Pat,
I needed a small reflow oven to support some small engineering tasks and I
wanted something a little better than a toaster oven.
Check Out: a T962 on Ebay
http://www.ebay.com/itm/T-962A-Heater-Infrared-Reflow-Wave-Oven-962A-300m-T9
62A-/190754534967?pt=LH_DefaultDomain_0&hash=item2c69db3637
It took a little time decoding the "Manual" but it works fine. I am not a
fan of IR but after setting up my own profile it does OK. Definitly a lot of
bang for the money.
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Goodyear, Patrick
Sent: Wednesday, November 14, 2012 3:26 PM
To: [log in to unmask]
Subject: Re: [TN] Reflux and reflow BGA rework
Thanks all, these and earlier posts give me the confidence to try it. I
don't have a reflow oven but plan on using a small convection toaster oven
to do the deed, it will go to 600deg, nice thing about the toaster is it
heats both sides.
The board is already toast so I might as well butter it up and see what
happens. This is for a non-work related job, I had a computer board go
intermittent after some temperature cycles, suspect a cracked solder joint
on one of the chips. I already have a replacement this is a learning
experience, hopefully I will be smarter in the end. Learning is doing.
I will heat it slowly then bake it for a few minutes, then allow natural
cooling.
Thanks again!
Pat
-----Original Message-----
From: Amol Kane [mailto:[log in to unmask]]
Sent: Wednesday, November 14, 2012 10:13 AM
To: TechNet E-Mail Forum; Goodyear, Patrick
Subject: RE: [TN] Reflux and reflow BGA rework
Patrick,
if you have any heavy components directly underneath the part you are
trying to rework, then they may potentially come off if the component weight
overcomes the surface tension forces. The components on the rest of the
board on the bottom side should be OK as they will not be heated to reflow
temperatures with a well-designed rework profile. You can always add a tiny
chip bonder/epoxy bead (Loctite 3609 comes to mind) to keep such components
on the board during rework. The curing time/temp of chip bonders is such
that they cure first before the solder hits reflow temperatures.
The following is a thumb rule I picked up from technet by EMPF you can use
to gauge if you need the epoxy application:
Here is the rule of thumb from the EMPF Boot Camp: Four grams per square
centimeter (25 gm/inch^2) of solderable surface area on the device or board,
which ever is less.
Regards,
Amol
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Goodyear, Patrick
Sent: Wednesday, November 14, 2012 9:08 AM
To: [log in to unmask]
Subject: Re: [TN] Reflux and reflow BGA rework
Ok since I have less than zero experience on this subject so my knowledge
level is nil at best I have a question. No laughing since I really don't
have a clue.
I have a double sided board, that needs a BGA reflow, has high density chips
on both sides, how is it positioned so that the chips on the down side
remain on the board? Can Kapton tape be used to hold the chips in place?
Does the weight of the board hold them in place? What about the chips that
have a lower profile? As you can surmise I have a potential project but I'm
completely clueless.
Pat
Clueless in Los Osos
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, November 14, 2012 8:06 AM
To: [log in to unmask]
Subject: Re: [TN] Reflux and reflow BGA rework
Absolutely agree with that. You need to understand if you have a plating
issue or some other issue that will prevent good soldering. But if you have
a BGA that is slightly skewed, for example, or was the subject of an
improper profile (insufficient heat) during initial reflow, or some other
process issue, then you can use the method I described.
But absolutely, you need to understand the root cause of the defect before
you blindly start reflowing BGAs.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Wednesday, November 14, 2012 9:28 AM
To: [log in to unmask]
Subject: Re: [TN] Reflux and reflow BGA rework
Hi George - good discussion and I completely agree. I should have been more
detailed in my response. We do not use the "reflux and reflow"
process as a routine procedure. As you detailed, we do a root cause
investigation and do not allow the process to be used without some due
diligence. And as Richard detailed in his response, our "reflux and reflow"
process is a detailed process with specific procedure steps that must be
used. Use of the "reflux and reflow" process without conscious thought can
get you into trouble as you suggested. A good example was one case where we
found that a lot of boards had crack microvias in the BGA pads so when the
BGA was reflowed, the solder electrically "reconnected"
the microvia giving the impression that there was a bad solder joint when in
fact there was a bad microvia fabrication process. I agree with you -
blindly using a "reflux and reflow" process can be dangerous practice.
Dave
From: "Wenger, George M." <[log in to unmask]>
To: <[log in to unmask]>
Date: 11/13/2012 09:30 PM
Subject: Re: [TN] Reflux and reflow BGA rework
Sent by: TechNet <[log in to unmask]>
Julie / Dave,
I'm going to stick my neck out and say that injecting flux and re-reflowing
is a risky repair process. You may be able to make a part that wasn't
working work again but just because it works again doesn't mean you have
reliable solder interconnections. I'm aware of a case were injecting flux
and re-reflowing did fix PCBA product well enough to pass functional test
and those "fixed" boards failed after being deployed. The problem with
"fixing" non-working BGAs is that the non-working BGAs may have been "fixed"
but you don't know what was "fixed" and you don't know how good the "fix"
is.
Before fixing any non-working BGAs I think the important thing to do first
is identify what you are trying to fix. Is the BGA non-working because of
Head-n-Pillow, Double Reflow, Insufficient solder paste dispensing, Plugged
stencil aperture and no dispensed solder paste, Poor wetting, De-wetting,
etc.
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer Andrew Corporation - Wireless
Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Tuesday, November 13, 2012 9:22 AM
To: [log in to unmask]
Subject: Re: [TN] Reflux and reflow BGA rework
Hi Julie - I don't know of any standards that cover this topic unless there
is something in the IPC-7711 specification. When we use our BGA repair
procedure, we use specific fluxes that are easily removed and we are very
conscious about the volume of flux used. "Bigger the glob, better the job"
is not a applicable process philosophy when utilizing fluxes for BGA repair.
Our focus for the process is to insure that we are using flux in such a way
that we don't cause a reliability issue that was not there prior to our BGA
repair actions. The example we discussed of the flux packed under the BGA in
the previous Technet thread is a classic case of not understanding how much
flux was necessary for successful BGA repair.
Dave Hillman
Rockwell Collins
[log in to unmask]
From: Julie Silk <[log in to unmask]>
To: <[log in to unmask]>
Date: 11/13/2012 07:51 AM
Subject: [TN] Reflux and reflow BGA rework
Sent by: TechNet <[log in to unmask]>
A discussion of the practice of re-flux and reflow of BGAs to rework them
has emerged within the "limits of flux residue" discussion. I'm taking it
out into a separate thread. This rework process injects flux under the BGA,
then reflows the BGA. The part is not removed. It will frequently make a
part that wasn't working work again. The heat damage to the board is less
(fewer cycles) than a replacement process. The question Joyce asked about
whether there are standards and reliability studies has not been answered.
What is the proper procedure for this rework process? Are there official
standards? Studies of effectiveness / reliability?
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