RF Welder

The Challenge

A medical device manufacturer needed to update a product design that included RF-based sterile welding capability by adapting their technology to a more highly integrated package and to satisfy updated international regulatory requirements. Success of the project would be measured by a reduction in size by one-fourth while meeting or exceeding performance and regulatory criterion.

The Solution

TCB Engineers brought 25 years of RF design experience to bear on the size reduction challenge through the development of compact magnetic design, a LabVIEW-based flat coil winder, and a metrology system for measurement of acceptance criterion.

Primary to any effort in reducing size of an RF circuit is the successful selection and implementation of components. In this case, the primary RF loading coil was constructed from air wound coil stock, which is physically large, expensive to integrate and susceptible to mutual inductance effects. TCB Engineers solved these problems by designing a modular potted inductor and shield assembly less than one-tenth the size of its predecessor while exhibiting superior magnetic performance. TCB Engineers also worked with the customer’s contract manufacturer (CM) to address the unique manufacturing challenges associated with producing high quality flat wire RF coil assemblies.

Figure 1 – Flat Wire Coil Provided 10:1 Reduction in Size

While the flat wire coil provided size and cost benefits, the task of producing them presented additional challenges. Preventing damage to wire insulation during winding and controlling finished dimensions were accomplished through design of a custom anvil and use of a precision motion system and associated LabVIEW control application. Using the winder and associated quality controls allowed the CM to produce finished goods with an inductance variation of less than 1% and minimal scrap, both of which contributed significantly to overall profitability.

Figure 2 – LabVIEW based Flat Wire Coil Winder

Putting it all Together

While preliminary EMC screening revealed a well-behaved and robust RF source, a specific harmonic non-compliance was noted. After considering several solution paths and associated business factors, addition of a simple passive filter was implemented. Evolution of the concept is shown and it proved effective toward homologation of the product to new markets while minimizing design changes.

Figure 3 – Harmonic Filter Development
Conclusions

These novel approaches allowed our customer to reduce their overall product size by 75% and demonstrates TCB Engineers’ unique ability to provide complete solutions to complex problems.

Services Used

RF Design
- Modeling, Simulation & Measurement
- Planning for and Achieving Regulatory Compliance
  - IEC-60101, FCC Part 15
- RF Welding
Software Engineering Services
- Systems Integration
- RF Simulation & Measurement
- LabVIEW Programming
- Instrumentation & Control Systems
Electrical Engineering Services
- Product Engineering
- Manufacturing Engineering
- RF Circuits, Systems and Test
- ESD‐EMC‐EMI Design/Mitigation
- Circuit Design & Development
Integration & Manufacturing Services
- Integration Services
  - Contract Manufacturer Selection, Management and Auditing
  - Strategic Analysis of Systems and Processes
  - Repeatability and Reliability
  - Validation and Verification
  - Design for Manufacturability
  - Microwave/mmwave Circuit Board Design
  - HALT-HASS Testing