prototyping with leadless surface mount

[[email protected]]

I've done prototyping with surface mount components where the leads at
least reach the side of the package. I want to solder a part where the
leads are completely underneath the package. How do you do hand
assembly with such a package?

 

[D from BC]

I've done prototyping with surface mount components where the leads at
least reach the side of the package. I want to solder a part where the
leads are completely underneath the package. How do you do hand
assembly with such a package?

I say solder paste and hot plate...


D from BC
British Columbia
Canada.

 

[Eeyore]

I've done prototyping with surface mount components where the leads at
least reach the side of the package. I want to solder a part where the
leads are completely underneath the package. How do you do hand
assembly with such a package?

With difficulty !

I suppose you could use a conductive epoxy. Or presumably oven it.

Graham

 

[Ecnerwal]

I've done prototyping with surface mount components where the leads at
least reach the side of the package. I want to solder a part where the
leads are completely underneath the package. How do you do hand
assembly with such a package?

Solder up the pads, which you have designed to stick out from the
package far enough to put a soldering iron tip on. Place the item, and
reflow either one pin at a time or with hot air gun.

If the pads stick out a long way, you can set the item, drop the iron on
the outside of the pad, and feed solder between the pad and the device.
hold it down well so it does not shift while you do 2 pins at opposite
corners, then go back and do the rest of the pins. Don't use too much
solder.

If the pads don't stick out, you have to go to paste and reflow, I think.

 

[DJ Delorie]

I say solder paste and hot plate...

I've done this, it's pretty easy. Look at the last few photos here:

http://geda.seul.org/projects/djs_pcbs/

Part of the trick is to extend the pads out far enough so that you can
still use an iron to heat up the copper enough to fix any problems.
But getting it right the first time certainly helps.

You can use the hotplate to take the chip back off if needed, too.

 

[[email protected]]

Solder up the pads, which you have designed to stick out from the
package far enough to put a soldering iron tip on. Place the item, and
reflow either one pin at a time or with hot air gun.

If the pads stick out a long way, you can set the item, drop the iron on
the outside of the pad, and feed solder between the pad and the device.
hold it down well so it does not shift while you do 2 pins at opposite
corners, then go back and do the rest of the pins. Don't use too much
solder.

Pretty much what I did for a CASON-8 package.

If the pads don't stick out, you have to go to paste and reflow, I think.

I put blobs on the PCB, tin the leads of the package, put some flux on
the PCB, plop the part on the PCB.
Then I use a long narrow conical bent tip with a bit of solder on the
tip, and solder one pin at a time under a good microscope (Carton
something or other) with an illuminator.
I put the board at an angle and I can see a bit under the package. The
problem is that if the first pin is jacked up too high, the other pins
won't bridge.
Which is ridiculous, because usually the universe makes sure that all
that solder does at those scales is bridge.

 

[[email protected]]

I've done this, it's pretty easy. Look at the last few photos here:

http://geda.seul.org/projects/djs_pcbs/

Part of the trick is to extend the pads out far enough so that you can
still use an iron to heat up the copper enough to fix any problems.
But getting it right the first time certainly helps.

You can use the hotplate to take the chip back off if needed, too.

This looks interesting. I think I get some junk parts and give it a
shot. Of course, those Aroma hotplates are made in China. This could
be dangerous.

 

[D from BC]

This looks interesting. I think I get some junk parts and give it a
shot. Of course, those Aroma hotplates are made in China. This could
be dangerous.

For more danger

I posted this some time ago...
"Hot Plate Soldering...On a Kitchen Stove"
with picture links too..
http://groups.google.com.au/group/sci.electronics.design/msg/6c08e9c9d8c85d76

Works for me


D from BC
British Columbia
Canada.

 

[skenn_ie]

I did some uWave stuff with copper tape, or better still, foil*,
positioned then trimmed with a scalpel. For soldering, a dab of
solder paste is best, then heat the exposed part of the pad. I am
searching for a high temperature adhesive which is still peelable.
Normal contact adhesive turns to jelly with heat.

