Flex Talk: Simplified Assembly of Aluminum Flexible Circuits

Averatek_Divyakant_Kadiwala.jpgFlexible circuit designs that come across my desk are predominately constructed with copper and polyimide laminates. As I learn more about automotive applications, I am intrigued by the possibilities of using aluminum in place of copper and the potential to use polyester in place of polyimide. Both aluminum and polyester have traditionally been difficult to solder to. One very interesting development has been the Mina™ chemistry. This coating not only simplifies soldering to aluminum, but it also enables the ability to automate low temperature soldering to polyester. Having many questions about this process, I sat down to discuss this Mina with Divyakant Kadiwala, vice president of manufacturing for Averatek. He has been instrumental in the development of this assembly process.

Tara Dunn: Divyakant, before we jump into the conversation about Mina, could you share a brief introduction to both Averatek and your background?

Divyakant Kadiwala: Averatek is a high-tech company based in Silicon Valley. It was founded by SRI International and private investors. It has two primary products: LMI™, a catalytic ink that enables the fabrication of very high-density circuits with the patented A-SAP™ process; and Mina, a surface treatment that enables soldering to aluminum. I am VP of manufacturing and my role includes overseeing process engineering, quality control, facilities management, and business development. I am leading our efforts on productization of Mina.

Dunn: Thank you. Let’s start the conversation with aluminum. What are the benefits of aluminum over other metals?

Kadiwala: Aluminum is the most abundant metal in the earth’s crust. This makes it more easily available and less expensive compared to other metals. It has different benefits when compared to other metals based on the field of use. For example, in automobiles, its superior strength at lower weight is a significant benefit against iron and its common alloy—steel. But in the field of printed electronics, its main competitor would be copper.

C_Dunn_March21_Fig2.jpgAluminum is more than three times lighter than copper. It has 68% of the conductivity of copper but has only 30% of the weight of copper. This means that a bare wire of aluminum weighs half as much as a bare wire of copper that has the same electrical resistance. This makes it the metal of choice for high voltage transmission cables. Also, it is three times less expensive than copper on an equal weight basis and six times less expensive on an actual usage basis. This is the biggest advantage that aluminum has over copper.

Dunn: Interesting. Why do you think aluminum is attractive specifically for automotive applications?

Kadiwala: Aluminum has been a boon for the automobile industry. Like any industry, the automobile industry has evolved due to various geo and political reasons over its 100-plus-year history. Whether it’s the oil embargo of the 1970s or global warming due to climate change, it has been constantly under pressure to improve fuel efficiency standards.

The easiest way to improve fuel efficiency is to reduce the dead weight of the automobile and improve the efficiency of the internal combustion engine. Aluminum helps reduce an automobile’s body weight by providing superior strength at lower weight when compared to steel and other alloys of iron. It also helps improve engine efficiency by providing better performance at lower weight.

Since most automobiles have their body and chassis made of aluminum, the integration of onboard electronics to aluminum is critical. Averatek’s Mina can provide a soldered connection to aluminum without any plating or surface finish. It can help ease manufacturing and reduce costs.

Dunn: Aluminum has historically been difficult to assemble to. What are the challenges of soldering to aluminum?

Kadiwala: Aluminum PC boards, whether rigid or flex, are limited in use due to challenges associated with soldering components to aluminum pads. This is because all aluminum surface is covered with a layer of aluminum oxide. Although self-limiting, this oxide layer cannot be overcome by flux in existing solder systems during reflow. It thus prevents the formation of a metal-to-metal bond. Even if this oxide layer is removed using etchants and fluxes, a new layer forms in situ upon exposure of clean aluminum to the atmosphere. This prevents the use of conventional SMT methods for attaching SMDs to assemble PC boards.

Dunn: Can you expand on a couple of ways that Mina could be utilized in automotive applications?

Kadiwala: Integrating electronics with the aluminum body and chassis of the car is an integral part of its manufacturing and design. Since aluminum is not easy to solder to, mechanical “crimp” and “pigtail” connections are common options.

Mina™ can provide a soldered joint instead of these mechanical connectors. It can help attach aluminum wire or PCB to aluminum chassis for grounding or other such connections. It can also help with attaching copper to aluminum PCB where applicable.

Dunn: This is exciting. With any new process, reliability is always a concern. What type of reliability data has been gathered?

