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Thread: Soldering components with small SMD pads when you are all thumbs?

  1. #1
    Senior Member+ KurtE's Avatar
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    Soldering components with small SMD pads when you are all thumbs?

    I know it is probably just me, as growing up, my brother would kid me that I was ambidextrous: Equally uncoordinated with both hands
    And now after my hands have had years (decades) of abuse with RSI or CTD ... At times I am finding it harder and harder to solder those small suckers.

    I can still get away with soldering reasonably small components like 0805s and the like, but as things get smaller
    For example getting those T4 SDCard ribbon connectors to work. I was lucky to get one out of two to work. Especially when you have two such connections. And Now there is the MicroMod connectors and the Himax Camera connectors, and ones up here that think the next Teensy should have a 400 pin connector with probably a .0005" spacing... Maybe slight exaggeration

    So wondering about different options and what others are doing. Note: I am make boards for myself and typically make 1 or 2 of them at most.

    0) Punt - Let someone else do it.
    a) Keep trying with magnifying light, lots of flux, solder braid, solder sucker and hope for the best. Which I am now just about to start a board again like this.

    b) Use a service like Seeedstudio or ??? and have them source and solder on some/all of the parts? If so who have you had luck with for really small runs.

    c) Solder paste with hot air station? I did buy a cheap station at one point to see if I could replace a part on one board... (I more or less melted the board )
    Suggestions on which Solder Paste? Did you apply by hand or use a mask?

    d) Like c) but with something like Hot Plate? or toaster oven?

    e) like c) or d) but instead a cheap reflow oven? Maybe something like: https://www.ebay.com/itm/124245533208 ?

    Just sort of wondering what others are doing and getting some ideas.

    Thanks

  2. #2
    Senior Member wwatson's Avatar
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    @KurtE

    Same for me . Will be interesting to see some responses.

  3. #3
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    Quote Originally Posted by KurtE View Post
    I know it is probably just me, as growing up, my brother would kid me that I was ambidextrous: Equally uncoordinated with both hands
    And now after my hands have had years (decades) of abuse with RSI or CTD ... At times I am finding it harder and harder to solder those small suckers.

    I can still get away with soldering reasonably small components like 0805s and the like, but as things get smaller
    For example getting those T4 SDCard ribbon connectors to work. I was lucky to get one out of two to work. Especially when you have two such connections. And Now there is the MicroMod connectors and the Himax Camera connectors, and ones up here that think the next Teensy should have a 400 pin connector with probably a .0005" spacing... Maybe slight exaggeration

    So wondering about different options and what others are doing. Note: I am make boards for myself and typically make 1 or 2 of them at most.

    0) Punt - Let someone else do it.
    a) Keep trying with magnifying light, lots of flux, solder braid, solder sucker and hope for the best. Which I am now just about to start a board again like this.

    b) Use a service like Seeedstudio or ??? and have them source and solder on some/all of the parts? If so who have you had luck with for really small runs.

    c) Solder paste with hot air station? I did buy a cheap station at one point to see if I could replace a part on one board... (I more or less melted the board )
    Suggestions on which Solder Paste? Did you apply by hand or use a mask?

    d) Like c) but with something like Hot Plate? or toaster oven?

    e) like c) or d) but instead a cheap reflow oven? Maybe something like: https://www.ebay.com/itm/124245533208 ?

    Just sort of wondering what others are doing and getting some ideas.

    Thanks

    I usually do my PCB's in my good old Weller RO26 PCB oven, but the Weller RO26 has a limit of 100*160mm in PCB size, so when doing larger PCB's I use underheating, Pre heating the PCB to around 100C (Piece of aluminum, Two power resistors and a cheap Chinese DS18B20 Thermal sensor with display.

    It much easier to make good quality soldering using Pre heating during hand soldering, both with solder paste (Hot air), and even with regular solder wire.
    For my old eyes a microscope is key here, I use an old (2010) video microscope and a 17" TFT screen, can do 0.5mm pitch with solder wire, if i have to.

