-
- News
- Books
Featured Books
- design007 Magazine
Latest Issues
Current IssueMechatronics
Our expert contributors discuss the advent of mechatronics in PCB design, the challenges and opportunities this creates for circuit board designers, and the benefits—to the employee and the company—of becoming a mechatronics engineer.
Creating a Culture of Collaboration
PCB designers could learn quite a bit from NASA and the private companies that develop spacecraft: Every one of these vehicles is a testament to the value of collaboration among disparate stakeholders. Without a collaborative culture, the rocket might never get off the ground.
Breaking High-speed Material Constraints
Do you need specialty materials for your high-speed designs? Maybe not. Improvements in resins mean designers of high-speed boards can sometimes use traditional laminate systems. Learn more in this issue.
- Articles
- Columns
Search Console
- Links
- Events
||| MENU - design007 Magazine
The Material Witness: Nonwoven Aramid Reinforcement is Back
October 22, 2015 | Chet Guiles, Arlon Electronic MaterialsEstimated reading time: 3 minutes
![](https://iconnect007.com/application/files/3516/3116/2672/chet.jpg)
In the 1st century AD, there was significant debate among Jewish theologians as to whether resurrection was possible. PCB designers in the early 21st century have had a similar concern about future availability of 85NT nonwoven aramid laminate and prepreg. The stakes may be somewhat less critical, depending on your theological bent, but the future of a wide variety of programs designed around the properties of (dare I mention the name?) Thermount® have been hanging in the balance. What was Thermount exactly and why was there such a furor when DuPont announced its premature demise? And where do we stand now with the redevelopment of a nonwoven aramid product?
The original 85NT product was based on high tensile-strength para-aramid fiber with a meta-aramid fibrid binder. The para-aramid fibers have a high tensile modulus (fiber modulus of about 19 mpsi) and a negative linear coefficient of thermal expansion with a CTE of about -4 ppm/oC meaning that the material shrank when heated, and the fibrid held the fibers together in a uniform matrix. Produced in a high-end papermaking process, the resulting substrate was a yellow aramid paper material that produced laminates with a unique and useful set of properties. For a polyimide aramid composite the benefits look like this:
- Tg of pure polyimide (250oC)
- Low in-plane (X,Y) expansion of 7-9 ppm/°C
- Excellent dimensional stability and enhanced registration
- Decomposition temperature of 426°C, compared with 300-360°C for typical high-performance epoxies, offering outstanding high-temperature life
- Polymeric reinforcement results in PCBs typically 25% lighter in weight than conventional glass-reinforced laminates
- Laser ablatable for high-speed formation of microvias as small as 25μm in clad laminates as thin as 0.002”
- Electrical and mechanical properties meeting the requirements of IPC-4101/53
- Compatible with lead-free processing
- RoHS/WEEE compliant
The earliest military adoption of aramid reinforced laminates was in the guidance system for the Tomahawk cruise missile, a significant success in terms of test results (thermal cycled better than the prior woven aramid technology) and field performance. The combat-proven Tomahawk gave the then relatively new substrate a kick-start. I still have the jacket patch that the Tomahawk PWB development staff gave me. And there was some real pride in achievement in the ongoing field success of that program.
Later uses of 85NT materials included a wide variety of military and commercial avionics. The first-generation avionics for the Boeing 777 were designed on this platform, and it replaced heavy copper-invar-copper (CIC) in a number of older designs. In addition to these, the Iridium telecommunications satellite constellation used 85NT for a number of its PWBs.
In July of 2006 the imminent demise of the DuPont Thermount product was announced to its customer base. In November 2006, a letter from Ralph Hutton, president of DuPont Teijin Advanced Papers, said, “Due to a dramatic reduction in demand for Thermount reinforcement for consumer applications in Japan, and a corresponding reduction in global demand for the foreseeable future, we are unable to continue accepting orders for Thermount reinforcement of any kind beyond December 31, 2006.”
Working with senior officials at major military and commercial OEMs, Arlon procured and stocked sufficient NWA product to sustain existing programs during the period required to find a suitable alternative source.
Well, nonwoven aramid is back. Although I have tried to keep this column non-commercial, Arlon is, as best I know, the only company that has committed the resources and time to work with potential suppliers to develop a polyimide NWA that meets all the performance criteria of the original 85NT product.
In fact, what we have now is a drop-in replacement that will match both in process and properties of the original. That was not easy to accomplish and several very well qualified vendors tried and failed to meet the exacting requirements for the substrate. The project took longer than had originally been expected, though stocks of the old material have held up well enough to protect ongoing programs for the entire duration of the development program.
As you can see from the following microphotographs, the registration and hole quality of the new aramid reinforcement is essentially identical to that of the original DuPont product. The12-layer test coupons were made in the same press and lamination cycle using parameters developed for the original 85NT product.
For those who have been frustrated trying to find alternative technologies for their critical SMT boards, I think I can say with a great degree of confidence that Arlon’s 85NT is back and that you won’t be disappointed with its processability or performance.
Until next time, this is the Material Witness wishing you happy fabrication and a great fall 2015.
Chet Guiles is a consultant for Arlon Electronic Materials.
Suggested Items
Enhance Your Electronics Expertise Through IPC Courses in August
07/25/2024 | Corey Lynn, IPCAs the global leader in standards, training, and certification for the electronics industry, IPC is pleased to announce an array of upcoming online instructor-led courses this August. These courses are designed to equip professionals with the latest skills and knowledge required to excel in the ever-evolving field of electronics manufacturing and design. Whether you want to deepen your expertise in PCB design and manufacturing, understand the intricacies of intermetallic compounds, or learn about counterfeit part mitigation, IPC has a course tailored for you.
The Knowledge Base: The Value of Industry Certifications
07/24/2024 | Mike Konrad -- Column: The Knowledge BaseIndustry certifications have become increasingly significant in the modern job market, offering a range of benefits to both individuals and employers. These certifications serve as formal recognitions of expertise and proficiency in specific areas, validating a person's skills and knowledge. In the context of the electronics assembly industry, certifications are particularly valuable, given the technical nature of the work and the rapid advancements in technology.
Tom Edman Leads IPC Board of Directors
07/17/2024 | Marcy LaRont, PCB007 MagazineIPC elected several new board members at IPC APEX EXPO in April, including new Board Chair Tom Edman, CEO of TTM, who assumes the role from Bob Neves, CTO and chair of Microtek Laboratories. Tom and TTM have long been active in many facets of IPC. I caught up with Tom and asked him about his new board appointment, IPC, and the industry he serves. He emphasizes IPC’s work in standards and advocacy as especially important for our industry.
Getting Clear About Certification With Charlie Capers
07/17/2024 | I-Connect007 Editorial TeamWalk through the entrance at Zentech Dallas and you’ll see a wall of certification plaques prominently displayed. Beyond being impressive and a point of pride, these certifications tell a story to potential customers: This company is ready to do business. Charlie Capers, former vice president and general manager, shares his insights on quantifying the ROI of certifications. You may not see it on paper, but it’s definitely there. He also talks about his expectations for new hires and shares a case study about the importance of collaborating with your PCB designers.
Winners of 2024 IPC Masters Competition China Announced
07/17/2024 | IPCFrom July 8-10, the 2024 IPC Masters Competition China was successfully held in Pudong, Shanghai. This year’s competition, was the largest in the history of the Greater China region, bringing nearly 400 electronics industry elites from 18 provinces and municipalities.