AVR-Chat

I just landed on the backyard of the ATmegas and the first prototype
is already on my sight.. however, as experience has taught me it is
always good to assemble hardware prototypes in sockets.
It happens that these ATmegas use 64 pins on MLF and TQFP which 
there is no easy fit around. Needless to say that it's impossible
to fit this IC on a protoboard...

Anyone has had such a hard time like this ? 

Thanks.

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

From: "Alex De Lara" <alex_de_lara@yahoo.com>
To: <AVR-Chat@yahoogroups.com>
Sent: Thursday, June 09, 2005 5:10 PM
Subject: [AVR-Chat] Any ideas on socket for ATmega128/64 ?


>I just landed on the backyard of the ATmegas and the first prototype
> is already on my sight.. however, as experience has taught me it is
> always good to assemble hardware prototypes in sockets.
> It happens that these ATmegas use 64 pins on MLF and TQFP which 
> there is no easy fit around. Needless to say that it's impossible
> to fit this IC on a protoboard...
> 
> Anyone has had such a hard time like this ? 

You can buy little PCBs to put them on, 'Surfboards' is one type.

Leon
--
Leon Heller, G1HSM
leon.heller@bulldoghome.com
http://www.geocities.com/leon_heller
---
[This E-mail has been scanned for viruses but it is your responsibility 
to maintain up to date anti virus software on the device that you are
currently using to read this email. ]

Several vendors make adapters.

One that comes to mind is:

  www.sparkfun.com

It should be in the Development Board section.  You'll
have to scroll down near the bottom.

HTH,

Jeff Engel
Arlington, TX
--- Alex De Lara <alex_de_lara@yahoo.com> wrote:

> I just landed on the backyard of the ATmegas and the
> first prototype
> is already on my sight.. however, as experience has
> taught me it is
> always good to assemble hardware prototypes in
> sockets.
> It happens that these ATmegas use 64 pins on MLF and
> TQFP which 
> there is no easy fit around. Needless to say that
> it's impossible
> to fit this IC on a protoboard...
> 
> Anyone has had such a hard time like this ? 
> 
> Thanks.
> 
> 
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
>     AVR-Chat-unsubscribe@yahoogroups.com
> 
>  
> 
> 
> 


Happiness is - positive intake manifold pressure.


		
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Good question.

One alternative already suggested is an adapter such as a "surfboard" 
or similar.  The problem is tha amount of square inches required for 
the conversion from smt to 0.1 spacing pins.  All those pins take up a 
huge amount of space!!!!

I just do not see how I can reliably solder all those tiny SMT 
connexions.  I would have to use my loupes for sure.  ALso a new iron 
with the 1/64" tip....

What I have done for my current project is to use a Mavric development 
board piggybacked to what will be my custom PCB which has the voltage 
regulation and glue logic and other specific devices to interract with 
the development board.  So, I am using the development board as a very 
complex (expensive) adapter for the 128, so all I need to do is 
concentrate on the application specific hardware.

Probably I will also make the power supply/regulation separate too.

However, I can see the need to use a socket for a 128 processor to cut 
costs.  Unfortunately the support hardware for the processor is an 
issue as well.

I may well end up using an Olimex board which is square and about 1.5" 
on a side or so.  It has most of the support hardware for the 128. 
(i.e. JTAG, crystals, etc.  It does not appear to have entirely 
adequate AVCC handling from what I saw.   I do not think it has the 
filtering recommended by Atmel.

-Tony


--- In AVR-Chat@yahoogroups.com, "Alex De Lara" <alex_de_lara@y...> 
wrote:

> I just landed on the backyard of the ATmegas and the first prototype
> is already on my sight.. however, as experience has taught me it is
> always good to assemble hardware prototypes in sockets.
> It happens that these ATmegas use 64 pins on MLF and TQFP which 
> there is no easy fit around. Needless to say that it's impossible
> to fit this IC on a protoboard...
> 
> Anyone has had such a hard time like this ? 
> 
> Thanks.