* Foil, as used for manufacture of PCB's, is thinner, and a harder
copper, so cuts cleanly.

 

[qrk]

I've done prototyping with surface mount components where the leads at
least reach the side of the package. I want to solder a part where the
leads are completely underneath the package. How do you do hand
assembly with such a package?

I use a waffle iron with flippable plates. One side of the plates is
for waffles, the other side of the plates are smooth for grilled
cheese sandwiches. I use the smooth sides. Stick the board in, shut
the lid, and in a minute or two your board should be ready. Put a dab
of solder paste on a unused pad so you can tell when the solder melts.
I've done those awful parts with thermal pads under the body using
this technique.

 

[[email protected]]

I use a waffle iron with flippable plates. One side of the plates is
for waffles, the other side of the plates are smooth for grilled
cheese sandwiches. I use the smooth sides. Stick the board in, shut
the lid, and in a minute or two your board should be ready. Put a dab
of solder paste on a unused pad so you can tell when the solder melts.
I've done those awful parts with thermal pads under the body using
this technique.

Do you think it's a good idea to have heat applied from the top?

 

[JeffM]

[...]I want to solder a part
where the leads are completely underneath the package.
How do you do hand assembly with such a package?

Are you purposely trying to avoid the ideal tool?

*Homebrew reflow ovens*
Robert Lacoste
http://www.circuitcellar.com/library/print/0704/Lacoste_168

Kenneth Maxon
http://www.seattlerobotics.org/encoder/200006/oven_art.htm

Wagner Lipnharski
http://www.ustr.net/smt/index.htm

Some time ago Lewin Edwards was planning a controller for these
which one assumes would have a more narrow hysteresis:
http://groups.google.com/group/comp...WM-controller+reflow-oven+used-a-thermocouple

 

[Jamie]

I've done prototyping with surface mount components where the leads at
least reach the side of the package. I want to solder a part where the
leads are completely underneath the package. How do you do hand
assembly with such a package?

Hot air method.
position component on pre tinted surface, hold it down while applying
hot air at the edges via the a hot air iron.
(wave solder).


http://webpages.charter.net/jamie_5"

 

[Michael A. Terrell]

Hot air method.
position component on pre tinted surface, hold it down while applying
hot air at the edges via the a hot air iron.
(wave solder).

http://webpages.charter.net/jamie_5"

'Pre tinted surface'? Do you have a favorite color, or have you been
pushed down the steps too often to remember?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Rich Webb]

'Pre tinted surface'? Do you have a favorite color, or have you been
pushed down the steps too often to remember?

Yea, one of my favorite rants.

Gizmo comes with battery "pre-installed" means it comes with a battery
installed. Framitz comes "pre-assembled" means it is assembled.

 

[JeffM]

Yea, one of my favorite rants.
Gizmo comes with battery "pre-installed" means it comes with a battery
installed. Framitz comes "pre-assembled" means it is assembled.

....then there's the "tinted" vs "tinned" thing
(which, I believe, was Mike's point.)

 

[qrk]

Do you think it's a good idea to have heat applied from the top?

You want to heat the board evenly as much as possible. The grill
doesn't contact the top of the board or any of the components. This
waffle iron technique has the advantage of creating a hot air cavity
which heats up the components and gets the job done fast. I've used
this method on a few of Linear Technology's DFN and QFN packages with
the thermal tab under the part and 0.5mm pin pitch.

 

[Rich Grise]

.

I use a waffle iron with flippable plates. One side of the plates is for
waffles, the other side of the plates are smooth for grilled cheese
sandwiches. I use the smooth sides. Stick the board in, shut the lid,
and in a minute or two your board should be ready.

....

Then do you serve them with ketchup, or butter and syrup? ;-)

Cheers!
Rich