The video clips are on my sever to access them now use the following links. You will need RealPlayer to view the clips.

www.seminar-registrations.com/bw508.rm

www.seminar-registrations.com/bw507.rm

I produced the video clips for a flip chip and underfill workshop I was organising with Speedline Technologies in the UK at the start of the year. I was trying to show the problems of outgassing from the mask during reflow of no-flow underfills. The same issue can occur with traditional underfill but these can cause misaligment of the devices before the solder joint is formed on the connection pads.

I am currently conducting a project as part of team at NPL on solder mask related problems related to cure of masks.

The text below outlines the project and I have also used it for a abstract for the Printed Circuit Board World Convention.

Hope this all of interest.


Characterising Solder Resist/Mask Performance and Degree of Cure

Chris Hunt, Alan Brewing and Bob Willis 
National Physical Laboratory Teddington, Middlesex, England

Industry currently uses a number of simple ad-hoc evaluation test methods that correlate poorly with the mask performance during assembly. The industry has long understood that the test methods contained in national and international specifications to be inadequate. NPL is to evaluate a number of test methods and show the relevance to issues experienced during assembly operations. The project will also bench-mark the current test methods with new procedures.

Issues with voiding during underfill cure have been documented, where out-gassing from the solder mask has occurred. Voids in the underfill can dramatically impact on the reliability performance of the solder joints and the mechanical strength of devices to the resist surface. This is particularly important with modern electronics. Evolution of gas and changes in surface tension can significantly influence the occurrence, or the adhesion of solder balls, during soldering. Absorption by solder masks of solvents and other components from cleaning, which then can be desorbed, will significantly impinge on solder wetting.

The aim of the NPL project in conjunction to leading solder mask supplier and soldering material manufacturers will help to achieve the following project goals:

Produce a code of practice to define test methods and criteria to allow companies to simply define and test printed circuit boards prior to assembly or supply.

Investigate current and new methods of assessing the degree of cure of solder masks after fabrication and prior to assembly.  Define test methods which could be economically introduced to assembly and fabrication operations.

Compare assembly defects like resist out-gassing, underfill voiding and solder balling and the variations on selected solder resist surfaces.

Propose these test methods and procedures to national and international standards committees to incorporate into future standards to reduce the variation of test results in the industry.

This technical paper will outline the work conducted and the results obtained.




Bob Willis
Electronic Presentation Services
2 Fourth Ave, Chelmsford, Essex, CM1 4HA England

See us at APEX 2002  www.bobwillis.co.uk/workshops/apex/apex.htm

www.bobwillis.co.uk
Tel: (44) 01245 351502 Fax: (44) 01245 496123

Single solution to your seminar, conference or roadshow www.seminar-registrations.com
  ----- Original Message ----- 
  From: Creswick, Steven 
  To: [log in to unmask] 
  Sent: Tuesday, November 20, 2001 3:40 PM
  Subject: Solder mask outgassing


  Bob,

  I for one am interested in seeing the RealTime video clip/s on solder mask
  outgassing

  Steven Creswick - Gentex Corp