SHT1x

Humidity & Temperature Sensmitter

Application Note Soldering Procedure

1 Introduction

The SHT 1x precision relative humidity (RH) and temperature sensor requires specific handling during and after the soldering process to prevent damage to its sensing elements. The SHT 1x can be soldered using standard reflow professional ovens (including lead free soldering) at maximum 260°C for 30 seconds.

2 Handling Procedure

2.1 Solder Paste

Please use “No-Clean” solder paste only.

2.2 Recommended Soldering Profile

Convection orIR/Convection VPR Average ramp-up rate (183°C to Peak) 4°C/second max. 10°C/second max. Preheat temperature 160( 10)°C 90 seconds max. Temperature maintained above 183°C 60 seconds Time within 5°C of actual peak temperature 30 seconds 60 seconds Peak temperature 260°C (lead free soldering)
1 233°C (lead free soldering)
2 Ramp-down rate 6°C/second max. 10°C/second max. Time 25°C to peak temperature 6 minutes max.
Note: All temperatures refer to top side of the package, measured on the package body surface.

2.3 PCB cleaning

Please do not clean or wash the Printed Circuit Board (PCB) after soldering. Due to the use of “No-Clean” solder paste cleaning is not necessary.

2.4 Post soldering treatment

After the soldering process is completed, a temporary change of the humidity signal can be observed. This is caused by the extreme temperatures during the soldering process. For a rapid return of the humidity sensor to its nominal condition it is recommended to store the soldered device for at least 48h at >74% RH and >20°C.

2.5 Manual soldering

Contact time must be limited to 5 seconds at up to 350°C.

2.6 Soldering Quality

For best connection to the PCB the solder connection should fill the via almost to the top.

2.7 Warning

Exposure of capacitive relative moisture sensors to solvents (e.g. during soldering) may temporarily offset the signal. Recondition the sensor by heating it up to 100°C for one day may return it to calibration conditions.
1 For devices with date code before ‘144’ (=week 14 of 2004) 235°C is peak temperature 2 For devices with date code before ‘144’ (=week 14 of 2004) 219°C is peak temperature www.sensirion.comSensirion1/2