    /Gigabyte

  4. #4
    Senior Member brtaylor's Avatar
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    I do prototyping down to 0603 with a toaster over, solder paste, and a stencil. I've done some stuff down to 0402, but typically require rework when I get to that size. Recommend getting a good pair of tweezers. OSH Stencils has good prices for stencils, jigs, and paste.

    For leaded paste, I do a pre-heat of at least 6 minutes with parts in the oven at 250F. This lets everything get up to temperature and stabilize. Then I step up to 450F for 2 minutes once at temperature to reflow the paste. After that I turn off the toaster oven and open the door to cool.

  5. #5
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    For the smallest stuff, I prefer soldering under the microscope. With a small Metcal Ultrafine tip.

  6. #6
    Senior Member crees's Avatar
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    Toaster over with solder mask applied boards. I use a timer to simulate ramp up temperatures etc but also put solder paste on the chips and Board(s) to verify reflow. A good solder paste jig and some hole alignments really help making it less likely that you will need to fix any solder bridges etc. use larger footprints to allow easier Placements. I have done 0402 parts with this method.

    Click image for larger version. 

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    I usually use the "solder drag" technique and remove bridges with a wick. I used to use small pin point irons but actually it works best wit a large tip which quickly transports heat. I find aligning the parts prior to solder most time consuming.

    Here an example of a quite small assembly I did a few months ago:



    Following that I did a simple DIY hot plate which is very convenient. I prefer this over ovens (which I also used) because I somehow always want to observe the process but that is probably just me :-)



    To apply the solder paste I use those small 1ml syringes (the size they use for the Covid vaccination) and metal tips. The ones I used in the video are way too long, i meanwhile use short bended tips which are more convenient to use (e.g. https://www.amazon.de/gp/product/B07...?ie=UTF8&psc=1)

    And, these days I find these quite inevitable


    I'm still looking for some good and affordable solder paste which is easily dispensable with syringes (i.e. low viscosity). Ideally with a low melting point. Any suggestions?

  8. #8
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    Hi,

    I use to sold prototypes per hand "as I can, if I can". But I tend to use more and more my hot plate. The problem with the hot plate is when you have big PCB because it blend it...

    When I have to do more than 2 pieces, I use a reflow owen like the one Kurt give a link, with a little mod that one can find easily :
    https://hackaday.com/2014/11/27/impr...2-reflow-oven/

    In most case, I order my PCB from https://jlcpcb.com/ and always buy the framed stencil with it. I have a stencil printer like this one :
    https://www.ebay.com/itm/14402390491...0AAOSw-IdginIh
    You can find it at very lower price on aliexpress.

    As per paste, I use this one : https://www.mouser.fr/ProductDetail/...dDQtYwxQ%3D%3D
    easy to use, no need to put it in the fridge and long lasting paste (one year).

    With this, I never missed a single PCB.

    Recently I used https://jlcpcb.com/smt-assembly as a service. It's really cheap and have good quality. The only "requirement" is to use components from there "stock" :
    https://jlcpcb.com/parts

    I noticed that there components are cheaper than if you buy them from known distributor. For example, the well know ADM3202ARNZ :
    JLCPCB : https://jlcpcb.com/parts/componentSe...Txt=adm3202arn
    Mouser : https://www.mouser.fr/ProductDetail/...MHlWZQaA%3D%3D

    do the maths ;-)

    The only thing is to prepare the rights files for SMTassembly. It take a learn session to understand, but after that it's easy (and cheap).

    And as Luni said, I need to use googles :-(
    I bought this one : https://zoomiglass.com/products/prec...39371597676734
    They are not comfortable for a long run.... I need to figure which one I should source to allow me to work for 4 hours without any problem. Maybe a CAM and a screen.

    Best regards,
    Manu
    Last edited by Manu; 05-23-2021 at 09:14 AM.

  9. #9
    Senior Member+ KurtE's Avatar
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    Thanks everyone... And hopefully those to come.

    I went ahead and ordered a couple of Solder masks from OSH Stencil as well as their lead free Solder paste. I also ordered some
    low melt stuff from Amazon: https://smile.amazon.com/gp/product/B017RSGPI8/

    Not sure which approach I will experiment first with.

