🚀 go-pugleaf

On Sep 25, 7:02 pm, mickgeyver <eyezku...@yahoo.com> wrote:
> I'm trying to make a 10x scope probe that is capable of dealing with
> slightly higher voltage levels of about +/- 20v yet at a high
> impedance ~20Meg. This link "http://picasaweb.google.com/
> UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
> the probe and board warpage. The board was made from double sided
> 0.020-inch stock etched with a PCB milling machine (perhaps part of
> the problem). It is (obviously) hand assembled.  I would appreciate
> any tips or techniques that I could use to keep this board from
> turning into a potato chip during assembly.
>
> Thank you.
>
> al

dang G00gle.....

"http://picasaweb.google.com/UncleAltheKiddiesPal/Probe#"

mickgeyver wrote:
> 
> On Sep 25, 7:02 pm, mickgeyver <eyezku...@yahoo.com> wrote:
> > I'm trying to make a 10x scope probe that is capable of dealing with
> > slightly higher voltage levels of about +/- 20v yet at a high
> > impedance ~20Meg. This link "http://picasaweb.google.com/
> > UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
> > the probe and board warpage. The board was made from double sided
> > 0.020-inch stock etched with a PCB milling machine (perhaps part of
> > the problem). It is (obviously) hand assembled.  I would appreciate
> > any tips or techniques that I could use to keep this board from
> > turning into a potato chip during assembly.
> >
> > Thank you.
> >
> > al
> 
> dang G00gle.....
> 
> "http://picasaweb.google.com/UncleAltheKiddiesPal/Probe#"


   It looks like you used cheap phenolic PCB materials. Fiberglass is a
lot more stable.


-- 
You can't have a sense of humor, if you have no sense!

On Fri, 25 Sep 2009 16:02:55 -0700 (PDT), mickgeyver
<eyezkubed@yahoo.com> wrote:

>I'm trying to make a 10x scope probe that is capable of dealing with
>slightly higher voltage levels of about +/- 20v yet at a high
>impedance ~20Meg. This link "http://picasaweb.google.com/
>UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
>the probe and board warpage. The board was made from double sided
>0.020-inch stock etched with a PCB milling machine (perhaps part of
>the problem). It is (obviously) hand assembled.  I would appreciate
>any tips or techniques that I could use to keep this board from
>turning into a potato chip during assembly.
>
>Thank you.
>
>al


  Use 0.032" media.  Bake under a flat press upon receipt of the bare
boards.

  Hand assemble...  no wave solder, no IR oven.

  Those are the only techniques that yield 100% positive results.

  Any automated process will certainly have a poorer prime pass yield.

  That is, unless the PCB maker was real good at stress relief during the
making of the boards.

On Fri, 25 Sep 2009 16:02:55 -0700 (PDT), mickgeyver
<eyezkubed@yahoo.com> wrote:

>I'm trying to make a 10x scope probe that is capable of dealing with
>slightly higher voltage levels of about +/- 20v yet at a high
>impedance ~20Meg. This link "http://picasaweb.google.com/
>UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
>the probe and board warpage. The board was made from double sided
>0.020-inch stock etched with a PCB milling machine (perhaps part of
>the problem). It is (obviously) hand assembled.  I would appreciate
>any tips or techniques that I could use to keep this board from
>turning into a potato chip during assembly.


<http://picasaweb.google.com/UncleAltheKiddiesPal/Probe?feat=directlink>

Is that a Polysulfone board?

With 0.020 inch anything, and all that copper, it's going to warp no
matter what you do.  Any differential heating, on one side of the
board, is going to cause the board to bend.  

I ran into the same problem years ago with wave and hand solder in
thin boards.  Going to thicker boards, with some kind of stiffener was
not an option because of weight limitations.  However, you apparently
don't have that problem.  Try 0.032 or 0.0625 boards, keep the heating
to a minimum, and it might work.

I think you might be entertained by what happens to just the board,
without any components.  Clamp one end of the board into a vice.  Heat
one side of the board with a hot air gun or soldering iron.  The
copper will expand, causing the board to warp.  In other words, the
large copper areas are what's causing the warping.

