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Flex Talk: Mina—Enabling Soldering to Aluminum

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

Tara Dunn: Divyakant, I am excited to learn more about Mina™. Before we start, could you introduce Averatek and your role there?

Divyakant Kadiwala: Averatek is a high-tech company based in Santa Clara, California. 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 the director of manufacturing, and my role includes overseeing process engineering, quality control, facilities management, and business development. Lately, I have been concentrating on promoting Mina™.

Dunn: It sounds like you are busy. I am sure it is exciting to be working with new product development. Can you please explain Mina™ for us?
Kadiwala: Absolutely. Mina™ is a unique surface treatment that enables soldering to aluminum just as is done to copper and even at low temperatures. The reason this is unique is that, normally, there is an oxide that is present on all aluminum surfaces that inhibits solders from bonding with the core metal. To tackle this oxide, processes exist that involve a series of etchants and treatments that remove this oxide. This is commonly called the zincate process. Once the oxide is removed, the surface is plated with a noble metal finish like ENIG or ENEPIG to cover the surface and protect it from forming a new oxide layer.

Mina™ eliminates the need for all the wet chemistry and surface finishes. It is printed onto the pads using a stencil printer and cured at low temperatures. Cured Mina™ is non-conductive, so this leaves the pads with a uniform coat of Mina™. This helps with easy print registration, should the trace and space of a component’s pads be too tight. After this, the boards can be stored to prepare for assembly because cured Mina™ remains stable, or the boards can go straight through the component assembly process wherein solder will be printed onto the pads, followed by loading of components in the pick-and-place and then reflow. Mina™ activates during the reflow cycle and ensures a good solder joint to the core aluminum.

The unique thing is that the solder selection depends on the substrate. A common use of aluminum is associated with aluminum on PET substrates or Al-PET substrate. PET cannot withstand high temperatures for an extended time, so low temperatures solders become the only option. 

Dunn: This appears to significantly simplify the current standard process. Are there other benefits of Mina™ that we should be aware of?

Kadiwala: Yes, there are several benefits to using Mina™. It is green because it eliminates several wet chemistry process steps that would otherwise be needed to solder to an aluminum pad. It also widens the scope for the use of Al-PET substrates. These are often limited to inexpensive applications like RFIDs that are assembled using silver epoxy. With the ability to solder components, Al-PET substrates can now replace single layer copper-based circuits for applications like smart tags, LEDs, and other applications. Overall, aluminum is about one-third of the cost of copper, and when combined with the cost-benefit of PET film over polyimide, it is one-eighth the cost of copper on a usage basis. This is a significant cost savings. From a performance perspective, soldered joints are electrically superior and more reliable than those made using conductive epoxies.
Dunn: What industry segments do you see as the early adopters of this technology?

Kadiwala: From our conversations, I expect that the early adopters will be those industries that are already using Al-PET substrates. Again, these include smart tags, LEDs, automotive, RFIDs, and those using aluminum for EMI shielding and similar applications. Once these adopt, we will start targeting other conventional copper-based circuits that will be driven to aluminum for its cost advantages.

Dunn: Is Mina™ commercially available at this time?

Kadiwala: Yes, it is available now. It has been qualified for use by some customers and is under testing at others.

Dunn: What type of testing and development has been completed?

Kadiwala: The testing and development are always specific to the end application of the product. Mina™ has passed the surface insulation resistance (SIR) test. This was done at an independent lab per IPC specifications. We routinely do shear tests to confirm adhesion while qualifying new solders. We get shear values that are greater than 15 N/mm2, and typically, failure mode is between the aluminum and PET film. We also examine the joints using X-ray to examine for voids. The voids are consistently within expected norms of less than 30%. It has been tested and qualified for use in soldering to aluminum for an EMI shielding application. Further, it is undergoing testing for LEDs, smart tags, and automotive applications.

Dunn: Will there be any specialized equipment, or storage or handling procedures that will need to be addressed before bringing this into a manufacturing environment?

Kadiwala: Mina™ is very simple to use and requires no special handling other than common PPE per best practices when handling a chemical-based product. These would include gloves, eye protection, aprons, etc. We recommend that it be stored at room temperature, away from direct sunlight. It does not require refrigeration. Thus, it is cost-effective to store when compared to silver epoxies that need freezers for storage.

Mina™ can be printed using conventional stencil printers and cured in reflow ovens that already exist in SMT assembly shops. Therefore, there is no need for any specialized equipment, storage, or handling constraints around bringing Mina™ into a manufacturing environment. This makes it very easy to adopt.

Dunn: How can people learn more?

Kadiwala: People can visit our website or email me at divyakant@averatek.com.

Dunn: Divyakant, thank you so much for talking with me and educating us about Mina™. The ability to solder directly to aluminum is certainly an exciting development with many benefits.

Kadiwala: Thank you.

 
This column originally appeared in the FLEX007 section of the April 2020 issue of Design007 Magazine.