Hello,

From my experience, I've not found it necessary to use a socket when
building a pcb board prototype. The sockets are usually quite large and
costly and you have to design the pcb to handle them. I try to have any bugs
worked out before building pcbs.

My technique is (usually) to use a STK500 and STK501 to carry the m128
processor and wire up the other things by wirewrap, cables, or whatever to
get a platform to do early software and hardware check out.

When I get to building an actual pcb board, it is not necessary to use a
socket on the pcb as the hardware and software are pretty well checked out.
There is always, it seems, changes required for the production board but it
usually is something I forgot or a value change of component.

Best of luck,

Jim


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

From: "Alex De Lara" <alex_de_lara@yahoo.com>
To: <AVR-Chat@yahoogroups.com>
Sent: Thursday, June 09, 2005 9:10 AM
Subject: [AVR-Chat] Any ideas on socket for ATmega128/64 ?


> I just landed on the backyard of the ATmegas and the first prototype
> is already on my sight.. however, as experience has taught me it is
> always good to assemble hardware prototypes in sockets.
> It happens that these ATmegas use 64 pins on MLF and TQFP which
> there is no easy fit around. Needless to say that it's impossible
> to fit this IC on a protoboard...
>
> Anyone has had such a hard time like this ?
>
> Thanks.
>
>
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>

> One alternative already suggested is an adapter such as a "surfboard" 
> or similar.  The problem is tha amount of square inches required for 
> the conversion from smt to 0.1 spacing pins.  All those pins take up a 
> huge amount of space!!!!
> 
> I just do not see how I can reliably solder all those tiny SMT 
> connexions.  I would have to use my loupes for sure.  ALso a new iron 
> with the 1/64" tip....
> 

Tony,

Hand soldering a TQFP is dead simple...  as long as you have the knack.
Have a look at the app notes on the Metcal site for the mini-hoof tips & 
their use in drag soldering. Pace may also have an app note for their 
'mini-wave' tip series. Googling 'drag solder' brings up a squillion hits.

Once you have an idea of the drag soldering technique as used with blade 
& concave tips you will find it quite easy to work with these packages. 
It will take a little practice but you can get this by removing and 
refitting packages on old computer cards. Pull them off with a paint 
stripper gun & then clean up & refit them with your drag technique. 
Using controlled heat it is quite possible to do this cycle > 20 times 
on an FR4 PCB without lifting tracks.

There are a number of concave tips available for common brands of iron 
these days. There was a video of the process on the net ages ago but I 
don't know where ( too much red is bad for the head Ned! )

Key things are:
1. Good heat control
2. Tons of flux
3. Good vision - use bino glasses or even better a cheap stereo microscope

It is much faster to fit a TQFP than it is to hand solder a 64 pin 
adapter package using thru-hole.


Cheers

Don

On Sat, 11 Jun 2005 13:01:56 +1000 you wrote:


>Key things are:
>1. Good heat control
>2. Tons of flux
>3. Good vision - use bino glasses or even better a cheap stereo microscope

http://www.electroniccity.com/shopping/pricelist.asp?prid=951&brandinc=58 is
cheap and useful.
--
Ralph Hilton
http://www.ralphhilton.org
C-Meter: http://www.cmeter.org
FZAOINT http://www.fzaoint.net

Tony, as for your note about soldering them, it's not really that
difficult, do you own a cheap toaster oven?

