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Need a little advice about Solder Paste's and Hot Air Soldering.

Discussion in 'General Electronics Discussion' started by wade7575, Sep 16, 2018.

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  1. wade7575


    Jul 24, 2016
    I was able to score a major deal on a Quick 816DW Hot Air Rework station,I was talking to a guy who I sometimes buy some electronics stuff from and he told me about 4 to 5 months ago a guy asked him to order a Quick 816DW for him over the phone and he said the guy seemed like a really stand up guy and did not ask for a deposit and when it showed up the guy never came in to get it and would not return phone calls.

    I was told about and asked how much and I told I could have it for he paid for it and he even took a picture of what he paid and emailed it to me and it was 189.00 so I sure I'll take it and he knows he can trust me from dealing with him in the past so I'm getting it sometime this week.

    I was thinking before about getting a hot air set up for soldering SMD resistors and Caps when it comes to the really small ones as I really struggle with the smaller ones,I had thought about getting a Baku hot air unit but I heard to mixed reviews about them and other ones I got scared off pulling the trigger and man I sure am glad I did because I have seen many techs such as Louis Rossman say they like the Quick 816DW better then the Hakko and to me that's saying something.

    What I was wondering is what advice can anyone give me about hot air soldering,I'm wanting to know more about what kind of solder paste's you like the best.

    To start me off I just got some MECHANIC XG-Z40 stuff that was dirt cheap for some small project hobby boards as I seen a few guys on youtube saying they found it to work pretty good and figured I'd try it because 2.78 a tube off ebay didn't sound to bad to me.

    What temp's would you guys start off at for melting solder paste,I'm just looking for a good starting point and I understand I'll have to play with nozzle size and air flow if I find the parts are blowing away on me and also how close to hold the nozzle.
  2. Ylli


    Jun 19, 2018
    Forget the paste - it is a pain to work with. Simply tin all the pads, (optional - add a bit of flux from a flux pen), place the device on the pads hold it down and reflow.
  3. H2814D


    Nov 4, 2017
    I disagree with Ylli. Hot air soldering and solder paste is great to work with, with SMD components. Very easy to use and the results are pretty impressive. Are you really talking about the Quick 861DW? A nice gun, but there are far less expensive ones out there, if you want to try one of those first.

    Since those (SMD) components are often very small in size, tweezers are going to be your friend. So is a magnifying glass. Solder paste is very easy to use. You need to check on the melting temperature for your applications. If you didn't already know, solder paste is basically regular solder powder held together with some type of binding agent, which is usually a flux based material. You can read about what it is exactly if you want to know more.

    Solder paste usually has a stated melting temperature on the tube. I typically use one that melts at 137 degrees C (278F). It has a no clean flux. Simply adjusting the air temp on the gun to the melting temp (or a bit higher) with a relatively light airflow has been successful for me. It usually comes in a syringe type of tube with different sized application nozzles.

    When using solder paste, you apply a small amount (you will learn that amount for each application after using it a few times) to the PCB contacts. You then take your component and place it into the paste (solder paste is sticky before it is heated up. It is like a cream) and the paste holds the component in place. You can actually place the solder paste on the pins and place several components on the board before applying the heat. Then you apply the heat with a hot air solder gun. Moving the air around the component will eventually melt the flux away and the residual solder will melt and form into a solder joint, just like using a regular solder iron and solder.

    One of the other nice things about solder paste is that even though the component may look like it is placed on the contact surface crooked, the melting of the paste often aligns the component without having to actually physically touch it, and it usually ends up aligned on the board very nicely. The component kind of just flows into an aligned position as the paste melts.

    As the paste melts and the solder turns into melted solder it will change color from a gray color to the shiny silver color of melted solder that you are familiar with. You may think you have over-applied the solder paste, but much of the "blob" of paste shrinks down to just a bit of actual solder. I have actually noticed a lot less bridging when using solder paste when installing ICs and chips, even though the paste may appear to be cover more than one pin when you set the component. It kind of just collects on the pins and separates itself as it is heated up. Obviously, the right amount of paste is also important.

