Homebrew PCBs

Want to hand solder 44pin qfp's.  Need a new soldering iron that 
won't break the bank. (less than $50).  Suggestions?

Phil

Get a cheap iron and grind the tip
Or the "economy" weller station can use the full line of st tips, but that
be closer to 60-70 w/shipping.w/ a  extra tip
http://www.mouser.com/catalog/617/1183.pdf
(at the bottom right of the page)

JT


----- Original Message ----- 

From: "Moore" <pminmo@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, March 16, 2004 9:55 PM
Subject: [Homebrew_PCBs] Fine soldering iron


> Want to hand solder 44pin qfp's.  Need a new soldering iron that 
> won't break the bank. (less than $50).  Suggestions?
> 
> Phil
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs 
> Yahoo! Groups Links
> 
> 
> 
>  
>

that's certainly one approach.  I think you will find a ground tip 
wont last that long.  I went through a succession of cheap irons and 
finally got a temperature controller soldering station (hakko - $90 
including tax) and a couple of fine tips.  very glad I did.  You can 
get similar new for 70-80 and maybe cheaper if you shop around.  
here's a used hakko on ebay (same model I got) for about your price. 
http://cgi.ebay.com/ws/eBayISAPI.dll?
ViewItem&item=3803309151&category=58293  These come up a lot on ebay. 
They have a lot of tips (including very fine ones) for around $5 each.

I really encourage you to not skimp on an iron - a good one will last 
a long time.  cheap out and not only will soldering be harder but you 
will replace it in a year or less.

By the way, there is a technique for soldering qfps and other fine 
pitch devices that doesn't use a fine tip iron - you just slather on 
the solder and use wick to clean the bridges.  People claim to have 
gotten good enough to not require any wick.  I found it by googling 
for the obvious keywords.
 
--- In Homebrew_PCBs@yahoogroups.com, "Jeremy Taylor" <jt@j...> wrote:
> Get a cheap iron and grind the tip
> Or the "economy" weller station can use the full line of st tips, 
but that
> be closer to 60-70 w/shipping.w/ a  extra tip
> http://www.mouser.com/catalog/617/1183.pdf
> (at the bottom right of the page)
> 
> JT
> 
> 
> ----- Original Message ----- 
> From: "Moore" <pminmo@c...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Tuesday, March 16, 2004 9:55 PM
> Subject: [Homebrew_PCBs] Fine soldering iron
> 
> 
> > Want to hand solder 44pin qfp's.  Need a new soldering iron that 
> > won't break the bank. (less than $50).  Suggestions?
> > 
> > Phil
> > 
> > 
> > 
> > 
> > Be sure to visit the group home and check for new Bookmarks and 
files:

> > http://groups.yahoo.com/group/Homebrew_PCBs 
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> >

On Wed, 17 Mar 2004 02:55:46 -0000, Moore <pminmo@...> wrote:

> Want to hand solder 44pin qfp's.  Need a new soldering iron that
> won't break the bank. (less than $50).  Suggestions?
>
> Phil
>
>

Why not apply paste and bake it in the oven? much quicker...

I was told metcal is the ultimate manufacturer for smd irons, maybe
you can find one at ebay.... (maybe a defunct in this price range and 
repair).
there is a "drag tip" for the metcal which someone here has and says good 
words of.


However i would try the baking method first...

ST

--- In Homebrew_PCBs@yahoogroups.com, "Phil" <phil1960us@y...> wrote:
...
> I really encourage you to not skimp on an iron - a good one will last 
> a long time.  cheap out and not only will soldering be harder but you 
> will replace it in a year or less.
...

I agree. A ground down tip will be bare copper, which will get eaten
away by the solder very quickly.

And if you pay a bit too much for a tool that is a bit more than you
need, you're only out the little bit more you paid. If you buy a cheap
tool that is not quite up to snuff, you wasted the entire purchase price.

I bought a Weller with a fine tip for about $70 from a surplus store
here in Tacoma. He rebuilds them so they are used but in very good
condition, often with new elements. These are the kind with the tips
that you change to change the temp. I actually prefer those, I find
the temp more constant. Since the tip itself works as the temp
detector, it responds pretty much instantly to temp drops. Whereas
many variable temp irons, first the tip cools a bit and then a
thermistor must cool before the heating element gets kicked in again.
Sometimes the thermistor is in the heating element, which introduces
even more delay.

