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www.sensirion.com Rev. 4 May 4 1/6 –201
Handling Instructions
For SHTxx Humidity and Temperature Sensors
Applicability
This document is applicable to all Sensirion SHTxx
humidity and temperature sensors.
ESD protection
The sensor shall be protected from ESD (Electrostatic
Discharge) only be handled in ESD protected areas and
(EPA) under protected and controlled conditions
(ground all personnel with wrist-straps, ground all non-
insulating and conductive objects, exclude insulating
materials from the EPA, operate only in grounded
conductive floor, etc.). Protect sensor outside the EPA
using ESD protective packaging.
Protection against ESD is mandatory.
Exposure to Chemicals
Humidity and Temperature sensors are highly accurate
environmental sensors and as such they are not
ordinary electronic components. The opening in the
package exposes the sensor to the environment and
makes it susceptible to pollutants. While applying
sensors in the field in ambient environment is not
critical, pollutants are known to occur in manufacturing
environments and during storage. Please carefully
follow the guidelines in this application note to ensure
that you can benefit of the sensor’s outstanding
performance.
The sensor shall not get in close contact with volatile
chemicals such as solvents or other organic
compounds. Especially high concentration and long
exposure must be avoided. Ketenes, Acetone, Ethanol,
Isopropyl Alcohol, Toluene, etc. are known cause to
drift of the humidity reading irreversibly in most of the –
cases. Please note that such chemicals are integral
part of epoxies, glues, adhesives, etc. and outgas
during baking and curing. These chemicals are also
added as plasticisers into plastics, used for packaging
materials, and do out-gas for some period.
Acids and bases may affect the sensor irreversibly and
shall be avoided: HCl, H2SO4, HNO3, NH3 etc. Also
Ozone in high concentration or H2O2 have the same
effect and therefore shall be avoided. Please note, that
above examples represent no complete list of harmful
substances.
The sensor shall not get in contact with cleaning agents
(e.g. PCB board wash after soldering) or strong air
blasts from an air-pistol (not oil-free air). Applying
cleaning agents to the sensor may lead to drift of the
reading or complete breakdown of the sensor.
Ensure good ventilation (fresh air supply) to avoid high
concentrations of volatile chemicals (solvents, e.g.
ethanol, isopropanol, methanol, acetone, cleaning
solutions, detergents…).
Packing and Storage
Prior to assembly or use of the sensors it is strongly
recommended to store the sensors in original the
sealed ESD bag at following conditions: Temperature
shall be in the range of 10°C 50°C (0 5°C for – – 12
Preface
Sensirion SHTxx are relative humidity and temperature
sensors of high quality. For taking advantage of their
outstanding performance some precautions must be
taken during storage, assembly and packaging.
Therefore, please read the following instructions
carefully - preferably during design-in phase and before
production release of the respective device. Special
attention is required regarding the exposure to volatile
organic compounds, i.e. high concentration and long
exposure time to respective gases shall be avoided.
Such conditions are known to occur in manufacturing
environment and/or during storage. Therefore proper
handling and choice of materials are crucial. Applying
sensors in the field in ambient environment is not
critical.
SHTxx Handling Instructions
www.sensirion.com Rev. 4 May 4 2/6 –201
limited time) and humidity at 20 60%RH (sensors that –
are not stored in ESD bags).
Store sensors in original, unopened ESD bag. Place
additional stickers only on the outside of the ESD
bag.
Once sensors have been removed from the original
ESD we recommend to store the individual sensors bag
as well as devices with assembled sensors in metal-in
antistatic shielded ESD bags In particular, it is .
recommended not to use any adhesive or adhesive
tapes to reseal the sensor bag after opening. Therefore
reclosable bags with zipper are preferred.
For a recommendation on specific ESD bags please
contact Sensirion.
Sensors as a component or mounted into the final
product shall not be packaged in outgassing plastic
materials which could cause sensor pollution. Besides
m -In antistatic shielded ESD , paper or etal bags
cardboards based packaging, deep drawn plastic trays
(PE, PET, PP) may be considered. Do not use antistatic
polyethylene bags (light blue, pink or rose color); be
very careful with bubble foils and foams.
