How to achieve signal integrity in high-precision medical PCBs？

How to achieve signal integrity in high-precision medical PCBs？

Medical imaging equipment (such as CT, MRI, ultrasound diagnostic equipment, etc.) has extremely high requirements for PCB accuracy, reliability and signal integrity. Such equipment needs to process microvolt signals and high-frequency data transmission, and must pass strict EMC/EMI tests. The manufacture of such PCBs requires multi-dimensional optimization from material selection, stacking design, process control, etc. The following are key technologies and experience sharing.

1. Material selection: high frequency and biocompatibility are preferred

Medical imaging equipment PCBs often use Rogers RO4000 series or Isola FR4 high-speed materials to reduce dielectric loss and ensure signal stability. For example, in a customer case, Jie Duobang recommended Rogers RO4350B material to a certain ultrasound probe manufacturer. Its dielectric constant (Dk) is stable at 3.48±0.05, which effectively reduces high-frequency signal attenuation. In addition, the surface treatment needs to use ENIG (chemical immersion gold) or immersion silver to avoid oxidation and ensure welding reliability.

2. Stacking design and impedance control

ONESEINE Multilayer PCB (usually 8-16 layers) needs to use simulation software (such as SI9000) to accurately calculate impedance. For example, with the technical support of JDB, a customer adjusted the differential pair line width/spacing to 4.5/5 mil and the dielectric thickness to 3.2 mil, achieving 100Ω±5% impedance matching, significantly reducing the crosstalk problem of MRI equipment.

3. High-precision processing and defect avoidance

Laser drilling technology: Microholes with a hole diameter of ≤0.1mm need to be drilled with CO2 laser or UV laser to ensure that the hole wall roughness is less than 25μm.

Solder mask process: Use LDI (laser direct imaging) exposure machine to increase the solder mask accuracy to ±10μm to avoid edge jaggedness caused by traditional exposure. JDB has used this process to help customers solve BGA area bridging defects, and the yield rate has increased by 12%.

4. Signal integrity (SI) and EMC design

Power integrity (PI): Adopt the "solid copper + multiple decoupling capacitors" solution. For example, a CT device deploys a 0.1μF + 10μF capacitor combination on the PCB to reduce the power noise to less than 50mV.

Shielding technology: Add a copper foil shielding layer between the DDR4 wiring layers, and verify it through the 3D structure simulation of JDB, which reduces EMI radiation by 15dB.

5. User decision scenario: How to verify the supplier's capabilities?

When screening PCB suppliers, a medical equipment manufacturer requires IPC-A-600 Class 3 certification and ISO 13485 medical system certificate, and passes the following tests:

Tg (glass transition temperature) ≥ 170℃ (to ensure high temperature reliability);

CAF (conductive anode wire) resistance test (voltage 500V, time 60s without failure).

JDB finally won the bid with the above qualifications and actual test data, and the customer reported that the defect rate of mass production batches was <200PPM.

The manufacturing(oneseine) of medical imaging PCBs is a comprehensive reflection of material science, process technology and design experience. From high-frequency materials to laser micro-hole processing, each link needs to be strictly controlled. Choosing suppliers with medical industry experience such as JDB can significantly reduce R&D risks and accelerate product launch.