On 6/10/05, arhodes19044 <spamiam@comcast.net> wrote:
> Good question.
> 
> One alternative already suggested is an adapter such as a "surfboard" 
> or similar.  The problem is tha amount of square inches required for 
> the conversion from smt to 0.1 spacing pins.  All those pins take up a 
> huge amount of space!!!!
> 
> I just do not see how I can reliably solder all those tiny SMT 
> connexions.  I would have to use my loupes for sure.  ALso a new iron 
> with the 1/64" tip....
> 
> What I have done for my current project is to use a Mavric development 
> board piggybacked to what will be my custom PCB which has the voltage 
> regulation and glue logic and other specific devices to interract with 
> the development board.  So, I am using the development board as a very 
> complex (expensive) adapter for the 128, so all I need to do is 
> concentrate on the application specific hardware.
> 
> Probably I will also make the power supply/regulation separate too.
> 
> However, I can see the need to use a socket for a 128 processor to cut 
> costs.  Unfortunately the support hardware for the processor is an 
> issue as well.
> 
> I may well end up using an Olimex board which is square and about 1.5" 
> on a side or so.  It has most of the support hardware for the 128. 
> (i.e. JTAG, crystals, etc.  It does not appear to have entirely 
> adequate AVCC handling from what I saw.   I do not think it has the 
> filtering recommended by Atmel.
> 
> -Tony
> 
> 
> --- In AVR-Chat@yahoogroups.com, "Alex De Lara" <alex_de_lara@y...> 
> 
> wrote:
> > I just landed on the backyard of the ATmegas and the first prototype
> > is already on my sight.. however, as experience has taught me it is
> > always good to assemble hardware prototypes in sockets.
> > It happens that these ATmegas use 64 pins on MLF and TQFP which 
> > there is no easy fit around. Needless to say that it's impossible
> > to fit this IC on a protoboard...
> > 
> > Anyone has had such a hard time like this ? 
> > 
> > Thanks.
> 
> 
> 
> ________________________________
> Yahoo! Groups Links
> 
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Michael Haisley wrote:
> Tony, as for your note about soldering them, it's not really that
> difficult, do you own a cheap toaster oven?
> 


We use both, well a proto reflow oven with profile controller, but a 
word of caution...

Choice of parts that can live in the oven is important, be aware that 
not everything can survive a reflow oven.

The other issue is that the surface finish on component leads degrades 
rapidly. The toaster oven tends to be a more critical process with 
respect to solder wetting and more so on fine TQFP leads. Drag soldering 
under a magnified vision system has the benefit that you tend to perform 
QA testing on the fly thus the first pass level of reliability tends to 
be better.

Pick & place lines are very carefully nurtured to provide low defect 
levels, it is difficult to emulate this in proto systems so inspection 
is king.

Having said this, the toaster oven is great for placing heaps of 
passives. High density packages still tend to be hand placed at our 
operation. A good operator can achieve this reliably at high relative speed.

Failing that, I have seen some interesting results with a paint stripper 
gun and alfoil shields ;-)

Cheers

Don

I will look into drag soldering!  I have the binocular loupes 
covered.  I have a really nice set of loupes.  I can see the detail 
well below my ability to manipulate it, and they have good field of 
view.

THe soldering is the trick.  I will definitely try it with old 
computer cards.  I have enough of those!!!

-Tony

--- In AVR-Chat@yahoogroups.com, Don Ingram <don@l...> wrote:
> 
> > One alternative already suggested is an adapter such as 
a "surfboard" 
> > or similar.  The problem is tha amount of square inches required 
for 
> > the conversion from smt to 0.1 spacing pins.  All those pins 
take up a 
> > huge amount of space!!!!
> > 
> > I just do not see how I can reliably solder all those tiny SMT 
> > connexions.  I would have to use my loupes for sure.  ALso a new 
iron 
> > with the 1/64" tip....
> > 
> 
> Tony,
> 
> Hand soldering a TQFP is dead simple...  as long as you have the 
knack.
> Have a look at the app notes on the Metcal site for the mini-hoof 
tips & 
> their use in drag soldering. Pace may also have an app note for 
their 
> 'mini-wave' tip series. Googling 'drag solder' brings up a 
squillion hits.
> 
> Once you have an idea of the drag soldering technique as used with 
blade 
> & concave tips you will find it quite easy to work with these 
packages. 
> It will take a little practice but you can get this by removing 
and 
> refitting packages on old computer cards. Pull them off with a 
paint 
> stripper gun & then clean up & refit them with your drag 
technique. 
> Using controlled heat it is quite possible to do this cycle > 20 
times 
> on an FR4 PCB without lifting tracks.
> 
> There are a number of concave tips available for common brands of 
iron 
> these days. There was a video of the process on the net ages ago 
but I 
> don't know where ( too much red is bad for the head Ned! )
> 
> Key things are:
> 1. Good heat control
> 2. Tons of flux
> 3. Good vision - use bino glasses or even better a cheap stereo 
microscope

