From One Engineer to Another

Oxidation Barrier: The Secret to HF Solder Paste Success

Monday, May 4, 2009 by Tim Jensen [Tim Jensen]

Shhhh.  Don't tell anyone but I have a secret.  The activators used in halogen-free solder pastes aren't as effective as their halogen contained counterparts.  The real secret is coming up with a technology that overcomes the deficiency.  Indium Corporation's approach to this has been to focus on the oxidation barrier of the solder paste.  The theory here is that if you can prevent oxidation from occurring through the preheat and soak stages of the reflow process, then the activators have to work less to remove oxides.  Indium Corporation used this approach in developing the Indium8.9HF solder paste.  This solder paste clearly outperforms most solder pastes in reducing head-in-pillow and graping defects by preventing oxidation.

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Comments for Oxidation Barrier: The Secret to HF Solder Paste Success

Tuesday, July 7, 2009 by Tim Jensen:
There are several ways to prevent the formation of oxide films during the preheat and soak stages of the profile. In the simplest form, you need to prevent oxygen from coming in contact with the solder powder or the surface being soldered. This can be accomplished by using an inert environment such as nitrogen. That approach, while effective, can be very costly. From a solder paste perspective, one can design a flux that remains on the surface of the solder paste deposit and doesn’t allow the oxygen to come into contact with the metal surface. That is what is defined as an oxidation barrier. Rosins are commonly used in fluxes as oxidation barriers.

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