You can somewhat minimize the effect by pre-heating and post-heating
the board.  We found that freon vapor reflow soldering produced
absolutely flat boards.  That because the entire board was heated
evenly, and cooled down evenly and slowly.  Heat one side of the board
more than the other (i.e. differential heating) and it's going to warp
unless you're very careful on cooling it down evenly.  When we went to
surface mount devices, small traces, and 0.5 oz Cu traces, the warping
was gone.

0.020 is thin enough that the board can be straightened by the
mounting arrangement.  Instead of the round brass tube, it might be
possible to use an aluminum tube, with two grooves milled into the
inside diameter.  Your current board does not have enough unused area
along the lengthwise edges to do this, but it can be expanded
somewhat.  This also has the advantage of providing a nifty ground
connection to the case.  However, inside milling is expensive.  A
square aluminum extrusion is possible, but even more expensive.

Good luck.
-- 
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com               jeffl@cruzio.com
# http://www.LearnByDestroying.com               AE6KS

mickgeyver wrote:
> I'm trying to make a 10x scope probe that is capable of dealing with
> slightly higher voltage levels of about +/- 20v yet at a high
> impedance ~20Meg. This link "http://picasaweb.google.com/
> UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
> the probe and board warpage. The board was made from double sided
> 0.020-inch stock etched with a PCB milling machine (perhaps part of
> the problem). It is (obviously) hand assembled.  I would appreciate
> any tips or techniques that I could use to keep this board from
> turning into a potato chip during assembly.
> 
> Thank you.
> 
> al


Tin the tracks with hot solder on the side outside the curve, as it
cools and contracts it will straighten the board.

On Sep 25, 8:35 pm, Archimedes' Lever <OneBigLe...@InfiniteSeries.Org>
wrote:
> On Fri, 25 Sep 2009 16:02:55 -0700 (PDT), mickgeyver
>
> <eyezku...@yahoo.com> wrote:
> >I'm trying to make a 10x scope probe that is capable of dealing with
> >slightly higher voltage levels of about +/- 20v yet at a high
> >impedance ~20Meg. This link "http://picasaweb.google.com/
> >UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
> >the probe and board warpage. The board was made from double sided
> >0.020-inch stock etched with a PCB milling machine (perhaps part of
> >the problem). It is (obviously) hand assembled.  I would appreciate
> >any tips or techniques that I could use to keep this board from
> >turning into a potato chip during assembly.
>
> >Thank you.
>
> >al
>
>   Use 0.032" media.  Bake under a flat press upon receipt of the bare
> boards.
>
I'll try to find thicker stock. Like Joerg there is no expense money
available for this project so I gotta use whatever is available.
There is a connector on the other end that I'm using to leech power
from the scope so I have limitations here.
>
>   Hand assemble...  no wave solder, no IR oven.
Done that. Perhaps if I make a frame to clamp it flat during assembly.
>
>   Those are the only techniques that yield 100% positive results.
>
>   Any automated process will certainly have a poorer prime pass yield.
>
>   That is, unless the PCB maker was real good at stress relief during the
> making of the boards.
I'm the PCB maker all contained in house with a mill machine.

On Sep 25, 11:41 pm, Jeff Liebermann <je...@cruzio.com> wrote:
> On Fri, 25 Sep 2009 16:02:55 -0700 (PDT), mickgeyver
>
> <eyezku...@yahoo.com> wrote:
> >I'm trying to make a 10x scope probe that is capable of dealing with
> >slightly higher voltage levels of about +/- 20v yet at a high
> >impedance ~20Meg. This link "http://picasaweb.google.com/
> >UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
> >the probe and board warpage. The board was made from double sided
> >0.020-inch stock etched with a PCB milling machine (perhaps part of
> >the problem). It is (obviously) hand assembled.  I would appreciate
> >any tips or techniques that I could use to keep this board from
> >turning into a potato chip during assembly.
>
> <http://picasaweb.google.com/UncleAltheKiddiesPal/Probe?feat=directlink>
>
> Is that a Polysulfone board?
No. Just a scrap of fiberglass board from long ago. I have some Rogers
flex board, but the surface appeared too rough to get good results on
my PCB mill.
>
> With 0.020 inch anything, and all that copper, it's going to warp no
> matter what you do.  Any differential heating, on one side of the
> board, is going to cause the board to bend.  
>
> I ran into the same problem years ago with wave and hand solder in
> thin boards.  Going to thicker boards, with some kind of stiffener was
> not an option because of weight limitations.  However, you apparently
> don't have that problem.  Try 0.032 or 0.0625 boards, keep the heating
> to a minimum, and it might work.

