Consortium for Climatically Reliable Electronics

An industrial consortium under CELCORR aiming at providing continuous support to industries on climatic reliability issues. Prospective consortium members are companies who wish to get support in on reliability issues of their products at various levels. CELCORR group through CreCon consortium provides reliability support to a number of industries through research, product support, testing, advice, net-working, unique laboratory facilities, skills development, education, and a member only datatabase website providing information on all aspects of climatic reliability. Participation of companies in the consortium is through an yearly modest membership fee, while the return on the investment is many times higher than the membership fee.

Part of CreCon activities include research and development directed by the industrial members of the consortium. Following are the CreCon sub-projects presently carried out based on the needs of the industrial partners.   

Project 1: Improving performance of conformal coatings for PCBA applications

Aim of this sub-project is to bench mark the presently available conformal coating for their performance on PCBA with cleanliness levels presently used in the industries, and arrive at any simple modification that is possible from cleanliness aspects, application of coating, or modification of coating. Work includes:

  • Identifying best PCBA cleanliness levels for conformal coating
  • Performance of various types of conformal coatings under humid conditions
  • Performance of potting materials such silicone gel for various applications
  • Conformal coating, potting materials, and sulphur gases
  • Water permeability of conformal coatings under humid conditions

 

Formation of blisters on conformal coated laminate due to flux residues

Flux residues from wave and selective soldering process causing blister formation after exosure to humidity

 

Project 2: Contamination issues on PCBAs and soldering process

This sub-project will focus on understanding the role no-clean flux, soldering process, and PCBA design on PCBA surface contamination causing problems during humidity exposure. Aim is to define best cleaniness levels that could be achieved based on various parameters. Work under this project includes:

  • Understanding the importance of chemistry of no-clean fluxes and residues on PCBA
  • Difference between various flux activators on contamination levels
  • Bench marking no-clean flux systems for corrosion reliability
  • Trapping flux residue under components and defining factors
  • Thermal decomposition of various no-clean flux systems
  • Bench marking average contamination levels on PCBAs based on design, soldering process, and flux use

Average levels of contamination on PCBA after various types of soldering process

         

Hygroscopic nature of flux with two flux activators - before and after exposure to humidity

 

Project 3: Humidity effects on PCBA reliability: Synergistic effects of  flux residue, PCBA design, bias, and humidity

Various design related factors related to PCBA can influence the corrosion reliability together with the effect of flux residue, bias, and humidity. Work under this sub-project focus on effect of design related aspects such as components, PCBA design, thermal aspects of PCBA surface etc. together with contamination and other factors. Aim is to develop a methodology for predicting humidity related effects on a PCBA design and design rules achieving for reliable design. Work includes:

  • Investigation of leak currents and ECM events on PCBAs under humid conditions
  • Effect of contamination on leak current levels and probability for ECM
  • Electrical properties of Water layer using AC impedance measurements
  • Hygroscopic nature of flux residue and Water layer formation
  • Bench marking of flux systems based on electrical effects under humid conditions
  • Effect of pulse voltage on ECM on PCBA surface
  • Identification tin dissolution due to corrosion using gel method for visualization

Difference between two flux systems containing different activators on leak current under humidity expousure

 

Project 4: Limits of test methods and standards for contamination analysis

Various standards and test methods used for contamination analysis such as ROSE does not provide localized contamination levels. This sub-project will focus on test methods for localized contamination profiling of PCBA surface and producing guidelines for allowable contamination levels.

Localized contamination profile on: (A) reflow, (B) wave, and (C) selective soldered PCBAs, using Residues RAT gel test method