Technical Notes

CR1 – A Breakthrough in Thermistor Coatingfor Harsh Environment Applications

What distinguishes
the CR1 from otheravailable coatings?

Conventional coatings for environmental protection and insulation of thermistors are usually
a compromise in terms of performance.
Epoxy encapsulation gives good thermal shock properties and corrosion resistance but low
flexibility, limited temperature performance and slow time response.
Silicone coatings, by contrast, perform well up to 200°C, are flexible and allow tightdimensional control for fast time response. They, however, are limited in their thermalshock performance and resistance to acids.
The use of CR1 in the current innovation overcomes these limitations and addresses aneed for improved protection for temperature sensors in harsh environments, such as Euro
6 compliant emission reduction systems in diesel engines.

TechnicalAdvantages of
CR1:

Chemical resistance in harsh environments is one of the fundamental performanceadvantages of CR1. The coating is resistant to a wide range of acids, fuels, solvents andmoisture. Heat resistance up to ~300°C is possible although the part is usually limited by
the melting point of the solder used to attach lead wires to the thermistor.
A proprietary Amphenol Advanced Sensors process allows the polymer to exceed thevoltage standoff requirement for automotive sensors, with associated advantages forcoating thickness reduction. Coating with CR1 allows accurate dimensional control of thecoated thermistor giving fast thermal time response. The tensile strength of CR1 [>4x thatof silicone] extends thermal shock performance and ensures good mechanical integrity ofthe thermistor chip package.
For example, when overmolding or inserting into a sensor housing, mechanical flexibility
enables the thermistor lead wires to be formed once the protective coating has been
applied. The low level of porosity in the polymer structure gives good moisture resistance,
which is important for applications where condensation or high humidity are present, suchas air conditioning condenser units.

CR1 – A Breakthrough in Thermistor Coatingfor Harsh Environment Applications
Benefits of CR1
Coating:• Tested to AEC Q200 (Material 4A Types)• Resistant to Acid/Gasoline/Diesel/Biofuel/Urea• High temperature performance up to 190ºC• High thermal shock resistance• Water immersion, silver migration resistance• Insulation up to 1000V DC at 25ºC
• Flexibility 180° bend around 1mm mandrel

Economic
Advantages of
CR1 Coating:• A alternative to glass-encapsulated devices by solving glass/metal interface corrosion
issues• May be exposed to corrosive environments where over-moulding or potting ofstandard sensors is normally required• Automated production process using established coating technology minimizes costand ensures product quality through 100% digital image inspectionwww.amphenol-sensors.com

Amphenol
Advanced Sensors

Registered Office: Amphenol Thermometrics (UK) Ltd,Crown Industrial Estate, Priorswood Road, Taunton, TA2 8QY, England
Registered in England No: 2310013© 2019 Amphenol Corporation. All Rights Reserved.
Specifications are subject to change without notice.
AAS-939-171C

09/2019