SF2 Handling and Assembly Datasheet by Sensirion AG

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www.sensirion.com Version 1 December 2011 1/4
Handling and Assembly of SF2 Filter Cap
For use with SHT2x Humidity and Temperature Sensors
Applicability
This document is applicable to SF2 filter cap for use
with SHT2x humidity and temperature sensors supplied
by Sensirion.
General Handling Instructions
Handling of SF2 Filter Cap
A SHT2x sensor which is protected by a SF2 filter cap
measures the humidity which diffuses through the
PTFE filter membrane of the filter cap, hence whenever
the pores of the filter membrane are clogged, the
diffusion of humidity may be restricted. The filter
membrane protects the sensor surface from particles
and liquids and any damage on the filter membrane can
reduce the protective effect of the filter cap.
Prevent Membrane Clogging
The risk of clogging or damaging the filter membrane
through improper handling of the filter cap can be
reduced by following the below precautions:
SF2 filter caps should be handled with appropriate
tools, e.g. vacuum tweezers with rubber tips,
pick&place tools with rubber tips, tweezers with
rounded tips.
Whenever possible, contact of the handling tools
with the filter membrane should be avoided.
If contact of the handling tools with the filter
membrane cannot be avoided, the handling tools
must be clean, i.e. free of oils, adhesives, etc.
Mounting of SF2 Filter Cap
For insertion of the filter cap into dedicated holes in the
PCB, some force may be required. This force should be
applied to the membrane-free parts of the plastic
housing or the outer ring of the circular membrane
surface. If the force is applied to the center of the top
surface, damaging of the filter membrane is probable.
Conformal Coating
If a conformal coating is used to seal the solder pads
prior to assembly of the filter cap, the conformal coating
must not cover the holes in the PCB for mounting of the
SF2 filter cap. Otherwise, the SF2 filter cap cannot be
assembled.
Preface
The SF2 filter cap provides protection for SHT2x
humidity and temperature sensors against particles and
liquids. The SF2 filter cap can easily be mounted onto
the PCB. Depending on the protective requirements of
the final product, there are two ways of mounting the
SF2 filter cap to the PCB. Clipping it into the
designated holes in the PCB without the use of any
adhesive provides good protection of the sensor against
dust and liquid droplets, whereas mounting the cap to
the PCB with adhesive can provide IP67 protection for
the sensor. In order not to affect sensor performance
some precautions have to be followed when handling
and assembling the SF2 filter cap.
force can be
applied
force must not
be applied
Figure 1: Areas of the filter cap suitable for application of
force during mounting process. Red area is restricted, green
and grey frame area is allowed
Using Clips membrane SENSIRION THE sense»: COMPANY
Handling and Assembly of SF2 Filter Cap
www.sensirion.com Version 1 December 2011 2/4
S H T 2 1
D 0 A C 4
Assembly of the SF2 Filter Cap
There are two possible ways to assemble the SF2 filter
cap. For applications where no hermetical seal is
required between the PCB and the SF2 filter cap, the
SF2 filter cap can easily be assembled to the PCB
using the integrated clips. No adhesive is required for
this type of mounting. For applications where sealing
between SF2 and PCB is required, the filter cap may be
assembled using adhesive.
Please note, that when using the clips to mount the
filter cap, there can be a very small gap between the
filter cap and the PCB due to unevenness of the two
joining surfaces. This means that the interior space of
the filter cap is not hermetically sealed to the outside.
This may be a problem whenever the interface between
the filter cap and the PCB is supposed to be water
(pressure) proof, or when the filter cap is used as an
interface to the housing. In the latter case, air can pass
from the inside volume of the housing into the interior
volume of the filter cap (see Figure 2). This air
exchange could potentially lead to misreading, as the
environmental air can mix with the air inside the
housing. In both cases, it is recommended to use
adhesive for mounting the filter cap in order to seal the
interface between filter cap and PCB.