> 
> It is much faster to fit a TQFP than it is to hand solder a 64 pin 
> adapter package using thru-hole.
> 
> 
> Cheers
> 
> Don

arhodes19044 wrote:
> I will look into drag soldering!  I have the binocular loupes 
> covered.  I have a really nice set of loupes.  I can see the detail 
> well below my ability to manipulate it, and they have good field of 
> view.


It amazed me when I started as to how your muscles etc 'servo' to what 
your eyes can see. if you have the magnification for the eyes, the hands 
can do some extremely fine work. On protos I often ended up soldering 
bits of kynar wire onto fine legs of IC,s to add a quick logic analyser 
test socket or the like.

Cheers

Don

> 
> THe soldering is the trick.  I will definitely try it with old 
> computer cards.  I have enough of those!!!
> 
> -Tony
> 
> --- In AVR-Chat@yahoogroups.com, Don Ingram <don@l...> wrote:
> 
>>>One alternative already suggested is an adapter such as 
> 
> a "surfboard" 
> 
>>>or similar.  The problem is tha amount of square inches required 
> 
> for 
> 
>>>the conversion from smt to 0.1 spacing pins.  All those pins 
> 
> take up a 
> 
>>>huge amount of space!!!!
>>>
>>>I just do not see how I can reliably solder all those tiny SMT 
>>>connexions.  I would have to use my loupes for sure.  ALso a new 
> 
> iron 
> 
>>>with the 1/64" tip....
>>>
>>
>>Tony,
>>
>>Hand soldering a TQFP is dead simple...  as long as you have the 
> 
> knack.
> 
>>Have a look at the app notes on the Metcal site for the mini-hoof 
> 
> tips & 
> 
>>their use in drag soldering. Pace may also have an app note for 
> 
> their 
> 
>>'mini-wave' tip series. Googling 'drag solder' brings up a 
> 
> squillion hits.
> 
>>Once you have an idea of the drag soldering technique as used with 
> 
> blade 
> 
>>& concave tips you will find it quite easy to work with these 
> 
> packages. 
> 
>>It will take a little practice but you can get this by removing 
> 
> and 
> 
>>refitting packages on old computer cards. Pull them off with a 
> 
> paint 
> 
>>stripper gun & then clean up & refit them with your drag 
> 
> technique. 
> 
>>Using controlled heat it is quite possible to do this cycle > 20 
> 
> times 
> 
>>on an FR4 PCB without lifting tracks.
>>
>>There are a number of concave tips available for common brands of 
> 
> iron 
> 
>>these days. There was a video of the process on the net ages ago 
> 
> but I 
> 
>>don't know where ( too much red is bad for the head Ned! )
>>
>>Key things are:
>>1. Good heat control
>>2. Tons of flux
>>3. Good vision - use bino glasses or even better a cheap stereo 
> 
> microscope
> 
>>It is much faster to fit a TQFP than it is to hand solder a 64 pin 
>>adapter package using thru-hole.
>>
>>
>>Cheers
>>
>>Don
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

At 01:04 AM 14/06/2005, you wrote:
>I will look into drag soldering!