Can't go too thick here as I'm leeching power from a Tek P6204 probe
cable.
>
> I think you might be entertained by what happens to just the board,
> without any components.  Clamp one end of the board into a vice.  Heat
> one side of the board with a hot air gun or soldering iron.  The
> copper will expand, causing the board to warp.  In other words, the
> large copper areas are what's causing the warping.

I'll try that just for grins. Never thought of thin PCB material as a
bi-metalic thermostat element.
>
> You can somewhat minimize the effect by pre-heating and post-heating
> the board.  We found that freon vapor reflow soldering produced
> absolutely flat boards.  That because the entire board was heated
> evenly, and cooled down evenly and slowly.  Heat one side of the board
> more than the other (i.e. differential heating) and it's going to warp
> unless you're very careful on cooling it down evenly.  When we went to
> surface mount devices, small traces, and 0.5 oz Cu traces, the warping
> was gone.
>
> 0.020 is thin enough that the board can be straightened by the
> mounting arrangement.  Instead of the round brass tube, it might be
> possible to use an aluminum tube, with two grooves milled into the
> inside diameter.  Your current board does not have enough unused area
> along the lengthwise edges to do this, but it can be expanded
> somewhat.  This also has the advantage of providing a nifty ground
> connection to the case.  However, inside milling is expensive.  A
> square aluminum extrusion is possible, but even more expensive.

I was concerned that too much bending would crack some of the
components giving me problems later on. I don't want this to get too
big as it  lets me attach this unit to a probe manipulator to use
under a microscope to hit those tiny nodes. Like I've stated
before.... I'm leeching power from the business end of a TEK P6204
probe. The 3/8 brass tube mates up nicely with the Tek probe cable
strain relief at the probe end.  I'll post more photo's of the other
end for the groups viewing pleasure.
>
> Good luck.
> --
> # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
> # 831-336-2558
> #http://802.11junk.com              je...@cruzio.com
> #http://www.LearnByDestroying.com              AE6KS

On Sat, 26 Sep 2009 06:34:12 -0700 (PDT), mickgeyver
<eyezkubed@yahoo.com> wrote:

>> � Hand assemble... �no wave solder, no IR oven.
>Done that. Perhaps if I make a frame to clamp it flat during assembly.
>>
  Then your dwell time on each solder joint is way too high.

  Try 1/20th gram per joint, not the half gram per joint the picture
appears to show.  You know...  NASA soldering specs.  As little solder as
is possible and perform the operation quickly.  What I saw looked like
several time the amount needed in the dip chip.  Even the connector was
huge and blobby on the solder joints. The builder does not need to flood
those pins with solder.  The solder only needs to be between the pin and
the board ala SMD soldering.  FILLET not BLOB.

  The soldering iron should also be at 600� F, NOT 800� F.

  If you are having wetting problems due to age of the leads of your
parts or such, you may need to try different solders to see if a
different flux choice might yield a good solder joint faster than your
current choice.

  RMA is harder to clean (hot alcohol bath) but it does make a good, well
wetted solder joint faster in some instances.  I am not sure which flux
choices are the most active these days.  It has been a long time since I
did production level soldering, and we currently use odd technology since
we get exempted from RoHS compliance.

On Sat, 26 Sep 2009 06:52:30 -0700 (PDT), mickgeyver
<eyezkubed@yahoo.com> wrote:

>Can't go too thick here as I'm leeching power from a Tek P6204 probe
>cable.

Ok.  I just noticed that the backlighting LCD inverter in a typical
laptop is constructed similarly to your prototype.  Very thin G10
board, 10mm wide, and all the parts on one side.  To make matters
worse, a big routed hole in the middle for the xformer.  Huge copper
ground plane on one side of the board.

