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Version:V1.0 —— May 2021

AHT20 Data Sheet

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Figure 7 The relationship between typical supply current and supply voltage at 25℃ Curve (sleep mode), please

note that the deviation of these data from the displayed value may reach ±50% of the displayed value. At 60℃, the coefficient

is about 15 (Compared with table 2)

4 Applications

4.1 Welding Instructions

SMD I/O pads are made of copper lead frame plane substrates, except these pads are exposed and are used for

mechanical and circuit connections. For use, both I/O pads and bare pads need to be soldered to the PCB. To

prevent oxidation and optimize welding, the solder joints at the bottom of the sensor are coated with Ni/Au. On the

PCB, the length of the I/O contact surface should be 0.2-0.3mm larger than the sensor's I/O sealing pad, and the

width should be 0.1-0.2mm larger than the sealing pad. The part near the inner side should match the shape of the

I/O pad, and the ratio of the pin width to the SMD sealing pad width should be 1:1, as shown in Figure 8.

For mesh and solder layer designs, it is recommended to use copper foil defined pads (SMD) with openings in the

solder layer larger than the metal pads. For SMD pads, if the gap between the copper foil pads and the solder

resistance layer is 60μm-75μm, the size of the solder resistance layer opening should be greater than the size of

the pad 120μm-150μm.The square portion of the sealing pad shall match the corresponding square solder mask

opening to ensure that there is sufficient solder mask area (especially at the corners) to prevent solder intersecting.

Each pad shall have its own solder layer opening to form a network of solder layers around adjacent pads.

Figure 8. Recommended sensor PCB design size (unit:

mm), the outer dotted line is the external size of the SMD

package.

For solder printing, laser cutting stainless steel mesh with electronic polishing trapezoidal wall is recommended,

with recommended thickness of 0.125 mm. The steel mesh size of the pad should be 0.1 mm longer than PCB pad

and placed 0.1 mm away from the packaging center. Steel mesh with bare pads must cover 70% - 90% of the pad

area - that is, the central position of the heat dissipation area reaches 1.4 mm x 2.3 mm.

Due to the low SMD mounting, it is recommended to use no-cleaning type3 solders tin and to purify it with nitrogen

during reflux.