Causes of Bad Insulation
The following table shows some of the causes of bad insulation, how a Cirris tester will report insulation errors, and measures you can take to catch insulation errors sooner and prevent them from occurring again.
| Cause of Bad Insulation | Possible Errors* | Countermeasure / Process Change |
|---|---|---|
| Extraneous wire |
|
Guided assembly |
| Mis-registration in IDC connectors (tines have destroyed insulation). |
|
Inspect cable |
| Solder bridges |
|
Inspect cable |
| Wire insulation that has been damaged and pierced due to compression (cable ties, strain reliefs), heat (heat shrinking, soldering), or stripping (to inner conductors during outer jacket or shield removal). |
|
Learn more about compression errors here. |
| Loose strands of wire outside of termination, including braided or foil shielding. |
|
Inspect cable |
| Loose metal particles such as metal flake or cut strand of wire. |
|
Inspect cable |
| Combination of leakage and arcing between layers of insulation. |
|
Look for non-homogeneous (more than one kind) of insulation. You may need to change sensitivity or else use a different cable. |
| Burn/carbon trail from breakdown; also some flux residue. |
|
Learn more about flux problems here. |
| Ionic contamination like salt or RMA flux on connector body. |
|
Learn more about flux problems here. |
| Hydroscopic plastics/insulators that absorb moisture in humidity. |
|
Experiment by checking IR before and after drying connectors or cable in an oven to determine if they are absorbing water. Check manufacturer’s specs. PTFE and other Teflon wire types have excellent properties in humidity. |
| Plywood, paint and most phenolic materials (as often used in fixturing), but only if used as an insulator for connections. |
|
Learn more about material choices here. |
| Test fixturing to the device under test that has any of the problems above. |
|
Inspect fixturing |
*Based on severity, test may or may not detect defect. Tests are not 100% effective in detecting all of the defects.