[ShinyFalcon]

I just wanted to share my misfortune with everyone... it's mostly about soldering the PCM2702.

I was confident enough that I could make a BantamDAC as my first SMD project. And I was excited that I finally done it when I seemingly soldered my PCM2702 in. Unfortunately I should have stopped there and moved on to the rest of the parts. Instead, I decided to play around with the soldering some more, because I felt that I did not put in enough solder.

Just to keep things short, I couldn't get rid of a couple of solder bridges resulting from my mistake in the above paragraph, plus my board is an absolute mess from fixing it. My tips and my sponge didn't seem to like each other, as I had a very difficult time cleaning the tip off of excess solder, which affected my ability to do anything. My equipment also may not be ideal... So far I have attempted to debridge the 2702 for three hours, and I can tell that this will not work out for me. I don't know of the heat tolerance of the 2702, but I know that at a certain point it was painfully hot to touch... which means I probably fried it.

I am further saddened because this year has brought nothing but bad luck for me. I wished for this Christmas to be a joyful and happy Christmas for me, so I have gathered much needed self confidence and bought the stuff I need to recable my headphones, have a great DAC to complement my Lyrix amp, and to start a New Year knowing that I have pushed the misfortune of 2008 away.

With things as they are now, I do not have the desire to spend any more money nor the desire to continue with my DAC. I have a feeling that my DAC is not dead yet, but I want to save myself the misery because I absolutely hate how my board looks right now. I know, the Bantam wasn't the best for me to start with...

Now, will someone out there help me fulfill my wish for a cable BantamDAC? My parts came strictly from the BOM, so I would prefer it if it was the same. I bought the bantam box, the USB pigtail, C7, and C12 from Beezar. I intend to have a cable BantamDAC, and plan to use Canare LE6S as the interconnect... I think I can handle the casework by myself. I want to prevent any difficult soldering for now. Even a board with the PCM2702 presoldered is enough for me.

Thank you for reading... I want to get this off my back, and I really want a BantamDAC. The Gamma1 is out of my price range unfortunately... I would have definitely gone for it if I scrounged up $100 more...

 

[synaesthetic]

One of my biggest problems with doing tiny SMD soldering like this was using an iron that was too hot, a tip that was too blunt and using way too much solder. It almost always ended up in bridges and ugly solder joints, burned fingers or an overheated IC. Or all of the above.

I eventually figured out a technique that works quite well, though your mileage may vary. Make sure the board is very secure--with a bench vise, helping hands or whatever you have available. Get a second lower-power soldering iron for this kind of work (I use a 15W iron for this stuff) and use the pointiest tip you can find.

Coat the pads with a bit of solder without the chip on the board, then place the chip down, lining the pins with the pre-soldered pads. Just very carefully remelt the solder on a pad until it flows over the pin of the chip. Let it cool for a while, then move on to the next pin. I found it easiest to solder one corner pin on so the chip stays put, then while making sure all the pins are aligned with the pads, soldering each corner pin until all four corners are soldered down. Then finish the ones in between.

The key to doing this kind of small detail work is to go slowly, be meticulous, allow 20ish seconds between soldering each pin. I have done it this way for some time now, and I haven't had a problem with bridging pads, big globs of solder or any cold joints, nor have I burned any chips. When it's finished, it looks very neat and tidy, almost machine-soldered.

 

[ShinyFalcon]

Thanks for the tip! I'm feeling a bit better after a night's sleep. You're probably right. My iron is a 25W Weller from Home Depot, and I thought that the tips were a bit big to use myself.

I think I'll give this another try, even though it may cost me a bit more. Any suggestions on a 15W iron? Frys has a Hakko for $25, which I think is slightly expensive...

Edit: One thing that was bothering me was that Mouser gave me two extra SMD capacitor for a total of four when I needed two. Should I be worried about the possibility of wrong parts?

 

[DaMnEd]

Forget the irons and get a temperature controlled station, even a lower wattage iron will be at max temp all the time, OK, with the lower wattage it wont be able to maintain the temp as much, but still, SMD stuff won't really get the temp down all that much, the heat has no where to go, small stuff.

You have pretty decent stations available for cheap these days, you should really consider it specially for SMD where the temp ideally shouldn't be more than 320/350C (600/660F).

Anyway, you can easily remove excess solder with solder wick, and some flux would help, some wicks are pre-fluxed you may try to find some, but be careful with this method, it is very easy to burn stuff. Or you can just pass the iron tip fast and several times over the pins, the excess solder will get stuck on the tip and clear the bridges, but you have to be able to clean the tip properly, and you seem to be having trouble at that.

For tip cleaning I would recommend you try something like this:

You can find these types of cleaners everywhere easily, but here is a link to one at Frys since you mentioned it: FRYS.com*|*Hakko

Also, please take the time to see video 4 from Tangent: Tangent Tutorials (Covers some de-soldering techniques)

And these videos for SMD soldering techniques:
Curious Inventor - Guides : Surface Mount Soldering (Covers de-soldering also)
YouTube - Professional SMT Soldering No. 2 (Revised) - Surface Mount

Doesn't take much solder for SMD, you can see this clearly in the last videos posted.

P.S Make sure your sponge is wet, dry sponge wont do you any good, it is meant to be wet (remove excess water).

