Research
Stencil Printing Yield Improvements
Overcome Nodules and Scratches on Wire Bondable Plating on PCBs
Solder Paste Selection for Bottom Termination Components Attach
Jetting Solder Paste Opens Up New Possibilities
Advances Autonomous Driving V2X Technologies
Surface Insulation Resistance of No-Clean Flux Residues
Jetting Conductive Adhesives with Silver Coated Polymer Particles
Residues on Probing PCBAS-Consistent Connections Across No-Clean Fluxes
MORE RESEARCH
Latest Industry News
Applying Strategic Sourcing Principles to Modern Procurement
Should You Trust Apple's New Blood Oxygen Sensor?
Cobalt demand for 5G technology to challenge electric vehicles
S. Korea to launch supercomputer for biotechnology in 2023
China needs first mover advantage in digital currency race
Top 10 Digital Transformation Trends For 2021
Chinese leaders split over releasing blacklist of U.S. companies
It's getting harder for tech companies to bridge the US-China divide
MORE INDUSTRY NEWS

PCBA Cleaning with Sodium Bicarbonate



PCBA Cleaning with Sodium Bicarbonate
Is there an effect on PCBA long-term reliability when cleaned with a sodium bicarbonate scrub followed by DI water rinse? The Assembly Brothers, Jim Hall and Phil Zarrow, answer this question and share their own expertise.
Board Talk
Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting.
Process Troubleshooting, Failure Analysis, Process Audits, Process Set-up
CEM Selection/Qualification, SMT Training/Seminars, Legal Disputes
Phil Zarrow
Phil Zarrow
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.
Jim Hall
Jim Hall
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.

Transcript


Phil
Welcome to Board Talk. This is Jim Hall and Phil Zarrow, the Assembly Brothers, coming to you from high atop Mount Rialto here in New Hampshire.

Jim
Our question today is about cleaning. It comes from L.P. "Is there an effect on PCBA long-term reliability for assemblies cleaned with a sodium bicarbonate scrub followed by DI water rinse to remove tarnishing of silver immersion plating?

I assume that you have checked the compatibility of all the materials on your circuit board, your components, compatibility with the sodium bicarbonate and your cleaning operation. But most important is that sodium bicarbonate to the best of my knowledge is a caustic solution, as many traditional cleaners have been, and you absolutely need to get it all off the board when you're done.

Phil
We would suspect that DI water probably is not quite hacking it.

Jim
It depends upon the components on your board, the clearances and so forth and the mechanical action during this "scrub," whether it's forcing sodium bicarbonate under low clearance parts such as a QFNs. 

If you leave sodium bicarbonate on your board, you are definitely taking a risk.

Phil
He may be talking about a bare board that they've stored too long and they're tarnished.

Jim
He's talking about an assembly so I interpret that as having soldered components on the printed circuit board, or a printed wiring board if we want to be more descriptive.

Phil
Immersion silver finish has been around for a while now. And it's becoming really popular.  This is a common problem. I would check with some of the industry cleaning companies.

Jim
You want to get a product that's designed to be compatible with all your electronic materials.  

Phil
Happy scrubbing and happy cleaning. And when you go to solder those boards, whatever you do -

Jim
Don't solder like my brother.

Phil
Don't solder like my brother.


Comments

I notice that the picture associated with the article is of a box of washing soda, which is sodium carbonate, not sodium bicarbonate. We use sodium bicarbonate (baking soda) routinely in our cooking, but not washing soda so much.
Wayne Miller, Wayne Miller Associates
Sodium bicarbonate is frowned upon as a cleaning method for flux removal or for other soils requiring a neutral pH solvent. Potassium bicarbonate, on the other hand, is the main ingredient in many saponifiers such as Armakleen 2000, for example. They clean extremely well and render a pH-neutral solution when mixed with clean DI water at about a 6 to 10% ratio. The downside however, is that ANY bicarbonate-bearing product is not completely soluble, so you will deal with bicarbonate build-up on all of the surfaces of the cleaning equipment, including pump seals, bearings, etc., that are almost impossible to clean off.

Richard Stadem, General Dynamics Mission Systems
Sodium bicarbonate can act as a mild abrasive but it it may enter the surface of whatever you are scrubbing (the same as any abrasive), leaving a possibility of problems. I would say it is imperative to give a mild acid rinse (say 3-5% hydrochloric acid) at room temperature for 5 minutes BEFORE at least 2 good DI rinses. This will decompose any poorly-soluble weak ionic residues into very soluble ones, which will dissolve in the rinses.
Brian Ellis

Submit A Comment


Comments are reviewed prior to posting. You must include your full name to have your comments posted. We will not post your email address.

Your Name


Your Company
Your E-mail


Your Country
Your Comments



Board Talk
Solder Pallets With Titanium Inserts - Yes/No?
What Rate is World Class for SMT Machines?
Selective Solder Pot Temperatures
Top Side Reflow Causing Solder Balls
Trends for Printing Ultra Miniature Chips
Should We Measure Solder Paste Thickness?
Cleaning R.F. Circuits - Aqueous or Vapor?
Why Should We Consider Smart Feeders?
MORE BOARD TALK
Ask the Experts
SMT Target Component Placement
Problems With Large Voids
Stainless Steel Benches and ESD
Exposed Copper Defect
What's Causing Cloudy Conformal Coating
Channels To Reduce Voids in Large Pads
Options for Reballing BGA Components
Aluminum Trays and Rapid Static Discharge
MORE ASK THE EXPERTS