high density SMT relow

[Jon Slaughter]

Anyone done any non-hand soldering high density SMT's? 403's, high pin
count(maybe even BGA's), tight pitch stuff, etc.

I need to do some stuff manually for testing before mass producing the
boards and I do not really want to solder it all by hand simply because it
is very boring and error prone not to mention I get my yearly dose of lead
at each sitting.

I've done 603's without any real problem(the biggest simply being not having
a solder mask) and it's actually quite easy. I imagine with a proper tip for
the iron I wouldn't have any problems with 403's. I do have some QFN's I'm a
little worried about though but I guess some solder paste should take care
of that.

But I also imagine that using relow/wave or some other method would be much
easier. Simply tack the pieces down somehow and pass solder over them(these
boards will have a solder mask so...). I've heard of people using toaster
ovens to do such things so I imagine it can't be that difficult.

1. Tack components down.
2. Bake in oven

? (not saying it's that simple but thats the basic idea) ?

 

[petrus bitbyter]

Anyone done any non-hand soldering high density SMT's? 403's, high pin
count(maybe even BGA's), tight pitch stuff, etc.

I need to do some stuff manually for testing before mass producing the
boards and I do not really want to solder it all by hand simply because it
is very boring and error prone not to mention I get my yearly dose of lead
at each sitting.

I've done 603's without any real problem(the biggest simply being not
having a solder mask) and it's actually quite easy. I imagine with a
proper tip for the iron I wouldn't have any problems with 403's. I do have
some QFN's I'm a little worried about though but I guess some solder paste
should take care of that.

But I also imagine that using relow/wave or some other method would be
much easier. Simply tack the pieces down somehow and pass solder over
them(these boards will have a solder mask so...). I've heard of people
using toaster ovens to do such things so I imagine it can't be that
difficult.

1. Tack components down.
2. Bake in oven

? (not saying it's that simple but thats the basic idea) ?

It's the basic idea, yes. There are some other things to be taken into
account:
- The correct amount of solder.
- On the correct places.
- The correct temperature traject both up- and down.
Still only the most important.

Carcia Circuit Cellar published a design using some kind of toaster oven.
Elektor did the same but somewhat later in time. Now Elektor sells reflow
ovens, priced some 1200 Euros. (FAIK ex. VAT and shipment)

petrus bitbyter

 

[DJ Delorie]

I've done home reflow with paste and a $20 hotplate. I do 0.5mm pitch
quite regularly, 0.5mm QFNs occasionally, and 0603 is HUGE I've
done CSPs but my home-brew boards are too flexible for them to stay
attached.

I recently added an alumimum plate to the hotplate, so if you go
searching, choose an alumimum hotplate instead of cast iron. My
process is basically "apply paste, place parts, heat until reflow".

 

[qrk]

Anyone done any non-hand soldering high density SMT's? 403's, high pin
count(maybe even BGA's), tight pitch stuff, etc.

I need to do some stuff manually for testing before mass producing the
boards and I do not really want to solder it all by hand simply because it
is very boring and error prone not to mention I get my yearly dose of lead
at each sitting.

I've done 603's without any real problem(the biggest simply being not having
a solder mask) and it's actually quite easy. I imagine with a proper tip for
the iron I wouldn't have any problems with 403's. I do have some QFN's I'm a
little worried about though but I guess some solder paste should take care
of that.

But I also imagine that using relow/wave or some other method would be much
easier. Simply tack the pieces down somehow and pass solder over them(these
boards will have a solder mask so...). I've heard of people using toaster
ovens to do such things so I imagine it can't be that difficult.

1. Tack components down.
2. Bake in oven

? (not saying it's that simple but thats the basic idea) ?

0403 parts are fairly easy to solder by hand if you work under a
microscope. Using flux will make life much easier. Any leaded IC is
easy to solder by hand down to 0.5mm pitch. Non leaded ones are
harder, but can be done by hand if the part leads come out to the edge
of the part. If parts need to be soldered to a plane, preheat the
board to 150 deg C.

If you want to do BGA or QFN, lay down a thin layer of solder paste on
flat glass and dip the BGA into the solder paste. Place the part on
the board and bake. I use a waffle iron with reversable plates. I use
the flip side has flat plates for doing grilled cheese sandwiches.
Works better than a toaster oven. Use no-lead paste for BGAs since the
balls are most likely no-lead (don't mix solder chemistries). Another
technique I use is tinning each PCB pad, coat the part pads with flux,
place and bake. This is very useful for leadless parts like power
supply controllers.

You can get hot simple hot air rework equipment for under $400. Made
in China, but works well for occasional rework.

Hot air preheat plate. Need to raise the plate by 1/4". Making the
plate larger in area is also helpful.
http://www.ntscope.com/Merchant2/me..._Code=MTC&Product_Code=QK853&Category_Code=RS

Hot air rework
http://www.ntscope.com/Merchant2/me...Code=MTC&Product_Code=QK857D&Category_Code=RS

Soldering iron. The PS-800 might be on its way out, so may need to go
to PS-800E or 900E.
http://www.hmcelectronics.com/cgi-bin/scripts/product/5635-0199/OKI-PS-800/
Hmc has a poor selection of tips.