I think the ones with the hole in the back of the tip place the
thermistor inside the tip? Anyone know?

Steve

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan
<stefan_trethan@g...> wrote:
> On Wed, 17 Mar 2004 02:55:46 -0000, Moore <pminmo@c...> wrote:
> 
> > Want to hand solder 44pin qfp's.  Need a new soldering iron that
> > won't break the bank. (less than $50).  Suggestions?

> Why not apply paste and bake it in the oven? much quicker...
> 

Have you done this yet? I've followed the EZ Bake list and it's not so
simple. To get repeatable results, you need a time and temp controlled
oven that can heat up and cool down quickly (which means convection)
and programmed soak and bake cycles. The goal is to keep the board at
solder melting temp as short as possible to avoid destroying
components, while still getting 100% good soldered joints.

Steve

I was just trying to keep him in budget.
Grinding a tip, then using a quality tip tinner has served me well in the
past, but alas these day I'm with you guys. I paid over $600 for my station
~used.

JT
----- Original Message ----- 

From: "Phil" <phil1960us@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, March 17, 2004 4:03 AM
Subject: [Homebrew_PCBs] Re: Fine soldering iron


> that's certainly one approach.  I think you will find a ground tip
> wont last that long.  I went through a succession of cheap irons and
> finally got a temperature controller soldering station (hakko - $90
> including tax) and a couple of fine tips.  very glad I did.  You can
> get similar new for 70-80 and maybe cheaper if you shop around.
> here's a used hakko on ebay (same model I got) for about your price.
> http://cgi.ebay.com/ws/eBayISAPI.dll?
> ViewItem&item=3803309151&category=58293  These come up a lot on ebay.
> They have a lot of tips (including very fine ones) for around $5 each.
>
> I really encourage you to not skimp on an iron - a good one will last
> a long time.  cheap out and not only will soldering be harder but you
> will replace it in a year or less.
>
> By the way, there is a technique for soldering qfps and other fine
> pitch devices that doesn't use a fine tip iron - you just slather on
> the solder and use wick to clean the bridges.  People claim to have
> gotten good enough to not require any wick.  I found it by googling
> for the obvious keywords.
>
> --- In Homebrew_PCBs@yahoogroups.com, "Jeremy Taylor" <jt@j...> wrote:
> > Get a cheap iron and grind the tip
> > Or the "economy" weller station can use the full line of st tips,
> but that
> > be closer to 60-70 w/shipping.w/ a  extra tip
> > http://www.mouser.com/catalog/617/1183.pdf
> > (at the bottom right of the page)
> >
> > JT
> >
> >
> > ----- Original Message ----- 
> > From: "Moore" <pminmo@c...>
> > To: <Homebrew_PCBs@yahoogroups.com>
> > Sent: Tuesday, March 16, 2004 9:55 PM
> > Subject: [Homebrew_PCBs] Fine soldering iron
> >
> >
> > > Want to hand solder 44pin qfp's.  Need a new soldering iron that
> > > won't break the bank. (less than $50).  Suggestions?
> > >
> > > Phil
> > >
> > >
> > >
> > >
> > > Be sure to visit the group home and check for new Bookmarks and
> files:
> > > http://groups.yahoo.com/group/Homebrew_PCBs
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > >
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>

every tip I ever ground wound up with massive pits in it after maybe 
2 hrs of total soldering time.  My hakko has got probably 10X that 
time and after one wipe on the wet sponge, it looks the same as the 
day I bought it.

