Ian White GM3SEK wrote:
ken scharf wrote:


Now to solder those chip caps and resistors! (They should be easier,
the AD9851 was the worst part to place with the tight spacing, all the
other parts have lead spacing at least twice as wide).

It's MUCH easier to begin with the easy parts! Start with the largest
chip caps and resistors, continue with the rest of the simple passives,
and then the largest ICs (largest pin spacing).

Finally, when you've honed your SMD skills, solder the large ICs with
the small pin spacings.

And give up the industrial-strength coffee for the duration :-)


For some reason the instructions that came with the DDS-60 kit have you
solder all the ic's on first, then the resistors and caps.

After thinking I had done a good job on the AD9851 I put the board under
my binocular microscope for a close in look. I saw what looked like
microscopic solder bridges between the chip leads. I was able to remove
these with a stiff piece of paper slid between the chip leads. I still
see strange 'hair like' structures all over the board under the
microscope. I may be seeing dust, bits of flux, who knows! The
microscopic world is strange, especially in 3D.

Personally, I'd do the DDS chip first, before the resistors and
capacitors. One of the tricks I use is to clean the IC pins with rubbing
Alcohol after soldering and removing shorts.

Then, I apply a hot air gun, SLOWLY bringing the temperature up on the
pins of the IC. I try to get to barely melting the solder, but not burning
the main board. A slow application allows the IC to heat up gradually.

This tends to remove the hairline solder bridges and clean up between the
pins of the IC. Since the main DDS chip is the only part on the board, I
don't have to worry about heating up and blowing the resistors and
capacitors clean off the board !!!

I can, and have, used this same method on a completely assembled board,
but I have to pay close attention to the small parts, the tend to want to
blow away. In that case, I build a heat shield with tin foil and I press
it down on the board all around the IC I want to solder flow and that
usually keeps the other parts on the board where I want them.


This all takes a delicate touch, it's pretty easy to get things too hot,
but it does provide nice and clean solder joints.


Jim Pennell
N6BIU


--

23:10 Pacific Time Zone
Dec 28 2006

International Time
07:10 UTC
29.12.2006

I've been working on a high-power HF autotuner design that I'd just
about shelved because of the necessity of soldering the DDS chip. (it
uses an internal RF source to power the phase detector)

This thread has helped a lot. When time permits I may order up some
parts and give it a try. I have a good-quality magnifier lamp and a
fine-point temp-controlled pencil, what I don't have is OEM eye lenses
and flexible finger joints... ;-)

Jim, N7CXI

ken scharf wrote:
Ian White GM3SEK wrote:
ken scharf wrote:

Now to solder those chip caps and resistors! (They should be easier,
the AD9851 was the worst part to place with the tight spacing, all the
other parts have lead spacing at least twice as wide).

It's MUCH easier to begin with the easy parts! Start with the largest
chip caps and resistors, continue with the rest of the simple passives,
and then the largest ICs (largest pin spacing).

Finally, when you've honed your SMD skills, solder the large ICs with
the small pin spacings.

And give up the industrial-strength coffee for the duration :-)


For some reason the instructions that came with the DDS-60 kit have you
solder all the ic's on first, then the resistors and caps.

After thinking I had done a good job on the AD9851 I put the board under
my binocular microscope for a close in look. I saw what looked like
microscopic solder bridges between the chip leads. I was able to remove
these with a stiff piece of paper slid between the chip leads. I still
see strange 'hair like' structures all over the board under the
microscope. I may be seeing dust, bits of flux, who knows! The
microscopic world is strange, especially in 3D.

Jim Barber wrote:
I've been working on a high-power HF autotuner design that I'd just
about shelved because of the necessity of soldering the DDS chip. (it
uses an internal RF source to power the phase detector)

This thread has helped a lot. When time permits I may order up some
parts and give it a try. I have a good-quality magnifier lamp and a
fine-point temp-controlled pencil, what I don't have is OEM eye lenses
and flexible finger joints... ;-)

Most of my SMD work is done using half-moon reading glasses - the
strongest and cheapest available from the drugstore - in front of my
normal glasses. When not in use, they hang from a neck cord.

After publishing this suggestion, a very generous person *gave* me a
professional-quality binocular microscope. This is wonderful for big
jobs like assembling a whole new board... but to be honest, I still tend
to use the double glasses more, because the "setup process" is much
quicker.

