SMD soldering

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Mike6158
Posts: 409
Joined: Fri Nov 12, 2004 1:01 am
Location: Weimar, Texas
Contact:

SMD soldering

Post by Mike6158 » Sun Nov 23, 2008 12:48 pm

I'm thinking about dusting off some boards that I had made a few years ago and putting them together to see if they'll smoke :shock: or work :grin: A big reason for why I didn't build them that I used SMD components in a few places. Not many... but enough to be really irritating to try to solder to the board. Have there been any advances in this department in the last few years? My little Weller is great for TH mount stuff but it doesn't like SMD resistors and caps.
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

User avatar
haklesup
Posts: 2978
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Post by haklesup » Sun Nov 23, 2008 2:27 pm

Well, there does seem to be more choices in lower cost SMT tools from China if you check eBay.

Other than that, it has not gotten easier to use a single pointed soldering iron and roll of solder to asemble or especially rework boards.

SMT is as much a commitment as it is a technology. If you go all in with stencils, pick and place and reflow assembly, its a dream.

Assembly is not too bad but you can't load up the board with as many components before grabbing the iron again so it goes slowly. A solder paste dispensed by a needle tip can act as a temporary adhesive allowing you to load a bucnh of components then reflow or hand solder more efficiently.

Engineer1138
Posts: 458
Joined: Thu Feb 05, 2004 1:01 am
Location: Minneapolis, MN
Contact:

Post by Engineer1138 » Sun Nov 23, 2008 3:23 pm

Do you have any recommendations for manual P&P machines?

I thought of building my own, but I can probably find one cheap on the used market.

haklesup wrote:Well, there does seem to be more choices in lower cost SMT tools from China if you check eBay.

Other than that, it has not gotten easier to use a single pointed soldering iron and roll of solder to asemble or especially rework boards.

SMT is as much a commitment as it is a technology. If you go all in with stencils, pick and place and reflow assembly, its a dream.

Assembly is not too bad but you can't load up the board with as many components before grabbing the iron again so it goes slowly. A solder paste dispensed by a needle tip can act as a temporary adhesive allowing you to load a bucnh of components then reflow or hand solder more efficiently.

User avatar
philba
Posts: 2050
Joined: Tue Nov 30, 2004 1:01 am
Location: Seattle
Contact:

Post by philba » Sun Nov 23, 2008 7:31 pm

Soldering SMT components isn't very hard at all. I use a decent heat controlled soldering iron (Hakko 936). If your weller has heat control you should be fine. Even if it doesn't, you can get by.

The trick is to tin one of the pads with a small dab of solder. Then using tweezers (or foreceps), hold the component in place and touch your iron the tinned pad. It should flow and attach the component. Then solder the other side. For 805s and 1206s it's about as easy as can be. 603s are possible though you might want some magnification. You will find it faster to solder SMDs than TH. You can also do SMD ICs the same way. Tin a corner pad, hold the IC in place and though the iron to the pad. Then solder the remaining leads. I'm totally serious, it's easier than TH. Use wick to soak up excess solder.

Mike6158
Posts: 409
Joined: Fri Nov 12, 2004 1:01 am
Location: Weimar, Texas
Contact:

Post by Mike6158 » Sun Nov 23, 2008 7:50 pm

Well... I guess I'll dive in and see what happens :grin: Thanks for the info. I've got a Weller WES51. Can you suggest a heat range to operate at?
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

Bigglez
Posts: 1282
Joined: Mon Oct 15, 2007 7:39 pm
Contact:

Re: SMD soldering

Post by Bigglez » Mon Nov 24, 2008 12:15 am

Mike6158 wrote:I'm thinking about dusting off some boards that I had made a few years ago and putting them together to see if they'll smoke or work A big reason for why I didn't build them that I used SMD components in a few places.
I'm curious if these are a kit, or your own design,
and if the latter whether you had the boards fabbed
or you etched them yourself?

Mike6158
Posts: 409
Joined: Fri Nov 12, 2004 1:01 am
Location: Weimar, Texas
Contact:

Re: SMD soldering

Post by Mike6158 » Mon Nov 24, 2008 4:12 am

Bigglez wrote:
Mike6158 wrote:I'm thinking about dusting off some boards that I had made a few years ago and putting them together to see if they'll smoke or work A big reason for why I didn't build them that I used SMD components in a few places.
I'm curious if these are a kit, or your own design,
and if the latter whether you had the boards fabbed
or you etched them yourself?
Not a kit. My concept. The design was done by me with a little help from National Semiconductor's Webench (online) application. I knew what I wanted to do, just not how I wanted to do it and Webench was a blessing. I used CadSoft Eagle to do the board layout. I had the boards etched. I etched the boards for the original design myself but it was a different design (TH as well as different components and different function). I also etched a board for a little crawler robot that I built. The board worked, the robot had "skeletal issues" :smile:

BTW- It's not a very complicated project but since it involves a flyback regulator there's a better than even chance that I have designed a one-shot smoke generator :grin: My strong suit is PLC programming not electronic circuit design :smile:
"If the nucleus of a sodium atom were the size of a golf ball, the outermost electrons would lie 2 miles away. Atoms, like galaxies, are cathedrals of cavernous space. Matter is energy."

