PCB Contamination Testing Discussion


What is Ionic Contamination Testing?

PCB can suffer from a variety of problems if the surface is contaminated with electrically conducting materials. Combined with moisture, this results in a lowering of resistance between tracks and pads and can lead to corrosion of metals.

Since the elimination of solvent-cleaned rosin assembly practices, the electronics industry has turned to alternative manufacturing processes such as aqueous cleaning water-soluble and no-clean processes over the past 15 years.

The use of these alternate processes has resulted in a growing number of field failures due to electro-migration or corrosion issues. This poorer field performance has been directly tied to the changes in process residues (types, levels, and reactive states).

Our understanding of these changes has come from the investigation of the failures, process improvements, process qualifications, validations and monitoring of these alternative manufacturing methods through ionic testing equipment.

Contamination Testing Standards

The ionic contamination level is calculated from the ionic conductivity of the wash solution and the total board area. The result is an average value across the whole surface.

The development of standards of cleanliness and standard test methods date back to the early 1970s in the US, culminating in the publication of the original American MIL standards. It was from this work that the original pass/fail criteria of 10μg NaCl equivalence /inch or 1.56μg NaCl /cm2 were first proposed.

Cleanliness testing is now a routine procedure and manufacturers of both bare and populated boards are commonly asked to ensure their products meet contamination specifications based on this limit.

Today following standards are widely used for ionic contamination tester

ionic contamination testing

Ionic contamination testing

IPC ionic contamination limit

IPC-TM-650 2.3.25: Resistivity of Solvent Extract (ROSE) Test Method

The ROSE test method is used as a process control tool to detect the presence of ionic contamination. The IPC limit is set at 1.56 μg/NaCl/cm.sq. The tester should be realized by an ionic testing unit, in this way of testing it does not identify specific ions present. This process draws the ions present on the PCB/PCBA into the testing solution. The results are reported as the total ions present on the PCB per square inch/cm.

IPC-TM-650 2.3.28: Ion Chromatography

This test method involves a thermal extraction similar to the modified ROSE test. After thermal extraction, the solution is tested using various standards in an ion chromatograph tester. The results indicate the individual ionic species present and the level of each ion species per square inch.

Modified ROSE

The modified ROSE test method involves a thermal extraction. The PCB is exposed to a solvent solution at an elevated temperature for a specified period. This process draws the ions present on the PCB into the solvent solution. The solution is tested using a Neotel Cleanliness Tester likes testing unit. The results are reported as bulk ions present on the PCB per square inch

IPC standards download page:https://www.ipc.org/sites/default/files/test_methods_docs
What IPC ionic contamination testing standards say on Dynamic vs. Static
Since the birth of ionic contamination testing, there has been some confusion over the so-called dynamic or static testing methods. Both sides claim they could deliver more benefits than the other.

To overcome these issues, Noetel cleanliness tester gives you the flexibility to adopt the method whatever you prefer as both are cited by IPC standards. This is especially important for OEM manufacturers; their various customers may require different methods of analysis, and this saves the purchasing of the two types of equipment

What is Neo Cleanliness Tester?

Neo Cleanliness tester is developed by Neotel Technology for ionic contamination testing. Unlike any supplier in the market, Neo Cleanliness Tester is featuring with 2 testing methods: dynamic and static testing as both are recognized by IPC standards. Users can have 2 testing results in one machine.

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