Hi Wee Mei,
First off, thanks for the kind words. Necessity is the mother of invention,
and I don't think I'm doing anything special that anybody else wouldn't do when
faced with similar circumstances. I just like to let everyone know that these
Flextac stencils really do work, and do a very good job at it.
No this wasn't tacky flux that I was talking about, but a pressure sensitive
adhesive on the stencil itself. This provides for very good gasketing of the
stencil to the substrate.
I needed to print paste since the PowerPC BGA is a ceramic device and has
high temp solder balls. If the solder balls were standard 63/37 eutectic balls,
then yes, tacky flux would be applied, instead of solder paste. The high temp
balled devices need some solder paste applied since they don't collapse and wet
to the pads like eutectic balls do.
-Steve Gregory-
Steve,
Thanks for the sharing. You has never failed us with your
innovativeness. It is a very wonderful process.
By the way, I would like to check with you regarding the contact
adhesive mentioned below. Is it anyway also known as "tacky flux"? The
use of this tacky flux is not something new, right? I am sure tacky flux
has been in use for sometime to replace solder paster to mount PBGAs.
Regards,
Wee Mei
Steve Gregory wrote:
>Hi All!
>
>Most of the time when I post, I've got some sort of problem. Well, today is
>different.
>Not only is it Monday, but I actually had a success today with something that
>I had originally thought was going to be a problem.
>
>One of the Project Engineers came to me last week and asked me for a
>favor...I usually run away, but I went ahead and asked; "What kind of favor?"
>"Oh just help me figure out how to solder a part to an adapter..." I said;
>"you don't need me for that. He said; "Oh yes I do..."
>
>He then hands me a 256-ball, PowerPC BGA, and then this little 1" square BGA
>to PGA adapter and asks; "Can you solder the BGA to the adapter for me?" You
>can see the adapter and BGA at http://www.stevezeva.homestead.com and look at
>"Socket & Power PC and Socket & Power PC2"
>
>I said; "Just how in the heck am I going to do that?" He said; "That's why I
>came to you, you always figure something out."
>
>To make a long story short, I did. I want to preface what I have to say by
>stating that I have no interest in Circuit Technology Center, nor have I been
>asked to post anything on the Technet about this. But their Flextac stencils
>really work! This was my first time using them. I could have possibly gotten
a
>stainless steel stencil made, but then I would have had to figure out some
way
>to fixture everything to be able to print paste on the socket, but with these
>flextac stencils with the contact adhesive (kinda like post-it notes
adhesive)
>this was really simple.
>
>I posted pictures of the whole thing on my page. There's a picture with the
>stencil mounted on the socket, followed by a picture of the actual paste
print
>(picture is a little fuzzy), followed by the BGA placement (I did that with
my
>rework machine. I have a PDR Lightmaster Pro), and finally followed by reflow
>with the focused Infrared light. Lastly, there's a picture of the finished
>piece...
>
>Just like to post about the good things that go right once inna' while...
>
>-Steve Gregory-
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