Kadiwala: Flexible PCBs were made using an Al 9-mm/PET 38-mm substrate and components were soldered using low temperature Sn/Bi/Ag solder paste. The fully assembled PCBs were then subjected to these tests:

  • K-09 - “Damp Heat, Cyclic (with Frost)”
  • M-04 - “Vibration”

Both these come under the LV-124 European automobile standards.

1. Characteristics of the Test K09 – “Damp Heat, Cyclic (with Frost)”

  • Chamber temperature: without cold phase: 23°C to 65°C; with cold phase: -10°C to 65°C
  • Chamber humidity: 95% RH
  • Duration: 10 d = 10 cycles at 24 h
  • Cycling: 5 cycles with cold phase, then 5 cycles without cold phase
  • Operation of samples: here not operated (usually intermittent operation = 30 s on, then 30 s off)

2. Characteristics of the Test M-04 – “Vibration”

  • Chamber temperature = 8 h, profile between -40 and 80°C
  • Broadband random vibration according to vibration profile D in LV-124 → 5-2000Hz → 30.8 m/s² → X-axis, Y-axis, Z-axis → 8 h each axis

Dunn: What materials does Mina work well with? Rigid, flex materials, others?

Kadiwala: Mina works well with both—flex and rigid materials. The alloys of aluminum that we have proven for our customers include Al1235, Al6061 and Al5052.

Dunn: Understanding the benefits of aluminum over copper and understanding the benefits of flexible materials such as polyester, the combination seems like a natural fit for automotive applications and a wide range of other applications. Which markets do you see as the early adopters of Mina taking advantage of the simplification of the soldering process for these materials?

Kadiwala: In addition to automotive, we see significant interest from the LED, SmartTag and heat-sink and high-power industries.

C_Dunn_March21_Fig3.jpgThe LED industry would not only benefit from lower costs due to cheaper Al-PET substrate but also it would be a better product. A soldered LED operates much cooler compared to one attached using conductive epoxy. Based on information from a large LED manufacturer, the lifetime of an LED doubles with every 10°C reduction in operating temperature. Thus, soldered LED panels will be more reliable.

SmartTags have more components and are larger in size compared to generic RFID tags. They use a lot more silver epoxy and thus are more expensive to make than RFID tags. Also, SmartTags are designed to be used multiple times while RFID tags are usually meant for single use. Hence, longevity is important for SmartTags. A tag made with its components soldered will be more reliable and cheaper compared to one made using silver epoxy.

Heat management is important for high-power devices. Aluminum is commonly used to build heat sinks. Soldering a high-power device to aluminum would require a plated surface finish like ENIG and ENEPIG. These add costs and so other means like thermal tape, etc., are used at the cost of performance and life of product. Mina addresses all these issues by enabling direct soldering to aluminum heat sinks.

Dunn: Divyakant, thank you so much for talking with me about the Mina process. Working with flexible circuits for many years, it is always exciting to learn about new applications that change the way we look at flex assembly and integration.

Kadiwala: Thank you, Tara.

mina_process_hero.jpg

This column originally appeared in the FLEX007 section of the March 2021 issue of Design007 Magazine.

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2021

Flex Talk: Simplified Assembly of Aluminum Flexible Circuits

03-18-2021

Tara Dunn sits down to discuss Mina™ with Divyakant Kadiwala, vice president of manufacturing for Averatek. He has been instrumental in the development of this assembly process.

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Flex Talk: Demystify Flexible Stack-ups

01-26-2021

The sheer number of flexible laminate materials and constructions can be a bit daunting for those new to flex and rigid flex design. Tara Dunn sits down with Jeff Martin from Omni PCB to hear his insight into flexible laminates and his advice when working on a flex stack up.

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2020

Flex Talk: Communicating Outside the Box Is Key to Flex DFM

12-17-2020

What do you do when you are designing a flexible circuit and need to go “way outside the box” to get the desired end-result? Tara Dunn looks at a few success stories, including gold conductors and complex rigid-flex, and emphasizes the power of communication.

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Flex Talk: Communication Goes Both Ways

09-30-2020

Technology, whether new to you or new to the industry, both require communication between the end-user and the fabricators. Tara Dunn explains how a collaborative approach benefits not only the end-user seeking the information but also the fabricator that will be providing the technology.