    Luni - your plate looks interesting as I mentioned on your other thread.

    Ovens - Have you modified them at all or just doing it by timing? There was a a blog entry on Sparkfun this last year where he modified the temperature knob and thermo... and looked like a simple change to do.

    But wondering to self, if requires buying a toaster oven plus several other things maybe that reflow oven is not that much more expensive?

    Glasses/Scope - Yes I have a pair of those like glasses that I have tried before. Most of the time I use my magnifying lamp which I purchased a couple of years ago:
    https://smile.amazon.com/gp/product/B07BYCFVRF Obviously a scope would be even better.

    I do have two solder stations, an older Weller WSL unit which I usually have a fine tip on... Probably needs some TLC. And a HAKO with a wider tip on it... Usually I used the WSL when doing smaller parts and the HAKO for things like soldering in breakout pins. But from one thing said wondering if for smaller pitch items like the MicroMod connector if I would be better off using bigger tip?

    Also wondering, would also using paste on these pads and using the soldering Iron to melt it into place work? Or better off using wire solder with lots of flux?

    Thanks again!

  10. #10
    Senior Member brtaylor's Avatar
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    Quote Originally Posted by KurtE View Post
    Ovens - Have you modified them at all or just doing it by timing? There was a a blog entry on Sparkfun this last year where he modified the temperature knob and thermo... and looked like a simple change to do.
    I've seen a lot of blogs on modifying ovens, but I just manually turn the knob while timing with a phone - works well enough with leaded paste and my temperature profile is so simple that I haven't seen a reason to mod the oven.

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    I like Marco Reps channel on Youtube for entertainment mostly, although sadly he makes videos less often these days. In one he uses a DIY vapour-phase reflow oven to solder some components. Not for everyone, but someone might be interested.

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    I'll jump on the band wagon - some sort of reflow is pretty easy. There are a few tricks that take practice: getting the right amount of paste on and knowing when the reflow is actually complete (if you don't have a real reflow oven).

    A stencil is crucial for the first but also takes good technique.

    The second one requires observation and a bit of experience to know where your reflow device is hot or cold. You hear a lot of people preaching the "gospel" of reflow profile but there is a huge amount of latitude and some seemingly crude techniques work surprisingly well. I've seen people using frying pans on a hot plate. Just pick your reflow device and practice. There is something really exciting when you get it right and see all the parts magically float into position courtesy of the Gods of surface tension. I still get a little giddy when I have a good reflow session.

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    Quote Originally Posted by PhilB View Post
    I still get a little giddy when I have a good reflow session.
    Best not to inhale the solvent vapours then

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    Quote Originally Posted by MarkT View Post
    Best not to inhale the solvent vapours then

    just the kool-aid

  15. #15
    Senior Member+ KurtE's Avatar
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    Thanks

    I received the low temp solder paste from Amazon yesterday, today I believe the package from OSH Stencil should arrive in town, probably pickup tomorrow or next day. And then maybe try a few different ways before I go out and buy something. Maybe try my hot air board burner. Maybe soldering iron or maybe a hot plate some form...

  16. #16
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    What do people think about using low temp solder paste (eg, Sn42/Bi57/Ag1) for all prototype work? Certainly less risky in terms of damaging a part by overheating.

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    Fine - although its pretty rare to damage a part by overheating if you have the right equipment (ie temperature controlled).
    Its probably helpful if there's a lot of rework going on as it will be quicker to work with when the melting point is low.

    One thing to beware of, mixing different alloys on the same tools isn't a great idea, you'll end up without a eutectic
    alloy and horrible pastiness. You might want to do a bit of research about any particular alloy as there may be some
    pitfalls (like high diffusion rates, corrosion, mechanical creep, lack of strength).

  18. #18
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    I agree with Mark, you have to work at it to damage a component when using "normal" solder.

    It really doesn't take that much practice to learn how to solder and when doing reflow you can use a thermometer and a timer to stay within the datasheet soldering profile.

    One place where low temp solder may be of value is if you are reflowing components with lower temp plastic - think connectors. There are a fair number of cheap connectors that don't like getting reflowed. Personally, I do them by hand.

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