Performing precise, high-bandwidth measurements on high-voltage power circuits, such as those incorporating GaN and SiC devices, has always been challenging. The combination of small differential signals and large common-mode voltages can easily compromise measurement accuracy. PMK’s FireFly® Series optically isolated probes solve this longstanding issue by offering unmatched measurement capability:

• Bandwidths exceeding 1.5 GHz
• Industry-leading Common Mode Rejection Ratio (CMRR) of >180 dB at DC to 500 kHz and still an impressive 80 dB at 1 GHz
• Ultra-low temperature drift (<0.05% per °C)
• Complete galvanic isolation ensuring clean, interference-free signals
• Compatibility with any oscilloscope through universal BNC outputs

To fully leverage the FireFly’s exceptional performance, your test board’s connection points must be carefully selected and implemented. The FireFly system conveniently supports standard connector types, including MMCX and square pin connectors. Let's explore how to create optimal measurement points for each connector type.

Why MMCX and Square Pin Connectors?

MMCX connectors have become industry favorites for their compact size, rugged coaxial construction, and excellent RF characteristics up to GHz frequencies. These connectors provide a fully shielded environment up to the measurement node, greatly enhancing measurement fidelity in challenging environments.

For higher voltage and differential measurements, especially where robustness and ease-of-use are priorities, square pin connectors offer secure, mechanically stable connections. PMK FireFly probes accommodate both connection types effortlessly, allowing test engineers flexibility depending on their measurement needs.

Example Installation #1: MMCX Connectors on a Through-Hole GaN/SiC Evaluation Board

Many GaN or SiC evaluation boards with TO-220 or similar packages offer convenient through-hole nodes for easy measurement access. For these scenarios, MMCX connectors offer an ideal test solution.

Installation Steps:

1. Selecting an MMCX Connector
   Choose a sturdy, surface-mount MMCX connector with a solid body and coaxial center pin. Ensure connector impedance ratings align with the FireFly probe tip cables (available from ±1V up to ±250V measurement ranges).

2. Identifying Nodes and Preventing Shorts
   Clearly identify gate (high impedance) and source (low impedance) nodes. Place a small insulating Kapton tape under the connector body to prevent accidental shorts from solder-mask pinholes or imperfections.

3. Secure Soldering
   First, solder the connector body firmly to the source node for stable mechanical and electrical grounding. Once secure, carefully solder the center pin to the gate node.

4. Inspection and Testing
   Visually inspect connections thoroughly. Verify no shorts exist using an ohmmeter, confirming proper electrical isolation and solid continuity.

5. Mechanical Reinforcement
   MMCX connectors feature strong insertion/extraction forces. Protect your PCB by reinforcing the connection points with epoxy adhesive for long-term reliability.

With this robust test point established, you can confidently use FireFly’s MMCX-compatible probe tip cables (e.g., FF-MMCX-10V or FF-MMCX-50V) to achieve clean and reliable measurements.

Example Installation #2: Square Pin Connectors on a Compact Chip-Scale PCB

When your board utilizes miniature, densely packed chip-scale packages, creating secure test points can be more challenging. The FireFly probe’s square-pin connector tips (FF-WSQ series) offer a stable, easy-to-use solution, especially at higher voltages (up to ±2500V).

Installation Steps:

1. Selecting and Preparing a Square Pin Connector
   Select a robust square-pin connector suitable for your measurement voltage range. Trim or remove unnecessary pins carefully with a precise cutting tool like a Dremel, adjusting pin lengths for easy board access.

2. Exposing Test Nodes
   Carefully scrape away the solder mask from gate and source nodes, clearly exposing metallic contact areas. Clean and inspect multiple times, ensuring adequate and stable soldering surfaces.

3. Pre-tinning and Connector Placement
   Apply solder flux and generously pre-tin both gate and source pads. Ensure sufficient solder for solid mechanical and electrical joints. Position the square-pin connector carefully, soldering the mechanically supportive source pin first for stability.

4. Soldering and Verification
   Once the source pin is securely soldered, solder the gate pin, taking extra care due to limited workspace. After soldering, use precise ohmmeter probes to confirm electrical isolation and reliable connectivity.

5. Final Reinforcement and Protection
   If multiple connectors are closely positioned, insert insulating tape between them to avoid accidental shorts. After verifying all connections electrically and visually, reinforce mechanically using epoxy.

These square-pin connectors now offer robust, easily accessible measurement points perfectly suited for the FireFly’s WSQ tip cables, enabling safe and accurate high-voltage measurements.

Leveraging the Power of FireFly®: Easy Connectivity and Unmatched Measurement Accuracy

The FireFly® system’s clever probe head design, compact angled tip configuration, and versatile compatibility with industry-standard MMCX and square-pin connectors make it remarkably easy to add or retrofit high-quality test points on nearly any PCB.

Combined with FireFly’s extraordinary performance—high-bandwidth measurements, outstanding isolation, and superior CMRR—proper connector installation allows you to unlock powerful insights into your high-voltage GaN and SiC circuit designs. PMK’s commitment to precision engineering ensures every FireFly system delivers consistent, ultra-stable results, even under challenging thermal and electromagnetic conditions.

Explore the full line of FireFly® probe tip accessories, ranging from MMCX tips (±1V to ±250V) to square-pin connectors (±500V to ±2500V), to effortlessly match your measurement requirements and optimize your circuit testing accuracy.

Ready to achieve unparalleled measurement fidelity? Equip your test boards today with robust MMCX or square-pin connectors, paired seamlessly with PMK’s groundbreaking FireFly® probes, and experience a new benchmark in isolated high-voltage testing.

For more details on FireFly® probes and compatible accessories, visit: PMK FireFly Series