Complex assembly for the highest standards

Cicor is working together with the automotive supplier AB Elektronik Sachsen GmbH to manufacture highly sensitive exhaust sensors used for aftertreatment of exhaust gas in trucks.

The trend toward networked communication is also shaping new developments in the automotive industry. More and more areas of vehicles are being monitored with sensitive sensors and the data collected sent directly to the driver or to the upstream systems. This makes it possible to detect and fix malfunctions, signs of wear and tear or failures of
individual vehicle components at an early stage. Exhaust sensors play an important role in exhaust gas aftertreatment. They measure the pressure which is used to determine the current load of the downstream diesel particulate filter and ensure that it is regenerated.

Sensors to meet the highest standards

Headquartered in Klingenberg, Germany, AB Elektronik Sachsen GmbH is an automotive supplier belonging to the British Group TT Electronics. As an accredited partner for the production of sophisticated sensor solutions, AB Elektronik cooperates with Cicor to develop and manufacture sensors that are used, among other things, in the aftertreatment of exhaust gas in trucks. Lawmakers have set limits to minimize truck exhaust emissions which are mandatory for vehicle manufacturers. The diesel particulate filters used in trucks help satisfy these standards. Upstream of the particulate filter is an exhaust sensor which monitors its current load. The Cicor exhaust sensor measures the dynamic pressure of the exhaust before the particulate filter and reports its current load to the upstream systems. If excessive counterpressure caused by the exhaust particulate load blocks emission of the exhaust gas, this is detected by the sensor and filter regeneration is initiated by burning off the excess particulate.

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Totally reliable even in the harshest conditions

 

Cicor developed the processes for the assembly and interconnect technologies for the customer. The exhaust sensor is based on thick-film ceramic made of aluminum oxide (Al2O3) that is assembled by Cicor with a number of components. The SMD elements, with SMD 0402 as the smallest component used, and the housed chip are soldered to the substrate. The naked sensor chip, on the other hand, is attached directly to the ceramic in a complex process and protected from external influences by an additional chip protection ring.

The greatest challenge in manufacturing the product is accounting for the high temperatures and environmental conditions prevalent inside the exhaust system. The finished sensor system must maintain pressure of up to 6 bar within a large temperature range of − 40 °C to 130 °C and function properly. Special processes for the assembly and interconnect technologies were used to guarantee reliability and long-term stability.

The sensor chip is attached with silicone adhesive to part of the thick-film ceramic to ensure 100% impermeability. Silicone adhesive is able to absorb the mechanical tensions through the different temperature coefficients of the materials. The material properties of the silicone adhesive, how- ever, are not beneficial for further processing (wire bonding). The sensor chip also has to be attached to be able to ensure the stability of the circuit. Additionally integrated adhesive points made of SMD adhesive under the chip make heatintensive bonding with gold wire possible and give the chip the necessary stability for wire bonding. Gold is a very robust precious metal which shows minor signs of fatigue even when temperatures fluctuate significantly. Monolithic connection systems, in this case gold with gold, produce reliable connections which are stable over the long run. To increase process reliability, bonding is performed with active bond process control. With this non-standard interconnect technology, Cicor ensures the bonding of a chip adhered with silicone meets the highest quality standards.

Highest quality standards

 

Cicor is a leading manufacturer of sophisticated microelectronics and high-quality substrates. In the area of microelectronics, we offer state-of-the-art assembly and interconnect technologies as well as packaging technologies, while the manufacture of highly complex rigid, rigid-flex and flex circuit boards and thin- and thick-film interconnect devices is what marks us out from the competition in the area of substrate manufacturing and processing.

When manufacturing components and solutions for the automotive industry, compliance with tolerance ranges and the absolute reliability of all production processes plays a central role. Strict process control guarantees that production meets the highest quality standard that meets the needs of our customers and ensures the reliability of application.

The key to innovative solutions

The challenge

  • Reliability and functionality
    • Extremely reliable even in the harshest conditions
    • Temperature and pressure resistance
    • Low incidence of defects
    • Complex assembly
    • Sensitive sensor chip
    • Absorption of mechanical tensions
    • Circuit protection
  • Quality assurance
    • Consistently high quality for high volumes
    • Flexible outsourcing

The requirements

  • Materials
    • Durable and resilient
    • Resistant to temperature and pressure
    • Gold
    • Technological expertise
    • Consideration for different material properties
    • Combination of various assembly processes
  • Quality
    • Standardized processes
    • Strict monitoring of faults
    • Guaranteed product quality
    • Experience
    • Innovative technologies
    • Competent personnel
  • Partnership

The Cicor solution

  • Assembly of the thick-film ceramic
  • Circuit resistant to temperature and pressure
  • Circuit protection of the sensor
  • Highest product quality
  • Individual micro assembly

The benefits

for AB Elektronik Sachsen GmbH

  • Experienced partner in micro assembly
  • Highest level of manufacturing expertise
  • State-of-the-art production facilities
  • Absolute delivery reliability
  • Customer product development

    for the end customer
    • Fault-free functioning of the diesel particulate filter
    • Compliance with legal regulations