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Umut Tosun
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Application Technology Manager
Zestron America
Mr. Tosun has published numerous technical articles. As an active member of the SMTA and IPC organizations, Mr. Tosun has presented a variety of papers and studies on topics such as "Lead-Free Cleaning" and "Climatic Reliability".

Umut Tosun has submitted responses to the following questions.
Urethane Conformal Coating Problem
First of all, I suggest confirming that the surface is clean with sufficient surface energy for good conformal coating adhesion ...
Cleanliness Testing
The following are well-known cleaning and cleanliness identification from IPC standards: IPC-A-610 (Section 3.3.X; 10.6.X) Visual Cleanliness IPC-CH-65 (Section 6.X) Guidelines ...
ENIG Solderability Issues
ENIG Surface Industry Standards and Common Practices Per IPC-4552, there should be 2-5 micro-inches of immersion gold applied over 120 ...
Contamination Using Solvent Dispensers
Most likely you are dragging contamination back into the solvent dispenser, and I would highly recommend cleaning the dispenser prior ...
Spotting After DI Water Cleaning
The client needs to let us know if they started to use any cleaning agent or additives (such defoamer etc.) ...
Class 2 vs. Class 3
The first difference between the two classes of products is based upon the definition itself. Class 2 products are defined ...
What Causes Black Pad?
Gold thickness results above the specified range (Thickness > 2 to 5 micro-inches) shall result in an attack on the ...
Zip-lock Bags vs. Heat Sealed Bags
Both vacuum & heat - sealed ESD bags would actually be a perfect solution for storage purposes, client could pass ...
Silver Solder for Audio Circuits
Compared to conventional tin& lead alloys, a much greater corrosion favoring effect exists with silver-based solders due to the high ...
Class 3 Cleaning Requirements
Yes, there are certain spec changes, for example amount of rosin based residues left behind on the board surface differs ...
Tacky Substance Under Zero Clearance Parts
In order to answer this question, we first need to determine the cause of the failure and understand the nature ...
White Discoloration After Ultrasonic Cleaning
White discoloration means a lot of possibilities... Could be partially cleaned flux residues, or some interaction with joint etc. A ...
Gold Edge Contact Flux Contamination Failures
The only way to find out whether flux would cause functionality problems or not later on is to assess the ...
Immersion Gold PCB's with Oxidation
It is possible to remove oxidation from the pad areas, however this will require a cleaning agent and most likely ...
Cleaning Reballed BGA Components
A defluxing process consists of wash, rinse and drying cycles. In the below explanation, the client mentions that he used ...
Ultrasonic Cleaning Solution
Yes, there are aqueous and solvent based cleaning agents that are designed for use in ultrasonic equipment and cleaning both, ...
Dewetting of Acrylic Conformal Coating
Factors that influence dewetting usually involve ionic and non-ionic contamination such as: Residues from board manufacture including silicone surfactants from ...
Uneven Conformal Coating
In regards to the below customer issue; there was another customer who had a similar issue during our conformal coating ...
Delay Before Washing Water Soluble Flux
Water-soluble fluxes have high percentage of organic activators and are generally corrosive in nature. For this reason, it's always recommended ...
Water Washing Pressure
The factors influencing the impact pressure are liquid flowrate, spray angle, spray pressure, droplet size, spray distribution and spray nozzle ...
BGA Rework Clean-up?
A photo could have been helpful to determine if the solder mask is attacked by an aggressive flux or if ...
Cleaning Conformal Coated Boards After Rework
It really depends on the chemical formulation and the solubility of the coating material in water at specific wash temperature. ...
Ultrasonic Cleaning Solution Recommendation
Any water based or solvent based PCB cleaning agents could be used in your ultrasonic equipment depending on the brand ...
Abrupt Decrease in DI Water Resistivity
If a solvent or water based cleaning agent is currently used in the wash process, those could be the reason. ...
Post Print Inspection Issue
Below is the feedback pertaining to question posed on the Circuitnet recently. The process requirements for double-side misprints differ only ...
Pros and Cons of Cleaning No-clean
Points to consider: The no-clean flux residues are more difficult to remove than other fluxes. No-clean solder pastes cannot be ...
Flux Residue Causing Test Issues
No-clean type of flux residue does not necessarily mean it would not require a wash process. No clean paste or ...
