Heart Rate Variability Analyzer

Project Overview

A leading medical device manufacturer approached NimblePCB to produce the core PCB assembly for their next-generation portable heart rate variability (HRV) analyzer. The device needed to capture subtle micro-volt cardiac signals with exceptional accuracy while maintaining FDA-class manufacturing traceability.

Challenge

• Signal integrity: HRV analysis requires capturing micro-volt level bio-signals with minimal noise, demanding tight impedance control across all analog signal traces.
• Miniaturization: The portable form factor required dense component placement with 0201-size passives and fine-pitch QFN packages on a compact 6-layer board.
• Regulatory compliance: All PCB manufacturing and assembly processes needed full IPC Class 3 compliance with lot traceability for medical device certification.
• Mixed-signal design: Analog front-end and digital processing sections on the same board created challenges in noise isolation and ground plane management.

Solution

NimblePCB’s engineering team worked closely with the customer’s design engineers to optimize the PCB stackup and manufacturing process:

• Stackup optimization: Designed a 6-layer controlled-impedance stackup with dedicated analog and digital ground planes, using high-Tg FR-4 (TG170) for thermal stability.
• Precision manufacturing: Achieved 4/4 mil trace/space with +/-5% impedance tolerance on critical signal lines.
• Assembly excellence: Single-sided SMT with selective THT for robust connector attachment. X-ray inspection on all BGA and QFN packages.
• Full traceability: Implemented lot-level tracking from raw laminate through final test, supporting the customer’s FDA 510(k) submission.

PCB Specifications

Results

• Passed all EMC and signal integrity validation tests on first prototypes
• Achieved 99.7% first-pass yield in production runs
• Full regulatory traceability documentation delivered, supporting FDA clearance
• Scaled from prototype to 5,000 units/month within 8 weeks