On Dec 5, 2:42 am, " wrote:
On Dec 2, 10:18 pm, "Tony Burch" wrote:

Hi all,

I have just released a new site about low cost soldering techniqueshttp://SuperSolderingSecrets.com

It's a set of videos intended for hobbyists and small companies.

There is a free membership with 5 videos on hand soldering quad flat packs.
There is also a "gold" membership with videos on "toaster oven soldering",
"frying pan solder pot soldering", removal of flux residue etc.

Cheers,

Anthony Burch

Why do you think all this is so "secret"? My assemblers do all you
mention as well as LGA chips and BGA and all using lead-free solder.
Can you do that?

Paul

Well this is a discussion group, so the disadvantage of posting on
here if you're trying to sell something is that you put the whole
topic up for comment!

So why not put forward ideas.

The biggest mistake any beginner makes is to try to solder surface
mount components like they are through hole, and many people think you
just need a very fine tip soldering iron (which just results in little
heat transfer and frustrating soldering by the way).

Your biggest friend is flux, I prefer a flux pen as its controllable.
Some people use spray flux but personally I find that messy, though it
works. Flux is such a good friend because it helps the solder
adhere. More importantly it gives the solder mobility, which means
that you can remove solder bridges between pins just by applying flux
and putting a clean soldering iron on.

Always start with larger components. Because if you get it wrong the
easiest way of removing larger components (without a desoldering
station) is with a heat gun (hot air paint stripper). And this will
blow away any smaller components you already have placed....very
annoying.

Before you do any surface mount soldering always use the flux pen to
flux the pad. If you have a home made PCB its good to abraid the
surface with fine emery paper, clean with flux cleaner (a electrical
cleaning solvent spray usually has a brush with it) before fluxing,
and if you really want the best tin by running the soldering over the
fluxed pads with a small amount of solder. If you tin the pads you
need to make sure you dont have an uneven surface as surface mount
components need to be flat to solder correctly. In this case put more
of the trusty flux on the pads...get some de-solder braid, run it
around the pads hot with the soldering iron on it, this will flatten
the solder again. Usually with a clean pad without tin is fine if
you've cleaned and fluxed, but sometimes on a home made bare copper
board applying heat to adjacent pins causes the already cleaned pads
to oxidise so they need cleaning again.

SOICs: These are easy, they are relatively large pitch. After
preparing the pads, put a little bit of solder on you iron, place the
chip on the pads, hold it still and dab one corner pin with the
iron...this is just enough to fix the device in place. Go to the
other corner and dab again. Then run the flux pen over the other pins
and solder as you would any component, just use solder sparingly. If
you end up with a solder bridge, make sure the tip of the soldering
iron is clean, reflux the pins that have a poblem, and move the
soldering iron tip down onto the joint and then away across the
board. Surface tension and the flux will pull solder from the bridge
to the iron. If theres still solder bridging, reflux, clean the iron
on the sponge and do it again. The flux is useless when it burns off,
so dont hold the iron on the joint for ages...or it wont work, you
will get a knack for it...just long enough to melt the solder and a
little bit.

Solderpaste method: Solderpaste is available in small syringes and
comes with a small tip that allows you to put down a fine bead of
solder. I find you need to widen it a little, but if you overdo it
you will end up with huge amounts of uncontrolled paste all over your
board and you will have to buy another tip. Solderpaste is expensive,
but it goes a long way. Frustratingly it also "goes off" and gets
unusable after a time and when exposed to the air, so if you havent
use it in a week you may find the nozzle blocked, put some tape over
the end in an attempt to stop air getting in. Your supposed to keep
solder paste in the fridge...though I dont.

On you SOIC, flux the pad, wait a moment so the flux isnt wet, then
dab a small bit of solder paste on the pads. Again you will need some
practice. Then carefully place the soic the pads, hold and put the
tip of your soldering iron on a corner joint. You should be able to
run round all the joints now and each pad usually solders without
bridging as theres lots of flux in the paste aswell. (the reason for
pre-fluxing the pin is that it makes it slightly sticky, otherwise the
bead of paste can slide off the pad!).

Using solderpaste and a small heat gun: Pros use a hot air station
which can control the heat and amount of blow, and have a small nozzle
to direct the blow. If you have access to one of these you turn the
blow down low...otherwise the gael wil blow your components off the
board. With the component sitting on the solder paste prepared pads
just apply heat until the solder melts. You can also use those
portable soldering irons with the heat blow option tip, this has a
catalyst so there is no flame (you dont want a flame on your board of
course).

Soldering larger QFP type devices: You can use the solderpaste and
the above method for soldering these too. However, here is a
soldering iron method I learned from a guy who re-worked PCBs on a
production line.
Prepare the pads with flux. Place the part down, hold it and use the
iron to tack down the corner pins. This is important...if you get the
1st tack wrong you can heat it up and remove the component...if you
get more than one area partially soldered you will need a hot air heat
gun to remove it!!!
Once the part is positioned and tacked, go over the pins with the flux
pen. Then take the hot soldering iron (you need a good 25W+ iron with
a flat tip for max heat transfer as this method relys on not holding
the iron in a fixed spot).
Orient the board with a strip of pins on the right (if your right
handed), put the iron on the top with a little solder and then win a
smooth movement take the solder tip back and forth (left to right)
across the pins as you move smoothly and fairly fast down the row of
pins. You will notice the surface tension of the solder and the flux
cause the solder blob to move down with the iron. The left right
movement allows the solder to move up over the pad and pin, while the
movement down the row pulls the solder blob down leaving cleanly
soldered pins. It looks like a machines had soldered them.
Now often you will leave solder bridges where the flux has got
overheated and stops working, and there will usually be a blob at the
bottom of the row...but dont worry. Now reflux the row, clean the
soldering iron tip and place the tip on the solder bridge moving it
off to the right one the solder has melted. Clean the tip reflux and
do again until the bridge is removed. You may have to do this several
times if you put too much solder on in the first place.
You can also start with solder paste on the pads (rather than using
normal solder), but sometimes I find you can get bridges under the
chip if you do this. After doing all the pins inspect with a
magnifying glass.
This is how I put down all fine pitch devices, its a knack but can be
very fast and clean when you get it sorted.

Small devices like 0602, 0805 components: You can solder these with a
soldering iron and tweezers, though it is fiddly. You can to hold the
device down with tweezers and dab the end with the soldering iron.
Put solder paste on the pad makes it easier...though I find this
frustrating as most of the time the heat moves through the component
and you end up with it sitting on the end of your soldering iron tip!
Better to flux and dab a small amount of solder paste on the pads,
place the part on the pads (it will stay there due to the tackiness of
the paste) then use gas soldering iron on hot air blow (no flame!) to
gently melt the solder. Better, use a hot air soldering station with
the air volume turned down low.
You cant use a paint stripper type hot air gun for this as there is
too much air coming out and your parts will all be blown away!


I hope thats useful. Any one else have tips and tricks for this?

Andy