--- In Homebrew_PCBs@yahoogroups.com, "Jeremy Taylor" <jt@j...> wrote:
> I was just trying to keep him in budget.
> Grinding a tip, then using a quality tip tinner has served me well 
in the
> past, but alas these day I'm with you guys. I paid over $600 for my 
station
> ~used.
> 
> JT
> ----- Original Message ----- 
> From: "Phil" <phil1960us@y...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Wednesday, March 17, 2004 4:03 AM
> Subject: [Homebrew_PCBs] Re: Fine soldering iron
> 
> 
> > that's certainly one approach.  I think you will find a ground tip
> > wont last that long.  I went through a succession of cheap irons 
and
> > finally got a temperature controller soldering station (hakko - 
$90
> > including tax) and a couple of fine tips.  very glad I did.  You 
can
> > get similar new for 70-80 and maybe cheaper if you shop around.
> > here's a used hakko on ebay (same model I got) for about your 
price.
> > http://cgi.ebay.com/ws/eBayISAPI.dll?
> > ViewItem&item=3803309151&category=58293  These come up a lot on 
ebay.
> > They have a lot of tips (including very fine ones) for around $5 
each.
> >
> > I really encourage you to not skimp on an iron - a good one will 
last
> > a long time.  cheap out and not only will soldering be harder but 
you
> > will replace it in a year or less.
> >
> > By the way, there is a technique for soldering qfps and other fine
> > pitch devices that doesn't use a fine tip iron - you just slather 
on
> > the solder and use wick to clean the bridges.  People claim to 
have
> > gotten good enough to not require any wick.  I found it by 
googling
> > for the obvious keywords.
> >
> > --- In Homebrew_PCBs@yahoogroups.com, "Jeremy Taylor" <jt@j...> 
wrote:
> > > Get a cheap iron and grind the tip
> > > Or the "economy" weller station can use the full line of st 
tips,
> > but that
> > > be closer to 60-70 w/shipping.w/ a  extra tip
> > > http://www.mouser.com/catalog/617/1183.pdf
> > > (at the bottom right of the page)
> > >
> > > JT
> > >
> > >
> > > ----- Original Message ----- 
> > > From: "Moore" <pminmo@c...>
> > > To: <Homebrew_PCBs@yahoogroups.com>
> > > Sent: Tuesday, March 16, 2004 9:55 PM
> > > Subject: [Homebrew_PCBs] Fine soldering iron
> > >
> > >
> > > > Want to hand solder 44pin qfp's.  Need a new soldering iron 
that
> > > > won't break the bank. (less than $50).  Suggestions?
> > > >
> > > > Phil
> > > >
> > > >
> > > >
> > > >
> > > > Be sure to visit the group home and check for new Bookmarks 
and
> > files:
> > > > http://groups.yahoo.com/group/Homebrew_PCBs
> > > > Yahoo! Groups Links
> > > >
> > > >
> > > >
> > > >
> > > >
> >
> >
> >
> > Be sure to visit the group home and check for new Bookmarks and 
files:

> > http://groups.yahoo.com/group/Homebrew_PCBs
> > Yahoo! Groups Links
> >
> >
> >
> >
> >

>
> Have you done this yet? I've followed the EZ Bake list and it's not so
> simple. To get repeatable results, you need a time and temp controlled
> oven that can heat up and cool down quickly (which means convection)
> and programmed soak and bake cycles. The goal is to keep the board at
> solder melting temp as short as possible to avoid destroying
> components, while still getting 100% good soldered joints.
>
> Steve
>

No i haven't done it on tqfp, only smd transistors and one 8 pin...

I used a professional oven then.

I described it some time ago, it seems very simple to build.
you do not want to have the oven heating up, you put the board in the 
heated oven.

It is simple, you make a slot in the side and put two metal rails in.
on this rails you put a carriage. (the surface of the carriage i used was 
some
kind of fabric but i guess fine steel mash would work too)

then you put some handle on the carriage...

You need to have two zones, one preheat and one soldering.
The preheat zone is just inside the oven, but is shielded by a piece
of sheetmetal from the heating. the temperature is somewhere aronud 100 to 
150 degree
there. (you can find precise temperature curves on the www and even in 
datasheets).


there is is a relatiely long time, i think 30 seconds (but the curves show 
that too).
then you push it wider in, in the actual heating chamber. there is is only 
a short time.

then out again and ready.


The preheat is important for two things:
a) less difference in actual soldering --> shorter
b) the flux is melted and dried. if you put the past
 from cold to soldering temp the flux will virtually explode, resulting in 
tiny beads
of tin which can cause big trouble.