Do you need to wear outrageous clothes and make up too??
Sorry...could not resist that :-D


Regards

John Samperi

******************************************************
                         Ampertronics Pty. Ltd.
   11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
          Tel. (02) 9674-6495       Fax (02) 9674-8745
                Email: samperi@ampertronics.com.au
                  Website  http://www.ampertronics.com.au
* Electronic Design   * Custom Products   * Contract Assembly
******************************************************

John Samperi wrote:
> At 01:04 AM 14/06/2005, you wrote:
> 
>>I will look into drag soldering!
> 
> 
> Do you need to wear outrageous clothes and make up too??
> Sorry...could not resist that :-D
> 

Not unless Machinery Forum has moved to the Cross ;-)

> 
> Regards
> 
> John Samperi
> 
> ******************************************************
>                          Ampertronics Pty. Ltd.
>    11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
>           Tel. (02) 9674-6495       Fax (02) 9674-8745
>                 Email: samperi@ampertronics.com.au
>                   Website  http://www.ampertronics.com.au
> * Electronic Design   * Custom Products   * Contract Assembly
> ******************************************************
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
>

--- In AVR-Chat@yahoogroups.com, Don Ingram <don@l...> wrote:
> It amazed me when I started as to how your muscles etc 'servo' to 
what 
> your eyes can see. if you have the magnification for the eyes, the 
hands 
> can do some extremely fine work. On protos I often ended up 
soldering 
> bits of kynar wire onto fine legs of IC,s to add a quick logic 
analyser 
> test socket or the like.


yes, I have done some extremely fine work with sufficient 
magnification.  The finest work I ever did was dissecting one layer 
of nerve cells from another in a retina.  I forget what 
magnification it was, but it was quite tedious.

I also found that fine motor tremor was noticeably worse if I had 
even one beer the night before.  Since I did that work on weekends 
(in college), it put a crimp in my partying.

The loupes I currently use have much less magnification, but with my 
crude soldering iron.....  it has more than enough mag.

I was considering getting a 1/64" tip for an iron, but now I think 
that something slightly wider (chisel tip shape) may be better 
for "drag soldering".

I still have not found a good reference on the technique of drag 
soldering?  I t seems as if the technique is to make a blob of 
solder and drag it across all the pads on one side of the chip.  I 
guess the solder mask prevents bridging?  I would have thought that 
all the pins would just get shorted together in one big glom of 
solder....

-Tony

On Tue, 14 Jun 2005 12:28:22 -0000 you wrote:

>--- In AVR-Chat@yahoogroups.com, Don Ingram <don@l...> wrote:
>> It amazed me when I started as to how your muscles etc 'servo' to 
>what 
>> your eyes can see. if you have the magnification for the eyes, the 
>hands 
>> can do some extremely fine work. On protos I often ended up 
>soldering 
>> bits of kynar wire onto fine legs of IC,s to add a quick logic 
>analyser 
>> test socket or the like.
>
>
>yes, I have done some extremely fine work with sufficient 
>magnification.  The finest work I ever did was dissecting one layer 
>of nerve cells from another in a retina.  I forget what 
>magnification it was, but it was quite tedious.
>
>I also found that fine motor tremor was noticeably worse if I had 
>even one beer the night before.  Since I did that work on weekends 
>(in college), it put a crimp in my partying.

Vitamin B1 and calcium/magnesium supplements seem to help with that :-)

>The loupes I currently use have much less magnification, but with my 
>crude soldering iron.....  it has more than enough mag.
>
>I was considering getting a 1/64" tip for an iron, but now I think 
>that something slightly wider (chisel tip shape) may be better 
>for "drag soldering".
>
>I still have not found a good reference on the technique of drag 
>soldering?  I t seems as if the technique is to make a blob of 
>solder and drag it across all the pads on one side of the chip.  I 
>guess the solder mask prevents bridging?  I would have thought that 
>all the pins would just get shorted together in one big glom of 
>solder....

