Interested in getting comfortable with SMT?

[chromesphere]

Im starting to see Tayda as a limited option for SMD.  No electro smd caps.  No smd chips (i dont think).  No smd diodes.  Half the average board will still be throughhole.  Which would probably still save some room.  But it would be nice to do majority smd, or have that option.  Dont tell me i have to go back to futurlec

Anyway Tayda staff might want to start reading this thread

Hadnt been to futurlec for a while, just had a look.  They have electro SMD's, but no resistors or caps.  I would think you could cover 90% of smd orders between tayda and futurlec, im sure i used to see smd chips at futurlec (accidentally ordering a couple on occasion lol).

Paul

[pickdropper]

Paul,

Check out Mouser as well.  It's more expensive than Tayda, but not always too bad.  I usually buy resistors 100 at a time, so they are 1.4 cents each.  A bunch of the caps I just bought were 2.4 cents each when I bought at least 50 pcs.  Caps are all over the place, though.

[J0K3RX]

I am pretty much comfortable with the idea of hybrid SMT and through-hole at this point... Like AMT for example is SMT but all caps above pF are through-hole... The less drilling and lead clipping the better! I prefer SMT over through-hole any day, hands down! It's a win win in my opinion...

[chromesphere]

Paul,

Check out Mouser as well.  It's more expensive than Tayda, but not always too bad.  I usually buy resistors 100 at a time, so they are 1.4 cents each.  A bunch of the caps I just bought were 2.4 cents each when I bought at least 50 pcs.  Caps are all over the place, though.

Thanks Pickdropper.  Unfortunately Mouser hates international orders (postage wise).  Also, i hate their online store  I reckon i could get the bulk of it through tayda and futurlec though...Postage is pretty cheap from both stores.

EDIT: forgot to mention in my early post, looking at the size of the pads of 0805, i reckon i could etch this with toner transfer.  Bridges are probably the biggest issue but im pretty keen to give it a try now!!  Might have to make up a simple boost in diptrace and give it a try.


Paul

[J0K3RX]

Paul,

Check out Mouser as well.  It's more expensive than Tayda, but not always too bad.  I usually buy resistors 100 at a time, so they are 1.4 cents each.  A bunch of the caps I just bought were 2.4 cents each when I bought at least 50 pcs.  Caps are all over the place, though.

Thanks Pickdropper.  Unfortunately Mouser hates international orders (postage wise).  Also, i hate their online store  I reckon i could get the bulk of it through tayda and futurlec though...Postage is pretty cheap from both stores.

EDIT: forgot to mention in my early post, looking at the size of the pads of 0805, i reckon i could etch this with toner transfer.  Bridges are probably the biggest issue but im pretty keen to give it a try now!!  Might have to make up a simple boost in diptrace and give it a try.


Paul

Try Newark/Farnell?
http://www.newark.com/

Jameco..
http://www.jameco.com/

[pickdropper]

I am pretty much comfortable with the idea of hybrid SMT and through-hole at this point... Like AMT for example is SMT but all caps above pF are through-hole... The less drilling and lead clipping the better! I prefer SMT over through-hole any day, hands down! It's a win win in my opinion...

Yep, sometimes hybrid is your only choice.  On the screwdriver board I did, it had to be hybrid.  Not too many surface mount Germaniums out there.  :-)

[chromesphere]

Heres my....attempt....at an SMD layout i just slapped together.  A booster (yay).  Very simple.  You could get the smds (0805) from tayda, resistors and caps.  Thought it might be good practice.  The booster is not my design but you can use my layout however you want.

UNVERIFIED
http://www.chromesphere.com/x/pedal/Pub_PCB_Layouts/SMD_Boost.pdf

Cheers,
Paul

[Jdansti]

Digikey has just about everything available in SMD, but I don't know how their pricing or shipping compares to others.

[Jdansti]

Do you think that deflector could be used to tin a PCB?  I'm wondering if you cold heat it up, melt some solder on the rounded outside part and then drag it across the traces to tin them.  Maybe with some flux on the board first.  I almost want to buy one just to try.

I agree with R.G. I think the deflector/concentrator is used to concentrate heat ~360 deg around a small piece of tubing or other smallish object. You place the thing you want to heat inside the curled part. I think I've used it on the lowest setting to heat up heat-shrink tubing.

[Ronan]

I own one of those Portasol irons, same as in the pic, I use it 99% for heatshrink, and soldering in an emergency, when mains power is simply not available. It will do hot air, but in a very small localised area.

One of the points I was trying to make earlier is that you don't need to "gear up" to do SOIC IC's (pins are spaced at half the interval of a DIP IC) or 0805 components. You can use your standard "pedal" soldering iron. Also, hybrid is fine, this thread is about "getting comfortable" with SMT, not becoming a slave to it. I prefer to use the MKT box caps or green poly caps anyway, and SMT for small ceramics, and standard through-hole for electro's, at this stage.

[chromesphere]

I ordered a few 'ceramic' smd caps from tayda thinking that they were the norm for smd, but i realised that you can get film smd's as well (elsewhere).  Does it matter sound wise?  I know most caps make no difference, but im sure for through holes they are one of the capacitors most people suggest only using when specified.
Paul

[Ice-9]

Yes indeed, my post above yours also points to one of those but for the Irodo iron which is better, I have used both and there best used hot, but quick. If your temp is too low they you just sit there slow boiling the IC and not melting the solder. If it's hot it melts solder in a matter of seconds without getting the chip exposed to heat for a long time., but it takes practice and everyone will have a prefered way.

