Soldering 0805 SMD resistors and QFP-52 ICs question
T&E Engineer
Posts: 1,396
I am having a couple of PCB's made up from Futurlec that I designed with ExpressPCB. I used 0805 SMD resistors and have some QFP-52 ICs on it. I am getting the soldermask feature and silkscreening done. I don't have much experience with surface mount components other than a couple of ICs. I do however, have 30 years experience with soldering in general and will be using a 15W soldering iron from radio shack.
Will this do the trick? I heard about solder paste but thought that was for those ovens. I do have one of their solder stations with the magnifying lense also.
What do I need to do this for about 90 of these resistors and 3 QFP-52 ICs (14mmx14mm)? I want to get what I need soon so that when the PCBs come back, I can start.
Thanks.
Will this do the trick? I heard about solder paste but thought that was for those ovens. I do have one of their solder stations with the magnifying lense also.
What do I need to do this for about 90 of these resistors and 3 QFP-52 ICs (14mmx14mm)? I want to get what I need soon so that when the PCBs come back, I can start.
Thanks.
Comments
Your best bet is to get a solder stencil made that has openings in it for solder paste to go through. There are cheap mylar or Kaptan stencils available all over the net for around 25$ with fast turn around. I suggest building a frame to support the stencil that stretches it, even silk screen type hinges make for a much nicer set up that lowers the stencil onto the pcb, search stencil printer to see the idea.
The best is to get a stainless stencil, but they are expensive but well worth it, especially if you are running a bunch of boards. Use a stainless squeegie on it.
You can get water soluable solder paste from manncorp.com with lead that works great, lead is much easier to learn on.
A Quisinart Exact Heat oven will flow the boards nicely in 5-6 minutes.
I think it is time to get a good soldering station and all the required parts for SMD and regular discrete component soldering. Do you know where I can get all of this stuff at? (e.g. flux, correct sized solder, paste(?)). Seems like I'm always having to replace the tip on my Radio Shack 15w soldering iron. Online sugestions are probably best. I need to "get it all" for a "reasonable" cost. What about reflow ovens, etc? Is it really needed?
I want to start getting away from solderless breadboards if possible and start learning more about SMD components and need a starters package or basic components to work with in my home lab.
http://www.radioshack.com/product/index.jsp?productId=3132686
Get any fine solder at radio shack if you are not near an electronics store, I often use their silver type, very thin for components. $79.00?
Solder past is for ovens, you apply it with a stencil. 45$ There are syringes available to dispense more liquid type solder, manncorp, zehptronics.com, digikey.com
Soldering with the oven is very easy to do. Get the Quisinart Exact Heat, use convection bake, set it 3 minutes at 150 then 3 minutes at 500, 6 minutes total and the board is done. 139$ or so all over the web, also in stores. Black and decker makes the same identical model so try sears, etc.
You really just have to dive in a get started, screw up some and figure it out, it is really quite simple though and after you make an SMT board you will never mess with through hole boards again, I mean unless you board it just a couple of components that is.
I will look into that more and probably stick with this method for my 2-3 boards. It's just for me at the moment, unless I start selling my design and have to get more boards made. Currently Futurlec sells these 210mmx185mm double layer boards for about $100 for 1, $140 for 2 and I bought $180 for 3. My parts and PCB alone is going to run about $175-$200·per board. Seems pretty expensive to do a project.
Also Radio Shack sells this Flux paste and not the liquid flux in the bottle. Have you used this or should I get the liquid flux online with everything else?
I use drag-soldering with a Metcal mini-hoof cartridge and plenty of gel flux for QFP parts.
Leon
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Amateur radio callsign: G1HSM
The Exact temp oven technique sounds great. Would you mind sharing the temps and times that you use?
thx
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Searider
Press temp, set to 150F
Press timer, press minute and bump it to 3 minutes
Timer sounds at 3 minutes
Then press temp, set to 500
Press timer, set minutes to 3
Timer sounds at 3 minutes
Board done.
The temp never gets to 500 in that short period. This works consistently for lead paste and the quisinart/Black and Decker Exact Heat convection over.
If using lead-free SAC305
Put board with solder paste and parts in oven
press convection bake.
set temp to 425 (450 if using an alloy without CU)
Press start/stop
When the oven beeps ready, the board is done (it may take a few extra seconds if you have a lot of mass on the board).
Press start/stop again (to stop the oven process), and open door. Let cool in place.
What I don't understand about Todd's method is the 150 degree setting. Ideally that would be 300 Degree (150 C), which is the activation temperature of the flux in the paste.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
Post Edited (James Long) : 10/29/2009 2:46:19 AM GMT
All of this oven stuff sounds intriguing, but how does the stencil thing work? Do you need a stencil made specifically for each and every particular PCB to cover the whole board, or do you use a stencil for, say, a 20 pin DIP, then another stencil for the 4 pin DIP next to it and so on until the whole board is covered?.... or what?
I hate soldering, so if I can easy-bake everything I'd be in heaven less burning in hell.
thanks,
Mark
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Watching the world pass me by, one photon at a time.
Mark,
Typically, you have a stencil made for every board. On the other hand if you can have a few stencils made together (as one), you could cover a few different projects with a single stencil order. I however do not recommend this method. You may be sorry if you are not a careful person. Solder paste can get everywhere......and really is sticky because of the flux in it.
Hey....keep an empty seat next to you. We can always talk electronics for eternity.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
Amazon has this oven for $138 I think my next board will use some surface mount parts.
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Searider
It should be noted:
Do not use this oven for any food items. Doing so will be taking your health into your own hands!!!. Even Lead-free solder has some nasty chemicals in it!!!
You have been warned. I also do not recommend doing this inside your house, especially if you are married. You will be sleeping with the dog if you do. Your garage is fine, if you have a door open.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
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Searider
Kapton stencils get gunked up with paste after a few uses. Take it to the sink and run warm water over it and it will be good as new with very little effort(just don't tell the wife).
I have not tried the oven on dip parts. if you are doing a lot of 1 ofs you can by solder paste in a syringe. works great for stuff you don't do that often. Stencils make fine pitch and repetitive work much easier though.
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24 bit LCD Breakout Board coming soon. $21.99 has backlight driver and touch sensitive decoder.
Post Edited (mctrivia) : 10/29/2009 5:04:26 AM GMT
Also......just for information.....be careful with Kapton and water. Kapton is moisture sensitive, and you do not want to wet it unless you have time for it to loose the moisture content you introduce into it (usually a couple of days). The larger the piece of Kapton, the more out of spec it will be. It is 1% moisture sensitive.
With regular parts that is not a big deal. With fine pitch it can be a problem. Panelized boards of significant size (6 inches and over), you will not be happy.
99% denatured Isopropyl alcohol is the preferred method of cleaning stencils. Use an old toothbrush for the small holes (just remember to not use it again on your teeth).
I am not all knowing about these things, just trying to help prevent someone from being extremely unhappy with their results. Plus most of them...I had to learn the hard way.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
Post Edited (James Long) : 10/29/2009 5:21:18 AM GMT