High Density Interconnect Design for Medical PCBAs

March 20, 2020 , in Blog, Medical

The trend in PCB design and development for at least the past couple of decades has been to continually make boards smaller, while increasing functionality instead of sacrificing it. This obviously leads to more complex routing schemes, which cannot be accommodated on single-sided or double-sided boards. Therefore, multilayer PCB design is the norm. The ability to route signals on the board surface and on virtually any number of internal layers desired has enabled the form-factor for PCBAS to shrink dramatically, while capability expands and functionality increases.

Medical device utilization of HDI

Heart monitor on mobile phone HDI PCBA

These seemingly inversely proportional trends of decreasing size and increased functionality would not be possible without the use of SMDs, with high pin, pad, or ball numbers packed into smaller component packages, especially ICs. And the underlying technology that makes this complexity and density possible is micro-vias. These vias are defined as having aspect ratios (drill hole depth to board thickness) of 1:1 or less, which makes it possible to have very thin dense groups of traces running vertically through the board. This capability enables the use of high density interconnects for PCBA layouts. Let’s see how this technology is used in medical devices and then how to incorporate it into your board design process.

High Density Interconnect Usage for Medical Devices PCBAs

High density interconnect or HDI technology enables circuit boards to be made smaller with more complex routing. Benefits that can be realized with HDI implementation include the ability to design and build PCBAs that can perform advanced functions, process large amounts of data, and/or require a small or non-standard form factor. These capabilities make HDI especially well-suited for embodiment in medical devices and systems.

Applications of HDI PCBAs in Medical Devices and Systems?

Medical devices are heavily scrutinized and there are many regulations and standards for the design, manufacturing, and quality management of these systems and the PCBAs of which they are principally comprised. Some applications for medical device HDI PCBAs are listed below.

High Density Interconnect (HDI) PCBA Applications in Common Medical Devices

  • Instrumentation

Photometers, electron microscopes, and many other measuring and analysis devices.

  • Scanners

Ultrasound and computed tomography (CT) scanners.

  • Controllers

Fluid infusion and flow rate control.

  • Monitors

Heart rate, blood pressure, and blood glucose meters.

  • Biomedical devices

Pacemakers, blood analyzers, X-ray equipment and electroencephalogram (EEG) and  electrocardiogram (ECG/EKG).

The above is certainly not an exhaustive listing of medical devices; however, it does serve to illustrate that PCBAs, and especially HDI PCBAs, are critical elements without which many of the tools currently available to medical professionals would not be.

How to Design HDI Medical Devices Boards

To be clear, HDI technology is not exclusively used for medical device boards. In fact, it is common to find HDI used for the fast transfer of high volumes of data in many applications. Most notably, HDI is used in computers, laptops and mobile phones to transfer high frequency signals between miniature components on internal boards and high-density data between electronic devices. However, there is much broader and extensive usage for medical devices due to miniaturization and complexity requirements. Therefore, your medical devices PCBA design will likely necessitate that you incorporate HDI, which merits the establishment of some guidelines for effectively doing so.

High Density Interconnect Medical Devices PCBA Design Guidelines

Designing your best medical devices HDI board will require that you apply both a minimization and maximization strategy to your design process. One of the reasons that you are using HDI in the first place is probably to minimize your board size to meet some medical device installation constraint(s). In conjunction with this goal, you need to minimize your design’s complexity as much as possible. This may seem counterintuitive, but consider the more uniform your design is (in terms of the least number of different component types, trace widths, and via types and sizes), the more efficiently you can utilize the space and optimize the density of traces, components, etc. Thus, your minimization strategy should include the following:

  • Minimize
      • Trace widths
      • Different types and numbers of components
      • Via types and sizes
      • Board height

And to ensure that your design is indeed manufacturable, you need to maximize the involvement of your contract manufacturer (CM). The most important aspect of this is acquiring and fully utilizing your CM’s DFM rules and guidelines. To achieve this requires that you rely on your CM for guidance to facilitate fabrication and assembly, which includes DFA rules.

  • Maximize
      • DFM incorporation
      • DFA incorporation

For more detailed information on how to design for the most effective HDI board builds, see DFM for HDI Printed Circuit Boards.

The miniaturization, complexity and quality demands placed on medical devices circuit boards is tremendous. Yet, there are no signs that this will end or even lessen any time soon. Therefore, understanding and utilizing HDI technology is often imperative. In order to do so, you need to follow good design guidelines, as listed above. Equally important is that you partner with a CM that can effectively build these high-performance boards for you with no loss in manufacturing quality or turnaround time

Tempo's Advanced Custom PCB Manufacturing Service for Complex Medical Systems Development
  • Works with 4 of the top 10 medical devices manufacturing companies.
  • ISO-9001, IPC-600 and IPC-610 commitment to quality certifications.
  • Accurate quote in less than a day.
  • DFM support from Day 1 of design.
  • Fastest turnkey PCB manufacturing in the industry.
  • Rigid, rigid-flex and flex board capabilities for wearables and embedded biosystems.
  • Custom automated BOM verification tool.
  • Sources components from the most reputable suppliers in the industry.
  • Software-driven robotics assembly.
  • Standard quality testing, including X-ray and inline AOI.
  • Superior open, transparent PCB manufacturing experience.

Tempo Automation is the industry’s leading fast turnaround, high quality PCBA manufacturer for prototyping and low-volume production and we have the advanced equipment and expertise to deliver HDI PCBAs that will meet all of your objectives.

And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on high density interconnect PCBA design, contact us.

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