Not so long ago, a doctor’s visit was required to check your vitals. Today, however, it is easy to keep tabs on your blood pressure, heart rate, oxygen level and biological parameters from home or anywhere with wearable health monitors. These devices, along with other advances such as telemedicine, have expanded accessibility to physical wellness by allowing users to leverage data and expertise to optimize their health.
The collaborative approach to healthcare that properly vetted electronic medical devices enables has raised expectations in terms of fitness, quality of life and longevity. However, these advantages would not be possible without the circuit boards that drive devices and test equipment used by medical practitioners and individuals. Developing these electronic medical systems, in many cases, is not without the challenges of high frequency accuracy.
What Are the Challenges of High Frequency Accuracy For Medical Electronics?
Many biometric measurements that provide insight into a medical patient’s health are low frequency electrical signals. These include the following:
Biological signal frequencies
- Heart rate < 2 Hz
- Brain waves
- Delta < 4 Hz
- Theta 4 to 8 Hz
- Alpha 8 to 12 Hz
- Beta 12 to 35 Hz
- Gamma > 35 Hz
- Respiration 0 to 40 Hz
- Blood pressure 0 to 200 Hz
Once the signals listed above are captured, they often are converted to digital for high frequency processing and transfer. However, these are typically low-level signals that are susceptible to the signal integrity challenges listed below.
Signal Integrity Challenges for High Frequency Accuracy
- ➛Component quality
The medical device industry is one of the most regulated areas where electronic devices are readily applied. A primary reason for this level of scrutiny is to protect patients from counterfeit or substandard components.
- ➛Placement and Clearance Issues
Signal sensitivity considerations should be a major concern for high speed medical PCBA design and development. This begins with the board layout—specifically the placement of components and their spacing away from other surface elements. Failing to provide sufficient clearances can lead to signal degradation, crosstalk and other EMI problems.
- ➛Trace Routing Issues
In many cases, your medical PCBA may contain HDI, differential or some other routing that requires special consideration. For these and other routing schemes, you should consider material issues such as copper roughness and dielectric constant, as these issues can significantly affect signal integrity.
- ➛Grounding Issues
High speed PCBAs typically include multiple signal types such as digital, RF and power DC. Ideally, these signal types should be grounded separately to avoid interference; however, this is not always possible due to design constraints.
- ➛Impedance Issues
Impedance matching is another important consideration for high frequency boards used in medical devices. Not only is this important for signal progression along and within the constructed board through vias and the stackup but also to ensure maximum power transfer for wireless transmission or over wired connections.
As the list above shows, challenges arise when developing medical PCBAs to ensure high-speed signal accuracy. Fortunately, there are strategies for mitigating the impact of these issues.
DFM for High-Speed Digital PCBs
How to Ensure Accuracy in High Frequency Medical PCBAs
Many of the high frequency accuracy challenges you face when developing medical boards are also encountered in other PCBA designs. These and other medical electronics board-specific actions, as listed below, should be incorporated into your development process.
Guidelines for Ensuring Medical PCBA High Speed Accuracy
- Choose components from registered sources
The best way to guard against bad and low-quality component selection, as well as counterfeits, is to source only from well-respected, FDA-registered vendors that provide adequate documentation, including datasheets. Additionally, you can utilize GIDEP to weed out potentially counterfeit components.
- Make sure your board build process meets regulatory standards
There are rules and standards that must be adhered to when building medical PCBAs, especially for minimally invasive and invasive boards. These include guidance for clearances, component placement, routing, impedances—and other electrical constraints. You should engage your CM early in the design stage to ensure that your development satisfies all PCBA medical device regulatory requirements; otherwise, the process for registering your electronic device may be delayed or halted altogether to ensure patient safety.
- Ensure the cleanliness of your boards
One of the most important considerations for medical PCBAs, where measurement fidelity is a premium requirement, is board cleanliness. The adequate removal of ionic contamination, for example, is critical because it can affect signal integrity and lead to inaccurate readings for medical devices.
- Work with a CM experienced in critical system board development
Perhaps the most important decision you can make to ensure that you meet the challenges of high frequency accuracy for your medical PCBA is to engage an experienced critical system CM early. This will ensure that your boards are built by a manufacturer familiar with important medical industry standards and able to assist you in satisfying their requirements.
|Tempo's Advanced Custom PCB Manufacturing Service for Complex Medical Systems Development
Tempo Automation, the industry leader in building high-quality PCBAs with the fastest turnaround, is not only experienced in building boards for the medical devices industry but is also ISO 13485 certified. We will work with you to ensure your boards meet industry standards.
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 successfully meeting the challenges of high frequency accuracy for your medical boards, contact us.