HS411x Datasheet

R36DS0025EU0102 Rev.1.02

Apr 28, 2022

Page 11

7.

Soldering Information

This section discusses soldering considerations for the HS411x.

for use with the JEDEC J-STD-020D standard soldering profile is 260°C. For manual soldering, the contact time

must be limited to 5 seconds at up to 350°C. In either case, if solder paste is used, it is recommended to use ‘no-

clean’ solder paste to avoid the need to wash the PCB.

When a relative humidity sensor is exposed to the high heat associated with the soldering process, the sensor

element tends to dry out. To avoid an offset in the relative humidity readings, the sensor element must be

rehydrated after the soldering process. Care must also be taken when selecting the temperatures and durations

involved in the soldering process to avoid irreversibly damaging the sensor element.

The recommended soldering profile for a lead-free (RoHS-compliant) process is shown below.

Figure 15. Recommended Soldering Profile

It is important to ensure this temperature profile is measured at the sensor itself. Measuring the profile at a larger

component with a higher thermal mass means the temperature at the small sensor will be higher than expected.

For manual soldering, the contact time must be limited to 5 seconds with a maximum iron temperature of 350°C.

In either case, a board wash after soldering is not recommended. Therefore, if a solder paste is used, it is

strongly recommended that a “no-clean” solder paste is used to avoid the need to wash the PCB.

After soldering, the recommended rehydration process should be done. Otherwise, there may be an initial offset

in the relative humidity readings, which will slowly disappear as the sensor get exposed to ambient conditions.

Recommended rehydration process:

■

A relative humidity of 75% RH at room temperature for at least 12 hours.

or

■

A relative humidity of 40% to 50% RH at room temperature for 3 to 5 days.