Yet, all the boards in my collection are quite straight.  That
demonstrates that it can be done.  I'm not sure what you're doing
that's wrong, but I agree with others that suggest you're using far to
much solder and heat.  Smaller parts, less solder, and less heat will
help.

Incidentally, when I say less heat, I don't mean less temperature.  I
use the hottest iron tip I can get away with, and work fast.  That
minimizes the energy transfered to the solder joint and therefore
reduces the heat affected zone.

>I was concerned that too much bending would crack some of the
>components giving me problems later on.

PCB warping will certainly cause problems.  It really depends on the
physical size of the components.  Parts with flexible leads (xsistors,
IC's) are not much of a problem because the leads absorb the flex.
Parts that are soldered directly to the board, will either crack, or
rip the traces off the board.  If you can't fix the flexing problem,
switch to a flexible PCB design and apply an insulating stiffener
board on the circuit side.  It can't be prototyped with at PCB router,
but at some point, you're going to have to commit to a PCB layout.
Might as well do it early.

-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

In article <ob7vb5hbtk1jft1ju767hq0k8ofnjo23dc@4ax.com>,
 Jeff Liebermann <jeffl@cruzio.com> wrote:

> Yet, all the boards in my collection are quite straight.  That
> demonstrates that it can be done.  I'm not sure what you're doing
> that's wrong, but I agree with others that suggest you're using far to
> much solder and heat.  Smaller parts, less solder, and less heat will
> help.
> 
> Incidentally, when I say less heat, I don't mean less temperature.  I
> use the hottest iron tip I can get away with, and work fast.  That
> minimizes the energy transfered to the solder joint and therefore
> reduces the heat affected zone.

I think one problem is that this is a home made board. The holes are 
likely too large for the components (because most people don't have very 
small drills on hand or even the drill chuck to hold them) and obviously 
they aren't plated through. That can make it necessary to glob on the 
solder.

As far as temperature, I agree with you. I've never found a need to 
solder anything at less than 800F. Smaller parts just require shorter 
dwell time.

I have no idea why the OP is using such thin stock, though. It looks 
like he'd have room for something as robust as .050".

On Sun, 27 Sep 2009 11:59:32 -0700, Smitty Two <prestwhich@earthlink.net>
wrote:

>In article <ob7vb5hbtk1jft1ju767hq0k8ofnjo23dc@4ax.com>,
> Jeff Liebermann <jeffl@cruzio.com> wrote:
>
>> Yet, all the boards in my collection are quite straight.  That
>> demonstrates that it can be done.  I'm not sure what you're doing
>> that's wrong, but I agree with others that suggest you're using far to
>> much solder and heat.  Smaller parts, less solder, and less heat will
>> help.
>> 
>> Incidentally, when I say less heat, I don't mean less temperature.  I
>> use the hottest iron tip I can get away with, and work fast.  That
>> minimizes the energy transfered to the solder joint and therefore
>> reduces the heat affected zone.
>
>I think one problem is that this is a home made board. The holes are 
>likely too large for the components (because most people don't have very 
>small drills on hand or even the drill chuck to hold them) and obviously 
>they aren't plated through. That can make it necessary to glob on the 
>solder.

  Good observation. The lead size, and hole size and even the annular
ring width all inter-relate if one is to produce minimalist 'NASA' style
soldering results.

>As far as temperature, I agree with you. I've never found a need to 
>solder anything at less than 800F. Smaller parts just require shorter 
>dwell time.

  This one is off the mark.  Perhaps you meant "at MORE than 800�F"
That would certainly be an upper max for me, and it is quite easy to
solder at much lower temperatures.  Well over a 100 degree differential,
and that is significant.

>I have no idea why the OP is using such thin stock, though. It looks 
>like he'd have room for something as robust as .050".

  He could make little SMD circuits that he places on Silica wafers, and
then place those wafers on the substrate with epoxy, and wire the
sections together.