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Flex Talk: The Black Magic in the Business

08-25-2020

When you work with flex or rigid-flex, the communication between designer and fabricator needs to be impeccable, and the primary method of transferring information is through the fabrication notes. Tara Dunn gives a recommendation that, although not strictly required by the fabricator to build the product, will certainly benefit the end-user.

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Flex Talk: Additive and Subtractive—When Opposites Attract

07-27-2020

Market dynamics in the electronics industry are quickly changing. Some solutions add considerable cost to the PCB and often introduce reliability and yield concerns. Tara Dunn explains an alternative that has been installed in three U.S.-based PCB fabrication facilities: the A-SAP™ process, which is Averatek’s semi-additive process.

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Flex Talk: It’s the Little Things

05-15-2020

Let me share a personal moment. Shortly after we started staying home and socially distancing, I came down the stairs from my home office and noticed something colorful on the sidewalk. Keep in mind that I live in Minnesota, and anything colorful is extremely eye-catching while in stark contrast to the winter grass and leafless trees. Looking closer, someone had colored big, beautiful hearts all along my sidewalk and driveway, leaving a fun message at the end of all those colorful hearts. That simple act of kindness made me smile for days, anytime I looked outside and saw the chalk drawings and messages. It also reminded me that in the midst of uncertainty and life being unsettled, one small thing could make a significant impact.

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Flex Talk: Unintentionally Adding Cost?

04-16-2020

When designing a PCB, rigid or flex, there is a continuing series of choices and trade-offs, some with greater cost impact than others. Tara Dunn discusses a few things that can easily be overlooked when putting together the puzzle pieces of a design and that may have an unintended impact on the overall cost.

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Flex Talk: Mina—Enabling Soldering to Aluminum

04-15-2020

Averatek recently launched Mina™, a chemistry that offers exciting benefits over traditional methods of soldering to aluminum. Tara Dunn had the opportunity to speak with Divyakant Kadiwala, director of manufacturing at Averatek, to learn more.

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Flex Talk: Additive PCB Technology for Next-generation Electronics

02-18-2020

Semi-additive PCB processes help to enable very fine features, with trace and space down to 25 microns and below, significantly reducing space and weight for next-generation electronics. Tara Dunn speaks with Todd Brassard and Meredith LaBeau from Calumet Electronics about how the company is the first domestic PCB manufacturer to license Averatek’s A-SAP™ process and will be presenting information on the industrialization of this process at this year’s IPC APEX EXPO.

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Flex Talk: The Challenge of Change

01-20-2020

I recently kicked off a presentation on flex and rigid-flex by asking for a show of hands of those who had never worked with flex materials or considered themselves to be just learning how to design with flex. Over half of the room raised their hands, which excited me because I could help them learn something new. In my opinion, the best way to lessen the challenges and uncertainty of change is to arm yourself with as much knowledge as possible.

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2019

Flex Talk: Additive Electronics Momentum

11-14-2019

I have been involved with additive electronics for the past several years, and I have seen the discussion of and demand for sub-75-micron feature sizes slowly grow. Conversations, questions, and research about SAP and mSAP increased significantly when it was announced that the mSAP process was used to create the circuitry in the more recent versions of our smartphones. While this process is available in very high volume in some areas of the world, it is still in the early stages of development in other areas.

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Flex Talk: Don’t Build Flex That Doesn’t Flex

10-10-2019

One of the primary advantages of moving to a flexible circuit design from a rigid board is the ability to package the flex in three dimensions, bending or folding into imaginative configurations and saving precious space in the final package.

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Flex Talk: When You Do Everything Right and Something Still Goes Wrong

08-02-2019

This industry is full of tales describing the work and effort needed to overcome fabrication hurdles to produce a complex design. Tara Dunn shares a case study of one of those types of designs.

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Spark an Idea

07-11-2019

One of the favorite parts of my job are the days when I meet with a group of engineers and designers to talk about flex and rigid-flex. We might do a "lunch and learn" with a general overview of the technology or address a specific challenge. It is always helpful to bring samples to pass around and show different features. Usually, looking at a sample will spark an idea and the comment, "I wonder if we could do something like this.” From there, the brainstorming begins.

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Flex Talk: New Materials or New to You?

