Technical cleanliness: Clean or Not Clean?

Is Technical Cleanliness still guaranteed without the intermediate cleaning step?

Sensitive high-voltage components can be impaired in their function by particle contamination from previous process steps. To keep this risk as low as possible, many production lines have extra cleaning systems for particle removal. This was also the case with our customer, who, in order to keep the risk of residual dirt as low as possible, even cleaned his components in an extra production step before protective lacquering. Since the protective coating used was also permissible as an insulating material, there was a chance to dispense with this additional step and achieve a cost saving.

Analysis of purity determination of electronic assemblies | © @The Sour Cherry Fotografie - Michaela Curtis

problemQuestions About Questions

The following questions arose: Is the particle contamination so low that the use of the particle removal system can be dispensed with? Can Technical Cleanliness still be guaranteed without cleaning? And can the high quality standard of the corresponding high-voltage assembly still be maintained?

analysisClimatic Test Provides Answers

However, before the intermediate cleaning step could be dispensed with, it was necessary to thoroughly check whether the protective coating was still serving its purpose without prior cleaning. To safeguard against potential risks and causes of failure, the corresponding assembly was subjected to a climatic stress test both with and without particles.

It was found that the Technical Cleanliness achieved was irrelevant to the resistance of the assembly under humid climatic stress. With this test result, there was nothing to prevent the planned particle removal system from being dispensed with for the time being.

Analysis_Technical_Cleanliness
hamster – stock.adobe.com

analysis
But Does the Protective Coating Live Up to its Promise?

However, the analysis revealed another, not insignificant weak point in the assembly. The applied insulating material showed an insufficient protective effect against moisture stress under higher voltages.

In the worst case, this defect could endanger the functionality of the assembly and lead to a high failure rate.

Technical_cleanliness_analysis_PCB
oyoo – stock.adobe.com

SolutionOptimized Drying of the Insulation Material Provides a Remedy

Good advice was now expensive. In order to be able to guarantee the high quality standards in the future, a solution to the problem had to be found quickly. A ZESTRON specialist for protective coatings was called in. Together, the ZESTRON team worked out new process parameters that optimized the flash-off and drying of the insulation material.  Through this measure, the customer achieved a higher degree of crosslinking of the insulation material, which in turn counteracted degradation under the combined stress of high voltage and humidity.

In this way, the customer was able to realize the desired cost savings while still guaranteeing the consistently high quality and reliability of its end products.

 

whitepaper-collectionTechnical Cleanliness in Electronics Manufacturing

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Surface cleanliness Zestron Strixner | © @The Sour Cherry Fotografie - Michaela Curtis
Author: Stefan Strixner
PCB_surface_particle_measurement

technologie coachingRisk Assessment of Particles on Electronic Assemblies

Technical cleanliness Particle contamination | © @The Sour Cherry Fotografie - Michaela Curtis

Technical cleanliness risk assessment (TechSa):
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