GM5: Least-cost USB-MIDI Interface Chip for 4.50 EUR

[Sasha]

30 min? I expected you to be faster than that.  ;D As I recently successfully soldered my first SMD ICs and realized it is not hard at all I`m ready for next step. This looks like good project to improve the skills. Thanks for posting the pic.

[TK.]

It was the first time I used flux and desoldering wick after I got an hint from Seppoman - this made SMD soldering really fast (and secure) :)

This is an helpful video which shows the approach: http://www.ulrichradig.de/gfx/video/SMD_einloeten.wmv

Best Regards, Thorsten.

[dstamand]

It was the first time I used flux and desoldering wick after I got an hint from Seppoman - this made SMD soldering really fast (and secure) :)

This is an helpful video which shows the approach: http://www.ulrichradig.de/gfx/video/SMD_einloeten.wmv

Best Regards, Thorsten.

I really like this technique:

More expensive but it is so clean job.

http://www.youtube.com/watch?v=0O2UEGLJeAI

I'm gonna use a video camera mounted on my microscope now  ::)

[Sasha]

It was the first time I used flux and desoldering wick after I got an hint from Seppoman - this made SMD soldering really fast (and secure) :)

This is an helpful video which shows the approach: http://www.ulrichradig.de/gfx/video/SMD_einloeten.wmv

Best Regards, Thorsten.

How would situation be using this technique on self etched PCB and unmasked traces under the IC? I`m afraid of creating a solder bridge under IC.

[sineSurfer]

How would situation be using this technique on self etched PCB and unmasked traces under the IC? I`m afraid of creating a solder bridge under IC.

"Improve" the self etched pcb by removing any traces under the IC? ;D

the pcb looks good TK!

[seppoman]

It was the first time I used flux and desoldering wick after I got an hint from Seppoman - this made SMD soldering really fast (and secure) :)

actually I didn't mention desoldering wick ;D - the wick method is a bit dangerous because if the wick gets stuck and you try to remove it again while it isn't heated enough, you can tear off IC legs or even solder pads.

The method I'm using is the so called "drag soldering". here's a youtube link:

this guy is cheating a bit because he's only resoldering an already soldered IC. but you can see the type of tip I'm using. the concave fillet in the tip takes up a bit of solder. After the IC is fixated by two solder joints, you apply a bit of flux everywhere, take up only a little bit of solder and then drag the tip along the IC until the solder is gone, then take a bit more solder etc.

If you've applied too much solder somewhere, you can even use this tip instead of using desoldering wick. Just wipe the tip very clean at the sponge and make sure the fillet is "empty", apply a bit of flux and drag the iron again. the fillet will suck up the extra solder, leaving behind a clean joint.

BTW, the tip for my Weller WS81 is called LT-GW.

With some practice, it's also possible to use this technique with a normal flat tip, like shown by this guy:

http://youtube.com/watch?v=wQXhny3R7lk

(you can skip the first minute... ;)) but the special drag tip really makes things easier.

here's an example pic soldered by me:

Happy soldering :)

S

[TK.]

Nice explanation, Seppoman! :) Actually I knew what you mean, but failed to find a video which shows this exactly.

I think, that desoldering wick is the last chance for the case, that you are trying this method the first time, and you are not able to remove the solder between the IC legs by heating them up again. But applying more flux before heading up sounds like a good idea - I will try this while soldering the next boards ;)

Best Regards, Thorsten.

[Pascal]

That´s the first sweets MB-MIDI Interaface :-)  ;D

@Seppoman: Thx for the Vids!!

[madox]

It was the first time I used flux and desoldering wick after I got an hint from Seppoman..

If I remember correctly, this has also been discussed in a previous thread (maybe regarding the OPL3 chips?).

I do surface mount soldering in my work every day. It is really very quick, with a little experience. I strongly recommend it to anyone who has a bit of hobby experience, and will do more than a few PCBs. If you can paint a lead miniature, you can definitely learn SMD soldering.

The real key to good SMD soldering, is using the liquid properties of the flux and hot (wet) solder. The flux reduces the surface tension on the wet solder, and allows it to flow, and bead very easily.

How would situation be using this technique on self etched PCB and unmasked traces under the IC? I`m afraid of creating a solder bridge under IC.

Again, the key here is the improved flow that the flux lends the solder. The solder will tend to wick to the exposed metal surfaces. The physics of the behaviour, is that the wet solder is in a lower energy state when it is beading on the metal, than if it is bridging accross the FR4 of the PCB. It requires less elastic energy in the surface of the solder to be in contact with metal. In practice, the flux reduces the bridging behaviour, and like beads of water, the bridges can be moved with more flux and reheating.

Flux is not cheap, but one only needs a really small amount in each application. So use it, but use it wisely.

The difficulty with self etched PCBs is that there is generally no solder mask/solder resist to separate the pads from the tracks. These are a little more difficult than manufactured PCBs. They can still be done though. I found that without solder mask, one has to work a bit faster, when running the tip over the pads, as the solder will flow away. Also, re-applying solder has the risk of overloading pads, with potential overflow. I wouldn't recommend this as a first attempt at SMD soldering.

