Homebrew PCBs

hi,

i have a ic that has a dimension of 5mm*5mm*1mm . it
has 32 pins it is surface mount. what are the options
available to solder this IC.(because this is so small
and i know only to solder by bouth)

thank you.
randeel.

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

From: "randeel wimalagunarathne" <randeelwrw@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, October 21, 2007 3:17 PM
Subject: [Homebrew_PCBs] soldering question


> hi,
>
> i have a ic that has a dimension of 5mm*5mm*1mm . it
> has 32 pins it is surface mount. what are the options
> available to solder this IC.(because this is so small
> and i know only to solder by bouth)

It sounds like a QFN package. Drag-soldering should work if you make the 
pads slightly longer than recommended for reflow soldering.

Leon

randeel wimalagunarathne <randeelwrw@...> writes:
> i have a ic that has a dimension of 5mm*5mm*1mm . it has 32 pins it
> is surface mount. what are the options available to solder this
> IC.(because this is so small and i know only to solder by bouth)

Two questions:

1. What chip is it?  I mean, does it have leads or just pads, is it
   bga, qfp, qfn, csp, etc?  A specific part number is best.

2. Have you made the board for it yet?

Bonus question:

* What's a bouth?


I've had luck soldering tiny qfn (no leads, just pads on the bottom)
chips using solder paste and a hotplate, but it helps to extend the
board's pads away from the chip enough to do manual repairs.

--- DJ Delorie <dj@...> wrote:

> 
> randeel wimalagunarathne <randeelwrw@...>
> writes:
> > i have a ic that has a dimension of 5mm*5mm*1mm .
> it has 32 pins it
> > is surface mount. what are the options available
> to solder this
> > IC.(because this is so small and i know only to
> solder by bouth)
> 
> Two questions:
> 
> 1. What chip is it?  I mean, does it have leads or
> just pads, is it
>    bga, qfp, qfn, csp, etc?  A specific part number
> is best.
> 
> 2. Have you made the board for it yet?
> 
> Bonus question:
> 
> * What's a bouth?
> 
> 
> I've had luck soldering tiny qfn (no leads, just
> pads on the bottom)
> chips using solder paste and a hotplate, but it
> helps to extend the
> board's pads away from the chip enough to do manual
> repairs.
> 

ic is trf 7960
1.
its (s-pqfp-n32)
2.
no haven't made a board for it. because we are
confused about soldering this tiny IC.

3.
it's the normal soldering iron with a tip having a pen
shape. 

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randeel wimalagunarathne <randeelwrw@...> writes:
> ic is trf7960

Ah, a QFN with a thermal pad.  I've done those with the hotplate, but
it's critical to get the right amount of paste down.

> no haven't made a board for it. because we are confused about
> soldering this tiny IC.

Rightly so, the thermal pad is going to be very difficult with an
iron, because you need a LOT of heat to heat it - after all, it's a
THERMAL pad, you need to design the board to suck heat away from the
pad, which makes it hard to solder.

> 3.  it's the normal soldering iron with a tip having a pen shape.

Ah, ok.


Depending on how critical the heat issue (thermal pad) is, there are a
couple of options.

If you're doing your own boards, and can't do through-plated vias, and
the heat issue isn't critical, you can just etch a rectangle to solder
to and hope the pcb substrate itself will move enough heat.

Without PTV if heat is an issue, cut a rectangular hole in the pcb the
size of the pad and attach a heat sink with silver thermal grease.

With PTV, put a bunch of small ones in that pad to pull heat to copper
on the other side of the board.

In any case, bring the pads for the QFN out far enough that you have
room to heat the pads with your iron.  Mine has a 0.020" tip so I pull
them out 0.020" past the side of the IC package.  Even if you use a
hotplate, you'll want this for any repairs.

Now, if there's copper under your thermal pad, you must use a hotplate
or oven to put this part on.  I use a hotplate[1].  Put solder paste
on the thermal pad but don't cover 100% else the chip won't seat low
enough to contact all the other pads.  The chip's PDF pas a
recommended paste stencil layout.  Put paste on the other pads too,
out past the body (you want more paste to ensure a connection, but you
don't want it underneath where it might short).  Place the part, but
try to get it right the first time and don't press down hard, either
will smear the paste and you'll have to start again.  Heat it.  With
the hotplate, you can press down a bit once it starts melting, to make
sure all the pins are contacted.  Make sure you don't bump the part
off the solder until the solder cools.

If you cut a hole under the part, you can use your iron.  You still
use paste, but only put it on the little pads.  Place the chip, and
use the iron to reflow the paste - touch the pad outside the body and
let it heat up the copper until the paste melts.  Start with opposite
corners, then do the rest.

To repair, again use paste - you can use an xacto blade to squeeze
paste under the chip, and reflow it with your iron.  Copper braid can
be used to remove most shorts.

