While there are many How to Solder tutorials, there are only a few that cover how to mount some of those tricky small pitched ICs. These .65mm and smaller pitches can seem overwhelming at first, but with the right equipment or even just enough patients they can be soldered, and with practice quite easily at that.
There are several different styles ranging from using small conical tips, to solder paste and re-flow, to drag soldering, but we will just cover drag soldering in this tutorial.
Soldering Station -Weller, Hakko, or similar type that has a good range of tips.(NTGW gullwing or T18-C2 bevel)
Solder -If you don't have some good quality solder do yourself a favor and pick some up, it is expensive but will last a very long time.
Flux -depending on your style and the part that is being soldered this may vary and some may prefer a tacky type to a liquid, I am using a Kester 2331-ZX type flux pen.
Clean Wipes- If your flux is the corrosive type you will want to clean up after the IC is finished, use some nice lint free wipes.
PCB and IC to solder!
The steps involved are really straight forward, and once you get the hang of this technique you will use those difficult ICs in more projects! The only real steps are 1) Position IC, 2) Tack or affix IC in place 3) Solder each side or pin!
Step 1: Initial Setup
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Now is a good time to take some initial steps which will pay off later in the process. Heat up your iron and prepare the tip cleaning method(distilled water w/ sponge or brass sponge) Tip maintenance is an important step in keeping your Iron and tips in working order and maximizing the use of them, it is important to keep it clean and when stored always keep a nice blob of solder on the working edges of the tip.
Start by cleaning, tinning, and then cleaning the tip again. This will make sure it is ready to go, with a "pure" surface that will transfer heat evenly and quickly. Apply a fair amount of solder on the tip to keep it from oxidizing and place it back in the stand while we ready the rest of the steps.
First take one of the wipes and a bit of isopropyl alcohol and thoroughly clean the pad and area where our IC will be mounted. We don't want any dust, old flux or other contaminants interfering with our work!
After we have cleaned off the pads we can apply an ample amount of fresh flux, don't worry if it extends too much in any direction most will burn off and we will clean the rest in the last step!
Place the IC carefully making sure the pins are lined up as well as they can be, on some of the larger pin count packages this can be a bit difficult. In some ways this can be the hardest step. Once properly lined up tack a few pins or use a high temp adhesive like Kapton tape to hold the IC in place. Were now ready to solder it!
Start by tinning our tip, clean it and fill the bevel with a bit of solder. This "pocket" of solder will glide over the pins heating them and depositing the perfect amount of solder on each one. Because of the flux, surface tension and temperature differences the solder makes very high quality fillets that usually require no solder wick as the right amount is deposited at each transition.
The key here is to make sure the is enough solder on the bevel to make good connection, but not too much to over load the "pocket". Drag time should be kept minimal but there should be enough time for a wetting action to occur. A good initial time is about 1 second per pin but this depends on a number of factors, and can be sped up. But it is a good place to start at first.
As shown in the video fill the bevel, and drag down the pins at a steady pace, the key is to gently glide. The pocket and solder do the work not pressure from the soldering iron. You are essentially gliding over the pins leaving a tiny bit of solder behind on each one.
Now using the wipes and a bit of distilled water or rubbing alcohol gently clean the IC, pins and area around and took a look at your work! If you have some solder bridges you can clean the tip and re-drag, or use a bit of solder wick to remove the bridge, once you get the hang of it this is pretty rare.
I hope you enjoyed this and found it useful!