Bottlehead Forum
General Category => General Discussion => Topic started by: Deke609 on April 29, 2020, 11:09:57 AM
-
What's the preferred finish? What does BH use for its boards?
I'll be using SMD components, in case that informs the recommendation.
Not doing anything too exciting - just an "Instructable" build of a milli-ohm meter. The inventor has published the gerbers, so all I need to do is order them. Reported to be accurate to 0.1 mOhm and can be programmed to also measure mV [edit: uV]. Looks like a fun build and I figure it might even be useful for measuring small value resistors.
cheers and many thanks, Derek
-
What will you be using to install the SMDs?
-
A cheap computer based magnifier, 0.02 solder and a really fine, pointy solder tip. I've read that solder wick can be used for some parts too - but I'm assuming that only works with HASL. I have a bunch of fine solder wick as well.
cheers and thanks, Derek
-
Do you have a link to the kit you're putting together? You could probably get away with using an iron to solder surface mount resistors, maybe, but pretty much everything else is going to require using a different method.
-
Thanks PB.
Two links:
http://www.danielrp.net/projects/proj-milliohm-meter-1 (http://www.danielrp.net/projects/proj-milliohm-meter-1)
http://www.instructables.com/id/Milliohm-Meter/ (http://www.instructables.com/id/Milliohm-Meter/)
-
That's not something I would consider solderable with a soldering iron.
You will need a hot air station, or maybe you can use the hot plate method. I would strongly recommend ordering a stencil with the boards to help you lay down the solder paste properly. Most of that stuff is lead free, but I would still use HASL.
-
Many thanks PB. I will look into getting all of that.
cheers, Derek
-
I am 67 years old. My eyes are not what they used to be when I was 25. I handsolder SMD parts with the pitch of your IC3 quite regularly. I sometimes use solder, sometimes paste, always decent amounts of flux. I also can't do it without good light and magnification.
You can see at least one recent SMD project that I handsoldered on diyaudio, same user name.
I can actually work faster with SMD parts and I prefer it. I even use a relatively large tip that I angle to get to the spot.
-
I tried the Schiit Coaster amp, and that was all SMD. Never could get it to work when soldering with an iron, and I didn’t want to buy a bunch of new equipment for one project.
I hate SMD. Best of luck.
-
Thanks grufti and Jameson -
The only thing that really gives me pause is that chip with a ton of tiny legs that looks like a metal millipede (the "IC3" that grufti refers to? I'm unfamiliar with SMD nomenclature). Not sure that I could pull that off with a soldering iron. Maybe if I use a stencil and paste and then heat each leg with fine soldering tip? Any thoughts/recommendations on this are welcome.
I usually like buying new gear, but I'm hesitant to invest in a hot air station. At least right now. I've mostly sworn off buying cheap "starter" tools b/c I inevitably end up later buying a well-made one and giving the first one away - completely undermining the "economy" of the first purchase. So the purchase would be pricey.
I wonder whether a regular heat gun -- the kind used for stripping paint, etc. -- might work? I have a good one, adjustable from something like 350F to 1300F with low and high fan speeds. It looks like after-market nozzles are available online that might get me an approximation of a hot air station. Anyone tried that?
Failing that, I will consider getting a hot air station. I've been steadily working on getting my son interested in STEM stuff (fyi - for those with kids or grandkids: watching Battlebots videos got my son hooked on fantasizing about robot designs and the metal carnage he hopes to one day wreak upon competitors -- although the glean in his eye noticeably lessened when I told him that building a similar contraption would require a lot of physics, engineering, math and programming know-how). So maybe a rework station wouldn't go to waste. But I can't see it being all that useful for my diy audio interests - I'm too much of a tweaker/rebuilder and need point to point.
cheers and thanks, Derek
-
I got the garbage hot air rework station on Amazon that's less than $15. If you turn it up all the way, it melts itself, but otherwise it's usable. That and some chipquik paste and flux got me far enough along to complete a bunch of surface mount projects. Good tweezers are nice too.
-
I did use a heat gun like what I use to strip paint or shrink heat shrink and it worked well enough with chipquik, but the problem is that even on its lowest setting it was blowing tiny components all over the board.
I guess I drink too much coffee, too, because my hands were too shaky to place things that small and have them stay put.
I'm with you, though, Derek. Having bought enough things a bunch of times in incremental steps up in quality (e.g., three soldering irons, three sets of wire strippers, etc.) I'm not really interested in buying cheap tools for one project. I either bail on the project or find enough other projects that an investment in quality tools is justified.