 

[Jon Slaughter]

I've done home reflow with paste and a $20 hotplate. I do 0.5mm pitch
quite regularly, 0.5mm QFNs occasionally, and 0603 is HUGE I've
done CSPs but my home-brew boards are too flexible for them to stay
attached.

I recently added an alumimum plate to the hotplate, so if you go
searching, choose an alumimum hotplate instead of cast iron. My
process is basically "apply paste, place parts, heat until reflow".

Do you paste by hand or have a stencil? Could you list the paste and glue
you use? I might do a few tests and see what I get. I'm assuming you don't
use any heating profile (I recall that was a big deal for "proper" reflow
methods.

Wave would be nice but seems to require a load of expensive equipment. Not
sure if it could be done successfully with DIY techniques.

 

[Jon Slaughter]

It's the basic idea, yes. There are some other things to be taken into
account:
- The correct amount of solder.
- On the correct places.
- The correct temperature traject both up- and down.
Still only the most important.

Carcia Circuit Cellar published a design using some kind of toaster
oven. Elektor did the same but somewhat later in time. Now Elektor
sells reflow ovens, priced some 1200 Euros. (FAIK ex. VAT and
shipment)

The heating profile is not necessarily hard to do. I've seen several DIY
modules for proper heating profiles. I'm not sure though how important it is
for DIY though.

 

[DJ Delorie]

Do you paste by hand or have a stencil?

I've done both. There's a local guy that laser cuts kapton sheets, or
you can just use a syringe.

Could you list the paste and glue you use?

I don't use glue. For paste, I use whatever's cheapest since I don't
bother refridgerating it.

I might do a few tests and see what I get. I'm assuming you don't
use any heating profile

Nope. My hotplate heats to reflow temps in about 5-6 minutes so it
all works out, I just manually remove the board once all the paste is
melted. The hotplate only heats the PCB, not the parts, so the paste
melts before the parts get as hot.

 

[petrus bitbyter]

I've done both. There's a local guy that laser cuts kapton sheets, or
you can just use a syringe.


I don't use glue. For paste, I use whatever's cheapest since I don't
bother refridgerating it.


Nope. My hotplate heats to reflow temps in about 5-6 minutes so it
all works out, I just manually remove the board once all the paste is
melted. The hotplate only heats the PCB, not the parts, so the paste
melts before the parts get as hot.

That's how you build up some stress in the components and solderjunctions
that may give problems over time.

petrus bitbyter

 

[Jon Slaughter]

I've done both. There's a local guy that laser cuts kapton sheets, or
you can just use a syringe.


I don't use glue. For paste, I use whatever's cheapest since I don't
bother refridgerating it.

So you get decent accuracy that way? I would imagine that in some cases the
leads wouldn't align properly? I guess the surface tension may do the job
though...

Nope. My hotplate heats to reflow temps in about 5-6 minutes so it
all works out, I just manually remove the board once all the paste is
melted. The hotplate only heats the PCB, not the parts, so the paste
melts before the parts get as hot.

I might just go look for a small toaster oven and build a simple controller.
Shouldn't be difficult. A triac, some temp sensor, and pic should do the
trick.

 

[Rich Grise]

I might just go look for a small toaster oven and build a simple
controller. Shouldn't be difficult. A triac, some temp sensor, and pic
should do the trick.

They come with a thermostat. It's a bimetal bang-bang, and I don't know
the hysteresis, but mine does pizza just fine. ;-)

Cheers!
Rich

 

[David L. Jones]

Anyone done any non-hand soldering high density SMT's? 403's, high pin
count(maybe even BGA's), tight pitch stuff, etc.

I need to do some stuff manually for testing before mass producing the
boards and I do not really want to solder it all by hand simply
because it is very boring and error prone not to mention I get my
yearly dose of lead at each sitting.

I've done 603's without any real problem(the biggest simply being not
having a solder mask) and it's actually quite easy. I imagine with a
proper tip for the iron I wouldn't have any problems with 403's. I do
have some QFN's I'm a little worried about though but I guess some
solder paste should take care of that.

But I also imagine that using relow/wave or some other method would
be much easier. Simply tack the pieces down somehow and pass solder
over them(these boards will have a solder mask so...). I've heard of
people using toaster ovens to do such things so I imagine it can't be
that difficult.
1. Tack components down.
2. Bake in oven

? (not saying it's that simple but thats the basic idea) ?

There are now nice looking SMD reflow oven on ebay for only a few hundred
bucks.
Buy one and start experimenting.
I think gone are the days of hacking a toaster oven etc.

Dave.

 

[DJ Delorie]

So you get decent accuracy that way? I would imagine that in some
cases the leads wouldn't align properly? I guess the surface tension
may do the job though...

The only key is to put the right amount of paste down. If you do, it
all works. If not, a little hand-cleanup with a fine tip iron is all
it takes.

 

[DJ Delorie]

DJ, have you had this problem? Do you use anything to make the
heating more uniform?

I use an aluminum plate (about 8x8x1/4") to equalize the heat.
Nothing above it. The only discoloration I've gotten was one time I
tried to do a couple boards in a row without letting the plate cool
down; the epoxy nearly caught fire. Circuit still worked though.