 

[DaKi][er]

What you need is Flux and solder wick. If you paste flux over all the pins and apply a small amount of solder to your iron tip, after tacking down 2 corner pins, just dragging the iron across all the pins at the same time will solder then pretty much perfectly as the flux will make sure that only just the right amount of solder is drawn from the iron tip onto the pins. You will get the occasional bridge if you have too much solder on your tip (really, only have the tiniest amount on there) and more flux and solder wick will take out the excess solder no problems.

Also, you'd be surprised at the amount of heat punishment chips can take, if you haven't physical damaged the pins too much, then it will probably still work

Here's a good video on soldering fine pitch SMD's using flux - Curious Inventor - Guides : Surface Mount Soldering

DaMnEd, your ninja edit with the video link beat me to it!

 

[naamanf]

I would also suggest spending a bit more and getting a good iron, especially if you think you will be doing more DIY work. Other than having better head control you will also be able to get better tips for it which makes the biggest difference.

If you don't find yourself up to soldering the 2702 I could do it for you.

 

[DaMnEd]

Quote:

Originally Posted by DaKi][er /img/forum/go_quote.gif DaMnEd, your ninja edit with the video link beat me to it!

Yeah, I decided to add more info, at the time I did the first reply I was lunching, it was not a very helpful reply.

And I just added second video for SMD techniques, the second video demos one of the fastest yet perfect techniques for SMD I've seen, very cool stuff, shows exactly what you talked about, flux+dragging movement and add solder.

 

[ShinyFalcon]

Thanks everyone. I did watch most of those videos and they do contain lots of good stuff. My attempt to copy them didn't go so well.

I think I'll go with the 15W Hakko Dash and buy the N452-T-SC .8mm tip from Frys along with that $8 copper sponge thing. Another $50 spent, plus maybe $20 for another 2702 + board. I wish I can justify a soldering station... but maybe I can find someone that has one.

Edit: I think my main problem is that the solder seems to be stuck underneath the pins. I don't think I could reach it with my wick, and adding more solder will probably make it worse.

 

[linuxworks]

PM me - I have a spare bantam dac 'packet' (parts and board). I'd be happy to do the main chip soldering for you. I have 2 bantams already and don't need a third

 

[DaMnEd]

Quote:

Originally Posted by ShinyFalcon /img/forum/go_quote.gif Thanks everyone. I did watch most of those videos and they do contain lots of good stuff. My attempt to copy them didn't go so well. I think I'll go with the 15W Hakko Dash and buy the N452-T-SC .8mm tip from Frys along with that $8 copper sponge thing. Another $50 spent, plus maybe $20 for another 2702 + board. I wish I can justify a soldering station... but maybe I can find someone that has one. Edit: I think my main problem is that the solder seems to be stuck underneath the pins. I don't think I could reach it with my wick, and adding more solder will probably make it worse.

So, 50$ in an iron+tip and the cleaning stuff, why not spend 62$ instead in the temperature controlled station? not that much to "justify" really, the station comes with a 0.5mm tip btw: Amazon.com: Aoyue 2900 Lead Free Soldering Station

Imho the money would be way better spent this way, but, you decide.

(I have one, no problems, and I use the sponge that comes with it)

 

[linuxworks]

if you have access to a heat gun, you can try heating the board from underneath and letting the chip 'drop' by gravity if you keep the board flat (not angled!) and wave the heatgun around to evenly heat the chip 'thru' the board.

I have not done that but I've seen the video where its done and it seems the better way to remove the chip.

but really - once you have a board that's been 'beaten up' it REALLY is worth getting at least a new board. you could be throwing 'good money at bad' by trying too much to salvage a $5 board..

I would not even trust that chip after so much heat - so start over with a fresh board and fresh chip. this was a learning board - and education is what this one is chalked up, to. its cheap education, too, as courses/tuition go! think of it that way

 

[ShinyFalcon]

Quote:

Originally Posted by DaMnEd /img/forum/go_quote.gif So, 50$ in an iron+tip and the cleaning stuff, why not spend 62$ instead in the temperature controlled station? not that much to "justify" really, the station comes with a 0.5mm tip btw: Amazon.com: Aoyue 2900 Lead Free Soldering Station Imho the money would be way better spent this way, but, you decide. (I have one, no problems, and I use the sponge that comes with it)

*headdesk* I haven't done my research! I see some cheaper ones, but is there something specific about the Aoyue 2900 that stands out besides having a .5 mm tip?

 

[linuxworks]

if you really do want to get semi-serious in soldering, why not treat yourself to a hakko 936? they are at frys (not discounted but those models rarely are).

I think that's your best bang/buck. you can turn the temp down low enough so that you dont' cook your chips

plus, its an iron that will last you years and be serviceable.

 

[cobaltmute]

The Aoyoue station looks really good.

I've got a WES51 and never looked back. Even the stock tip works really well for doing SSOP with the drag and wipe method. Temperature makes all the difference in the world. I'm using 0.031" solder and it takes the tiniest amount to do the whole chip. Literally a drop will do 4-5 pins at a time.

 

[DaMnEd]

Quote:

Originally Posted by ShinyFalcon /img/forum/go_quote.gif *headdesk* I haven't done my research! I see some cheaper ones, but is there something specific about the Aoyue 2900 that stands out besides having a .5 mm tip?

I choose the Aoyue for the slim handle (I hate bulky irons), multitude of tips available, and the fact that the heating element is present inside the tip not inside the iron, so if the element goes bad, just change the tip, easy, you don't have to open the iron or send it to get serviced, for the most part this is a function that you will only see on "pro" irons that cost much more.

You have finer tips available (0.1, 0.2) and many shapes.