  I used to use 0.020 wafers up to 2 x 2 inches to make little smd proto
circuits on.  I have glued smd parts on, and hand wired point-to-point
the nodes between the parts.  I have also 'dead bug' glued thru-hole 8
pin dips onto it and wired those nodes with hook-up wire. The leads were
shortened, of course.

  That sounds like a good proto build solution, but to make a production
run would require a different decision.

In article <r7l0c5l9457i2ug2u6143cp6pllirtrauu@4ax.com>,
 Archimedes' Lever <OneBigLever@InfiniteSeries.Org> wrote:

> >As far as temperature, I agree with you. I've never found a need to 
> >solder anything at less than 800F. Smaller parts just require shorter 
> >dwell time.
> 
>   This one is off the mark.  Perhaps you meant "at MORE than 800�F"
> That would certainly be an upper max for me, and it is quite easy to
> solder at much lower temperatures.  Well over a 100 degree differential,
> and that is significant.

Pardon my ambiguity. What I meant to say was "anything other than 800F." 
That's the upper limit on most fixed-temperature tips, or adjustable 
irons.

On Mon, 28 Sep 2009 06:21:13 -0700, Smitty Two <prestwhich@earthlink.net>
wrote:

>In article <r7l0c5l9457i2ug2u6143cp6pllirtrauu@4ax.com>,
> Archimedes' Lever <OneBigLever@InfiniteSeries.Org> wrote:
>
>> >As far as temperature, I agree with you. I've never found a need to 
>> >solder anything at less than 800F. Smaller parts just require shorter 
>> >dwell time.
>> 
>>   This one is off the mark.  Perhaps you meant "at MORE than 800�F"
>> That would certainly be an upper max for me, and it is quite easy to
>> solder at much lower temperatures.  Well over a 100 degree differential,
>> and that is significant.
>
>Pardon my ambiguity. What I meant to say was "anything other than 800F." 
>That's the upper limit on most fixed-temperature tips, or adjustable 
>irons.


 Yes, and despite most folks cranking the damned things up that high,
basic soldering operations (pre-RoHS) were NEVER meant to be performed at
that high a temperature.  Even on big 0.092" stock with lots of Copper.
In that case, one should pre-heat the whole assembly a couple hundred �F,
which will insure that all the solder joints wet well and flow through
properly.

In article <kk62c51rq1rhdq9he33du6t99nbjp1pqga@4ax.com>,
 Archimedes' Lever <OneBigLever@InfiniteSeries.Org> wrote:

> On Mon, 28 Sep 2009 06:21:13 -0700, Smitty Two <prestwhich@earthlink.net>
> wrote:
> 
> >In article <r7l0c5l9457i2ug2u6143cp6pllirtrauu@4ax.com>,
> > Archimedes' Lever <OneBigLever@InfiniteSeries.Org> wrote:
> >
> >> >As far as temperature, I agree with you. I've never found a need to 
> >> >solder anything at less than 800F. Smaller parts just require shorter 
> >> >dwell time.
> >> 
> >>   This one is off the mark.  Perhaps you meant "at MORE than 800�F"
> >> That would certainly be an upper max for me, and it is quite easy to
> >> solder at much lower temperatures.  Well over a 100 degree differential,
> >> and that is significant.
> >
> >Pardon my ambiguity. What I meant to say was "anything other than 800F." 
> >That's the upper limit on most fixed-temperature tips, or adjustable 
> >irons.
> 
> 
>  Yes, and despite most folks cranking the damned things up that high,
> basic soldering operations (pre-RoHS) were NEVER meant to be performed at
> that high a temperature.  Even on big 0.092" stock with lots of Copper.
> In that case, one should pre-heat the whole assembly a couple hundred �F,
> which will insure that all the solder joints wet well and flow through
> properly.

Uh-huh. I've personally hand soldered hundreds of thousands of joints at 
800F, and overseen the soldering of millions. Turning down the flame has 
only one result: It takes too damn long to build the board. It's sort of 
like the clock speed on a computer. It doesn't matter much if something 
takes 1 second instead of 1/10 second, but it makes a big difference if 
it takes an hour instead of 6 minutes. When I was a kid I built some 
Heathkit stuff and spent 30 seconds making every solder connection, 
because the iron was underpowered and I didn't know enough to know it.
Machine soldering is different, of course, but for hand work, 800 is 
perfect for everything and anything.

