|Ask the Experts|
January 14, 2020
How to Remove Oxidization from SMT Component Leads?
How do you suggest we remove oxidization from SMT component leads? The component leads are seriously oxidized due to long time storage. Are there companies that can rework oxidized SMT components?
|Expert Panel Responses|
There are ways to remove oxidation from SMT components if they are not mounted or attached to other hardware. Circuit Technology Center in Haverhill, MA can assist with this condition if you have not found a source at this time.
Circuit Technology Center, Inc.
From a soldering standing point if the components need to be retinned, then Google retinning electronics components and there are several companies offering this service.
I advise taking caution with the components, if they are oxidized, then it is likely there are other age issues. I get it, some legacy components have to be used, just be cautious as the end result/reliability may not be desirable.
If you are running them through a reflow oven, I would suggestion baking prior to use and I believe the retinning serves will do this as part of their service.
Director of Corporate Quality Assurance
Delta Group Electronics Inc.
Unless the device package is something out of the norm, they should be able to be retinned- there are many commercial services out there that should be able to do this for you.
Just make sure you validate that the retinnning process has no impact on the internals of the package and the device functionality.
S T and S Testing and Analysis
Oxides can be removed from SMT component leads using common soldering fluxes. A dip flux could be used in the pick and place process to dip the components into a flux before placement into the solder paste deposits.
I recommend using a dip flux that is compatible with or very similar to the solder paste. Alternately a higher activity solder paste could be used in order to help penetrate the oxides on the leads. I suggest checking with your solder paste supplier to see if they have a higher activity solder paste that could work.
Reworking the SMT component leads may be possible, but it could also damage the metallization on the leads. It is not easy to re-metallize component leads, so I would try to avoid that. If the components are sealed and compatible with a water wash, then rework may not be too difficult.
The parts would have to be loose (not in reels or trays). The parts could be immersed in a chemical oxide remover and the rinsed in DI water and dried. I suggest testing a few parts in this process to ensure there is no damage, before reworking the bulk of the parts.
Active flux can be applied to remove the oxide layer to achieve good soldering results. However, it is recommended to re-clean the bare board and re-apply surface finish if the level of oxide contamination is very high.
The bare board can be cleaned by a mildly acid aqueous solution that should work well. Also, it is important to provide appropriate storage such as ultra-low humidity desiccant technology.
Director of Sales and Marketing
Re-tinning the parts using a flux active enough to remove the oxidation is probably the best route. There are numerous sources that can do the tinning, clean them properly, and even re-tape them for SMT placement if needed.
PCBA Engineering Liaison
General Atomics Electromagnetic Systems Group
If the root cause of the oxidation is long-term storage, then the proactive step is to prevent oxidation from happening in the first place. SMT vacuum packages, if not opened, are good at preventing oxidation and extending the shelf life of the components. Once the SMT vacuum package is opened, the component should be stored using a dry cabinet under nitrogen flow.
If the above-mentioned preventions are not in place and the component leads are seriously oxidized, then rework may not be a good decision if the oxide layer thickness is in the micrometer range. Pre-thinning the oxide layer using more active flux can be done, but this could damage the component and is not recommended. In this case, replacement with new components should be considered.
If the oxide layer thickness is in the nanometer range, then plasma treatment can be used to remove it. Optimization of the plasma recipes using the appropriate gas mixture ratio (typically an H2/Ar mixture is used for this type of oxide removal) and tuning the critical parameters such as power, gas flow and processing time, are very important for performing effective plasma treatment. To help with the recipe optimization, additional information is needed such as the lead material (to identify the type of oxide, for example Copper or Nickel oxide), the oxide layer thickness (to tune the power and processing time), and the size of the component to select the correct plasma chamber size and configuration.
Director of Marketing
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