Flexible Thinking: Rules of Thumb: A Word to the Wise
Happy’s Tech Talk #29: Bend-to-Install Semi-flex FR-4
Connect the Dots: Five Best Practices for Designing Flex and Rigid-flex PCBs
Designs on Flex: Underwriters Laboratory and Flexible Printed Circuits
November 12, 2015 | Mike Morando, PFC Flexible CircuitsEstimated reading time: 1 minute
Underwriters Laboratory is a worldwide safety consulting and certification company headquartered in Northbrook, Illinois. UL certifies, validates, tests, inspects, audits, and advises on safety of electrical and electronic products.
I am sure you have seen the UL logo on many of your electrical and electronic products at home. Electronic equipment, in many cases, requires a UL certification. In turn, the components that make up the electronic or electrical system must be certified.
What Does UL test?
The test process for UL varies based on what is being certified, but in essence, the tests consist of determining how flammable a product is and the functionality of the circuit. In most cases, UL will perform flammability on the consumer product to insure its safety.
For UL 796F standard,
There are two categories of the safety test: flammability and function.
- Adhesion
- Bending / fatigue
- Current / voltage limit
UL 94 Standard
These requirements cover tests for flammability of plastic materials used for parts in devices and appliances. There are three grades of flammability rating:
1)Vertical Burning Test: V-0, V-1, or V-2
2) Thin Material Vertical Burning Test: VTM-0, VTM-1, or VTM-2
3) Horizontal Burning Test: HB
UL Testing of Flex Materials
To obtain UL certification for a flex circuit is a little different. UL does not require each flex circuit to be tested and certified, but, rather the materials that make the circuit- (specific stack up of polyimide, copper, FR-4 and adhesive).
To get approval from UL, a flex circuit manufacturer provides samples of a specific construction for flammability and flexibility testing. UL will test and approve that specific construction. Once the construction is approved, the flex manufacturer can use that specific construction on other circuits as a UL-approved construction.
Process
From a high level, here are the procedures to get specific flex materials certified for flammability from UL.
- Flex vendor submits request to UL have a flammability test
- UL evaluates and creates a test plan,, procedures and processes. Test plan includes flammability test
- Flex vendor manufactures test samples (coupons) and provides all required paperwork
Testing and certification takes 8-10 weeks.
Share on:
Suggested Items
Unlocking Advanced Circuitry Through Liquid Metal Ink
10/31/2024 | I-Connect007 Editorial TeamPCB UHDI technologist John Johnson of American Standard Circuits discusses the evolving landscape of electronics manufacturing and the critical role of innovation, specifically liquid metal ink technology, as an alternate process to traditional metallization in PCB fabrication to achieve ever finer features and tighter tolerances. The discussion highlights the benefits of reliability, efficiency, and yields as a tradeoff to any increased cost to run the process. As this technology becomes better understood and accepted, even sought out by customers and designers, John says there is a move toward mainstream incorporation.
Fresh PCB Concepts: The Critical Nature of Copper Thickness on PCBs
10/31/2024 | Team NCAB -- Column: Fresh PCB ConceptsPCBs are the backbone of modern electronics and the copper layers within these boards serve as the primary pathways for electrical signals. When designing and manufacturing PCBs, copper thickness is one of the most critical factors and significantly affects the board’s performance and durability. The IPC-6012F specification, the industry standard for the performance and qualification of rigid PCBs, sets clear guidelines on copper thickness to ensure reliability in different environments and applications.
Book Excerpt: The Printed Circuit Designer’s Guide to... DFM Essentials, Ch. 1
10/25/2024 | I-Connect007The guidelines offered in this book are based on both ASC recommendations and IPC standards with the understanding that some may require adjustment based on the material set, fabricator processes, and other design constraints. This chapter details high-frequency materials, copper foil types, metal core PCBs, and the benefits of embedded capacitance and resistor materials in multilayer PCBs.
The Cost-Benefit Analysis of Direct Metallization
10/21/2024 | Carmichael Gugliotti, MacDermid AlphaCarmichael Gugliotti of MacDermid Alpha discusses the innovative realm of direct metallization technology, its numerous applications, and significant advantages over traditional processes. Carmichael offers an in-depth look at how direct metallization, through developments such as Blackhole and Shadow, is revolutionizing PCB manufacturing by enhancing efficiency, sustainability, and cost-effectiveness. From its origins in the 1980s to its application in cutting-edge, high-density interconnects and its pivotal role in sustainability, this discussion sheds light on how direct metallization shapes the future of PCB manufacturing across various industries, including automotive, consumer electronics, and beyond.
Connect the Dots: Designing for Reality—Pattern Plating
10/16/2024 | Matt Stevenson -- Column: Connect the DotsIn the previous episode of I-Connect007’s On the Line with… podcast, we painted the picture of the outer layer imaging process. Now we are ready for pattern plating, where fabrication can get tricky. The board is now ready to receive the copper traces, pads, and other elements specified in the original CAD design. This article will lay out the pattern plating process and discuss constraints in the chemistries that must be properly managed to meet the customer's exacting manufacturing tolerances.