Wow, what a great idea!
I have been doing rework for over 14 years and but sometimes you lose your
creativity in solving a problem.
I have little doubt that your idea will not work.
Thank you for such a wonderful suggestion :)
David Tremmel
Technical Manager
Belmont Component Services
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of JaMi Smith
Sent: Monday, April 05, 2004 2:08 AM
To: [log in to unmask]
Subject: Re: [TN] BGA socket placement
David,
You say "The parts I want to replace are BGA CPU sockets (Pentium 4, Socket
478)",
and from this I assume that you are going to have to remove the existing
sockets /
parts, which I assume will be done with some sort of hot air removal tool.
It has been my experience that if you use a liberal amount of rosen flux in
the
removal process, that you will be left with a small and very uniform amount
of
solder on each of the existing pads on the board, and yes, a lot of rosin
too, but
the rosin is the key to the process, and it can be cleaned up after the
fact.
This is usually just about the right amount of solder to remount the new
part,
without having to tough up any of the pads, and without having to clean
(solderwick)
all of the existing solder off of the pads and then either re-apply
additional
solder paste vial a screen or via some other method.
In other words, if you use a lot of flux, and you are very careful in
removing the
old part, what you are left with is just the right amount of solder on the
pads to
go ahead and directly install the new part with out doing anything else at
all.
Yes, this is tricky, but it is worth a try to see if you can remove the old
parts
and leave just enough solder behind, and yes the flux is messy also, but
after you
remove the old part and inspect the pads, if you are not happy, and do not
think
that it will work, then you can go ahead and clean (solderwick) off all the
excess
solder from the pads and go about trying some of the other suggestions to
place the
new part, and you will have lost nothing.
JaMi Smith
----- Original Message -----
From: "David Tremmel" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, April 02, 2004 11:35 AM
Subject: Re: [TN] BGA socket placement
> Mr. Gregory,
>
> I would like to use a pre-formed tab to minimize labor costs and to
> compensate for the 'lack of dexterity' the people who will actually be
doing
> the rework have (or don't have).
>
> As far as 'wanting to add extra volume to the spheres' I think that I lack
> the eloquence (or technical wordage) to put it differently ;)
>
> The parts I want to replace are BGA CPU sockets (Pentium 4, Socket 478)
> which have SMD capacitors soldered to the PCB, in the center area of the
> socket. A preformed tab, if such a beast exists, would save us the
> time/cost of removing/replacement the components to avoid stencil co
> planarity issues.
>
> Thank you for your response.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> Sent: Friday, April 02, 2004 12:18 PM
> To: [log in to unmask]
> Subject: Re: [TN] BGA socket placement
>
> Hi David!
>
> Not sure quite you mean when you say; "Pre-formed tab to add extra volume
to
> the spheres." Can you elaborate further?
>
> You also say that you want to avoid adding solder paste, can I ask why? If
> the ball-pitch, ball count, and ball pattern is pretty standard, you can
buy
> 10
> Flextac stencils from Circuit Technonolgy Center for around $50. They work
> wonderfully too! Go to:
>
> http://www.circuittechctr.com/products/201-3120.shtml
>
> and check them out. I've got pictures up on my page of me using one to
> solder
> a Power PC BGA to a SMT-to-PTH adapter, which I'm sure if there wasn't
> something like Flextac stencils around, would have been a real bear to do.
>
> Give us a few more details...
>
> -Steve Gregory-
>
>
> > Hello Technetters,
> >
> > I have some BGA sockets which I am trying to solder to PCBs.
> >
> > The sockets have stand-offs which prevent the solder spheres from
> collapsing
> > and making a good mechanical/electrical connection.
> >
> > Ideally what I am looking for is a pre-formed tab to add extra volume to
> the
> > spheres. I do not have an in-house machine shop to make a stencil to
> apply
> > paste and quite frankly I would like to avoid that course if possible.
> >
> > Thank you in advance for your help,
> >
> > David Tremmel
> > Technical Manager
> > Belmont Component Services
> >
>
>
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