You will find that the tip of the soldering iron becomes much steadier
when seen under the magnifier. This feedback loop is a wonderful thing,
especially if you give it the best possible chance to work:

* "Use the scope, Luke!" - learn to concentrate exclusively on what
you're SEEING. This is harder than it seems, because for normal
soldering we also rely a lot on our sense of touch, and automatically
tend to press the tip of the iron against the parts being soldered. With
SMD this is a disaster - it simply pushes the parts out of position - so
you need to break that habit and concentrate on using ONLY your eyes.

* Steady your arm against the edge of the bench, so you're not trying to
stabilize your whole body.

* Stay off the caffeine - it creates a fine tremor that the brain cannot
stabilize (too much "noise" in the feedback loop).



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ian White GM3SEK wrote:
Jim Barber wrote:
I've been working on a high-power HF autotuner design that I'd just
about shelved because of the necessity of soldering the DDS chip. (it
uses an internal RF source to power the phase detector)

This thread has helped a lot. When time permits I may order up some
parts and give it a try. I have a good-quality magnifier lamp and a
fine-point temp-controlled pencil, what I don't have is OEM eye lenses
and flexible finger joints... ;-)

Most of my SMD work is done using half-moon reading glasses - the
strongest and cheapest available from the drugstore - in front of my
normal glasses. When not in use, they hang from a neck cord.

After publishing this suggestion, a very generous person *gave* me a
professional-quality binocular microscope. This is wonderful for big
jobs like assembling a whole new board... but to be honest, I still tend
to use the double glasses more, because the "setup process" is much
quicker.

You will find that the tip of the soldering iron becomes much steadier
when seen under the magnifier. This feedback loop is a wonderful thing,
especially if you give it the best possible chance to work:

* "Use the scope, Luke!" - learn to concentrate exclusively on what
you're SEEING. This is harder than it seems, because for normal
soldering we also rely a lot on our sense of touch, and automatically
tend to press the tip of the iron against the parts being soldered. With
SMD this is a disaster - it simply pushes the parts out of position - so
you need to break that habit and concentrate on using ONLY your eyes.

The problem with a 10x microscope is first FINDING the soldering iron
tip in the field of view. If I am looking into the microscope and
trying to place the iron on the work often the iron ends up way in left
field (or I push it into my other hand OUCH!) TOO much magnification
can be TOO much of a good thing. I wish I had another set of eye piece
lenses (or an other objective) so I could go down to 5X sometimes.

My microscope is a true binocular with poro prisms and dual objective
and eyepiece lenses. It was a 'gift' from a former employer (they were
cleaning up the lab and threw it out). I did have to jury rig a stand
since only the optic head was found in the trash, the unit originally
mounted on a long spring loaded 'gooseneek', like those circleline
magnifier lamps. (One of the focus knobs is cracked in half, but I can
live with that).

* Steady your arm against the edge of the bench, so you're not trying to
stabilize your whole body.

* Stay off the caffeine - it creates a fine tremor that the brain cannot
stabilize (too much "noise" in the feedback loop).



Damn Cuban Coffee (Well, I work in Miami!)

Thanks for the tips, gents.
Sounds like a binocular microscope would be a great tool; otherwise I
suspect depth perception might be an issue.

I'll keep an eye out for one.

Jim, N7CXI


ken scharf wrote:
Ian White GM3SEK wrote:
Jim Barber wrote:
I've been working on a high-power HF autotuner design that I'd just
about shelved because of the necessity of soldering the DDS chip. (it
uses an internal RF source to power the phase detector)

This thread has helped a lot. When time permits I may order up some
parts and give it a try. I have a good-quality magnifier lamp and a
fine-point temp-controlled pencil, what I don't have is OEM eye lenses
and flexible finger joints... ;-)
Most of my SMD work is done using half-moon reading glasses - the
strongest and cheapest available from the drugstore - in front of my
normal glasses. When not in use, they hang from a neck cord.

After publishing this suggestion, a very generous person *gave* me a
professional-quality binocular microscope. This is wonderful for big
jobs like assembling a whole new board... but to be honest, I still tend
to use the double glasses more, because the "setup process" is much
quicker.

You will find that the tip of the soldering iron becomes much steadier
when seen under the magnifier. This feedback loop is a wonderful thing,
especially if you give it the best possible chance to work:

* "Use the scope, Luke!" - learn to concentrate exclusively on what
you're SEEING. This is harder than it seems, because for normal
soldering we also rely a lot on our sense of touch, and automatically
tend to press the tip of the iron against the parts being soldered. With
SMD this is a disaster - it simply pushes the parts out of position - so
you need to break that habit and concentrate on using ONLY your eyes.