Be careful about stickers present inside the packing
(e.g. on the housing of the device). Sticker size should
be kept to a minimum, and the sticky side shall fully
adhere onto a surface.
Please note that many packaging materials may be
provided with additives (plasticizers) which may have a
polluting effect on the sensor. Generally speaking, if a
material emits a strong odor you should not use it.
Additives may also be added to materials which are
listed for recommended use. For high safety, device
housing and shipment packaging must be qualified.
Such a qualification test may contain exposure of the
final device with sensor in its shipment packaging to
temperature ≥65°C for at least 168 hours. (If shipping
or storage conditions are expected to be harsh, the
qualification test conditions for the packing material
have to be customized.) The sensor reading then shall
show no changed deviation against a reference
compared to same measurements before the exposure.
Do not use polyethylene antistatic bags (light blue,
pink or rose color). Do not use adhesive tapes
inside packaging.
For guidance on simple and straight-forward testing of
humidity sensors please consult the Testing Guide for
humidity sensors.
Assembly
Sensors in SMT packages are classified as Moisture
Sensitivity Level 1 (IPC/JEDEC J-STD- ). It is 020
recommended to process the sensors within 1 year
after date of delivery.
Before developing the assembly process please read
the User s Guide of the Datasheets carefully. In the ’
following, crucial items are underlined plus additional
items are given:
For soldering please read carefully the corresponding
Section in the User’s Guide of respective Datasheet.
Make sure that maximum temperatures and exposure
times are respected. In case the PCB passes through
multiple solder cycles (as is the case for e.g. PCB that
are assembled on top and bottom side), it is
recommended to assemble the SHTxx only in the last
solder cycle. This is to reduce risks of sensor pollution.
It is important that “no clean” solder paste is used and -
no board wash is applied once the sensor is assembled
to the PCB.
SHTxx Handling Instructions
www.sensirion.com Rev. 4 May 4 3/6 –201
Do not apply board wash.
No mechanical force all be applied to any part of the sh
sensor during assembly or usage. Especially, after
soldering no force shall be applied to the sensor cap
(SHT1x) to prevent weakening of the adhesive joint
between cap and PCB.
For application in corrosive environment such as –
condensed water or corrosive gases it may be –
necessary to protect the electronic assembly including
the soldered contacts of the sensor with a passivation.
Such passivation may be achieved by conformal
coating or by applying adhesive.
Low viscose conformal coatings or potting materials
may flow into the inside the sensor cap (SHT1x,
SHT7x), cover the sensor element and thus make the
humidity sensor inoperative. Use only high viscose
conformal coatings or potting materials, or seal the
interface between sensor cap (SHT1x, SHT7x) and
sensor PCB before applying conformal coating. Make
sure that used conformal coating is not outgassing.
If conformal coating is applied, the top surface of
the sensor must remain free of coating.
In any case, covering the humidity sensor opening with
any kind of coating must be avoided. Therefore, the top
surface of the sensor should remain free of coating.
The following table lists conformal coatings which have
been tested regarding pollution of the humidity sensor
and are known to be suitable applied and fully cured if
under good ventilation (fresh air supply) and according
to respective datasheet.
Conformal Coatings
Manufacturer
Product
Peters
Elpeguard SL 1301 ECO-FLZ
Dow Corning
1- 2577 Low Voc Conformal Coating
Do not apply spray to unprotected sensor.
Whenever using spray coating techniques (e.g. to apply
varnish or conformal coating, etc.) the SHTxx sensor
has to be covered by adhesive tape to prevent the
coating of the humidity sensor opening. The following
table lists adhesive tapes which have been tested
regarding pollution of the humidity sensor and are
known to be suitable.
Adhesive Tapes
Manufacturer
Product
3M
Electrical Tape 92
Do not apply any other adhesive tapes such as Scotch
Tape, Sello Tape, Tesa Film, etc.
XXX
Produktspecifikationer
| Varumärke: | Sensirion |
| Kategori: | sensor |
| Modell: | SHT21 |
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