bwshockley
New Head-Fier
- Joined
- Sep 4, 2012
- Posts
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First, I'm not saying that my methods will work for everyone. I'm just putting them down so that someone else may learn and they can try them for themselves and determine if it's right for their project.
That being said, I recently finished my first ever SMD project, the grubDAC. I purchased a kit from beezar.com and it was an extremely thorough kit and well packaged. You can see many photos of the build in my album shown in my signature.
Equipment: I used an Aoyue 936 with a 0.8D Tip set at 325C {Edited - thanks cobaltmute} the whole time. I also used the Aoyue brass sponge tip cleaner after each and every component placement. I used .022 diameter 63/35/2 solder from Radio Shack. I found it to be about perfect. I also used a flux pen for wetting the board, but I'm not sure it was 100% necessary.
I held everything in a set of "helping hands" and actually used the magnifying glass to work. I'd say 95% of the time I used the glass for the SMD parts. I didn't use it for the through-hole components.
I used some self-clamping tweezers, with long handles, to help hold components as well.
I followed tomb's excellent write up, so I will only list out of few of the things he doesn't mention or didn't do.
ICs
Starting with the ICs, I wetting the board with flux and tinned the first corner contact. I then used some blue painter's tape (doesn't leave residue) to hold the IC on the board while I used tweezers to press down and the soldering iron to melt the tinned contact. This worked out great and kept the tape on there while I did a few more pins. I then removed the tape and completed the job. I didn't necessarily work on one side first, then the next and I didn't go in pin order. I jumped around so that each edge/section of the chip had a little more cool time before doing the pin next to it. I would do each pin my placing the iron tip on the PCB contact butted up against the IC pin. I'd wait a couple seconds then try and apply the solder to the IC pin itself, down where it was butted against the iron tip. This worked well for most of them and the solder quickly slowed down the pin and onto the pad. I'd then quickly remove the iron tip. I'd check for a complete joint and reapply if needed. I found it was much easier to apply more solder than to remove excess solder. I did one pin at a time, again jumping round the IC so as to not heat one section of the chip too much at once. Doing this method I was able to complete the main IC ship in a few short minutes with only one easily fixable bridge. Between each and every solder, I cleaned the tip of the iron to remove added solder. I think this was key to being consistent.
I proceeded to the Wolfson chip with the same method, starting with blue painter's tape and the single tinned pad. I completed about 3-4 pins before removing the tape and continued like before. No bridges on this chip.
SMD Components, including VDO Regulator and Oscillator
For the SMD parts, I started by following Tom's suggestion of tinning one pad, placing the component, then completing the other side. However, I was finding this very difficult to do, as I'd sometimes end up with the component not seated down on the board, but the end on the pre-tinned side up a bit. Maybe if I had different tweezers it would have worked better, but I could seem to get the leverage needed on the tiny part to drive it down onto the board. If you do use this method of pre-tinning, put just a tiny bit of solder on the pad. You can add more later, you just need enough to tack the component on the board.
The method I found most useful to me was using my large tweezers to clamp the component on the board without any pre-tinning. Being very careful of what is under the board, I'd clamp the component down on the PCB board, used something to prop the other end of the tweezers so I didn't add a moment to the board. The tweezers did not have a strong enough clamping force to worry that I'd crush a component, but they were enough to hold the component in place. Id's then proceed to solder both ends of the component and carefully remove the tweezers. If you follow this method, wrap a tiny bit of tap around the tips of your tweezers and mind the bottom of the board that you don't crush/scrap/jab or otherwise damage anything on the board. This might have required more time per component, since I had to align it, then try and clamp without moving it, readjust as necessary, but felt it provided more precision and the soldering part was faster and easier and meant less time with high temps on the board and fewer retries. I did this method for all SMDs, the VDO and oscillator.
Through-Hole Components
This is where most DIYers have experience and again use the method that works best for you. For me, to get a clean close to the board mount, I would place the component on the board, with the leads through the holes as close as I could without bending the leads on the underside of the board. I'd then tack one lead, then put the solder down and using pliers and the iron reheat the tack and pull/push the component into position, then remove heat. Then I completely solder the other lead in place then go back to the first and complete that one. For the larger capacitors on this build, I'd tack them, then using my thumb, push on the top of the capacitor while I reheated the tack until the cap was completely seated. This works okay if you are fast, they can heat up quickly if you aren't careful.
Upon completion I double checked all my solder joints. My advise is to start with what you think might be too little. It is easier to add more solder than take it away. Or course, having a solder wick or solder suction bulb is helpful. Again, clean your tip after every component placement or if you feel you have additional solder on the tip before starting a new joint.