I would disagree here, hot and fast can cause thermal stress damage to the IC, normal temp curves for smt soldering show a 1 - 3 minute preheat time then a shorter time at a higher temp to melt the solder. I typically hold the heat gun further away from the chip for a minute or two to evenly heat the entire area then bring it in a bit closer to melt the solder. It is not the heat that damages the chips, it is the sudden change or unequal distribution of heat that does.

I see what you are saying Frank and thanks for the info, but in the last 15 years of using the solderpro butane hot air iron on its hottest setting removing , reprogramming and replacing countless 48 pin TSOPS using this method I have not had a single failure. Then again it could be that the solderpro 120's hottest setting might not be that hot.

I have also removed / soldered 2 FV-1 chips over a dozen times to different PCB's this way and they still perform without any problems.

To give a bit more detail, when removing an IC it usually would take about 30 seconds to get the temp upto the point that the solder will begin to flow and I also heat at a little more distance and then move in to melt the solder. Hope that makes it sounds more clear in how I remove IC's. I will give the lower temp 3minute way a try next time I'n doing some smt components to see if it works better.

[Ronan]

I ordered a few 'ceramic' smd caps from tayda thinking that they were the norm for smd, but i realised that you can get film smd's as well (elsewhere).  Does it matter sound wise?  I know most caps make no difference, but im sure for through holes they are one of the capacitors most people suggest only using when specified.
Paul

I don't think it matters much between surface mount or through-hole caps. I built a circuit with all through hole components and compared to the commercial total surface mount circuit which was basically the same circuit, I could hear little difference. With filters, there can be a noticeable difference between ceramic and film caps, with people having a preference for one or the other, often it just depends on the particular circuit and the tastes of the listener/builder.

[R.G.]

As a bit of technique, I've had really good results from the following.

- If you etch your own boards, tin the SMD pads before trying to solder. Even better, tin, then use desoldering braid to leave a very thin and level surface film of solder. Lumps of solder will make SMD difficult.
- In an ideal world apply solder mask around the pad to help prevent shorts. A thin layer of nail polish will do in a pinch. Not mandatory, but helpful.
- Flux the pads for the SMD part. Liquid flux is handy because it leaves only a very thin layer, and the rosin film it leaves is sticky.
- Stick the part in place somehow. Sticky rosin works. I suspect solder paste preapplied to the pad would work, although I have not tried this. Anything to keep the part from moving as you solder is good.
- When all is ready, I clean the iron's tip and apply heat to the pad away from the lead. When the pad is at soldering temp, it reflows the solder on the pad and generally sticks the part to the pad. For me, this is the critical step - getting the first solder joint done so the part no longer moves when touched.
- Now solder the other leads. Heating the pad, not the lead is simplest for me. When the pad is molten, the lead solders. If the pad is not quite touching the lead, you can feed a tiny bit of solder onto the pad and this will build up and touch the pad.
- Use the smallest gauge solder you can get, so as to not leave huge blobs of solder on the pads.

Well, then there's that B&L stereo zoom microscope. Otherwise I have no chance of seeing what I'm doing. You young kids may be able to do this without optical assistance, or with just a visor, but I can't. 

[ElectricDruid]

Hi Taylor,

Yeah, I'm interested if you get a kit of parts together to get me into SMD. I keep meaning to take the leap, but never do, so I could use a helping hand/kick up the backside. Once I'd done a few, I'm sure I'd be easy about it, but there's always something else going on that means I don't need the hassle *right now*. So yeah, go for it.

Thanks,
Tom

[pickdropper]

A lot of good advice in RG's post above.  Personally, I feel that flux is the key to getting good joints with SMT.  The Kester 186 pens are great.

As far as the B&L stereo zoom microscopes, those are great but expensive.  If you aren't allergic to Chinese made scopes, I purchased one from Amscope that is very high quality.  I've been using it for about 5 years now and have been very pleased with it.

[chromesphere]

Edit: thanks Ronan for the response!

My confidence shrunk when i realised I had the wrong dimensions for 0805 components.  Correct size being 1mm x 2mm



I'm going back to being scared again.

Paul

[Perrow]

Anyone who can spare about $2.52 and the smallest of boards can take a whack at this LPB-1 layout.



All component are $0.01 each except the transistor which is $0.02 or $0.03 depending on choice (from Tayda that is). Resistors and caps have to be bought in packs of 50, but transistors can be bought in single quantities (so building 25 of these would still be just $3.00 and you'd have half of the resistors left over  ). The transistor should drop nicely onto the "triangle" pads in the middle.

The board is square with about 1.5 cm sides, that's 0.6 inch sides. The image should be 300 dpi. This should be etchable with both toner transfer and photo resist.

Component numbers corresponds to Beavis schematic for the LPB-1.

N.B. This project is unverified, you might loose your $2.52, at least the $0.08 in components that's going onto this board.

Edit: Can't count.

[chromesphere]

I wasnt sure if i should mention it, but yeah, my layout is the LPB1 and you can also check the schem on Beavis's site.  The pdf is at the right size to print.
I just printed the layout off myself, i'm really starting to see HOW SMALL these components are!
Paul

[Ronan]

Nice one Pelle, that would be a great start into SMT, thanks for sharing.