Bigglez
Posts: 1282
Joined: Mon Oct 15, 2007 7:39 pm
Contact:

Re: SMD soldering

Post by Bigglez » Mon Nov 24, 2008 8:00 am

Mike6158 wrote:I used CadSoft Eagle to do the board layout.
I use EAGLE. Would you be willing to share your
SCH and BRD files? I'd like to see your circuit.

User avatar
haklesup
Posts: 2978
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Post by haklesup » Mon Nov 24, 2008 9:57 am

Do you have any recommendations for manual P&P machines?
Yes, your hands holding a tweezer.

AFAIK, P&P is an automated process and rarely inexpensive, generally requiring programming and not very useful for small lots.


I just bought a bunch of stuff on eBay for BGA reballing including a small benchtop reflow oven. I'll let y'all know how it goes after I get the stuff. The oven has preprogrammed temp profiles for different types of solder. Practically the only one you see when you search "BGA reflow", "SMT rework" gets a bunch more tools.

Engineer1138
Posts: 458
Joined: Thu Feb 05, 2004 1:01 am
Location: Minneapolis, MN
Contact:

Post by Engineer1138 » Mon Nov 24, 2008 4:45 pm

Nice :-)

The manual P&P "machines" I've seen are really glorified handrests that reduce hand shake...depending on how much coffee I've had, that can be quite a bit. Ideally I'd like to talk to someone who's used one to find out just how much better/faster they are than doing it with just tweezers.

Must be nice to have a real oven. I use the "skillet method" which actually works really well.
haklesup wrote:
Do you have any recommendations for manual P&P machines?
Yes, your hands holding a tweezer.

AFAIK, P&P is an automated process and rarely inexpensive, generally requiring programming and not very useful for small lots.


I just bought a bunch of stuff on eBay for BGA reballing including a small benchtop reflow oven. I'll let y'all know how it goes after I get the stuff. The oven has preprogrammed temp profiles for different types of solder. Practically the only one you see when you search "BGA reflow", "SMT rework" gets a bunch more tools.

User avatar
Dave Dixon
Posts: 436
Joined: Thu May 01, 2003 1:01 am
Location: Wichita, KS
Contact:

Post by Dave Dixon » Tue Nov 25, 2008 5:59 am

I totally agree with Philba's approach, but one more thing. I usually try to resolder the leg that I tacked down in the first place. The component can, and often will shift while soldering all the other pins down. Rehitting the first joint will hopefully remove any stress that it was under. Just one of those little details!

User avatar
Janitor Tzap
Posts: 1460
Joined: Sat Aug 12, 2006 5:17 pm
Contact:

Post by Janitor Tzap » Tue Nov 25, 2008 8:38 am

Hi guy's

Well since your all looking at ways to hold, and solder down SMD's.
I thought you should consider this SMD Holder,
that I came a cross in an old issue of Nut&Volts.
Image
This is my own design, and feel free to make any changes.
The only problem with this design is it doesn't take into account double sided SMD Boards.


Signed: Janitor Tzap

User avatar
haklesup
Posts: 2978
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Post by haklesup » Tue Nov 25, 2008 9:10 am

I totally agree with Philba's approach, but one more thing. I usually try to resolder the leg that I tacked down in the first place. The component can, and often will shift while soldering all the other pins down. Rehitting the first joint will hopefully remove any stress that it was under. Just one of those little details!
Good practice with lead/tin solder, bad practice with lead free solder.

The higher temp for lead free and the alloy used causes intermetallic alloys to form between the pin and solder which can eventually lead to electromigration/cold solder failures down the road.


I watched a video (on the IPC website I think) about lead free assembly and it stated that touching up ugly but otherwise functional solder joints was to be strictly avoided in a production environment. It did a better job explaining the failure mechanism than I just did.

It also noted that mixing lead tin solder and lead free parts may lead to problems as well. (or was it lead free solder with leaded pins on devices)

For a 1 off assembly, it may not matter at all.

User avatar
Dave Dixon
Posts: 436
Joined: Thu May 01, 2003 1:01 am
Location: Wichita, KS
Contact:

Post by Dave Dixon » Tue Nov 25, 2008 9:44 am

Great reply Hacklesup! I wasn't even thinking about that damn lead-free soldering! That is the best reference you could give to someone who wants further information on all types of soldering. IPC is THE standard, and has tons of great information as well as forums.

User avatar
haklesup
Posts: 2978
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Post by haklesup » Tue Nov 25, 2008 10:23 am

Many smaller manufacturers in the US are ignoring lead free assembly. For consumer goods, you pretty much need to go lead free but for capital equipment, the Europeans can either suck it up or go without our products AFAIAC

Post Reply

Who is online

Users browsing this forum: No registered users and 8 guests