Free Trials

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

Altium Online Store

Buy any Altium Products with few clicks or send us your quote to contact our sales


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

    Altium Online Store

    Buy any Altium Products with few clicks or send us your quote to contact our sales


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

    • 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

    Flexible Circuit Base Materials

    Tara Dunn
    |  March 4, 2019

    Question:  As someone new to designing with flex materials, what is important to understand about the base materials?

    For people new to calling out flex materials, it can be a little intimidating. Just like their rigid material counterparts, there are so many options to choose from, it can be mind-boggling. But, also just like their rigid material counterparts, once you learn the “basics”, most designs will fit within common parameters. Once those basics are understood, the special circumstances can more easily be handled.     

    For this blog post, I will talk about flex-only constructions to help narrow the focus and we can dive into rigid flex material considerations in a future blog post.  Although there are many flexible materials, let’s start with the most common: laminate constructions with copper and polyimide. 

    There are two primary constructions for flex base materials, adhesive based and adhesiveless.  Both are typically supplied with a layer of rolled-annealed copper and a layer polyimide. Adhesive-based materials can be spec’d with either standard acrylic adhesive, or flame retardant acrylic adhesive, depending on the end application requirements.  

    First, what is the difference between rolled annealed copper and electrodeposited copper?

    Rigid materials are typically manufactured with electrodeposited (ED) copper. ED copper is formed by electrolytic deposition onto a slowly rotating polished drum from a copper-sulfate solution. When an electric field is applied, copper is deposited on the drum as it rotates at a very slow pace; the slower the pace, the thicker the copper. The side against the drum provides the smoother finish.                                               

    Flexible laminates are typically constructed with rolled annealed copper. Rolled annealed (RA) copper foils are created by successively passing an ingot of solid copper through a rolling mill, and then applying high temperature to anneal the copper. RA copper foil has higher ductility and elongation than ED copper which is why it is best for bending applications. 

    When would you select adhesiveless materials instead of adhesive-based materials?

    Adhesive based materials are the workhorse of flexible circuit materials, especially for flex-only applications. They have been used for decades and are most commonly used in single and double sided designs. These materials are typically lower cost than adhesiveless materials, and doesn’t that seem crazy? There is more material involved, but it is less expensive?  

    A typical adhesive based laminate will be constructed with a layer of copper, a layer of 1 mil adhesive, a layer of polyimide, another layer of adhesive, and a second layer of copper.  

    Adhesiveless material, as you would expect, eliminates the adhesive layers and typically reduces that double sided laminate by 2 mils. 

     Adhesiveless materials are most commonly spec’d when the design is a higher layer count flex or a rigid flex construction. In both cases, adhesiveless material is recommended for quality and reliability reasons. The z-axis expansion rate of the acrylic adhesive is a concern for plated through hole integrity. In higher layer count, flex-only applications, there is also a material thickness concern. Eliminating 1 mil of adhesive thickness per copper layer can significantly decrease overall thickness and increase flexibility in the final product.     

    What material constructions are available?

    There are so many material constructions available. Copper is typically available from ¼ ounce to 2 ounces. This doesn’t mean that you can’t have copper thicker than 2 ounces, it simply means that your fabricator would need to create that laminate with raw copper, adhesive and polyimide, rather than purchasing a pre-made laminate. Adhesive thicknesses range from half mil to 2 mil. Polyimide thicknesses range from half mil to 5 mil. You can literally purchase nearly any combination of these materials and thickness if you have a specific end-use requirement.  

    What material constructions are most common and most available?

    Just because you can spec in any combination of material thicknesses, doesn’t mean that is necessarily the best approach. If you are looking for the common constructions to help reduce both cost and lead-time associated with a special order, try to stick to constructions with 1 mil adhesive (if you are selecting adhesive-based materials), and a combination of ½ oz or 1 oz copper and 1 or 2 mil polyimide. These constructions are typically the most common constructions which often means lower cost and shorter lead-times to procure the material supplier and will help keep costs down with your flex stack up.   

    What is more important than common material constructions to keep costs down?

    Now that I have explained which the most common materials are, which should be materials that are most readily available and lower cost, there is one more critical piece to this.  That is, what material does your preferred fabricator stock? At the end of the day, each fabricator has a material set that they commonly stock and that will have a meaningful impact on your material costs and lead-time. Let me explain. Adhesive based material is less expensive than adhesiveless material. BUT, if your fabricator manufacturers a significant percentage of rigid flex or higher layer count flex, they will likely purchase more adhesiveless material, which reduces costs, and will likely have more of the adhesiveless material in stock, which reduces lead time.  My best recommendation? Work with your fabricator early in the design process. Most fabricators are happy to supply a stack up for you. If you specifically ask for their more common materials, you can ensure materials that do not require a special order and should not require an extended lead time. 


    Future blog posts will dive into rigid-flex material considerations and tips to ensure that the material set you select, along with your design, meet flex material design guidelines. I would love to hear your specific questions. Leave a comment and we will be sure to address it!

    About Author

    About Author

    Tara is a recognized industry expert with more than 20 years of experience working with: PCB engineers, designers, fabricators, sourcing organizations, and printed circuit board users. Her expertise is in flex and rigid-flex, additive technology, and quick-turn projects. She is one of the industry's top resources to get up to speed quickly on a range of subjects through her technical reference site and contributes regularly to industry events as a speaker, writes a column in the magazine, and hosts Her business Omni PCB is known for its same day response and the ability to fulfill projects based on unique specifications: lead time, technology and volume.

    most recent articles

    Back to Home