Datasheet Filter Cap SF2 For Humidity and Temperature Sensors SHT2x/3x/4x, SHTC1 and SHTC3 Protection against dust and particles Protection against water immersion Designed to match humidity and temperature DFN type sensors Optimized for response time of sensor Product Summary The filter cap SF2 is made of a single piece of The filter cap SF2 protects SHT2x/3x/4x, SHTC1 and SHTC3 humidity and temperature sensors against dust, Polybutylene Terephthalate (PBT) with a filter membrane welded on it. The SF2 filter cap is designed to be mounted water immersion as well as against contamination by particles. The cavity inside is made such that the volume after soldering by clipping the four pins into openings in the PCB. Together with the sensor it provides a compact between membrane and sensor is kept minimal and entity which may serve as an adaptor to the device hence the impact on response time for humidity measurements is reduced to a minimum. The filter cap housing. A waterproof mounting solution is achieved by adding adhesive and an o-ring. SF2 is available in black color with a black filter membrane. Dimensions Technical Specifications R3.2 Parameter Value Operating Range -40 125C 1 IP IP67 RoHS Compliant Body material Polybutylene Terephthalate (PBT) A A Body Color Black UL94 (Body material only) UL94 V-0 (0.73mm) Filter material PTFE with polyester scrim 1.0 Filter Color Black A-A Filter Thickness 0.13 mm 5.05 Filter pore size 1.5 m 0.27 3.0 R0.5 2 Filtration efficiency 99.99% 3 Oleophobic Rating (Filter) 8 SHT21 Mullen Hydrostatic >100mbar (>1m water) 1 IP67: dust tight, protected against harmful water immersion up Figure 1: Drawing of the filter cap SF2 (body only). Dimensions to 1m water column. ( Datasheet Filter Cap SF2 Users Guide Filter Cap SF2 Mounting Instruction 5.1 (5.28) The filter cap SF2 is mounted to the PCB after soldering the sensor by clipping the four pins into the openings in the PCB. The filter cap may be fixed by adhesive or by the force of the pins itself compare Figure 2. By choosing 0.3 0.4 different distances between the openings the SF2 either clips itself on the PCB by mechanical force or the pins can be used for positioning only compare Figure 3. The recommended PCB thickness for mounting with clips is 0.8mm. Please note that when mounting the filter cap with clips, a hermetic seal between filter cap and PCB cannot be guaranteed. This should be considered for applications in which the filter cap is used to seal the volume around 2.4 the sensor against surrounding volume which is enclosed by a housing (compare Figure 2). In addition, the membrane or any part of the SF2 must be protected from 1.0 external forces or contact, so that no mechanical stress is 1.0 put on the SF2, which could result in shifting or breaking. This could be realized in a design as in Figure 2, where the membrane is protected behind the housing, i.e. no part Figure 3: PCB layout example of SHT2x and filter cap SF2 all of the SF2 is exposed or sticks out of the housing. For DFN sensors of smaller size to be placed according to the further information on handling and assembly of SF2 filter example in the center of the SF2 outline. Dimensions are given caps please refer to the application Note Handling and in mm (1mm = 0.039 inch). The distance of the openings is Assembly of SF2 Filter Cap. 5.1mm 0.05mm if the sensor should clip on the PCB and 5.28mm if the pins are used for adjustment only. By varying the openings distance about 0.05mm the clipping force may be membrane o-ring adjusted. housing SF2 SHTyx Mounting against housing wall PCB The filter cap SF2 not only protects against dust and water immersion, it also helps to mount the sensor to the housing wall. If mounted to a housing wall towards the outside, the sensor is perfectly exposed to the Figure 2: Side view of SF2 filter cap mounted between PCB environment of which humidity and temperature shall be and housing wall. The volume below the membrane is kept measured. minimal and the membrane is separated from the surrounding In order to protect the inside of the device housing against volume enclosed by housing. water immersion it is recommended to place an o-ring between filter cap and housing wall compare Figure 2. For such o-rings Sensirion recommends the following Measures for higher protection specifications: For hermetic seal, adhesive must be added between filter Inner diameter: 5mm cap and PCB. Such seal provides higher security against Cross section: 1mm water leakage, condensation inside the housing, and Material: NBR corrosion of the soldering pads of the sensor. If corrosion of the solder contacts is a potential problem, it is Important: Please ensure that the air path to the measured recommended to cover the solder joints with adhesive as volume is not blocked by another membrane. This may well. For further information on application of adhesives increase response time of the sensor dramatically. with SF2 filter caps, please refer to the application Note Handling and Assembly of SF2 Filter Cap. Labeling of the shipment www.sensirion.com Version 4 April 2021 2/5 5.1 (5.28) 0.7 1. 6 Sensor filter cap 0.2 0.4 1.0
