To adequately address the question of how to avoid—or at a minimum reach—an acceptable level of PIM, consider three key aspects:
1. Low PIM Product Design
Products designed specifically with a low or ultra-low PIM quality generally adhere to the following design principles:
- Avoidance of ferrous material
- Minimal number of contact junctions
- Any contact junctions are precise and maintain good contact under pressure
- Avoidance of dissimilar metals in direct contact
- Plated surfaces to limit oxidation
2. Quality Manufacturing
A well-designed product can still become a major PIM generator if the manufacturing process does not ensure highest quality standards. Poorly aligned parts, inadequately torqued screws and fasteners, bad solder joints, insufficiently cleaned parts prior to plating, or poor plating adhesion can render the product ineffective for its PIM avoidance features.
3. Proper Installation and Maintenance
During the installation phase, the main source of problems arises at connection points where bent cables, over- or under-torqued connectors, and torsional loads on connector junctions may cause unwanted signal interference. Since some PIM-producing elements are not easily visually detectable, strict adherence to the manufacturer’s installation guidelines is crucial.
Having a well-designed product that is flawlessly built and properly installed may not, however, completely ensure low PIM performance over time. Natural elements, such as temperature variations, moisture, wind-induced vibrations and air-borne dirt, continuously work to break down and erode exposed parts of the component, weakening joints, separating connections, oxidizing materials, and allowing moisture and dust to enter. Visually check your components regularly and consider various PIM testing instruments to certify continuous low PIM performance.