    You'll like it, but of course, let us know after you've used it a few times.
  4. H2814D


    Nov 4, 2017
    One of the bad things about solder paste is that it does not last as long as regular solder wire. I don't mean on a board, but in storage. It should be kept refrigerated and it typically has an expiration date.
  5. wade7575


    Jul 24, 2016
    I want to do a lot of SMD hobby board stuff and I considered getting a cheaper Hot Air set up and went back and forth but then I could not decide on witch of the cheaper ones to buy as I was looking and then I contacted an electronics shop I know to order me a few thing's and told the owner I was wanting to get into Hot Air and he told me about the Quick 861DW he ordered for a guy and the guy never came back to get it.

    I couldn't pass up this deal as it's so cheap and the owner of the shop said he has no demand for the Quick 861DW and just want's to unload it as quick as he can to recover his cost in it.

    I know I'm going to enjoy Hot Air soldering as I have watched many video's and a few thing's I have wanted to do use the smallest SMD resistors that are made and it's just to small for me to hold with tweezers so I figured seeing as this deal came along I'd be fool not to take it,I read to many thing's about a lot of the cheap ones just up and dying without any warning and also seen a video where one guy had 2 Baku's and on the one the temp was easy to adjust and the other was extremely sensitive.

    H2814D what kind of solder pastes do you like and have you ever tried the Mechanic stuff and what o you think of it.

    I also seen in the video's I watched how the surface tension of the molten solder aligns the parts for you and though that was very cool.
  6. H2814D


    Nov 4, 2017
    Don't really concern yourself with which paste is the best. Most all of them are following product manufacturing guidelines and are making similar products with similar properties. Just look for a higher rated T4 solder with a rather low melting temp, like I mentioned above. The reason this is important is because of the type of components usually soldered with this method. They are extremely small and electronic components don't like heat very much. And even though the paste I use says no-clean, everything I solder is cleaned with alcohol and a cotton swab. Get in that habit. As far as if I have ever used the Mechanic stuff, I can't tell you if I have or not, but it doesn't sound familiar.

    Unless you know better and will be using a lot of it for sure, don't buy a ton of the paste. It only lasts about a year or so before the coagulant properties start to break down and it becomes more of a liquid than a paste. Also, keep the unused portion in a refrigerator until you plan on using it. That extends the life of it a bit. Those little tubes actually last a long time, so start with just one. They are all over the two major online shopping sites, so they are quick to get when you need it.

    Even though solder paste is the new (well not quite anymore) and fun thing to do, you will still need a regular soldering iron for those components that solder paste just doesn't cut it with. Solder paste has a low melting point, so it is best not used on those components that get hot during use. Components shouldn't get that hot anyway, but if they do, like in a component failure, and if the solder melts because of a low melting point, it could cause other issues. Very rare though. And you probably wont use it when soldering ports and connections that need to be strengthened (using a lot of solder and sometimes glue) when attached. Ok on the pins, but not on the anchors.

    I did notice the 861DW appears to only have one nozzle and the nozzle looks to be pretty large. If so, you may want to find smaller nozzles for it so you can concentrate the airflow. That is a benefit sometimes. Also, your statement about that model not being in demand should tell you something. For it's price, unless you really need a professional model, you may still want to reconsider. It's not my money, but I have been using an 858D for the last few years without a problem. I would replace it with the same model again if it stopped working, because I can get 5 of them for what you are paying for the one offered you. I don't remember exactly, but I think I did have problem with mine that involved taking apart the handheld blower portion, but it was easily repairable and must have been insignificant, because I don't even remember what it was now.

    A suggestion for a good project using SMD components and the hot air solder method, after you acquire your equipment of course, is the DIY DSO138 Oscilloscope sold with the SMD components not installed. Actually, I just looked for it and it may not be available with the naked PCB anymore, but see if you can find it somewhere. A fun project and you will be able to test your skills with the new equipment.

    Good luck...and come back and tell us how it goes.
  7. SMTnerd


    Oct 15, 2013
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