Using Clips
When using the clips to attach the SF2 filter cap, the
thickness of the PCB must be 0.8mm and the
mounting hole pattern shall be designed according to
the SF2 data sheet
Using Adhesive
For mounting the SF2 filter cap with adhesive, the
mounting hole pattern shall be chosen such that the
pins of the filter cap are used for positioning only. The
adhesive dispensing and curing process shall be
performed in a well ventilated area.
1. Application of adhesive. A closed line of
adhesive shall be applied around the SHT2x on
PCB. Ideally this is done with adhesive
dispensing equipment using a fine dispensing tip
(e.g. gage 22). The top surface of the SHT2x
must remain free of adhesive. The amount of
adhesive shall be determined in a test run. The
minimal amount is attained when a closed line of
adhesive around the SHT2x is present, the
maximum amount is reached before adhesive
gets visible in the opening of filter cap (see step
2).
2. Assembly of filter cap onto PCB. After placing
the filter cap onto the PCB, a slight adhesive fillet
should be visible around the filter cap. When
removing the membrane (this shall be done in a
test run in order to set up the adhesive dispensing
process), there should be no adhesive visible in
the filter cap opening. If adhesive is visible in the
filter cap opening, the used amount of adhesive is
too large.
3. Curing of adhesive. Curing temperature
according to adhesive data sheet .
Figure 2: Illustration of air exchange along the interface of
filter cap and PCB.
Figure 3: Dispensing of adhesive around SHT2x.
Figure 4: Assembled filter cap with adhesive fillet
(left views) and removed filter membrane for process
setup (right view).
SHT21
DOAC4
adhesive fillet
SHT2X
PCB
housing
o-ring
membrane
SF2
air exchange
to be avoided
to
air exchange
to be avoided
SENSIRION THE sense»: COMPANY
Handling and Assembly of SF2 Filter Cap
www.sensirion.com Version 1 December 2011 3/4
Recommended Adhesives
When choosing an adhesive for application with SHT2x
sensors and SF2 filter cap, carefully read the
Application Note Handling Instructions for SHTxx
Humidity and Temperature Sensors with material
recommendation or consult Sensirion support. The
following adhesives were tested for use with SF2 filter
caps and SHT2x: Electrolube SMA 10SL, DELO
MK096, DELO AD066, DELO 6093,EPO-TEK H70E/S,
EPO-TEK T6067, Lord MD-130.
SENSIRION THE sensor: COMPANY Dale Revision Changes December 2011 1 Initial revision SENS‘RION AG Sensinon Inc., USA Sensirion Korea Co. Ltd. info@sensirion.com www sensinon.com Sensirion AG (Germany) info@sensirion.com www sensinon.com info us@sensirion com www.5ensirion.com info@sensrrion.co.'g www.5ensirion.co.'g info@sensirion.co kr www sensmon.co.kr info@sensirion.com.cn www sensmon.com cn www.5ensirion oom/conlacl
Handling and Assembly of SF2 Filter Cap
www.sensirion.com Version 1 December 2011 4/4
Revision History
Date
Revision
Changes
December 2011
1
Initial revision
Copyright© 2011, SENSIRION.
CMOSens® is a trademark of Sensirion
All rights reserved
Headquarters and Subsidiaries
SENSIRION AG
Laubisruetistr. 50
CH-8712 Staefa ZH
Switzerland
phone: +41 44 306 40 00
fax: +41 44 306 40 30
info@sensirion.com
www.sensirion.com
Sensirion Inc., USA
phone: +1 805 409 4900
info_us@sensirion.com
www.sensirion.com
Sensirion Japan Co. Ltd.
phone: +81 3 3444 4940
info@sensirion.co.jp
www.sensirion.co.jp
Sensirion Korea Co. Ltd.
phone: +82 31 345 0031 3
info@sensirion.co.kr
www.sensirion.co.kr
Sensirion China Co. Ltd.
phone: +86 755 8252 1501
info@sensirion.com.cn
www.sensirion.com.cn
Sensirion AG (Germany)
phone: +41 44 927 11 66
info@sensirion.com
www.sensirion.com
To find your local representative, please visit www.sensirion.com/contact

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