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Questions relating to designing PCBs
By iceblu3710
#47621
Im just migrating into the surfacemount world and would like to buy a kit. Ive seen them before such as smtzone 125compartment cases that have a whackload of resistors/caps in 10-200quantites.

My questions are:
What size should I play with 0603 I can bearly see... 1206 seems a good size, small enough for tiny designs yet large enough to notice if swallowed.

I have a weller WES51 iron, whats a good tip?

Are their any other companies such as smtzone who sell the smt kits in handy containers like them?

Thanks!
User avatar
By bigglez
#47622
Greetings Trevor,
iceblu3710 wrote:Im just migrating into the surfacemount world and would like to buy a kit. Ive seen them before such as smtzone 125compartment cases that have a whackload of resistors/caps in 10-200quantites.
A kit is a good way to kick off your conversion
to SMT. I'm certainly not against kits, but I took a different
path. Most of my recent designs have used and reused
the saem part numbers. So I purchased small lots of
these in their SMT version. For passives I chose 1206,
for ICs I chose SOIC, and for diodes and transistors
I chose SOT-23 or SOD-23. These are all small compared
to their TH cousins, so I also got a 10x eye loupe magnifier
and anti-static tweesers. Everything went smoothly,
and over time I've added other 'stock' parts to my list
and inventory.

Next, I bought a Metcal rework station (used, on
eBay) and the seller bundled some nice tips, including
special ones for fine pitch parts I haven't used yet.
Your iron is probably okay, but as I don't know it I
can say one way or the other.

After building a few circuits with solder and iron I
realised that other options were opening up. I
bought a syringe of paste solder and some needles
(22 and 16 AWG), and use a hot air gun (previously
used for heatshink), to mass solder an entire board.
Most designs go straight from EAGLE to BatchPCB.

Soon it came time to rework experimental designs
and the best tool for removing small SMT parts was
the soldering iron bits sized for 1206 and SOIC
packages.

I still used my TH parts and traditional soldering
techniques on protoboard (with 100mil pitch holes).
One day I'll be closer to "all SMT" and won't have
to carry two sets of parts.

The only SMT kit I bought was for low value caps
(1 to 47pF). More for RF tuning than preparing for
an SMT switchover.

Comments Welcome!
By NleahciM
#47630
Here's a nice list of tips for your iron:

http://www.action-electronics.com/pdf/weet.pdf

It's best to have a couple chisel tips - a really fine one and a larger one. I'd probably get the ETH (for very fine pitched stuff), ETB (for larger stuff) and the ETD (for the very large stuff).

You will find that you get substantially better heat flow with a larger tip - so you'll want to use a larger tip when possible. But much of the time that simply isn't possible, so you want to have smaller tips available as well.
By Philba
#47641
I use 1206s but I know a lot of hobbyists also use 805s with good effect.

I'd get a magnifier of some sort. Head mount visors are fairly inexpensive. I've got one of those swing arm, lighted magnifiers.

Before you buy a kit, check out prices from places like mouser.com. I've bought kits before but found that I usually need only about 1/5 of the values in it so it's not quite the same value. I just buy extra for the projects I'm building. Since I almost always have to order something for a project, it doesn't slow me down.

As long as we are talking alternate ways to solder, you should check out the frying pan method that spark fun has been using. Defintiely easy.
By silic0re
#47642
I find that 0805's are a pretty useful size -- they're not too tiny, as long as you can see okay, and it seems like with anything bigger it's almost the same size/volume as a through-hole component anyway. :)

It would be neat to try smaller, but some of those 06 and 04s seem like they'd be difficult to hand-solder to me (but probably perfect if you need something tiny and are reflowing).
By khearn
#47651
I also agree with using 0805 parts. I recently built a few boards, some of which I had designed with 1206 and some with 0805, and I found the 0805s about as easy as the 1206s. In one instance, I got sent an 0201 part instead of the 1206 part I had ordered, and even managed to get it in place bridging across the 1206 sized solder pads. This was using a fine conical tipped iron. A decent, temperature controlled iron is essential.

Magnification is very helpful, and doesn't have to me expensive. I'm using a magnifying visorI got from Harbor Freight for $5.99. The lights on it are garbage, but the magnification works great. I find a visor is much more flexible than a lens on an arm, you can position things however you want without having to worry about being in front of the lens. It's also handy for removing splinters. :)

I started out buying just the parts I need for each project, but a couple of times as I was starting to do assembly I discovered I had missed ordering a resistor or capacitor. So I bought a 0805 resistor assortment from Jameco. I don't know if it's the best bargain on the web, but I live 10 minutes from Jameco, and I needed that missing resistor, and I could drive down and pick it up at their will-call desk. I also got a capacitor kit from them for similar reasons, but I can't find it on their web page.

To be honest, I'm not sure if getting a kit is a great idea or not. I highly recommend having a stock of through-hole parts that can be used on solderless breadboards. When you're prototyping is when you need to have a good variety of parts on hand. By the time you get down to soldering SMD parts, you should know exactly what parts you need, and can order exactly what you need. As long as you can remember to order everything you need, you should seldom need an assortment of SMD parts on hand.

On the other hand, I feel a little guilty when I order parts for a project and order single items of SMD passives. I spend a couple of cents for one part, and they have to cut it from the tape, put it in a ziploc bag, which goes into a padded envelope, with two labels printed up. It's got to cost them more for the packaging than I'm spending for the part. I guess if they were really losing money, they'd have a minimum quantity. But it still seems like a terrible waste. Having an assortment of parts on hand means I will seldom have to order single parts.

