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March 15, 2024 - Updated November 2, 2022 - Originally Posted How To Remove Oxidation On SMT Components
R.J. |
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Using a solder dipping or dragging process using an aggressive flux would help to restore solderability to the component leads. If the solder applied to the leads is not planar, then placement during SMT may be difficult due to non-planarity. Use of a more aggressive solder paste, like a halide containing water soluble, may enable soldering to the oxidized leads.
Field Applications FCT Assembly Tony has worked in the electronics industry since 1994. He worked as a process engineer at a circuit board manufacturer for 5 years. Since 1999, Tony has worked for FCT Companies as a laboratory manager, facility manager, and most recently a field application engineer. He has extensive experience doing research and development, quality control, and technical service with products used to manufacture and assemble printed circuit boards. He holds B.S. and M.B.S. degrees in Chemistry.
This is a challenging problem. It depends on the qty of parts and cost. You can apply a more active flux just before solder reflow but recommend running a few parts to verify solder results. Changing solder paste with a higher flux activation level should also be considered but could require flux removal after solder reflow if user is currently using no-clean flux solder paste.
President and Founder Contract Manufacturing Consultants, Inc. Robert Fried helps leading electronics OEM's develop world-class sourcing strategies for PCBA, cables, precision metals, plastics, modules and complete end-products. Other service areas are supplier risk assessment, comprehensive outsource ...
I recommend removing the oxidation on the leads before installation using a Robotic Hot Solder Tinning service. A mildly activated flux will assist in breaking down the oxidation, and the dynamic wave will act as a scrubbing and solder replenishment application. Circuit Technology Center in Haverhill, MA, can return the devices to a fully solderable condition with quick turn options. See the below link for a short video of the process. https://www.circuitrework.com/services/tinning.html
Engineering Manager Circuit Technology Center, Inc. Manufacturing Engineer of 20+ years. Involved in Industries relating to all sectors of defense, Commercial product Industries, RF - Microwave and Semiconductor industries. Vast knowledge and experience relating Mil-STD’s, IPC-STD’s, EAI-STD’s, GEIA-STD’s, J-STD’s and MIL-PRF-STD’s.
It is always difficult to remove oxidation once formed and is dependent on how safety critical the devices are. Ideally the components should be hermetically sealed under vacuum or in nitrogen atmosphere with moisture absorption thrown in just to be on the safe side. Once opened the bag components should have a realistic shelf life and a known process to either re-seal in a new bag or stored in a nitrogen cabinet to prolong the life as long as possible. But in the real world this is very often difficult. Take a step back and determine if the risk of a field failure is acceptable against the cost of buying fresh components or doing the work to try to re-use old components. If you cannot source the components anymore then this becomes a fairly straightforward choice as below. You can look at companies that will re-plate or clean the devices, the beauty of this is that if it goes wrong you have some limited opportunity to get them to do it again to make it work better. But essentially if this is something you are doing in house then your options are limited.
Given the choice and depending on the risk level you are willing to take, getting a third party to do this takes away some of the issues and worry of doing it yourself.
Global Product Champion Henkel Electronics Richard Boyle is a Global Product Champion at Henkel Electronics. He has over 25 years experience in the electronics assembly industry and is responsible for the global technical service of all of Henkel's solder materials.
If oxidation is the only impedance to solderability, a “good” flux should remove it. Ask your favorite flux/paste manufacture for advice. If the solderable finish on the lead has been removed or destroyed, it may need to be replaced and there are companies that specialize in refinishing/re-tinning SMT leads.
Senior Project Engineer Electronic Controls Design Inc Paul been with Electronic Controls Design Inc. (ECD) in Milwaukie, Oregon for over 39 years as a Senior Project Engineer. He has seen and worked with the electronic manufacturing industry from many points of view, including: technician, engineer, manufacture, and customer. His focus has been the design and application of measurement tools used to improve manufacturing thermal processes and well as moisture sensitive component storage solutions.
I’d start out with a low activity flux and inspection. If that does not work move to medium activity flux and then remove any leftover flux with Isopropy Alcohol. Make sure the leads are free of any flux. Use a solder pot to tin the leads to check for solder adhesion.
Senior Manufacturing Engineer Northrop Grumman Edithel is a chemical engineer with 20 year experience in manufacturing & process development for electronic contract manufacturers in US as well as some major OEM's. Involved in SMT, Reflow, Wave and other assembly operations entailing conformal coating and robotics.
Assuming that the parts are 100% tin plated, the oxide can be reduced using a solution of Thiourea and HCL. If the Sn has been converted to CuSn IMC then you will not be able to save the surface finish and will need to have the parts retinned.
President S T and S Testing and Analysis Gerald O'Brien is Chairman of ANSI J-STD 003, and Co Chairman of IPC 4-14 Surface Finish Plating Committee. He is a key member of ANSI J-STD 002 and 311 G Committees Expert in Surface finish, Solderability issues and Failure analysis in the PWA, PWB and component fields.
The best option would be to re-tin the parts if they are not expensive, replace if they are hard to get or expensive. I would try re-tinning with a mild flux and progress to a more active flux if needed. Going to a more active solder paste could help the problem but often a paste is qualified with a customer or your internal process for cleaning a highly active flux may not be verified. Adding a liquid flux before reflow may not help a lot as the flux elements in paste are designed to survive the reflow ramp and soak, liquid fluxes are designed to activate more quickly and may not prevent or remove oxidation after the reflow profile exceeds 100C or so. All of the active flux elements of a liquid flux may be driven off by that point.
PCBA Engineering Liaison General Atomics Electromagnetic Systems Group Kevin has over 30 years of experience in process and manufacturing engineering serving in both EMS and OEM companies. Expertise includes all aspects of SMT as well as wave solder and CCA materials such as PCBs, solder material, and component finishes. Kevin has developed processes for thousands of assemblies from stencil printing to conformal coating and testing.
I could not see the image but offer the following. If the condition is truly an oxidation of the surface finish, an easy way to fix the problem is to retin the component leads using a more aggressive flux than the production flux. Loose components are easily cleaned in water solvents so this would not impact the reliability of the assembly as they are assembled to the product. If this does work, then depending upon how many components are in this condition, they could all be sent to a tinning house for retinning.
Vice President, Technical Director EPTAC Corporation At EPTAC Corporation, Mr. Lambert oversees content of course offerings, IPC Certification programs and provides customers with expert consultation in electronics manufacturing, including RoHS/WEEE and lead free issues. Leo is also the IPC General Chairman for the Assembly/Joining Process Committee.
There are companies specialized on tinning services – depending on the components and applications, caution is recommended as the chemical and thermal processes can cause parts problems (immediate or latent failures) Internally, a more aggressive flux than the current one might yield good results – the same caution as above is advised.
Engineering and Operations Management Independent Consultant Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
Contact me at georgiansimion@yahoo.com. |
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