As for putting the paste itself down, you can either use a stencil (I
etch brass ones myself, but you can have mylar ones laser cut at
www.smtstencil.com) or an xacto blade.  A sharpened toothpick is great
for removing paste from between pads.

[1] http://geda.seul.org/projects/djs_pcbs/ at the bottom (note: I
    forgot the "rinse" step with the liquid tin; that's why the boards
    look corroded)

I haven't yet soldered any SMD IC's myself, but this tutorial may be 
of help:

http://www.sparkfun.com/commerce/present.php?p=SMD-HowTo-1

or

http://tinyurl.com/yjlf9n

-Clay

--- In Homebrew_PCBs@yahoogroups.com, randeel wimalagunarathne 
<randeelwrw@...> wrote:

>
> 
> --- DJ Delorie <dj@...> wrote:
> 
> > 
> > randeel wimalagunarathne <randeelwrw@...>
> > writes:
> > > i have a ic that has a dimension of 5mm*5mm*1mm .
> > it has 32 pins it
> > > is surface mount. what are the options available
> > to solder this
> > > IC.(because this is so small and i know only to
> > solder by bouth)
> > 
> > Two questions:
> > 
> > 1. What chip is it?  I mean, does it have leads or
> > just pads, is it
> >    bga, qfp, qfn, csp, etc?  A specific part number
> > is best.
> > 
> > 2. Have you made the board for it yet?
> > 
> > Bonus question:
> > 
> > * What's a bouth?
> > 
> > 
> > I've had luck soldering tiny qfn (no leads, just
> > pads on the bottom)
> > chips using solder paste and a hotplate, but it
> > helps to extend the
> > board's pads away from the chip enough to do manual
> > repairs.
> > 
> 
> ic is trf 7960
> 1.
> its (s-pqfp-n32)
> 2.
> no haven't made a board for it. because we are
> confused about soldering this tiny IC.
> 
> 3.
> it's the normal soldering iron with a tip having a pen
> shape. 
> 
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around 
> http://mail.yahoo.com
>

DJ Delorie <dj@...> writes:
> With PTV, put a bunch of small ones in that pad to pull heat to copper
> on the other side of the board.

Alternative if you can't do reflow - put a BIG via under the pad; big
enough for you to solder the pad from the other side, through the
hole.  Only works with plated vias, though, and only if your iron can
heat up that much metal at once without damaging the chip.

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

From: "DJ Delorie" <dj@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, October 23, 2007 6:22 AM
Subject: Re: [Homebrew_PCBs] soldering question


> 
> DJ Delorie <dj@...> writes:
>> With PTV, put a bunch of small ones in that pad to pull heat to copper
>> on the other side of the board.
> 
> Alternative if you can't do reflow - put a BIG via under the pad; big
> enough for you to solder the pad from the other side, through the
> hole.  Only works with plated vias, though, and only if your iron can
> heat up that much metal at once without damaging the chip.

That's what I do. My Metcal doesn't have any problems delivering the heat.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND and FT-857D transceivers
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

Regarding Metcal:

I am sure the metcal hot air station comes from the same production
line in china as the AOYUE units. It only has a different front panel,
and is otherwise the same down to the transport securing screw for the
compressor. It isn't even the best model, it's the cheapest oldest
most simple version with no display or extras.

Now the AOYUE stations are not bad, i have one myself, but it's
clearly made in china. That Metcal wants to put their name on it
surprises me, well, what can i say, "how the mighty have fallen" maybe
;-)

Anyway, if you want a metcal hot air station for 1/10th of the price, buy AOYUE.

That shows how companies (management) has changed, or do you think
metcal would have gotten their reputation with chinese gear? It's hard
to earn, but lost quickly, is what i say...

ST

On 10/23/07, Leon <leon355@...> wrote:

> That's what I do. My Metcal doesn't have any problems delivering the heat.
>
> Leon
> --

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

From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, October 23, 2007 10:49 AM
Subject: Re: [Homebrew_PCBs] soldering question


> Regarding Metcal:
> 
> I am sure the metcal hot air station comes from the same production
> line in china as the AOYUE units. It only has a different front panel,
> and is otherwise the same down to the transport securing screw for the
> compressor. It isn't even the best model, it's the cheapest oldest
> most simple version with no display or extras.

Which Metcal and which Aoyue?

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND and FT-857D transceivers
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

The HCT-900-21 from Metcal, which aoyue matches it best i dunno (950
maybe), several are pretty much the same just with different options
(displays etc.) and 2 different types of heaters are available.
Certainly one of the old ones with 23l diaphragm pump not a fan type.

ST

On 10/23/07, Leon <leon355@...> wrote:

> Which Metcal and which Aoyue?
>
> Leon

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

From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, October 23, 2007 2:17 PM
Subject: Re: [Homebrew_PCBs] soldering question


> The HCT-900-21 from Metcal, which aoyue matches it best i dunno (950
> maybe), several are pretty much the same just with different options
> (displays etc.) and 2 different types of heaters are available.
> Certainly one of the old ones with 23l diaphragm pump not a fan type.