SMDs only require a very small amount of solder. Everyone would have seen wave or oven soldered PCBs from an automated factory. These are done with a silk screened solder paste, and either EM wave heating, or oven heating. One can almost not see the solder.

Another thing to be aware of, is the way surface tension pulls an SMD. This pull can sometimes be used to snap a device to sit nicely on its pads, but not always. Usually, any device should be held well with fine tipped tweezers, as the amount of surface tension pull can be really surprising.

One technique which has not been mentioned here, is the use of hot air rework stations (cheapish ones from ebay are fine, pro brands are expensive though). These are concentrated hot air guns, with adjustable air flow and temperature. These are THE way to desolder large SMDs, and are also very good for soldering small devices. I use these stations a bit at work, and can solder a resistor in around a second in total. The heat is only applied for less than a second. In the same way, I can solder a dual op-amp (SO8) in around a second. Anything larger than an SO8 (SMD equivalent of DIP/DIL8) requires more skill to use a rework station, as there is the risk of overheating a device.

Desoldering large SMDs, such as FPGAs, will generally compromise the reliability of the chip, which would generally just be disposed of. Of course, desoldering shouldn't be performed unnecessarily.

I almost never use solder wick, and would not recommend it to beginners. Depending on how the PCBs are manufactured, some small surface mount pads are very weakly held to the PCB FR4 substrate. The pads can adhere to the wick, and tear away from the PCB. This can happen to the pads adjacent to the ones one is trying to desolder.

I also wouldn't recommend a flat or sharp iron tip, as these can also damage pads/tracks when wiping solder accross the pads.

Usually, to desolder a relatively small SMD, I will use two soldering irons at once, and heat all pads together. This avoids any damage to the PCB, and is also very fast, so heat will not need to be applied for an extensive duration.

Some of the difficulties with SMD soldering are somewhat eleviated by using good quality PCBs. Cheap ones (which I use a lot of) do not bond the copper as well to substrate. For thicker track/larger pad through hole designs, this is generally less apparent. High pin density SMD PCBs may have tracks of only 5 thousandths of an inch, which have only minimal bond strength to a substrate.

One reason I would really encourage hobbiests to learn SMD soldering, is that smaller devices and smaller PCBs reduce the cost of DIY electronics. Of course, when boards are not being made for a profit, the cost is paramount.

Anyone could practive SMD soldering/desoldering with something like a broken PCI card. Just remove brackets first, possibly hold the card in a vice, and start removing/replacing devices.

Hope this helps.

-madox

P.S. I also recommend watching the videos, as they are a great introduction, which I never had.

[madox]

I really like this technique:

More expensive but it is so clean job.

http://www.youtube.com/watch?v=0O2UEGLJeAI

I'm gonna use a video camera mounted on my microscope now  ::)

Hi dstamand:

Just watched this video. Although this technique looks very careful, and neat, it is really too slow, and actually far from ideal. He has used too much solder paste, and then had to apply heat for a lot longer than is necessary.

I believe that he has only used the microscope for the youtube video. This is not a practical way to solder an entire PCB. You will notice that he used the air gun at a very low angle of incidence. This blows hot air over the adjacent parts. With SMDs, this is very easy to blow other parts which you have already soldered, right off the board.

Probably, he would not usually use the air gun at that angle, but had no choice due to the microscope apparatus.

Also, rather than syringing solder paste onto the pads, it is very quick, cheap, and easy to pre-load the pads with solder from the tip of your iron. This leaves the pads with solid, rather than paste solder, but as soon as the heat gun blows on the pads, the solder liquifies. You can then easily place your chip into the pads, and hold the heat on for about a further 0.5 to 1.5 seconds (usually this is plenty).

The nature of heat damage should be understood for this kind of thing. A very high temperature, applied for a very short time, is much less likely to cause deep overheating of a device, than a low temperature applied for a longer time. This is the same principle with performing laser cutting, or laser surgery. One only wants to heat the very surface of the materials being soldered. Deep penetration of the heat can cause damage. With soldering, there is a practical limit to how hot one can go, as material start to de-nature or burn at some point, which dissalows solder bonding.

Well, I hope I am not coming off as a solder-control-freak here. Just want to share my experience.

Cheers.

[dstamand]

@madox

Thanks for the hints !

Which flux and solder (easy to buy online in the US or Canada) do you recommend to use for regulars SMD cap/resitors/ICs on home made pcb ?

[Sasha]

Hey madox, that was really extensive introduction. Thank you for the answers. I used wick for my first and only SMD soldering (OPLs) and I did just what you said... I puled it and peal the the trace. I bridge the missing piece with thin wire without much problem but after I did it I PCB didn`t look so perfect.

I have one more question for you... I talked to a guy at the shop that was buying flux... He said it should be mixed with alcohol before applying to the PCB. Does it make any sense, as you didn`t mentioned it.

@dstamand, I watched the video and almost fell asleep. I`m not even a SMD beginner but as I see that deep frying I thought it is a work of some amateur that hardy can be an example.

[madox]

Hi dstamand and Sasha,

Thanks for the thanks! Glad its appreciated.

