SHT20P datasheet(3/10 Pages) ETC2 | DFN type package

3 / 10 page

www.sensirion.com

Version 4 – May 2014

3/10

Users Guide SHT20P

1 Extended Specifications

For details on how Sensirion is specifying and testing

accuracy performance please consult Application Note

“Statement on Sensor Specification”.

1.1

Operating Range

The sensor works stable within recommended Normal

Range – see Figure 4. Long term exposure to conditions

outside Normal Range, especially at humidity >80%RH,

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

After return into the Normal Range it will slowly return

towards calibration state by itself. Prolonged exposure to

extreme conditions may accelerate ageing.

Figure 4 Operating Conditions

1.2

RH accuracy at various temperatures

Typical RH accuracy at 25°C is defined in Figure 2. For

other temperatures, typical accuracy has been evaluated

to be as displayed in Figure 5.

Figure 5 Typical accuracy of relative humidity measurements

given in %RH for temperatures 0 – 80°C.

2 Application Information

2.1

Soldering Instructions

The DFN’s die pad (centre pad) and perimeter I/O pads

are fabricated from a planar copper lead-frame by over-

molding leaving the die pad and I/O pads exposed for

mechanical and electrical connection. Both the I/O pads

and die pad should be soldered to the PCB. In order to

prevent oxidation and optimize soldering, the bottom side

of the sensor pads is plated with Ni/Pd/Au.

On the PCB the I/O lands8 should be 0.2mm longer than

the package I/O pads. Inward corners may be rounded to

match the I/O pad shape. The I/O land width should match

the DFN-package I/O-pads width 1:1 and the land for the

die pad should match 1:1 with the DFN package – see

Figure 6.

The solder mask9 design for the land pattern preferably is

of type Non-Solder Mask Defined (NSMD) with solder

mask openings larger than metal pads. For NSMD pads,

the solder mask opening should be about 120μm to

150μm larger than the pad size, providing a 60μm to 75μm

design clearance between the copper pad and solder

mask. Rounded portions of package pads should have a

matching rounded solder mask-opening shape to minimize

the risk of solder bridging. For the actual pad dimensions,

each pad on the PCB should have its own solder mask

opening with a web of solder mask between adjacent

pads.

Figure 6 Recommended metal land pattern for SHT2x. Values

in mm. Die pad (centre pad) may be left floating or be connected

to ground, NC pads shall be left floating. The outer dotted line

represents the outer dimension of the DFN package.

For solder paste printing a laser-cut, stainless steel stencil

with electro-polished trapezoidal walls and with 0.125mm

stencil thickness is recommended. For the I/O pads the

8 The land pattern is understood to be the metal layer on the PCB, onto which

the DFN pads are soldered to.

9 The solder mask is understood to be the insulating layer on top of the PCB

covering the connecting lines.

100 ±4.5 ±4

±4

±4 ±4.5 ±5

±5

90 ±4.5 ±4 ±3.5 ±3.5 ±3.5 ±3.5 ±4 ±4.5 ±5

±4 ±3.5 ±3

±3

±3 ±3.5 ±3.5 ±4 ±4.5

±4 ±3.5 ±3

±3

±3 ±3.5 ±3.5 ±4

60 ±3.5 ±3

±3

±3 ±3.5 ±3.5

50 ±3.5 ±3

±3

±3 ±3.5

40 ±3.5 ±3

±3

30 ±3.5 ±3

±3

20 ±3.5 ±3.5 ±3

±3

±4

±4 ±3.5 ±3.5 ±3.5 ±3.5 ±3.5 ±3.5 ±3.5

0 ±4.5 ±4.5 ±4

±4

Temperature [°C]

100

-40

-20

100

120

Temperature (°C)

Max.

Range

Normal

Range

1.0

0.3

0.4

2.4

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