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June 7, 2010

No Clean or Water Soluble for QFN Components

We are placing 32 lead QFN and 14 lead DFN components. We can use either a no-clean or water soluble process. Which do you suggest?

Is there a formula or standard that explains when to use a no-clean or water soluble process with these component types?

M. D.

Experts Comments

I would recommend the no-clean process. The problem with a water soluble process for QFN and DFN devices, is that cleaning underneath is very difficult due to their low standoff.

The residue from a water soluble process is corrosive, and, if not completely removed, can cause a variety of defects and, ultimately, package failure.

Unfortunately, there is no hard and fast rule for when to use a no-clean vs. a water soluble process. It really depends on the components you are placing and what your process needs are.

For example, if you have a board where excessive levels of oxidation or contamination are present, you may want to select a water soluble process for its ability to aggressively strip oxides.

Doug Dixon
Global Marketing Director
Henkel Electronics
Mr. Dixon has been in the electronics field for over twenty years and is the Global Marketing Director with the electronics group of Henkel. Prior to joining Henkel, he worked for Raytheon, Camalot Systems, and Universal Instruments.

These component types have very low stand off heights and will be very difficult to clean underneath. Water soluble flux residues are normally corrosive and must be removed therefore I would not recommend using this option.

No clean would seem to be your preferred route providing you are satisfied that it can stay on the board.

Bryan Kerr
Principal Engineer - CMA Lab
BAE Systems
Bryan Kerr has 35 years experience in providing technical support to PEC assembly manufacturing. His experience ranges from analysis of materials and components to troubleshooting and optimizing, selecting reflow, cleaning, coating and other associated processes.

This website from SMTNet is pretty informative on this subject.

Alan Cable
ACE Production Technologies
Alan Cable, Past President-Retired, ACE Production Technologies has over 40 years experience in the electronics manufacturing arena. Alan's expertise is high production manufacturing automation, equipment design and process engineering. For the past 25 years Alan has focused specifically on soldering issues relating to component solderability, lead tinning and selective soldering, owning several companies with this focus.

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