The oven i used was very expensive i think, but i know for sure it did not 
use a second heater
in the preheat. I would maybe build a second heater because it is much 
easier to set the
temperature then. the manufacturer spend surely a lot of time adjusting 
the preheat zone,
which saved a lot of money in the production. but if you build only one 
unit it costs nearly
nothing to make a second heater.



I do not read the ez_bake, do they have such ovens with a sliding carriage?
i would not attempt it different, it was so easy with that professional 
oven and i
think it is possible to get the same results with homebrew.

I think to avoid trouble you simply need to heat the pcb quick, which means
you need a oven which is already on temperature.

The reason i have not yet built one is that the solder paste is so 
expensive and
i do not have a applicator. (and i do not often use narrow grid smd ics)

ST

On Wed, 17 Mar 2004 16:52:07 -0000, Phil <phil1960us@...> wrote:

> every tip I ever ground wound up with massive pits in it after maybe
> 2 hrs of total soldering time.  My hakko has got probably 10X that
> time and after one wipe on the wet sponge, it looks the same as the
> day I bought it.
>


I agree totally on this. bare copper tips are horrible...
there is solder with 2% copper in it out there, with that they last much 
longer.

Has anyone thought of galvanizing a tip with iron?
I read the solder tips are iron coated, maybe it is possible to make that
at home for very special shapes...
Not information available on galvanizing on iron...
I wonder why this is not popular ;-)

ST

I have done several boards using solder paste and a cheap, non
convection  toaster oven. My most recent was a LQFP176. I have not
lost a chip yet to excessive heat or popcorning. I sometimes have to
wick solder bridges, but that is easy.
You still should have a good soldering iron, but using smd's and a
toaster oven makes things much easier in my opinion. 


--- In Homebrew_PCBs@yahoogroups.com, "Steve" <alienrelics@y...>
wrote:
> --- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan
> <stefan_trethan@g...> wrote:
> > On Wed, 17 Mar 2004 02:55:46 -0000, Moore <pminmo@c...> wrote:
> > 
> > > Want to hand solder 44pin qfp's.  Need a new soldering iron that
> > > won't break the bank. (less than $50).  Suggestions?
> 
> > Why not apply paste and bake it in the oven? much quicker...
> > 
> 
> Have you done this yet? I've followed the EZ Bake list and it's not
so
> simple. To get repeatable results, you need a time and temp
controlled
> oven that can heat up and cool down quickly (which means convection)
> and programmed soak and bake cycles. The goal is to keep the board
at

> solder melting temp as short as possible to avoid destroying
> components, while still getting 100% good soldered joints.
> 
> Steve

a new tip doesn't cost that much, that's probably why.

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> On Wed, 17 Mar 2004 16:52:07 -0000, Phil <phil1960us@y...> wrote:
> 
> > every tip I ever ground wound up with massive pits in it after 
maybe
> > 2 hrs of total soldering time.  My hakko has got probably 10X that
> > time and after one wipe on the wet sponge, it looks the same as 
the
> > day I bought it.
> >
> 
> 
> I agree totally on this. bare copper tips are horrible...
> there is solder with 2% copper in it out there, with that they last 
much 
> longer.
> 
> Has anyone thought of galvanizing a tip with iron?
> I read the solder tips are iron coated, maybe it is possible to 
make that

> at home for very special shapes...
> Not information available on galvanizing on iron...
> I wonder why this is not popular ;-)
> 
> ST

On Wed, 17 Mar 2004 18:08:42 -0000, Phil <phil1960us@...> wrote:

> a new tip doesn't cost that much, that's probably why.
>


I meant it is not popular because iron is normally not what you
want to make a surface, it is what you have in most cases..

I would like it for special shaped custom built tips.

i wonder which chemical is needed to plate iron.
(and i wonder if it would be useable at all, if the coating
is really iron..)

ST

I have several of the Hakko stations some ESD models and some 
standard, they work great.  If you do much work spending the extra 
money on a Hakko or other type station is well worth it.  Weller 
make a station that is in your listed price range.  