I do recommend ordering a couple of spares when you order parts for a project, though. Those little buggers have a tendency to disappear if you drop them.

So there's my vague lack of a recommendation. :)

Keith
By Philba
#47652
silic0re wrote:It would be neat to try smaller, but some of those 06 and 04s seem like they'd be difficult to hand-solder to me (but probably perfect if you need something tiny and are reflowing).
For anything that is non-polarized, it's not too bad. I grab one end with forceps and slide the other end into a molten solder blob on the pad. Takes a bit of a careful touch. However, I've got some phototransistors that are in an 06 (ish) package and I have to use my stereo microscope to figure out which is the emitter - very tedious.

I also agree with the sense that 1206s are BIG. They actually make layout a little clumsy. If I was stocking my bench today, I'd go with 805s. But since I started with 1206s, I'm kind of stuck with a stock of them. One advantage of 1206s is that you can run a pretty fat trace between the pads.
By iceblu3710
#47662
Thanks for all the input guys!

Heres a few responses to random statementd:
Ive done the skillet reflow before and it works better than I had imagined, I then robbed some parts of old isa/pci computer cards and with a syringe of solder paste I made a new board. It doesn't do anything, just seeing how well it works. I have a small hot air reflow station thats too small for anything over soic but works grand for some things, might find an electric skillit at a garage sale to help things out.

I quite like my WES51 iron, ive done a few smt parts without any issues though I will be needing new tips.

After thinking about it I agree ill only use 1.5 of the passives in kits and and I found a website that sells baggies of 10pc 603/805/1206 resistors and caps +-5% for $1.99, Im thinking of just buying the $25 128bin compartments or checking out the multipill drug boxes for storage and filling them myself. Kit cost $110 so I rater get 42values I actually need than 125 and still not have my precise values.

Im also going to go with 805 components, 604's a bit to small looks more like ground pepper than passives to me lol

I still proto everything on my breadbord, I bought a 80drawer storage unit and 2pacs of low/med/hi resistors/electrolitic/ceramic caps. Local store was selling the pacs of 100pcs for $10 so spent $100 and haven't bought through hole parts for quite a while.

Thanks for the links everybody!
By busonerd
#47663
I just wanted to second Philba about soldering small stuff using tweezers + pushing it into a molten solder blob.

I actually stock 0402's as my primary component size, and I do most of my projects with them [except when power dissipation forces me to use a larger size]. Once you have some practice, picking up an 0402, sliding it into the blob + soldering down the loose end becomes pretty fast.

RE: starter kits; I just buy from digikey the values I need. When I get 0402s, I usually buy at minimum 50, and sometimes up to 1000, that way I have stock for my next projects. [I only buy 1000's of 0.1uf, 1k, 10k, 100k, the really common values]. Its a bit more expensive, but having random component values kicking around can be a lifesaver when on a deadline.

The only recommendations I have are to use a flux pen on the board before you solder; makes the solder flow a lot nicer. Secondly, go back to the first solder joint + reheat/melt it after soldering down the second side. Its easy to get opens / cold solder joints on that first joint.

Cheers,

--David Carne
By iceblu3710
#47676
Nevermind, I suck at searching digi-key found $0.077 and $0.032 prices, much cheeper to piece my own set together, just ordered 20 of every type of res/cap ive used in every project $90 in total, all 0805 SMT
By winston
#47700
I've decided to standardise on 0603 size parts for passives where possible - nearly everything is available in 0603, they are large enough to hand solder but small enough such that you can get decoupling capacitors very close to something like an LQFP. I can hand solder 0603 parts as fast (or quicker) than through hole now, since you don't need to turn the board over and cut the tails of the leads off - just melt a small blob of solder on one pad, place the component and hold it with tweezers and remelt the blob, then quickly solder the other terminal.
By iceblu3710
#47706
winston wrote:they are large enough to hand solder but small enough such that you can get decoupling capacitors very close to something like an LQFP.
I imagine you could fit a decoupling cap in 0604 between pins of an soic. My problem is the electronics stores here don't carry ant smt so im working off a piece of paper and my micromiter to visualize the sizes...

do you have some pictures of a board with an easily recognizable part and some 0604/0805 smt's? Like a 44pin pic LQFP?

EDIT:

I believe top left - 1206, Top right 0603, one down from top right 0805. If thats true i dont think ill have much trouble with 0603 components their not much smaller than 0805 anyways. I agree that the 1210 packages are esentaly the same footprint as a TH electrolitic cap...

Image
By winston
#47770
A picture here of a board I did a few days ago:

http://spectrum.alioth.net/doc/images/2 ... eproto.jpg

Yes, I know the soldering's rather untidy, I'm experimenting with solder paste, and don't quite know how much to use! But you can see 0603 components all over the place. The Xilinx CPLD is a 0.5mm pitch TQFP, and the Wiznet chip is a 0.4mm pitch LQFP.
By iceblu3710
#47773
Wow, good looking work Winston! I almost didn't believe it!

I was diggin through the classified section of my newspaper and found an add for an elec wholesaler called ElectroSonic and my goodness their SMT passives are DIRT cheep. I just got a list 58 unique items, minimum 100pcs, commons 300pcs, 1k,10k,470,330 600pcs and im not even at $30. Their a lower mainland british columbia company if I like the parts and service ill report back about them.

Now to order 60uniqe values of caps..
By busonerd
#47786
Let me know how electrosonic goes, never used em, but always meant to. [I'm in Burnaby, BC, so they're close to me].

Digikey to here is great though, $8 overnight shipping. [I assume you're in the lower mainland if there are ads for electrosonic.]

Cheers,

--David Carne
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