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52 SMT007 MAGAZINE I JANUARY 2022 Knocking Down the Bone Pile by Bob Wettermann, BEST INC. e amount of charge generated in an elec- tronics rework and repair area is affected by a variety of factors, including but not limited to, the materials used and the amount of friction- al interaction between materials, as well as the relative humidity of the environment. During the cold winter months in northern climates when the heating systems dry out the plant air and the relative humidity falls, higher electro- static charges develop, all other things being equal. Lower humidity can increase the num- ber of ESD events, so theoretically it stands to reason that keeping the rework area at high- er humidity levels will reduce the chances for charged-induced damage to components. To get to the "right" relative humidity level in the PCB rework/repair area, several variables need to be taken into consideration. e elec- tronic components being reworked need to fall within their specified RH operating range. In addition, the rework processing steps, such as the length of time the repair epoxy takes to cure or the amount of time the conformal coat- ing material needs to cure, are some of the pro- cess steps which will be impacted by the hu- midity level. Too high of a relative humidi- ty level may result in unwanted quality prob- lems such as corrosion, hand soldering defects, and unwanted MSD damage to moisture sen- sitive devices. Solder paste will not have the Humidification for ESD Control in PCB Rework/Repair

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