"Smitty Two" <prestwhich@earthlink.net> wrote in message 
news:prestwhich-89E049.22383128092009@newsfarm.iad.highwinds-media.com...
> In article <kk62c51rq1rhdq9he33du6t99nbjp1pqga@4ax.com>,
> Archimedes' Lever <OneBigLever@InfiniteSeries.Org> wrote:
>
>> On Mon, 28 Sep 2009 06:21:13 -0700, Smitty Two <prestwhich@earthlink.net>
>> wrote:
>>
>> >In article <r7l0c5l9457i2ug2u6143cp6pllirtrauu@4ax.com>,
>> > Archimedes' Lever <OneBigLever@InfiniteSeries.Org> wrote:
>> >
>> >> >As far as temperature, I agree with you. I've never found a need to
>> >> >solder anything at less than 800F. Smaller parts just require shorter
>> >> >dwell time.
>> >>
>> >>   This one is off the mark.  Perhaps you meant "at MORE than 800�F"
>> >> That would certainly be an upper max for me, and it is quite easy to
>> >> solder at much lower temperatures.  Well over a 100 degree 
>> >> differential,
>> >> and that is significant.
>> >
>> >Pardon my ambiguity. What I meant to say was "anything other than 800F."
>> >That's the upper limit on most fixed-temperature tips, or adjustable
>> >irons.
>>
>>
>>  Yes, and despite most folks cranking the damned things up that high,
>> basic soldering operations (pre-RoHS) were NEVER meant to be performed at
>> that high a temperature.  Even on big 0.092" stock with lots of Copper.
>> In that case, one should pre-heat the whole assembly a couple hundred �F,
>> which will insure that all the solder joints wet well and flow through
>> properly.
>
> Uh-huh. I've personally hand soldered hundreds of thousands of joints at
> 800F, and overseen the soldering of millions. Turning down the flame has
> only one result: It takes too damn long to build the board. It's sort of
> like the clock speed on a computer. It doesn't matter much if something
> takes 1 second instead of 1/10 second, but it makes a big difference if
> it takes an hour instead of 6 minutes. When I was a kid I built some
> Heathkit stuff and spent 30 seconds making every solder connection,
> because the iron was underpowered and I didn't know enough to know it.
> Machine soldering is different, of course, but for hand work, 800 is
> perfect for everything and anything.



I concur - 700F tips are great - no problems in the last 15 years. The only 
time I go for a 700F is  terminating some cables where the insulation is 
super sensitive to the heat and shrinks back or melts through. 

"Nik Rim" <querty@kbd.com> wrote in message 
news:FMSdnRvn7tmFQVzXnZ2dnUVZ_rudnZ2d@westnet.com.au...
>
> "Smitty Two" <prestwhich@earthlink.net> wrote in message 
> news:prestwhich-89E049.22383128092009@newsfarm.iad.highwinds-media.com...
>> In article <kk62c51rq1rhdq9he33du6t99nbjp1pqga@4ax.com>,
>> Archimedes' Lever <OneBigLever@InfiniteSeries.Org> wrote:
>>
>>> On Mon, 28 Sep 2009 06:21:13 -0700, Smitty Two 
>>> <prestwhich@earthlink.net>
>>> wrote:
>>>
>>> >In article <r7l0c5l9457i2ug2u6143cp6pllirtrauu@4ax.com>,
>>> > Archimedes' Lever <OneBigLever@InfiniteSeries.Org> wrote:
>>> >
>>> >> >As far as temperature, I agree with you. I've never found a need to
>>> >> >solder anything at less than 800F. Smaller parts just require 
>>> >> >shorter
>>> >> >dwell time.
>>> >>
>>> >>   This one is off the mark.  Perhaps you meant "at MORE than 800�F"
>>> >> That would certainly be an upper max for me, and it is quite easy to
>>> >> solder at much lower temperatures.  Well over a 100 degree 
>>> >> differential,
>>> >> and that is significant.
>>> >
>>> >Pardon my ambiguity. What I meant to say was "anything other than 
>>> >800F."
>>> >That's the upper limit on most fixed-temperature tips, or adjustable
>>> >irons.
>>>
>>>
>>>  Yes, and despite most folks cranking the damned things up that high,
>>> basic soldering operations (pre-RoHS) were NEVER meant to be performed 
>>> at
>>> that high a temperature.  Even on big 0.092" stock with lots of Copper.
>>> In that case, one should pre-heat the whole assembly a couple hundred 
>>> �F,
>>> which will insure that all the solder joints wet well and flow through
>>> properly.
>>
>> Uh-huh. I've personally hand soldered hundreds of thousands of joints at
>> 800F, and overseen the soldering of millions. Turning down the flame has
>> only one result: It takes too damn long to build the board. It's sort of
>> like the clock speed on a computer. It doesn't matter much if something
>> takes 1 second instead of 1/10 second, but it makes a big difference if
>> it takes an hour instead of 6 minutes. When I was a kid I built some
>> Heathkit stuff and spent 30 seconds making every solder connection,
>> because the iron was underpowered and I didn't know enough to know it.
>> Machine soldering is different, of course, but for hand work, 800 is
>> perfect for everything and anything.
>
>
>