A few sizes of solder wick seem essential for cleaning up the globs.
--
Ralph Hilton
http://www.ralphhilton.org
C-Meter: http://www.cmeter.org
FZAOINT http://www.fzaoint.net

On Fri, 10 Jun 2005 16:23:45 -0000 you wrote:

>I may well end up using an Olimex board which is square and about 1.5" 
>on a side or so.  It has most of the support hardware for the 128. 
>(i.e. JTAG, crystals, etc.  It does not appear to have entirely 
>adequate AVCC handling from what I saw.   I do not think it has the 
>filtering recommended by Atmel.

I have used those boards and the AVCC connections seem adequate for normal
requirements. At 10 bits ADC output is stable.
--
Ralph Hilton
http://www.ralphhilton.org
C-Meter: http://www.cmeter.org
FZAOINT http://www.fzaoint.net

> 
> I was considering getting a 1/64" tip for an iron, but now I think 
> that something slightly wider (chisel tip shape) may be better 
> for "drag soldering".
> 
> I still have not found a good reference on the technique of drag 
> soldering?  I t seems as if the technique is to make a blob of 
> solder and drag it across all the pads on one side of the chip.  I 
> guess the solder mask prevents bridging?  I would have thought that 
> all the pins would just get shorted together in one big glom of 
> solder....
> 
> -Tony

The thermal mass of the iron tip & the flux are both important. This is 
why the minihoof and blade tips are used.  The concave in the mini-hoof 
will tend to draw the solder back to the tip, the sheer mass of the 
blade will also draw solder away from the joint. The flux will provide 
the thermal bridge and combination of the two will cause the joint to 
draw enough solder to form a joint but no more.

As you work along the chip with the 'blob' you will see it wet out and 
bridge pins at the leading edge while'snapping' away from pins at the 
trailing edge, leaving a good joint.

Be careful at the last few pins along each side as it is easy to leave a 
bridge on these.

The thing with magnification is that it gives you a very good idea of 
the subtlties what is happening so that you can refine your technique 
and later work with lower magnification.


-- 
Cheers

Don

> 
> 
> A few sizes of solder wick seem essential for cleaning up the globs.
> --

Or some flux and a miniwave tip.

We have no solder wick on the premises. I think it came from the old 
days when you forgot you still had your finger on the trigger on the 
mini-scope ( sorry kids that was back in the 60's ) iron & proceeded to 
lift the tracks as well.

Obviously by the roaring sales in solder wick the rest of the Planet 
feels differently ;-)


-- 
Cheers

Don

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

From: "arhodes19044" <spamiam@comcast.net>
To: <AVR-Chat@yahoogroups.com>
Sent: Tuesday, June 14, 2005 1:28 PM
Subject: [AVR-Chat] Re: Any ideas on socket for ATmega128/64 ? - Drag 
soldering


> --- In AVR-Chat@yahoogroups.com, Don Ingram <don@l...> wrote:
>> It amazed me when I started as to how your muscles etc 'servo' to
> what
>> your eyes can see. if you have the magnification for the eyes, the
> hands
>> can do some extremely fine work. On protos I often ended up
> soldering
>> bits of kynar wire onto fine legs of IC,s to add a quick logic
> analyser
>> test socket or the like.
>
>
> yes, I have done some extremely fine work with sufficient
> magnification.  The finest work I ever did was dissecting one layer
> of nerve cells from another in a retina.  I forget what
> magnification it was, but it was quite tedious.
>
> I also found that fine motor tremor was noticeably worse if I had
> even one beer the night before.  Since I did that work on weekends
> (in college), it put a crimp in my partying.
>
> The loupes I currently use have much less magnification, but with my
> crude soldering iron.....  it has more than enough mag.
>
> I was considering getting a 1/64" tip for an iron, but now I think
> that something slightly wider (chisel tip shape) may be better
> for "drag soldering".
>
> I still have not found a good reference on the technique of drag
> soldering?  I t seems as if the technique is to make a blob of
> solder and drag it across all the pads on one side of the chip.  I
> guess the solder mask prevents bridging?  I would have thought that
> all the pins would just get shorted together in one big glom of
> solder....