Normally filing down most tips is not a good idea, unless it is one 
of the solid copper tips then you have to file them as they wear.

> i wonder which chemical is needed to plate iron.
> (and i wonder if it would be useable at all, if the coating
> is really iron..)

Believe they call it Iron Clad.  If you break the coating the tip 
will not last long.

I use to use the copper tips in my old Ungar (now owned by Weller) 
irons, they worked great but did require reshaping with a file at 
times.  You had to keep it clean and tinned, but that is true for 
any iron to work well.

Also think that the hollow tips provide faster reheating or recovery 
time.

Pace has some newer rework stations. Their rework units are probably half as
good as Metcals, and about 30% of the price. I wonder if they have a
soldering station that might fit your price range.

I use a Weller WTCPS that I got surplus years ago with a 0.015 tip. The tips
seems to last about four - six months, but I do a lot of soldering.

Ron

I'm with the majority here. I started out with an "economy" 
soldering iron and very quickly regretted it. Thing took centuries 
to heat up and lost temp very quickly. I finally gave in and bought 
a Weller WTCPT station. Not fancy, temperature control is in the 
tips not on the station. The difference was staggering though, heats 
up in < 1 minute, doesn't lose temperature when soldering. Has a 
nice range of tips (which seem to last a LOOONG time).

As for the QFP - Some things I've read said that going with a fine 
tip might actually be harder than going with a wide one. They said 
go wide and solder several pins at once. Check for bridges when 
you're done and remove with a soldering wick.

I haven't tried a QFP but I have tried some SOTs this way. Seems 
that the solder rarely bridges unless you put loads of it on. Even 
then I usually just turn the tip sideways and reheat one of the pins 
and the bridge melts away in an instant.

Doesn't take a lot of practice to do this really. Thing is that I 
usually have the fine tip on when I'm soldering SMT caps and 
resistors etc and I can't be bothered to change tips (cool down 
time) so i just do them one pin at a time.


--- In Homebrew_PCBs@yahoogroups.com, "Moore" <pminmo@c...> wrote:

> Want to hand solder 44pin qfp's.  Need a new soldering iron that 
> won't break the bank. (less than $50).  Suggestions?
> 
> Phil

Well, i have a ERSA 60W 24V iron with a homebrew station,
it measures the temperature in the heating element by it's resistance.
nut the best method, but it works very nicely for me.
i never measured the temp ripple under normal soldering condidtions but
if someone is interested i will do it (I'm a bit curious too)

It uses the tips which slide on the outside over the iron.


You can't compare this to a cheapo iron without temp. control.
(I have written about the importance of closed loop control in another 
post)
It's worth more than the difference in costs...

You can change tips on this iron also when hot, just lift the spring with
pliers and slide the tip off. there are also special pliers for this job,
with a groove for gripping the tip, but any pliers will work fine.
never grip the business end with the pliers, you could destroy the coating.

I also agree on the "broad tip" thing, if you have the right amount of 
solder
it works fine...

Just seen a old small oven/grill on the attic today while looking for 
something else.
maybe when i find the time (and a cheap source for soldering paste) i will 
actually build
the oven...


Any ideas how to apply the paste? I used a syringe with a hose to a 
machine in school, there was a button
which caused the delivery of exactly the same amount each time at the tip.
the hose looked like a air hose, but i wonder if the compressibility is no 
problem.
(May have been water or oil in there also)

any ideas how to build this?
Any ideas if / how this could be fitted to a cnc drill?
is it possible to make such a automated dispenser??

ST

(I'm talking of smd resistors / caps here, ics take a bead, no individual 
dots)

On Thu, 18 Mar 2004 16:46:59 -0000, ghidera2000 <ghidera2000@...> 
wrote:

