Power supplies sometimes need to be exposed to harsh or damp environments. Power supply specifications therefore often include IPx4 or IPx7 requirements. In accordance with standard DIN EN 60529 the IP code (IP = Ingress Protection) describes the protection against ingress of foreign matters like dirt, dust or moisture. The abbreviation IPx4 stands for protection against splashes of water while IPx7 allows a temporary submersion of the power supply in water.
Usually there are two conventional types of power supplies with IPx7 protection: All components and contacts of the power supply are assembled in a housing and entirely potted with an electrically insulating resin or the housing is closed ultrasonically or sealed by an O-ring/sealing element (for example NBR).
Experience has shown that both variants have disadvantages: Full potting means that product weight and material consumption increase. In addition, failure analysis is massively obstructed since all components are inseparably enclosed by resin. Quality experts know that failure analysis is possible but is significantly complicated by the potting material. Another problem is possible leakage between the individual electrical components. Due to the standard requirements for EMC and efficiency, the latest generation of switch mode power supplies is increasingly designed with high impedance. Potting, however, has a resistive/capacitive effect on the electrical circuit. This apparent disadvantage is taken into account by FRIWO and compensated accordingly for new switch mode power supplies.
The alternative approaches of ultrasonic welding or sealing by sealing elements respectively may solve the described problems but create other disadvantages: these methods are distinctly less reliable than full potting, since the tightness of the housing is directly dependent on the welding quality and dimensional accuracy of the housing parts. Even the smallest deviations can have serious consequences.
In other words, the question is: How can we ensure a process-safe sealing without blowing the budget? The magic word is "partial potting". It refers to a manufacturing method, patented for FRIWO (EP 2458691 A1). But what does it mean? A1). The production process of a partially potted unit is described stepwise hereafter:
Image: Housing 1 (bottom) with molded AC contacts + DC lead
Image: PCB + potting material (epoxy resin)
The potting process is fully automated, however the number of nozzles on the potting machine, defines how many units can be potted at the same time. A connector for the DC lead can be used instead of a soldered joint. This concept is, of course, also applicable for variants with flexible primary leads.
Image: Partially potted unit with housing part 2 (lid)
|Image: Finished unit||Image: Potting level X-ray|
It is clear that partial potting would be the first choice when IPx7 requirements are involved. Considerable benefits of partial potting include:
FRIWO have been working with this patented potting process for 5 years with extremely positive results. Partial potting – could this be the best solution available for your application?
Contact us to find out more.