Power supplies are often exposed to harsh or moist environments, for example in humid areas like bathrooms or outdoors. 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 splash water, IPx7 even allows a temporary submersion of the power supply.
Usually there are two conventional types of power supplies with protection IPx7: either 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:
Step 1: Assembly of DC lead with housing part 1
Image: Housing 1 (bottom) with molded AC contacts + DC lead
Step 2: The DC lead is soldered to the printed circuit board (PCBA) and potted (to the specified potting level)
Image: PCB + potting material (epoxy resin)
The potting process is done fully automatic, whereas the potting machine's number of nozzles defines how many units can be potted simultaneously. 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.
Step 3: Housing part 2 is mounted to housing part 1
Image: Partially potted unit with housing part 2 (lid)
Result: Cost-effective IPx7 protection for the unit with high process safety thanks to partial potting
Image: Finished unit Image: Potting level / X-ray
At the end of the day it becomes clear that partial potting has to be first choice when IPx7 requirements are involved. Considerable benefits are:
- Production cost declines
- Potting material savings of up to 70 %
- Cycle times drop
- Weight reduction
- Analysis of failures is simplified/improved
- Significantly high process reliability
FRIWO have been working with this patented process for five years with very positive results.
Partial potting – the best solution for your application? You are welcome to contact us by mail sales(at)friwo.com or by phone +49 2532 81-0.