Typo - should have said 800F tips......

> I concur - 700F tips are great - no problems in the last 15 years. The 
> only time I go for a 700F is  terminating some cables where the insulation 
> is super sensitive to the heat and shrinks back or melts through.
> 

I'd probably try a couple of methods which may or may not help. In welding, 
the welds are often alternated from one side to the other, as the cooling 
phase causes distortion. The alternating method minimizes distortion.

Another method that I'd consider, would be to raise some of the axial-lead 
components slightly above the board surface, where space permits. A shim of 
file folder material may be enough to leave a small gap, so the lead 
positions wouldn't be so rigid. (the shim removed after the solder cools).

Jumper wires (soldered with a shim underneath them, or a slight hump) placed 
laterally where they wouldn't interfere with other components or signals, 
may add some flexibility to the overall assembly.

--
Cheers,
WB
.............

"mickgeyver" <eyezkubed@yahoo.com> wrote in message 
news:8ca1d668-3369-4f05-ac3c-a47ad550740b@d34g2000vbm.googlegroups.com...
> I'm trying to make a 10x scope probe that is capable of dealing with
> slightly higher voltage levels of about +/- 20v yet at a high
> impedance ~20Meg. This link "http://picasaweb.google.com/
> UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
> the probe and board warpage. The board was made from double sided
> 0.020-inch stock etched with a PCB milling machine (perhaps part of
> the problem). It is (obviously) hand assembled.  I would appreciate
> any tips or techniques that I could use to keep this board from
> turning into a potato chip during assembly.
>
> Thank you.
>
> al 

On Fri, 25 Sep 2009 16:02:55 -0700 (PDT), mickgeyver
<eyezkubed@yahoo.com> wrote:

>I'm trying to make a 10x scope probe that is capable of dealing with
>slightly higher voltage levels of about +/- 20v yet at a high
>impedance ~20Meg. This link "http://picasaweb.google.com/
>UncleAltheKiddiesPal/Probe?feat=directlink" has some photo's showing
>the probe and board warpage. The board was made from double sided
>0.020-inch stock etched with a PCB milling machine (perhaps part of
>the problem). It is (obviously) hand assembled.  I would appreciate
>any tips or techniques that I could use to keep this board from
>turning into a potato chip during assembly.
>
>Thank you.
>
>al

  Purchase rigid (of course) Silica plates (heat sink media).  You could
very likely get 0.020" thickness, no problem.  You could also likely get
the exact size you need as well.  Then you proto by dead bug (or not)glue
the chips and other parts on, and hand wire the nodes between them.  Your
proto could then turn into a flex circuit to replace all the hand wiring
for the SMD circuitry, glued (attached) onto one of your already existing
Silica base plates that you bought say 100 of for the first proto and
production runs.

  As small as it looked, I could easily build many of them a day even as
proto style.  But the flex circuit with the heat absorbing capable Silica
back plate sounds like a candidate for being called a solution.