The problem with a 10x microscope is first FINDING the soldering iron
tip in the field of view. If I am looking into the microscope and
trying to place the iron on the work often the iron ends up way in left
field (or I push it into my other hand OUCH!) TOO much magnification
can be TOO much of a good thing. I wish I had another set of eye piece
lenses (or an other objective) so I could go down to 5X sometimes.

My microscope is a true binocular with poro prisms and dual objective
and eyepiece lenses. It was a 'gift' from a former employer (they were
cleaning up the lab and threw it out). I did have to jury rig a stand
since only the optic head was found in the trash, the unit originally
mounted on a long spring loaded 'gooseneek', like those circleline
magnifier lamps. (One of the focus knobs is cracked in half, but I can
live with that).

* Steady your arm against the edge of the bench, so you're not trying to
stabilize your whole body.

* Stay off the caffeine - it creates a fine tremor that the brain cannot
stabilize (too much "noise" in the feedback loop).



Damn Cuban Coffee (Well, I work in Miami!)

Jim Barber wrote:
Thanks for the tips, gents.
Sounds like a binocular microscope would be a great tool; otherwise I
suspect depth perception might be an issue.

It still is an issue, because a microscope prevents you from using one
of the most natural ways of perceiving depth, by looking at the board
from a few different angles. Only a head-mounted viewer allows this.

A large lens on a spring arm is a kind of half-way option, but it
rapidly loses quality at off-axis angles.

Another problem that needs to be mentioned is focusing and depth of
focus. With a microscope, you have to put down the iron or the solder in
order to adjust the focus. With a head-mounted viewer, you simply move
your head to re-focus... but by the end of the day you'll probably have
neck strain.

Also we haven't mentioned lighting. All microscopes tend to suffer from
poor light-gathering power, so the work area needs to be very brightly
lit.


While we're on the subject, a friend has come up with yet another
option. Like many of us, he has a very good detachable zoom lens for a
35mm camera that he doesn't use any more. He has fixed this onto a
low-cost colour CCTV camera, and positioned it about 4 feet above the
workbench, looking straight down. This gives a moderately magnified view
of the work area on a TV monitor directly in front of him.

This has the big advantage of leaving the workspace completely
unobstructed, so he can switch very easily and naturally between the
monitor and the direct view. He reports that it avoids a lot of the eye
and neck strain.

The main practical problem that he still has to solve is "camera
shake", because of viewing from such a long distance. In his case, the
camera is mounted from the roof of a wooden shack, so he can't do SMD
work on a windy day.

If you have a suitable lens and a CCTV camera, this option would be well
worth trying.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Now that has potential:

By pure coincidence, I already have a Sony HDR-SR1 high-def (1080i)
camcorder and a 21" 16:9 LCD display with HDMI input in the lab.

Putting those two devices together and adding an appropriate macro lens
would seem to be a natural thing for this kind of work.

Great idea, Ian!

Jim, N7CXI


Ian White GM3SEK wrote:
Jim Barber wrote:
Thanks for the tips, gents.
Sounds like a binocular microscope would be a great tool; otherwise I
suspect depth perception might be an issue.

It still is an issue, because a microscope prevents you from using one
of the most natural ways of perceiving depth, by looking at the board
from a few different angles. Only a head-mounted viewer allows this.

A large lens on a spring arm is a kind of half-way option, but it
rapidly loses quality at off-axis angles.

Another problem that needs to be mentioned is focusing and depth of
focus. With a microscope, you have to put down the iron or the solder in
order to adjust the focus. With a head-mounted viewer, you simply move
your head to re-focus... but by the end of the day you'll probably have
neck strain.

Also we haven't mentioned lighting. All microscopes tend to suffer from
poor light-gathering power, so the work area needs to be very brightly lit.


While we're on the subject, a friend has come up with yet another
option. Like many of us, he has a very good detachable zoom lens for a
35mm camera that he doesn't use any more. He has fixed this onto a
low-cost colour CCTV camera, and positioned it about 4 feet above the
workbench, looking straight down. This gives a moderately magnified view
of the work area on a TV monitor directly in front of him.

This has the big advantage of leaving the workspace completely
unobstructed, so he can switch very easily and naturally between the
monitor and the direct view. He reports that it avoids a lot of the eye
and neck strain.

The main practical problem that he still has to solve is "camera
shake", because of viewing from such a long distance. In his case, the
camera is mounted from the roof of a wooden shack, so he can't do SMD
work on a windy day.

If you have a suitable lens and a CCTV camera, this option would be well
worth trying.