That's not actually a Metcal unit, it's got an OKI sticker on it. Metcal is 
owned by OKI, but the range is different.

Leon

Oh well, so it's OKI, which owns Metcal, that is selling chep gear for big $$.
People will notice it's not quite the same quality...

ST

On 10/23/07, Leon <leon355@...> wrote:

> That's not actually a Metcal unit, it's got an OKI sticker on it. Metcal is
> owned by OKI, but the range is different.
>
> Leon
>
>

"clayton.gilmore" <clayton.gilmore@...> writes:
> I haven't yet soldered any SMD IC's myself, but this tutorial may be 
> of help:
> 
> http://www.sparkfun.com/commerce/present.php?p=SMD-HowTo-1

The one thing those tutorials don't cover is chips with thermal pads,
which is what the OP is trying to solder.  You need a way to get heat
*under* the chip for those.

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> "clayton.gilmore" <clayton.gilmore@...> writes:
> > I haven't yet soldered any SMD IC's myself, but this tutorial may be 
> > of help:
> > 
> > http://www.sparkfun.com/commerce/present.php?p=SMD-HowTo-1
> 
> The one thing those tutorials don't cover is chips with thermal pads,
> which is what the OP is trying to solder.  You need a way to get heat
> *under* the chip for those.

Actually, that tutorial did specifically use an SMT IC with a thermal
pad. Check out the videos on Page 7.

I've not done this yet, but I think I'd feel better if it were sitting
on something to preheat the entire board.

Steve Greenfield

Steve wrote:
> --- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>   
>> "clayton.gilmore" <clayton.gilmore@...> writes:
>>     
>>> I haven't yet soldered any SMD IC's myself, but this tutorial may be 
>>> of help:
>>>
>>> http://www.sparkfun.com/commerce/present.php?p=SMD-HowTo-1
>>>       
>> The one thing those tutorials don't cover is chips with thermal pads,
>> which is what the OP is trying to solder.  You need a way to get heat
>> *under* the chip for those.
>>     
>
> Actually, that tutorial did specifically use an SMT IC with a thermal
> pad. Check out the videos on Page 7.
>
> I've not done this yet, but I think I'd feel better if it were sitting
> on something to preheat the entire board.
>   
So I should solder PCBs with SMT on a warm frying pan?

Cheers,

Bryan

"Steve" <alienrelics@...> writes:
> Actually, that tutorial did specifically use an SMT IC with a
> thermal pad. Check out the videos on Page 7.

So they do!  That's new since I last checked thm out.

> I've not done this yet, but I think I'd feel better if it were
> sitting on something to preheat the entire board.

Hence my hotplate.  But if you can do that, you can just use that to
do the soldering too.

Bryan Pope <bryan.pope@...> writes:
> So I should solder PCBs with SMT on a warm frying pan?

So sparkfun says, and I agree.  Get a cheap hotplate or electric
frying pan, and a syringe of paste (I use SynTECH - no refridgeration
needed).  Apply paste (stencil or syringe), place parts, heat pcb
until the solder melts, done!

The problem with the hotplate is that it won't work on PCBs with SMDs
on both sides, or will it?

ST

On 23 Oct 2007 20:49:42 -0400, DJ Delorie <dj@...> wrote:
>
> Bryan Pope <bryan.pope@...> writes:
> > So I should solder PCBs with SMT on a warm frying pan?
>
> So sparkfun says, and I agree.  Get a cheap hotplate or electric
> frying pan, and a syringe of paste (I use SynTECH - no refridgeration
> needed).  Apply paste (stencil or syringe), place parts, heat pcb
> until the solder melts, done!
>

"Stefan Trethan" <stefan_trethan@...> writes:
> The problem with the hotplate is that it won't work on PCBs with
> SMDs on both sides, or will it?

It won't.  It works well only because the hotplate heats the PCB
evenly (assuming you have even heat, or move the board around to heat
it evenly) and melts the paste before the parts get too hot.  You can
even touch up some of the parts while the solder is liquid, if needed.

I do the more densly populated side on the hotplate, and the other
side manually.  I still use paste and reflow, just not the hotplate.
My technique for the back side:

* Apply paste to the pcb using the syringe, manually.

* Place all components (sometimes I do all of one type at a time).

* For each part, hold it down with the tips of the tweezers or a
  toothpick, and touch your iron to each end.  That melts the paste
  between the part and the board.

Usually I only have resistors and capacitors on the back, they're easy
to solder.  The hotplate is most needed for QFNs, TQFPs, fine pitch
connectors, etc.  I use 0.5mm pitch parts a lot these days.

Sometimes I use the talon for parts on the back.  I can heat both ends
at the same time, move the part around with it if needed, and the
solder doesn't stick to the talon as much as it sticks to the iron.