That being said, I recently finished my first ever SMD project, the grubDAC. I purchased a kit from beezar.com and it was an extremely thorough kit and well packaged. You can see many photos of the build in my album shown in my signature.
Equipment: I used an Aoyue 936 with a 0.8D Tip set at 325C {Edited - thanks cobaltmute} the whole time. I also used the Aoyue brass sponge tip cleaner after each and every component placement. I used .022 diameter 63/35/2 solder from Radio Shack. I found it to be about perfect. I also used a flux pen for wetting the board, but I'm not sure it was 100% necessary.
I held everything in a set of "helping hands" and actually used the magnifying glass to work. I'd say 95% of the time I used the glass for the SMD parts. I didn't use it for the through-hole components.
I used some self-clamping tweezers, with long handles, to help hold components as well.
I followed tomb's excellent write up, so I will only list out of few of the things he doesn't mention or didn't do.
ICs
Starting with the ICs, I wetting the board with flux and tinned the first corner contact. I then used some blue painter's tape (doesn't leave residue) to hold the IC on the board while I used tweezers to press down and the soldering iron to melt the tinned contact. This worked out great and kept the tape on there while I did a few more pins. I then removed the tape and completed the job. I didn't necessarily work on one side first, then the next and I didn't go in pin order. I jumped around so that each edge/section of the chip had a little more cool time before doing the pin next to it. I would do each pin my placing the iron tip on the PCB contact butted up against the IC pin. I'd wait a couple seconds then try and apply the solder to the IC pin itself, down where it was butted against the iron tip. This worked well for most of them and the solder quickly slowed down the pin and onto the pad. I'd then quickly remove the iron tip. I'd check for a complete joint and reapply if needed. I found it was much easier to apply more solder than to remove excess solder. I did one pin at a time, again jumping round the IC so as to not heat one section of the chip too much at once. Doing this method I was able to complete the main IC ship in a few short minutes with only one easily fixable bridge. Between each and every solder, I cleaned the tip of the iron to remove added solder. I think this was key to being consistent.
I proceeded to the Wolfson chip with the same method, starting with blue painter's tape and the single tinned pad. I completed about 3-4 pins before removing the tape and continued like before. No bridges on this chip.
SMD Components, including VDO Regulator and Oscillator
For the SMD parts, I started by following Tom's suggestion of tinning one pad, placing the component, then completing the other side. However, I was finding this very difficult to do, as I'd sometimes end up with the component not seated down on the board, but the end on the pre-tinned side up a bit. Maybe if I had different tweezers it would have worked better, but I could seem to get the leverage needed on the tiny part to drive it down onto the board. If you do use this method of pre-tinning, put just a tiny bit of solder on the pad. You can add more later, you just need enough to tack the component on the board.
The method I found most useful to me was using my large tweezers to clamp the component on the board without any pre-tinning. Being very careful of what is under the board, I'd clamp the component down on the PCB board, used something to prop the other end of the tweezers so I didn't add a moment to the board. The tweezers did not have a strong enough clamping force to worry that I'd crush a component, but they were enough to hold the component in place. Id's then proceed to solder both ends of the component and carefully remove the tweezers. If you follow this method, wrap a tiny bit of tap around the tips of your tweezers and mind the bottom of the board that you don't crush/scrap/jab or otherwise damage anything on the board. This might have required more time per component, since I had to align it, then try and clamp without moving it, readjust as necessary, but felt it provided more precision and the soldering part was faster and easier and meant less time with high temps on the board and fewer retries. I did this method for all SMDs, the VDO and oscillator.
Through-Hole Components
This is where most DIYers have experience and again use the method that works best for you. For me, to get a clean close to the board mount, I would place the component on the board, with the leads through the holes as close as I could without bending the leads on the underside of the board. I'd then tack one lead, then put the solder down and using pliers and the iron reheat the tack and pull/push the component into position, then remove heat. Then I completely solder the other lead in place then go back to the first and complete that one. For the larger capacitors on this build, I'd tack them, then using my thumb, push on the top of the capacitor while I reheated the tack until the cap was completely seated. This works okay if you are fast, they can heat up quickly if you aren't careful.
Upon completion I double checked all my solder joints. My advise is to start with what you think might be too little. It is easier to add more solder than take it away. Or course, having a solder wick or solder suction bulb is helpful. Again, clean your tip after every component placement or if you feel you have additional solder on the tip before starting a new joint.