Organic Flux Residue Concerns
Here is our response, in a short and sweet way: The two most common failures are: Electrochemical Migration which results ...
Cleaning No-Clean Solder Paste
The causes of the white residue in this case could be related to one of the following: Lack of elevated ...
Is Baking Required After Aqueous Cleaning?
Ideally if the aqueous cleaning process takes place in an automated system, there should already be a drying stage, where ...
Contact Pin Corrosion Problems
Zestron does have a cleaning agent VIGON S100 to remove the oxidation from metal surfaces from copper mainly. However the ...
Which to Use - Rosin Flux or Water Soluble?
Rosin based fluxes are widely used in military and space electronics. The reasons could be listed as: They are noncorrosive ...
Flux Residue Visible After 3 Months
The board contractor may have to provide more information to us on cleaning and inspection of these boards. Do these ...
Hot or Cold DI Water Rinse
Surface tension of water can be reduced and its solvency can be increased by increasing its temperature. Hot rinse water ...
Tacky Flux Residue Problem
The best option in this case would be a spot cleaning with a rework /repair defluxing agent, as the observed ...
Hard Water Contamination
It is highly recommended using De-ionized water for rinse cycles as well as for mixing/diluting the water-based cleaning agents for ...
Can adhesive residues from tapes contaminate a cleaning solution?
Daily removal of such contaminants manually or through particle filtration (filter cartridges, filter bags,etc.) would help extending the bath lifetime ...
Staging time between wave soldering and cleaning
I am not aware of a specific industry standard, but we do have clients that clean their boards with our ...
No clean flux stains during reflow
Modern reflow systems do have the flux management units equipped with cooling units, filters, heat exchangers, filter panels which in ...
Ultrasonic Cleaning Causing Damage
Generally a spray-in-air (like diswasher type batch cleaning process where top and bottom spray bars rotate as they spray the ...
What is the Proper DI Water Resistivity
For defluxing cleaning applications, the recommended DI water quality should be 1 to 10 Microsiemens-cm. Any conductivity that is higher ...
Problem with 'No Clean' Solder Flux Residue
What is really meant by No Clean? "No-Clean" solder paste is a misnomer. There is no such thing as a ...
DI Resistivity for Wafer Dicing and Cleaning
I did some research found out that "For front end applications like this usually companies are working with a conductivity ...
IPA cleaning precautions
A) Precautions for Safe Handling and Use Steps If Matl Released/Spill: Wear proper protective clothing. Eliminate all sources of ignition. ...
Recommended DI Water Conductivity For Ultrasonic Cleaning
1 to 10 microsiemens-cm as 10 microsiemens-cm being maximum not more than that. ...
Cleaning PCB's after long-term storage
For such applications, you could find specially developed, acidic in nature, water-based cleaning agents, that create highly activated surfaces by ...
Clean water soluble flux
Dishwasher type batch cleaners do have a certain impact pressure on the board surface which should yield in better cleaning ...
Clean a no clean PCBA
There are two types of defluxing approaches in the electronics manufacturing industry, namely the automated and manual cleaning applications. With ...
Best Board Cleaning Methodology
Ultrasonic or Spray in Air technologies could both be used for solder ball removal from misprinted boards. The preference could ...
Resistivity and Cleaning
For defluxing cleaning applications, the recommended DI water quality should be 1 to 10 Microsiemens –cm. Any conductivity that is ...
Method for cleaning boards after misprint
Manual cleaning of the misprinted board through either wiping or scrapping results in entrapment of the solder balls in the ...
Cleaning an assembled board with IPA
IPA is not capable of removing "no-clean" flux residues properly. Using IPA will result in leaving either partially cleaned (white ...
Stencil printing lead free paste
Damp will provide a higher cleaning consistency. Make sure you chose a product that is stable and able to clean ...
Aqueous Cleaning Process
Neither. IPA is a very poor solubilizing agent. DI-water will only be able to clean inorganic contamination. You best bet ...
Is lead contamination during cleaning of PB-free stencils possible?
Cleaning processes consist of a wash, rinse and drying step. In your case, the wash process is cleaning the substrates ...
Cleaning Military Circuit Boards Contaminated with Sand
Acrylic conformal coatings are "thermoplastic" coatings which are used if the coating has to be removed easily or if through-soldering ...