06-10-2019

There are so many new processes and materials in the PCB segment that it can be a challenge to keep up with all the new developments. It is fun to start chasing the next new thing, but it is important to keep in mind that even materials and processes that have been around for a while are still new to someone.

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Flex Talk: New Engineering Talent Joining the Electronics Industry

05-27-2019

Last spring, Ross Olson, an undergraduate student at the University of Minnesota and member of the U of M Solar Vehicle Project team, attended the Geek-a-Palooza event in Minneapolis and displayed one of their race cars. Tara Dunn had the opportunity to get to know Ross, and recently sat down with him to talk about his interest in engineering and his thoughts on the future of the electronics industry.

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Flex Talk: Old-fashioned Networking

05-08-2019

We live in a connected world. Information is collected at an astonishing rate, and people are working diligently to put this information to good use. It is new, fun, and exciting. But I sometimes wonder what is going to happen to the good, "old-fashioned" networking. Not networked devices, but the act of going out and meeting people in our industry, learning about their story and expertise, and sharing yours—mutually beneficial sharing of information and resources.

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Flex Talk: FlexFactor—Imagination and Innovation

01-23-2019

The ultimate goal of FlexFactor is to create a generation of students who use their critical thinking, creativity, communication, and collaboration skills to create the materials and devices that will address and mitigate the biggest challenges of the future.

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2018

Flex Talk: The Myth About Rigid-Flex Costs

12-12-2018

Do you cringe when you think of the option of rigid-flex? It is not an uncommon reaction when talking with designers and engineering managers about using rigid-flex to solve a packaging problem. Why? The most frequent answer is, “They are so expensive.” While it is true that a rigid-flex PCB is typically more expensive on the surface when compared to rigid-board solutions with cables and connectors, a lot is being missed with that mindset.

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Flex Talk: Mina—RFID, LED and What Else?

09-17-2018

“The science of today is the technology of tomorrow.” This Edward Teller quote is an apt description of the Mina product. This advanced surface treatment, recently developed to enable low-temperature soldering to aluminum in the RFID market, is not only finding success in that market, but quickly finding a home in other markets, including the LED market, where the incentive is both cost and improved LED performance.

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Raising the Capability Ceiling: SMTA Upper Midwest Chapter Expo

06-25-2018

An energetic and engaged crowd filled the recent SMTA Upper Midwest Expo & Tech Forum. The event, held in June 14 in Minneapolis, Minnesota, hosted 57 exhibiting companies and had over 100 pre-registered attendees. The underlying theme for the technical presentations was "Raising the Capability Ceiling!" Here's a wrap-up of the event.

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Flex Talk: E-Textiles—the Wild Frontier

05-23-2018

How many hours is your car sitting idle outside in your driveway or a parking lot? What if your car was used for solar harvesting—converting heat to energy? What about biometric sensors in automotives: skin sensors for preventing DUI, posture identification to monitor driver fatigue, monitoring exposure to hazardous materials in a load for truck drivers.

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Flex Talk: Something New for Everyone

05-02-2018

Whether you are new to single- and double-sided flex, moving into rigid-flex construction, thinking of using bookbinder technology, or investigating an additive process, working with new technology can be both exciting and challenging.

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Flex Talk: Invited Guests to the Party

04-16-2018

Hanging on the wall in my office is this quote from Jeff Bezos: “We see our customers as invited guests to a party, and we are the hosts. It’s our job every day to make every important aspect of the customer experience a little bit better.”

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2017

FlexFactor: Faith in the Future

11-27-2017

Take just a minute and read through this list of new product ideas. Can you identify the common thread? Yes, they are all enabled by advanced technology, but would you believe that these products were all pitched in the last year by high school students?

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Flex Talk: The Man Behind the Curtain

10-03-2017

“Pay no attention to the man behind the curtain.” This famous quote from The Wizard of Oz conjures up the image of Dorothy, the Tin Man, the Cowardly Lion and the Scarecrow discovering that the great Wizard of Oz isn’t as grand or as magical as he seems.

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Flex Talk: Knowledge is Power

08-31-2017

“What can I do to help drive cost from my design?” This is a question that I am asked routinely. That question is often followed by, “Can I get these faster?” Both questions are even more predominant when talking about flexible circuits or rigid-flex.

