Case study

SPECIAL PRODUCT FOR A SPECIAL NEED

A New High Voltage Detector Board

Background

The HV-Board shown was developed for the Nikhef institute in Amsterdam. It is used in the detector of the LHCb’s (Large Hadron Collider beauty) outer tracker, to amplify the signal from a captured particle.

HV-board

The measurements are carried out at high voltage, while reliability, lifetime and signal-to-noise ratio play an important role in detecting the particles.

Our Aims

  • Development of a stable detector board
  • Prototype deliveries of HV-boards
  • Delivery of 2,000 HV-boards

Challenges

  • High voltage (breakdown at 3 kV)
  • Miniaturization (to improve resolution)
  • Reliability / aging
  • Signal-to-noise ratio and leakage current requirements
  • Volume (2000 PCBs with 64k capacitors)

Nikhef Amsterdam was responsible for the assembly and test.

Construction Process

For this project the usual method of encapsulating printed circuit boards with components on the outside couldn’t be used due to the possibility of air bubbles being present. Sooner or later breakdown would occur at these points due to the high voltage (3 kV).

The production process was modified to ensure optimum protection of the capacitors. They were mounted inside the printed circuit board.

Embedding the components in this way prevents the aging of the components. This is a very important requirement to ensure that the detector circuit continues to function well for a long period of time.

Because of the capacitors’ tight tolerance requirements, the choice was made to embed the physical components and not go for a solution whereby the capacitor material is etched.

Circuit BoardCircuit Board

Our Dutch subsidiary – Q.P.I. – has developed a new process to embed the physical components inside the printed circuit board. This new process involves pressing the capacitors into the PCB’s base material.

When pressing like this it is crucial not to damage the ceramic capacitors.  The result was that the capacitors are well protected from moisture, mechanical stress and aging.

Results

The project turned out to be a big success, and Q.P.I. was awarded the LHCB Industry Award by CERN LHCb Collaboration.

Nikhef:
“The HV-Board has improved the signal-to- noise ratio on a scale which is comparable to the improvement made in going from the LP to the Audio CD “