The flux I use is made by a company called Interflux. This is just the brand which my employer can readily purchase in Perth, Australia. Interflux was originally a Belgian company, though their flux manufacturing seems to be based in Asia now. I guess it would be available worldwide.

The product I use is Repair Flux IF 8300. Here is a link to the retail front of the supplier which my employer uses. It is not really cheap for hobby use, but it is very useful. Even at the fairly high price, it is still really worth using flux for SMD ICs. As seen, this flux comes as a syringe of fairly thick gel/paste, at room temperature. The flux thins very quickly with heat. The problem with this type of flux is that one generally ends up applying more than is really needed. Also, one must be careful not to allow the flux to continue flowing out from the syringe. I usually suck the flux back into the syringe, and also recap the tip if I am not going to use it for a while. It does work well though.

The flux which is used in the video that Thorsten posted, is a liquid flux. I think the liquid form allows greater ease in managing the small quantities which would usually be used. Unfortunately, I have only used the flux which my employer provides, so I can't offer a comparison of how they are to work with. The soldering in the video looks pretty good though, so I expect the liquid flux should work well.

For hobby use, I think liquid flux will probably give better value for money, as using the gel/paste type usually involves quite a bit more waste than what is demonstrated in the video.

I have not heard of diluting flux before, though it may be feasible. I use isopropyl alcohol for cleaning the flux from my PCBs once soldering is complete. If one has a nail-polish style brush dispenser, as used in the video, then I guess one could always have a try diluting some gel flux. When I use flux for work, the cost of materials, and the additional waste is not as significant a cost factor as the cost of my time, so I have not investigated alternative flux types at all. Sorry about that. I do want to try the liquid flux for home use, some time, though I don't have a strong motivation to do so while I am still in my current employment.

I have also heard of water soluble flux, though I have never used it. I know there is water soluble flux core solder (not sufficient flux for SMD though). This allows for neat soldering, and PCBs to be washed in distilled water rather than alcohol.

Another thing to note, is that Interflux claim that the IF 8300 I use, is "no clean". This is not true. The used flux probably could be left on the board, without harm (unlike acid flux), though it makes an unattractive scabrous looking mess. I use a large plastic fast food box as an alcohol bath, and a cut down cheap old paint brush to clean the finished PCBs. It should be noted that some components shouldn't be immersed in liquid, such as unsealed (or poorly sealed) pots, open wound transformers, etc. These devices may be able to handle an aerosole based cleaner, and good drying. Aerosoles cost more, of course, and also don't clean as thoroughly as the alcohol bath. My alcohol bath is less than an inch deep, and can be used for many PCBs.

Hope that helps.

[soulfulangus]

hi, i want 3 chips and 3 pcb, could u tell me how to pay and the totals ?

cheers

angus

[seppoman]

hi, i want 3 chips and 3 pcb, could u tell me how to pay and the totals ?

read the first posting in this thread, all information you need is there.

S

[TK.]

500 GM5 chips and 400 PCBs are ordered for this run, next run once we've reached n x 250 chips and m x 100 PCBs again

Best Regards, Thorsten.

[buhler]

500 GM5 chips and 400 PCBs are ordered for this run, next run once we've reached n x 250 chips and m x 100 PCBs again

Best Regards, Thorsten.

hey TK, can i still add 2 PCBs to my order or should i wait until next run?  sorry, i haven't kept up on this thread very well... my bad. :-[

[matyt]

.....a socket can't be used right? as i'm a little scared about frying the chip... ;D

[nILS]

Yep, no socket. Don't be scared, be careful, that'll help a lot more :-)

[madox]

Don't be scared, be careful, that'll help a lot more :-)

:) well put.

[TK.]

hey TK, can i still add 2 PCBs to my order or should i wait until next run?  sorry, i haven't kept up on this thread very well... my bad. :-[

Should be ok. At the --498-- GM5 chip mark we've currently less than 400 PCBs, so that everybody below this mark has to wait for the next order anyhow

Best Regards, Thorsten.

[TK.]

Everbody above the 498 chips mark got a PM, if I don't get a reply within 3 weeks (or no money once the final prices are known), people below this mark will be shifted up.

Best Regards, Thorsten.

[buhler]

Should be ok. At the --498-- GM5 chip mark we've currently less than 400 PCBs, so that everybody below this mark has to wait for the next order anyhow

Best Regards, Thorsten.

should i add those 2 PCB's to my order on the wiki or just add them when i respond to your email (i'm above the 498 mark)?  thanks for doing this TK!

[levon]

Wilba, Stryd_one.. and all other Australians.

How many of you are ordering some of these? it might be worth one of us receiving all the parts and mailing them out from with in Australia? i could do it from Adelaide.

Postage for a 250g satchel is $4 from Adelaide to Melbourne, or $7.40 for Express. the postage from TK in germany would be about $20 AUD including insurance and tracking

Anyone interested?

[StormB]

Hi

Thorsten

betreff [MBHP_USB_GM5] batch1 StormB

leider kommt die Mail immer wieder zurück obwohl ich mich genau an die anweisung von dir gehalten habe

Greetz

StormB