Just the right mix

Mass air-flow (MAF) and temperature manifold absolute pressure (TMAP) sensors help reduce emissions and are located in the engine compartment, or more precisely in the air intake system. MAF sensors have the primary task of communicating the incoming air mass to the engine control unit. This is needed in both gas and diesel engines to calculate various parameters. MAF sensors are somewhat more precise than TMAP sensors. A TMAP sensor measures both the pressure and the intake temperature and uses this data to determine air mass.

In order to protect sensors, extremely reliable epoxy resins from the DELO MONOPOX and DELO-DUOPOX portfolio are used that pass all the typical automotive tests. They are resistant to oil, gas, as well as transmission and brake fluid, and can survive in temperatures between -40 °C and +155 °C. Once the sensor is potted, when stored at these temperatures, these resins do not display any stress cracks. 

Under pressure

Sensors are also used to alert the driver in the event of low tire pressure. They are therefore very important with respect to safety, fuel efficiency, and wear. Driving with incorrect tire pressure can pose a huge risk an accident by significantly extending braking distance or negatively impacting stability when cornering.

For die attach, sealing, and bonding tasks, heat-curing DELO MONOPOX epoxy resins are preferably used, while 2C materials of the DELO-DUOPOX series are used for large-volume PCB potting. Either are especially resistant and repellant against media including motor oil and other automotive fluids, but also salt spray and cleaning solutions. They show impressive results in thermal shock, humidity storage, vibration and drop tests as well. To ensure that pressure measurement always works correctly, how tightly the sensor is fixed to the housing is checked with a typical pressure of 7 bar for the long term and 9.5 bar for the short term.

Finding the right balance

When position or speed need to be captured, Hall sensors are a surefire solution. These sensors are often located directly on the wheel rim, or even on the wheel hub. From there, they provide accurate information on how frequently the wheel is rotating. For their assembly, dual-curing (light/anaerobic-curing) adhesives are especially appropriate because they  exposed to high-intensity light upon initial dispensing, rapidly fixing the magnet, the magnet retainer, and the Hall sensor. Afterwards, they achieve final curing, even in shadowed areas, by oxygen deprivation. These adhesives are also highly resistant to media such as oil, gasoline, or even brake fluid, and also pass salt spray tests, reflow tests (JEDEC), vibration tests, and drop tests with flying colors.

Safe parking made easy

When it comes to ultrasonic parking sensors, it is essential that the driver be able to depend on its accuracy. If the sensor fails, it can be an expensive ordeal to repair the vehicle. Therefore, it is particularly important that, in addition to mechanical functionality, the adhesive used has good acoustic characteristics like oscillation behavior so that the ultrasonic signal is transmitted without interruption.

Due to their position in the bumper, parking sensors have somewhat moderate temperature requirements. The adhesives should be usable in a temperature range of - 40 °C to +85 °C. In addition, they have to pass special automotive tests such as temperature and salt spray tests. Light-curing DELO KATIOBOND epoxy resins meet exactly these requirements and allow for in-line processes and short cycle times in series production while allowing shadowed areas to be reliably cured by preactivation. 

Putting adhesives to work

RADAR sensors, meanwhile, have a host of adhesive applications. Their assemblies can be broken down into four basic layers: the radome, the antenna, the printed circuit board (PCB), and the housing. In each of these layers, oftentimes more than one bonding process is needed.

The antennas, for example, are fixed to the PCB by way of antenna bonding. Within certain antenna designs, layers can be bonded through thin bondlines of dual-initiator adhesive, with or without electrical contacting or EMI-shielding properties. Meanwhile, the PCB comes with its own functional applications through EMI-shielding or thermally conductive adhesives. Even more bonding tasks come with advanced packaging solutions on PCBs, such as potting or pin sealing applications. The PCB is then bonded inside the housing, followed by bonding the housing and radome to create the final assembly.

In each of these sub-applications, the general adhesive requirements are similar to those of ultrasonic sensors, including passing durability tests to ensure a long service life.