The trick is to use plenty of liquid flux. It helps if you have a special 
tip like Metcal's 'mini-hoof' which is made specifically for drag soldering:

http://www.metcal.com/tips/minhoof2.html#fine

Leon 


---
[This E-mail has been scanned for viruses but it is your responsibility 
to maintain up to date anti virus software on the device that you are
currently using to read this email. ]

I was at a hamfest a couple weeks ago and one person had a big box of 
solder wick rolls, 3 different sizes.  They were 4 for a dollar (quite a 
deal, actually).  I bought a handful of them.

He had sold the whole box in a couple hours.  This told me that building 
equipment (homebrew, as we say in ham radio) isn't dead yet, and that 
there are people out there who still know what solder wick is.

Zack W9SZ

On Tue, 14 Jun 2005, Don Ingram wrote:

> 
> Obviously by the roaring sales in solder wick the rest of the Planet
> feels differently ;-)
> 
> 
> --
> Cheers
> 
> Don
>

> 
> The trick is to use plenty of liquid flux. It helps if you have a special 
> tip like Metcal's 'mini-hoof' which is made specifically for drag soldering:
> 
> http://www.metcal.com/tips/minhoof2.html#fine
> 
> Leon 
> 
> 

A word of caution here too. We have found that the smallest concave tip 
is very rarely used, & a lot is done on 0.5mm & 0.65mm pitch TQFP's.

There are two main issues to consider with the miniwave tips. One is the 
thermal mass & the other is the solder reservoir capacity. I find that 
the best tip tends to be the one which just fits into the space between 
the edge of the IC & the passives at the periphery. That way I can do 2 
or 3 edges without restocking the tip & the higher thermal mass tends to 
provide a better joint with less bridging than the finest tip.

Sounds a bit frack to bunt but as I said earlier it is well worth 
finding big eyes at first to get a good feel for the process until you 
get the knack.

Similarly a huge blade tip is the last thing that you would expect to 
use but they too are quite good for drag soldering.

Get enough practice & you can graduate to the heated edge of a
garden shovel ;-)



-- 
Cheers

Don

Hi Tony,

On Tue, Jun 14, 2005 at 12:28:22PM -0000, arhodes19044 wrote:

> I still have not found a good reference on the technique of drag
> soldering?  I t seems as if the technique is to make a blob of
> solder and drag it across all the pads on one side of the chip.  I
> guess the solder mask prevents bridging?  I would have thought that
> all the pins would just get shorted together in one big glom of
> solder....

What I've found works best is to use a flux pen like this from Digikey:

  http://www.digikey.com/scripts/DkSearch/dksus.dll?PName?Name=KE1808-ND

It looks kind've like a highlighter.  First position the part and
while holding it in place, wet the leads on one side with the flux pen
and with a hot iron, tack the part in place - there will be enough
solder on the PCB to do this without adding any at this point.  Then
use the pen to wet all the leads.  With the part tacked down and all
the pins wetted with flux, use some 0.015" solder and lay it across
the pins, then drag the hot soldering iron across the solder and the
pins.  Control the amount of solder by pulling the solder away a
little as you drag the iron.  As long as you don't completely go
overboard on the solder, just enough will be applied to all the pins
and you won't have any bridges.  If you do find you have a bridge, it
will usually be on the last few pins.  With your soldering iron,
"comb" the tip on the pins dragging the solder toward the pin tips.
If there is a nearby via, you can dump the solder into the via,
clearing the bridge.  Otherwise, try adding a little flux if necessary
and redistribute the extra solder among the other pins by dragging
back in the other direction.

It's really very easy and takes only a little bit of practice before
you are an expert.  I just use a pretty standard 4x magnifying visor
which is plenty for me.

Don't forget to wash the board other wise the flux might react with
the copper or components.  I use water soluble flux and solder with
water soluble flux core which makes clean up with hot water and a
small brush easy.  Rinse in deionized water and air dry.

-Brian
-- 
Brian Dean
http://www.bdmicro.com/