> I'm with the majority here. I started out with an "economy"
> soldering iron and very quickly regretted it. Thing took centuries
> to heat up and lost temp very quickly. I finally gave in and bought
> a Weller WTCPT station. Not fancy, temperature control is in the
> tips not on the station. The difference was staggering though, heats
> up in < 1 minute, doesn't lose temperature when soldering. Has a
> nice range of tips (which seem to last a LOOONG time).
>
> As for the QFP - Some things I've read said that going with a fine
> tip might actually be harder than going with a wide one. They said
> go wide and solder several pins at once. Check for bridges when
> you're done and remove with a soldering wick.
>
> I haven't tried a QFP but I have tried some SOTs this way. Seems
> that the solder rarely bridges unless you put loads of it on. Even
> then I usually just turn the tip sideways and reheat one of the pins
> and the bridge melts away in an instant.
>
> Doesn't take a lot of practice to do this really. Thing is that I
> usually have the fine tip on when I'm soldering SMT caps and
> resistors etc and I can't be bothered to change tips (cool down
> time) so i just do them one pin at a time.
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "Moore" <pminmo@c...> wrote:
>> Want to hand solder 44pin qfp's.  Need a new soldering iron that
>> won't break the bank. (less than $50).  Suggestions?
>>
>> Phil
>
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan
<stefan_trethan@g...> wrote:
> Well, i have a ERSA 60W 24V iron with a homebrew station,
> it measures the temperature in the heating element by it's resistance.
> nut the best method, but it works very nicely for me.
> i never measured the temp ripple under normal soldering condidtions but
> if someone is interested i will do it (I'm a bit curious too)
> 
> It uses the tips which slide on the outside over the iron.

Did you build the temperature control part, then?
 
> Just seen a old small oven/grill on the attic today while looking for 
> something else.
> maybe when i find the time (and a cheap source for soldering paste)
i will 
> actually build
> the oven...

I really like the idea of a slide-through oven with a pre-heat chamber.
 
> Any ideas how to apply the paste? I used a syringe with a hose to a 
> machine in school, there was a button
> which caused the delivery of exactly the same amount each time at
the tip.
> the hose looked like a air hose, but i wonder if the compressibility
is no 
> problem.
> (May have been water or oil in there also)

Yes, I'd think compressability of air would rule it out.

How about a leadscrew and stepper motor?

Steve

ghidera2000 wrote:

> As for the QFP - Some things I've read said that going with a fine 
> tip might actually be harder than going with a wide one. They said 
> go wide and solder several pins at once. Check for bridges when 
> you're done and remove with a soldering wick.
> 
> I haven't tried a QFP but I have tried some SOTs this way. Seems 
> that the solder rarely bridges unless you put loads of it on. Even 
> then I usually just turn the tip sideways and reheat one of the pins 
> and the bridge melts away in an instant.

Yep.  The "solder blob swipe" technique works especially well when there 
is a solder mask layer on the board, I never seem to get bridges. 
Without the solder mask the bridges are much more likely but nothing a 
little wicking won't remove (as you mentioned.)

Just remember that flux is your friend.  "Be the flux."

Lately, though, I've noticed that there is sufficient solder finish on 
the SMT pads from my proto manufacturer to just heat the pin while 
applying slight pressure on the body of the part.  The pad finish melts, 
bonds to the pin, and it's done!  I've done many 0805 parts and even a 
couple VQ44 packages this way.  It seems to work well electrically and 
mechanically but I don't trust it that it could be so easy (these are of 
course home projects so I don't have to worry about commercial 
quality/reliability standards.  Still.)

-Johnathan

>
> Did you build the temperature control part, then?

Yes i did build it, no i don't have the schematic anymore.
Back engineering would work, it is not too hard.
it used a triac to switch the current, and there is a opamp
/ comparator somewhere. ther is also a led for voltage reference.
it has a display for temperature, which is so wildly inaccurate that
i do not use it (could calibrate it).
it can be built without the display too.
it is a simple control circuit, i could build it from scratch i think.
you have a potentiometer for setting the temperature you like. and a led
that blinks with the heating element. i added a piezo speaker which "ticks"
on each heating, sounds like a geiger counter but it doesn't let me forget
to switch it off (left it 2 times overnight before adding the ticker).
it is also a nice audible feedback if it is hot...


It was made some time ago in school. sorry i didn't keep the schematic.
(stupid i know...)

If one really needs to build one i draw it up from the pcb, it is not
too complicated.
However you need a 24V iron for it, which alone did cost 600ATS when i 
built the
unit. (50 eur or so) now you can get complete stations for less (ok they 
are bad..)