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Flex Talk: Mina—Trouble-Free Soldering to Aluminum

06-22-2017

Thinking about the RFID market and the significant growth projected in this market, I decided to do a little research on RFID tag manufacturing. During this research, I learned of a relatively new offering, Mina, an advanced surface treatment technology that addresses the common constraints of large scale manufacturing of aluminum on polyester (Al-PET) circuits.

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Flex Talk: Squink—Integrating Fabrication and Assembly in one Package

05-01-2017

When walking through trade show expos, I tend to be drawn into product demonstrations on the show floor. Recently, at the IPC APEX EXPO, I stopped in front of a piece of desktop printing equipment that was demonstrating with a flexible circuit.

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Flex Talk: Flex Material Handling—An Inside Peek

04-03-2017

As increasingly more designs move to flexible materials to take advantage of space, weight or packaging benefits, it has been clear that flexible circuits require a different set of rules than their rigid counterparts. We spend substantial time working through the design to ensure that he flex is as robust as possible.

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Flex Talk: Final Surface Finish—How Do You Choose?

01-26-2017

There are so many final surface finish options to choose from today. How do you decide which is best? HASL—both tin-lead and lead-free—immersion tin, immersion silver, ENIG, OSP, and ENIPIG are the primary finishes used in PCB fabrication.

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2016

Flex Talk: A Glimpse into PCB Sales

12-28-2016

Summarizing the feedback from both customers and manufacturers, the most successful PCB salespeople are organized, take a genuine interest in their customers’ needs and business challenges, have a better than average understanding of the PCB industry, fully understand the manufacturer’s strengths and capabilities and advocate for both to find the best solution.

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Flex Talk: Troubleshooting Flex Circuit Applications for Mil/Aero Projects

10-06-2016

I imagine that everyone has been in this position at one time or another: Despite everyone’s best attempt at creating the perfect design, PCB fabrication and assembly, something goes wrong and the troubleshooting begins.

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Flex Talk: Inaugural West Coast Geek-A-Palooza a Fun-filled Success

05-24-2016

Geek-A-Palooza kicked off the 2016 schedule May 12 in Irvine, California. Historically, Geek-A-Palooza has been held in Minneapolis but is expanding this year to include Orange County and Boston as well.

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Flex Talk: PCB Sourcing? One Size Does Not Fit All

04-18-2016

When analyzing a set of PCBs to improve yields and maximize profits, the first place to start is with a critical review of each PCB design. Are there any attributes that are pushing your manufacturer’s standard design rules? If so, is this necessary to the design or is there another approach that could improve the manufacturer’s yields, reduce cost, and ultimately increase profit?

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2015

Flex Talk: Thoughts on the IPC Flexible Circuits–HDI Forum

11-19-2015

As an attendee at the IPC Flexible Circuits–HDI Conference held October 28–30, I found myself in a room of people, all eager for technical information, with the opportunity to reconnect with industry friends and to make new connections. The audience was diverse with young people, new to our industry, sitting alongside industry veterans willingly sharing their knowledge and passion for HDI design and flexible circuit technology.

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Designing Flex Circuits for Domestic Prototyping

08-20-2015

Designing a flex circuit to be prototyped domestically? No problem. Designing a rigid-flex circuit for production offshore? Got it. Designing a part that will be prototyped domestically with a seamless transition to offshore production? That can be a little more challenging.

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Rigid Flex: Total Cost Comparison

07-09-2015

The transition to a rigid-flex design from the traditional approach of using cable assemblies to join two or more PCBs has obvious benefits—space, weight, packaging, reliability and increased currently carrying capabilities. Yet many times the perception that rigid-flex is a high-cost solution causes designers and engineers to hesitate.

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Primary Cost Drivers for Flex Circuit Designs

06-25-2015

Someone once told me that the potential applications for flexible circuits are really only limited by our imaginations. After pondering that a bit, I had to agree. In fact, one of the things I like best about what I do is that moment during a discussion when I can see the light bulb go off in a designer's head.

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The Flex-to-Fit Approach

06-04-2015

The flex-to-fit concept reminds us that creativity and engineering go hand-in-hand. When there is not ample space for a conventional approach, this process, which is the convergence of the mechanical world and the electronics world, results in the ability to design a flexible circuit along the contour of an existing, irregularly shaped structure.

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