-
Thanks PB. Are you referring to the little handheld air guns used for shrink tubing etc.? Those are the only really cheap hot air guns I can find on Amazon. I have one of those. I just looked up the reaction temp of chipquik and was surprised by how little heat is required! So it looks like it might work. Worth a shot, since I already have one.
@Jameson - yeah, I'm in the same boat. Cheap little tools are wasteful but at least they don't take up much space and come in handy when you can't find the good one in the pile of parts and tools on the bench. But what really swore me off "starter" tools was the bigger stuff: router, chop saw, circ saw, drill press, etc. I stopped buying really cheap versions of that kind of stuff 10+ years ago.
cheers, Derek
-
Thanks PB. Are you referring to the little handheld air guns used for shrink tubing etc.?
No, it's a hot air soldering station, not a heat gun. Do not use a heat gun, it will blow all your parts all over the place and probably blow your molten solder paste right off the board. It's the wrong tool for the job.
-
Many thanks PB. Hmm. I watched a couple vids about using solder wick to deal with tricky ICs and it looks doable. I'll try this method first. And if that fails, I'll get a hot air station. I'll have 5 pcbs, so there's room for some failed attempts.
cheers, Derek
-
It's just like everything else in my experience. You get better at it the more you do it.
Good tweezers are important and I can't stress chipquik flux enough. I sometimes tape the tiniest parts in place with little bits of masking tape when I solder them with an iron. Surface tension will take care of the alignment when you use a hot air station. Bring the general area up to temperature first, then get the paste to do its job.
You're going to be just fine. Start with the resistors to get a feel for the process. I try to avoid having to use solder wick except as a very last resort. Don't smother your small parts in solder because solder wick will cure it all. That's not my experience.
-
The hot plate method looked pretty attractive to me as well, especially if you aren't doing a ton of boards.
-
Many thanks all. I've got some good pin tip tweezers. I'll order a flux pen. Just watched some videos of people soldering tiny pitch parts with a soldering iron and it looks doable. But I've ordered a stencil just in case.
cheers, Derek
-
Magnification is essential. You can do what you can see. Surgeons, who work on eyes or infant's hands, and dentists who care about their work, could not do what they are doing without magnification.
-
Many thanks. Good there too. I only solder with magnification.
-
For the multi plan SMD's I pre tin the pads on the board then I have some really nifty flux I got in a SMD rework kit from Digakey. It comes in a syringe with a fine needle so you can get it just where you need it and it is sticky enough to hold your part in position. Then I add a very little soldier to a standard 2mm tip and very lightly run it down the row, the solder on tip is to transfer the heat, the pre tin is enough to make the connection. If it is a big chip. I tack a corner or two to help keep it in position...John
-
Thanks John. That's precisely the method I saw in a video today, and the one I plan to try.
cheers, Derek
-
You might to spend a little money and try a smd practice board like: https://www.amazon.com/Gikfun-Welding-Practice-Soldering-Training/dp/B00Y20JYTM . This one goes down to a form factor smaller than you will need for the intended project.
If your tweezers are magnetic, I would recommend getting a non-magnetic one. As already recommended, you will want liquid flux. Also, purchase extra small parts. You sneeze or cough and a 603 resistor will be gone for good. Use a magnifying glass while shining a light from the back side of the board to make sure none of the IC legs are connected by solder.
-
More good advice. Much appreciated!
.... try a smd practice board
I plan to test my smd-soldering mettle by trying to desolder and then resolder a bunch of parts on a pcb that came out of my DAC as part of an upgrade. I've read/watched about the the difficulties of desoldering those millipede iC's, so this should be "fun". Liberal use of a heat gun may be involved (for desoldering). What I lack in skill I make up for with dogged determination (aka stubbornness), so I am weakly confident that I'll figure it out. ;D
Also, purchase extra small parts. You sneeze or cough and a 603 resistor will be gone for good.
That already happens to me with parts that are an order of magnitude larger! Although usually not from sneezing. So I've ordered enough of the small cheap parts (wow are smd parts cheap compared to through-hole!) to populate 10 boards and enough of the more expensive ICs to complete 5. I've ordered the min 5 boards, but only need 1. So with luck I'll have a surplus of spare parts and have enough left over to complete at least 1 or 2 of the other boards.
cheers and thanks, Derek
-
Just one more hint from me. I've discovered that taking a high resolution photo in good light is sometimes the only way that I can tell whether or not all the legs of a millipede have made proper contact. They often do even when I'm not fully convinced while soldering. It becomes difficult to judge when it's just a small [correct] amount of solder.
-
The desoldering is actually harder, you need a heat gun or the kit I got has some busmith based solder like stuff that when you apply it to the row of legs melts the joints and stays molten for an uncanny amount of time.
I learned the basics on cheap DAC kits off eBay...John