> I really like the idea of a slide-through oven with a pre-heat chamber.
>

Me too. i think it is the only sensible approach.
even if you have a 3MW heating element ( ;-) ) then you would
still need to heat the air, the heating would take longer.
with a hot oven it is the fastest possible with air.



> Yes, I'd think compressability of air would rule it out.
>
> How about a leadscrew and stepper motor?

maybe a useable idea.
the paste comes filled in a syringe already...

I wonder if it would work on a cnc to automatically dispense the
paste, if one can ensure that the dot comes out and sticks to the
pad, not the needle. with some tweaking it might work....


then add a pick and place ;-)

ST

Hello Stefan, Steve,

The way compressed air is used to dispense a paste, is to use a two-
way valve or two valves. First the valve is on comperssed air for a 
specific time and pressure, providing the decided amount of paste.
Then the valve is switched to open air, so the pressure is released 
instantly, so no drips anymore.

Important in this is that there is no air or gas pocket in the 
syringe. The syringe will be normally airless for this reason if you 
buy it.

A leadscrew will of course also work, but will make the system very 
long and less practical to use.

Another option is a gearpump, dispensing the paste and then 
eventually suck back to compensate for trapped air. But this is much 
more complex.

Gertjan.


--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> 
> >
> > Did you build the temperature control part, then?
> 
> Yes i did build it, no i don't have the schematic anymore.
> Back engineering would work, it is not too hard.
> it used a triac to switch the current, and there is a opamp
> / comparator somewhere. ther is also a led for voltage reference.
> it has a display for temperature, which is so wildly inaccurate that
> i do not use it (could calibrate it).
> it can be built without the display too.
> it is a simple control circuit, i could build it from scratch i 
think.
> you have a potentiometer for setting the temperature you like. and 
a led
> that blinks with the heating element. i added a piezo speaker 
which "ticks"
> on each heating, sounds like a geiger counter but it doesn't let me 
forget
> to switch it off (left it 2 times overnight before adding the 
ticker).
> it is also a nice audible feedback if it is hot...
> 
> 
> It was made some time ago in school. sorry i didn't keep the 
schematic.
> (stupid i know...)
> 
> If one really needs to build one i draw it up from the pcb, it is 
not
> too complicated.
> However you need a 24V iron for it, which alone did cost 600ATS 
when i 
> built the
> unit. (50 eur or so) now you can get complete stations for less (ok 
they 
> are bad..)
> 
> 
> > I really like the idea of a slide-through oven with a pre-heat 
chamber.

> >
> 
> Me too. i think it is the only sensible approach.
> even if you have a 3MW heating element ( ;-) ) then you would
> still need to heat the air, the heating would take longer.
> with a hot oven it is the fastest possible with air.
> 
> 
> 
> > Yes, I'd think compressability of air would rule it out.
> >
> > How about a leadscrew and stepper motor?
> 
> maybe a useable idea.
> the paste comes filled in a syringe already...
> 
> I wonder if it would work on a cnc to automatically dispense the
> paste, if one can ensure that the dot comes out and sticks to the
> pad, not the needle. with some tweaking it might work....
> 
> 
> then add a pick and place ;-)
> 
> ST

On Fri, 19 Mar 2004 09:25:53 -0000, gk_impala <yahoo@...> wrote:

> Hello Stefan, Steve,
>
> The way compressed air is used to dispense a paste, is to use a two-
> way valve or two valves. First the valve is on comperssed air for a
> specific time and pressure, providing the decided amount of paste.
> Then the valve is switched to open air, so the pressure is released
> instantly, so no drips anymore.
>
> Gertjan.
>

oh thanks, that's it.
It sounded exactly like you describe it.

It works with the flowrate of the tip, i didn't think of that.


ST

--- In Homebrew_PCBs@yahoogroups.com, "gk_impala" <yahoo@i...> wrote:
> Hello Stefan, Steve,
...
> A leadscrew will of course also work, but will make the system very 
> long and less practical to use.

Why long? A very small stepper may be sufficient.

Steve