Tool

  • CircuitMaker

    Community Based PCB Design Tool


    Agile PCB Design For Teams

  • Altium 365

    Connecting PCB Design to the Manufacturing Floor

  • Altium Concord Pro

    Complete Solution for Library Management

  • Octopart

    Extensive, Easy-to-Use Component Database

  • PDN Analyzer

    Natural and Effortless Power Distribution Network Analysis

  • See All Extensions

    World-Renowned Technology for Embedded Systems Development

  • Live Courses

    Learn best practices with instructional training available worldwide

  • On-Demand Courses

    Gain comprehensive knowledge without leaving your home or office

  • Altium 365 Viewer

    View & Share electronic designs in your browser

  • Altium Designer 20

    The most powerful, modern and easy-to-use PCB design tool for professional use


    Annual PCB Design Summit

    • Forum

      Where Altium users and enthusiasts can interact with each other

    • Blog

      Our blog about things that interest us and hopefully you too

    • Ideas

      Submit ideas and vote for new features you want in Altium tools

    • Bug Crunch

      Help make the software better by submitting bugs and voting on what's important

    • Wall

      A stream of events on AltiumLive you follow by participating in or subscribing to

    • Beta Program

      Information about participating in our Beta program and getting early access to Altium tools

    All Resources

    Explore the latest content from blog posts to social media and technical white papers gathered together for your convenience


    Take a look at what download options are available to best suit your needs

    How to Buy

    Contact your local sales office to get started improving your design environment

    • Documentation

      The documentation area is where you can find extensive, versioned information about our software online, for free.

    • Training & Events

      View the schedule and register for training events all around the world and online

    • Design Content

      Browse our vast library of free design content including components, templates and reference designs

    • Webinars

      Attend a live webinar online or get instant access to our on demand series of webinars

    • Support

      Get your questions answered with our variety of direct support and self-service options

    • Technical Papers

      Stay up to date with the latest technology and industry trends with our complete collection of technical white papers.

    • Video Library

      Quick and to-the-point video tutorials to get you started with Altium Designer

    Paint by Numbers: Solder Paste Stencil Design Guidelines To Reduce Shortages

    December 6, 2017

    Completing a paint by numbers

    I’ve never had much artistic talent, but when I was a kid I loved those paint-by-numbers kits. Up until I saw those I’d only used watercolors, but I was enthralled with the thick, slow flow of the paint. I may also have killed some brain cells from breathing all the fumes. I was completely obsessed with keeping the paint in the lines, so I didn’t use the brush they gave you. Instead, I traced the outlines with a toothpick that had barely been dipped into the paint, then dipped the toothpick again and dripped paint into the outlines, relying on surface tension to distribute the paint evenly.

    Although that level of neuroticism can improve your PCB design, it's probably not healthy to apply in all areas of your life. Try and limit it to one or two places, like getting a totally perfect Printed Board stencil for your solder paste application.

    Solder paste is a cause of shorting in PCBs since the paste covers a large amount of your board surface and bridges can form easily. However, the solder paste itself is rarely the root cause of the shorting issues. At each stage of manufacturing, there are opportunities for defects to be introduced: starting with the stencil, during the solder paste application, or during reflow.

    Solder Paste Stencil Design Guidelines for Clean PCB Layouts

    Often, issues with your stencil will cause problems with the application of the solder paste. The stencil is a mask usually made from metal but sometimes out of Kapton (polyimide) for prototypes or low quantity runs. The stencil marks out where solder paste should be applied to the surface and is reused. It designates where solder paste should be applied to the surface like a spray paint stencil. No matter what it's made of, the stencil is reused as long as possible. That might be less than five times for polyimide or thousands of times for a metal stencil.

    Gloved hand applying spray paint over a stencil.
    A stencil for solder paste is like a stencil for spray paint, marking out where you want your material applied.

    Even a Solder Paste Stencil Is Subject to Solder Shortage Problems

    While it is tempting to think that with a solder paste stencil, you do not need to worry about potential problems or interferences, that is not always the case. Here are two primary ways in which your board may encounter problems, despite using a stencil:

    • Uneven solder paste: Pads that have too much solder paste applied are, unsurprisingly, more prone to forming solder bridges between neighboring pads. If too much paste is being applied consistently, either across a board or between different boards, you should consider decreasing the stencil aperture dimensions or the stencil thickness in your design.

    • Stencil resolution: Another stencil issue is having poor resolution or jagged edges. If the edges of the stencil aren’t clean, you’re more likely to have too much solder applied, uneven application, or a lack of definition around the edge of the joint. All of these situations are an open invitation to solder bridges shorting your pads together.

    Stencils Aren’t All to Blame for Your PCB Design Going from Painting to Palette

    Like working with paint, you can end up with heat exchanger solder paste in locations where you don't want it. The finished product is also affected by how the materials are handled after their application, though. Like paint cracking when it dries too fast, solder reflow temperatures have to be just right for a proper outcome.

    • Smearing: A less issue is a solder paste application that smears or slumps on the surface of the board. If you have a smear, you’ll lose clean edges no matter how sharp your stencil. Part of smearing is getting solder applied in unwanted areas. Sometimes this isn’t a major problem—just weakening the joint—but it is easy for the solder to form a short too. 

    • Reflow: If the temperature profile you use for solder reflow isn’t correct, the solder paste may not be adequately melted when you need it to bond to components. Initial temperature ramp rates are particularly troublesome. Too hot and too fast and your solder paste may flow away from designated pads.

    PCB entering reflow oven.
    Make sure to optimize your equipment to the exact specifications to avoid damages of excess. 

    Don’t Be Short-Sighted with Your Selective Soldering

    The best way to fix solder paste shorts is to verify stencil quality and reflow recipes with manufacturers early in production. This avoids the reworking of surface areas after excess solder is used and removes the potential for unnecessarily damaging and weakening the surface or neighboring joints. It is possible to heat and remove extra solder, but it isn’t recommended as that, too, may damage nearby surfaces and joints.

    When you design your Printed Board, the stencil is one of the layers in your Gerber file. You should choose a PCB design software that allows you the best control over your design. Look into better control of your designs with CircuitStudio® , and by talking to an expert at Altium.

    Check out Altium in action...

    Powerful PCB Design

    most recent articles

    Back to Home