www.sensirion.com

Version 5 – December 2011

3/12

Users Guide SHT1x

1 Application Information

1.1

Operating Conditions

Sensor works stable within recommended normal range –

see Figure 4. Long term exposures to conditions outside

normal range, especially at humidity >80%RH, may

temporarily offset the RH signal (+3 %RH after 60h). After

return to normal range it will slowly return towards

calibration state by itself. See Section 1.4 “Reconditioning

Procedure” to accelerate eliminating the offset. Prolonged

exposure to extreme conditions may accelerate ageing.

Normal

Range

0

20

40

60

80

100

-40

-20

0

20

40

60

80

100

120

Temperature (°C)

Figure 4: Operating Conditions

1.2

Soldering instructions

For soldering SHT1x standard reflow soldering ovens may

be used. The sensor is qualified to withstand soldering

profile according to IPC/JEDEC J-STD-020D with peak

temperatures at 260°C during up to 40sec including Pb-

free assembly in IR/Convection reflow ovens.

150sec. Ramp-up/down speeds shall be < 5°C/sec.

For soldering in Vapor Phase Reflow (VPR) ovens the

60sec and ramp-up/down speeds shall be limited to

10°C/sec. For manual soldering contact time must be

IMPORTANT: After soldering the devices should be stored

at >75%RH for at least 12h to allow the polymer to re-

hydrate. Otherwise the sensor may read an offset that

slowly disappears if exposed to ambient conditions.

Alternatively the re-hydration process may be performed at

ambient conditions (>40%RH) during more than 5 days.

In no case, neither after manual nor reflow soldering, a

board wash shall be applied. Therefore it is strongly

recommended to use “no-clean” solder paste. In case of

application with exposure of the sensor to corrosive gases

or condensed water (i.e. environments with high relative

humidity) the soldering pads shall be sealed (e.g.

conformal coating) to prevent loose contacts or short cuts.

For the design of the SHT1x footprint it is recommended to

use dimensions according to Figure 7. Sensor pads are

coated with 35µm Cu, 5µm Ni and 0.1µm Au.

Figure 6: Rear side electrodes of sensor, view from top side.

Figure 7: Recommended footprint for SHT1x. Values in mm.

1.3

Storage Conditions and Handling Instructions

It is of great importance to understand that a humidity

sensor is not a normal electronic component and needs to

be handled with care. Chemical vapors at high

concentration in combination with long exposure times

may offset the sensor reading.

For these reasons it is recommended to store the sensors

in original packaging including the sealed ESD bag at

1.97

2.47

1.07

Ø0.60

3.48

1.8

1.8

7.08

Time

preheating

critical zone