Homebrew PCBs

The problem with all of the suggestions made so far is that everyone 
is assuming that the pads already have solder on them.

But this is a brand-new home-made board with bare copper pads.

The first step is to tin all of the pads.  Use lots of flux - gel or 
paste flux works best but standard liquid flux will also work.  Flood 
all of the pads with solder, then apply more liquid flux on top of 
the solder blobs.  Hold the board vertically with the pads vertical, 
then use a soldering iron to draw the solder down to the ends of the 
pads and on to the tip.  Rotate the board 90 degrees and repeat until 
all of the pads are tinned and cleaned.  The pads should now have a 
thin, smooth layer of solder on top of the copper.

Do a very good inspection with magnification to ensure that you don't 
have any solder bridges.  Then follow the (excellent) advice already given.

Hope this helps!

dwayne

PS - we used to make hundreds and hundreds of our own PCB's in the 
early days of our business.  We would clean the boards mechanically 
with a fine-grit sander followed by a 3-step chemical cleaning 
process.  Blow the boards dry with warm air from a vacuum-cleaner 
motor, then feed the boards through a GBC laminater (modified for 
lower temperature and higher speed) loaded up with Dupont Riston 
dry-laminate film.  Exposed the boards with a modified mercury-vapor 
expose lamp and vacuum frame, then developed the exposed boards with 
a soda-ash (potassium carbonate?) solution.  Stripped the remaining 
laminate in a caustic-soda (sodium hydroxide) bath, rinsed, then 
etched in an Ammonium Persulphate bubble etch tank.

The whole process worked very well but it just took too much 
time.  We eventually went to CNC milling for PCB prototypes (several 
years), then quit that and just started using APC for prototype 
boards.  All of our production boards are now made in China - the 
quality is extremely high and the cost is astonishingly low.  APC 
still does our prototype boards.

dwayne


At 02:29 AM 11/7/2014, Dylan Smith dyls@... [Homebrew_PCBs] wrote:

>I find that it makes no difference and trying to apply to the pads 
>only is a frustrating waste of time.
>I just use a flux pen and draw over all the pads.
>
>I also use kapton tape to hold the IC down for soldering rather than 
>trying to tack corners down. You can stick the tape to the top of 
>the IC and hold the tape to align and once the pins are nicely all 
>on their pads, press the tape down onto the PCB. Then just drag 
>solder the two exposed sides, remove the tape, and solder the 
>remaining two sides.
>
>On 07/11/2014 09:12, Phil Quinton 
><mailto:phil.quinton@...>phil.quinton@... 
>  [Homebrew_PCBs] wrote:
>>James,
>>
>>Thanks for the reply.
>>
>>Do I need to keep the flux just on the pads ( appears fiddly ), or 
>>can I just apply to the whole of the pads as a "square" of flux?
>>
>>Am I correct in thinking that the latter would end up with more 
>>solder bridges due to the solder flowing between the pins due to 
>>the flux being between the pins?


-- 
Dwayne Reid   <dwayner@...>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing