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solderpaste : no clean versus water soluable
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solderpaste : no clean versus water soluable

by bootstrap on Sat Jun 19, 2010 12:45 am

I need to order some solder-paste to assemble my prototype PCBs, and need to decide whether to purchase "no clean" or "water soluable" (gonna try lead-free, but I guess this question applies in any case). What are the trade-offs? How should I clean the PCB after assembly... or should I not clean it at all (neither PCB has no card-edge or exposed contacts).

Also, how much solder-paste am I likely to need to assemble my prototype PCBs?
---- quantity 25 of a PCB with 300 components
---- quantity 50 of a PCB with 50 components

My wild guess was "one 500g jar". Does brand matter? What is a good source to order from? Here is the web-page that I was planning to purchase from (based on price, since I don't know any better about quality/brand/etc):
----- http://www.smtsolderpaste.com/order.php

Anyone know of a better solder-paste or better place to order (better prices, etc)?

I also need to order some lead-free solder-paste appropriate for a hand-operated plunger-type dispenser tool to apply solder-paste to a small number of places where the whole-PCB stencil does not handle properly. Any advice on either the solder-paste or dispenser?

PS: All components on these PCB are SMT, except 8 ribbon-cable headers and 1 axial filter cap.
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Re: solderpaste : no clean versus water soluable

by alphatronique on Fri Jun 25, 2010 1:28 pm

delete by me
Last edited by alphatronique on Thu Dec 19, 2013 10:48 pm, edited 1 time in total.
Best regard
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Alphatroniqe inc.
www.alphatronique.com
http://ca.groups.yahoo.com/group/MyData_Group

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Re: solderpaste : no clean versus water soluable

by bootstrap on Tue Jun 29, 2010 9:16 pm

!!! OUCH !!!

Well, live and learn. I wish I noticed your post sooner. After reading about 39 million web-pages about different kinds of solderpaste and their relative merits, I decided to buy "water soluble". Ouch.

So I guess you are saying that components may fall off unless the PCB is extremely well cleaned. Do all "water soluble" solderpastes have the same "acid" and "difficult to clean" characteristics? I bought the 500g jar of "lead-free water soluble solderpaste" on the following webpage. I also bought a 500g jar of regular water soluble solderpaste too (with lead).

What are the best chemicals to clean a PCB assembled with this [brand of] water soluble solderpaste? Can they be cleaned in a ultrasonic tank? That's probably a stupid idea, but what do I know? Answer: zip, zero, nada. How about some kind of hand cleaning with a [relatively] high-pressure spray nozzle? What must be done with the liquid in the cleaning tank when done? Is this safe to "flush", or must it be sent to some chemical disposal company, or can something be added to "neutralize it", or what?
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Re: solderpaste : no clean versus water soluable

by alphatronique on Tue Jun 29, 2010 10:44 pm

delete by me
Last edited by alphatronique on Thu Dec 19, 2013 10:49 pm, edited 1 time in total.
Best regard
Marc Lalonde CID.
IPC Certified PCB Designer.
Alphatroniqe inc.
www.alphatronique.com
http://ca.groups.yahoo.com/group/MyData_Group

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Re: solderpaste : no clean versus water soluable

by adshea on Fri Jul 02, 2010 12:39 pm

I've had good luck using the 3M Novec Electronics De-greaser or Novec Flux Remover. They're very similar and I usually use the degreaser as it's nicer to plastic components. They'll clean off just about any flux you use, but be sure to keep them off your hands.

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Re: solderpaste : no clean versus water soluable

by gallionc on Fri Aug 20, 2010 11:31 am

I just happened to stumble into this forum an decided that maybe I should put in my 2 cents to clear some things up. As a manufacturing engineer with over 15 years of SMT, wave solder and PCB washing experience in a medium volume electronics assembly facility, I can tell you with the most confidence and banned that using water soluble fluxes are not an issue if cleaned properly. This applies to leaded or lead-free assembly. First off, NEVER clean a PCB with banned tap water!! If you want a board that doesn't work for more than a couple months, have at it! You will get scaling and all sorts of problems that will cause board failures and future defects that will form down the road. If you are using water soluble flux, such as Kester 2331zx or Aim 715, you have at least a 24 hour window to clean your boards if the flux that is in your paste isn't too aggressive. Always clean your boards with Deionized water. For best results, it needs to be heated between 130 and 150 degrees Fahrenheit to properly dilute the acids in the flux. If you have access to a PCB washer that is the best way to thoroughly fine pitch smt components and BGA's. Ultrasonic cleaning was mentioned, and could work very well, although I have never done it this way. If you are using an additive such as Chemtronics Flux-off or Atron AC205, you can simply soak your boards in an ESD-save tub of a DI Water and Additive mixture, then simply rinse the boards with DI water and let them dry standing upright. This works for both water soluble and no-clean fluxes. If you have any other questions or concerns, I have found the folks at Kimco Distributing can answer your questions or supply you with the products you need for low-high volume PCB assembly.
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Re: solderpaste : no clean versus water soluable

by adafruit on Fri Aug 20, 2010 12:02 pm

thanks gallio, thats a lot of really good info!

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Re: solderpaste : no clean versus water soluable

by freaklabs on Wed Aug 25, 2010 4:08 am

Actually, I just use tap water (in Tokyo) and compressed air to dry off the boards. I have boards over a year old with no problems and no degradation in their solder joints. I have noticed that leaving the boards to air dry can leave a scaly residue but haven't had that problem using compressed air.
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Re: solderpaste : no clean versus water soluable

by daikii--- on Tue Oct 22, 2013 10:20 am

Hi gallionc, I have a question regarding water-soluble flux.

I've been using 2.4GHz AV transmitter IC, and I recently found out that the residues of water-soluble flux has been creating noise to the modulation signal. There were some resistance between the IC pins due to the residue, causing unwanted impedance. The circumstance was obvious - the transmitted video image had white-strip noise, but after I did some cleaning between the pins with a cotton, all the noise had disappeared. I observed this several times.

I used water-soluble flux and did not clean, so that obviously might be why, but even if I did clean this with a flux-remover, I don't know if this had resolved the problem. I feel it's better off using RMA no-clean flux (will be testing with no-clean flux in few days).

Can I get some opinion about this? Since I'm not an expertise, I would appreciate your thoughts. Thank you!
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Re: solderpaste : no clean versus water soluable

by phild13 on Tue Oct 22, 2013 1:59 pm

You should always clean and scrub water soluble flux very well from boards. The residue left is mildly corrosive at room temp and will cause issues with the board in a number of ways. No clean flux can in most cases be left on board as it is non-corrosive when not at solder temp. Some frequency critical boards will benefit from cleaning the no clean flux with electronics grade alcohol (not the stuff from a supermarket) and a toothbrush

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