Microvia Subcommittee Brings Industry Together, Hosts Open Forum

By Chris Jorgensen, IPC director, technology transfer; IPC staff liaison to V-TSL MVIA Weak Interface Microvia Failures Technology Solutions Subcommittee

In early 2018, Jerry Magera and J.R. Strickland, Motorola, answered a call for white papers from the IPC V-TSL Technology Solutions Committee. Their white paper, IPC-WP-023, casts a light on an issue that has been troubling the printed board manufacturing industry and upstream users of printed boards: failures at the microvia interface.

IPC-WP-023, an IPC Technology Solutions White Paper on Performance-Based Printed Board OEM Acceptance, Via Chain Continuity Reflow Test: The Hidden Reliability Threat – Weak Microvia Interface, proclaims stacked microvia reliability problems link to a weak interface between microvia target pads and electrolytic copper fill and provides data in support of their observations. Observations IPC would learn are being reported by numerous IPC OEM Member companies.

There was so much interest in this white paper, a new subcommittee, IPC V-TSL-MVIA Weak Interface Microvia Failures Technology Solutions Subcommittee, formed in summer 2018 to begin investigating the potential causes of these failures and to provide industry resources on the topic.

Over the course of multiple web meetings, this group, representing the entire supply chain and numerous end-market segments, broke ground on an activity to begin to attempt to flesh out the potential causes of these interface failures to propose to industry solutions to address the issue.

During IPC APEX EXPO 2019 in San Diego, the subcommittee hosted an open industry forum to share its activities, its plans for bringing industry together to work on solutions to the problem and its planned path ahead. This meeting attracted 97 attendees, almost all of whom raised their hands, when asked by V-TSL-MVIA chair Marc Carter, SAIC, “Who has seen this issue in their products?”

Carter shared the activities of the subcommittee to date, which is focused on gathering existing, open data on the issue and querying industry for the types of data their companies collect on the issue.
Rather than reinvent the wheel, and to best advise IPC on if and how to progress with industry studies, the group will work to gather information in the public domain that could provide common clues regarding the interface failures. The group will compile this research into additional resources to be made available through the IPC Technology Solutions Committee through white papers and other resources.

In its efforts to get an understanding of existing data “behind the curtain” with companies, the subcommittee has also created a survey for industry that will provide the subcommittee information on types of data that could be available. These surveys are submitted to IPC staff and all company information is removed from them before being submitted to an agent of the subcommittee for compiling.

By understanding what data are already available, the subcommittee could then identify common denominators in data collected to request the actual data from industry for developing initial reports and to be able to best advise industry on round robins or other industry research initiatives that would fill the gaps in existing data.

Carter explained that the next step for the subcommittee is to break into A-Teams based on high-level topic areas from a fishbone diagram the subcommittee created. These A-Teams will gather and disseminate data to present reports on its findings back to the subcommittee. These reports can then be compiled into larger reports or resources for industry.

The A-Teams are:
• Simulation and Modeling
• Characterization and Test Methods
• Laminate Materials
• Construction Design Elements
• Metallurgy
• Chemical Processes
• Hole Formation
• Data Collection

Carter stressed that although this subcommittee is open to anyone to join, a requirement of being a member of the subcommittee is that your company will share information or expertise as active participants. Others in industry who simply want to learn and observe will be able to do so through additional reporting sessions, white papers and other resources and reports from the subcommittee.

Following Carter’s introduction, J.R. Strickland, one of the IPC-WP-023 co-authors, presented Microvia Weak Interface Failures: Current Understanding and Mitigation. Based on the research shown in the presentation, their conclusions are to not use more than two stacked microvias and that staggering the microvias can make them much more reliable. One of the most interesting findings in their investigation was when they attached an electrical probe to their test boards they put through reflow, they could spot the actual moment the microvia detached from the interface and then reattached before coming out of the oven. This detachment would not be recognized by electrical testing before and after reflow.

Motorola also indicated they have seen failures between copper fill and electroless, electroless and electrolytic and electroless to copper pad. You can view the Motorola slide deck here.

Happy Holden, who is disseminating blind survey responses submitted to IPC staff, presented on the fishbone diagram developed by the subcommittee and the types of data the subcommittee is collecting. He also presented the early results of the industry survey. You can view Holden’s data mining slide deck here.

How You Can Get Involved
People with interest in this topic should get a copy IPC-WP-023, which is available from the IPC store, and share their experiences with IPC by e-mailing me at ChrisJorgensen@ipc.org. The more IPC can learn about the scale of this issue and companies that are affected by it, the better.

As mentioned, the IPC V-TSL-MVIA Subcommittee is open to anyone to participate, but your company will be required to actively participate through data and information sharing and/or providing expertise on the topic. If you have interest in learning about the subcommittee and your expectations as a member of it, e-mail me at ChrisJorgensen@ipc.org.

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