Micro Ring Magnets for Medical Device Encoder Assembly

Problem

A German medical device company needed ultra-small ring magnets for rotary encoders in a Class IIa implantable device. Requirements were extremely demanding:

• Dimensional tolerance of ±0.02 mm on all critical dimensions
• Biocompatible coating (parylene C) with verified uniform thickness
• Full material traceability and batch documentation per ISO 13485
• Consistent magnetic properties (Br ±2%) across production batches

Previous trial suppliers could not hold tolerances below ±0.05 mm at the required volume.

Solution

We identified a Ganzhou micro-magnet specialist factory with:

• Precision grinding equipment capable of ±0.01 mm on small NdFeB components
• In-house Helmholtz coil testing for 100% Br verification
• Experience supplying magnets for European medical device certifications

Quality system additions for this project:

• 100% dimensional inspection using automated vision system
• Batch-level CoA with Br, Hcj, BH(max) values and dimensional data
• Parylene coating outsourced to a certified coating house with thickness verification per batch

Specifications

• Material: NdFeB (N48)
• Shape: Ring
• Dimensions: Ø6 mm OD × Ø3 mm ID × 2 mm height
• Tolerance: ±0.02 mm on all dimensions
• Coating: Parylene C (10 μm nominal)
• Magnetization: Diametral (2-pole)
• Br tolerance: ±2% of nominal
• Volume: 10,000 pcs/year in quarterly batches

Results

• Dimensional tolerance held at ±0.02 mm across all 10,000 pieces.
• Parylene coating thickness verified at 10±2 μm per batch.
• Full traceability documentation accepted by customer's ISO 13485 auditor.
• Zero field returns after 12 months of deployment.

Next Steps

Share your encoder specifications and regulatory requirements. We will match you with a supplier qualified for precision micro-magnet production.