Improving cleanliness

26 February 2010

The Gen3 Systems Contaminometer (CM Series) have been revised, improved and simplified with two entirely new machines now added to the range; CM22 and CM33
The Gen3 Systems Contaminometer (CM Series) have been revised, improved and simplified with two entirely new machines now added to the range; CM22 and CM33

The Gen3 Systems Contaminometer (CM Series) have been revised, improved and simplified with two entirely new machines now added to the range; CM22 and CM33.

This makes the CM Series range more cost effective and provides better flexibility to suit all customers’ needs. There are now four individual machines from the CM Series range, each tailoring to specific needs.

CM11+ is a bench-top system, CM22 is a free-standing system incorporating a large capacity test chamber, CM33 is a free-standing system designed for larger boards or assemblies, and CM66 is an updated version of the CM60.

All CM Series (Contaminometers) machines feature:
• Solid gold measuring cell, ballistic amplifier giving a test accuracy of <0.005mS/cm (auto-ranging)
• Curvefitting analysis <5 minute test time
• Accurate measurement, even when the proportion of test solution to surface area under test are huge
• Automatic temperature compensation for each test
• Meets the requirements of all international and military specifications:
        • IPC-J-STD 001E & IPC-TM-650
        • MIL-STD 2000
        • MIL-P-28809
        • DEF standard 00-10/3
        • IEC specifications

Since the adoption of lead-free processes, no clean, or low solids fluxes, and controlled atmosphere soldering systems, ionic contamination monitoring has become an essential process control parameter in the manufacture of circuit boards, components and assemblies.

Standards such as IPC-J-STD001 refer to ROSE (Resistivity Of Solvent Extracted) or SEC (Solvent Extract Conductivity) testing but most commonly it is known as Cleanliness Testing.

Ionic contamination testing is required as ionic residues remaining from the PCB manufacturing process and the soldering process may affect the reliability of a finished assembly. In a humid environment, ionic contaminants can cause problems such as shorting between conductors by electrolytic dendrite growth, corrosion that erodes the conductors themselves or loss of insulation resistance. It is therefore important to monitor the level of ionic contamination, giving an indication of the cleanliness and thereby the expected reliability of an assembly.

Ionic contamination is measured by immersing a sample in a test solution of two-propanol and de-ionised water to dissolve the contaminants. The dissolved ionic substances cause a change in conductivity of the test solution; this change is precisely measured and converted into a contamination value expressed as μg/cm2 NaCl equivalence.

Testing a number of samples per hour or per day, any changes in ionic contamination level will be detected, rapidly alerting the operator to a process variation or fault affecting the contamination level and thus the quality of the boards.

The CM Series utilise a solid gold measuring cell, ballistic amplifier and a vigorous pumping system to achieve superior measurement accuracy of <0.005mS/cm even at very low conductivity values.

Automatic temperature compensation is incorporated in the electronic control system, and the method of temperature measurement is a thermistor positioned in the test cell. The Contaminometer software uses a complex algorithm to automatically compensate for ambient temperature, circuit volume and atmospheric absorption of iogenic gases. Temperature is monitored and all measurements are related to the international standard of 20°C (68°F).

The CM Systems have been designed to avoid polarisation effects between electrodes as might occur when using DC test currents.

Equally, error signals, caused by DC and AC currents, are eliminated and high accuracy is ensured even at low conductivity values.

This permits Gen3’s equipment to measure accurately, even when the proportion of test solution to surface area under test are huge.

Automatic temperature compensation is incorporated in the electronic control system, the method of temperature measurement being by a thermistor positioned in the test cell. The Contaminometer software uses a complex algorithm to automatically compensate for ambient temperature, circuit volume and atmospheric absorption of iogenic gases. Temperature is monitored and all measurements are related to the international standard of 20°C (68°F).


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