Philips L04E Service Manual page 5

2.3.3
Rework on BGA (Ball Grid Array) ICs
General
Although (LF)BGA assembly yields are very high, there may
still be a requirement for component rework. By rework, we
mean the process of removing the component from the PWB
and replacing it with a new component. If an (LF)BGA is
removed from a PWB, the solder balls of the component are
deformed drastically so the removed (LF)BGA has to be
discarded.
Device Removal
As is the case with any component that, it is essential when
removing an (LF)BGA, the board, tracks, solder lands, or
surrounding components are not damaged. To remove an
(LF)BGA, the board must be uniformly heated to a temperature
close to the reflow soldering temperature. A uniform
temperature reduces the chance of warping the PWB.
To do this, we recommend that the board is heated until it is
certain that all the joints are molten. Then carefully pull the
component off the board with a vacuum nozzle. For the
appropriate temperature profiles, see the IC data sheet.
Area Preparation
When the component has been removed, the vacant IC area
must be cleaned before replacing the (LF)BGA.
Removing an IC often leaves varying amounts of solder on the
mounting lands. This excessive solder can be removed with
either a solder sucker or solder wick. The remaining flux can be
removed with a brush and cleaning agent.
After the board is properly cleaned and inspected, apply flux on
the solder lands and on the connection balls of the (LF)BGA.
Note: Do not apply solder paste, as this has shown to result in
problems during re-soldering.
Device Replacement
The last step in the repair process is to solder the new
component on the board. Ideally, the (LF)BGA should be
aligned under a microscope or magnifying glass. If this is not
possible, try to align the (LF)BGA with any board markers.
To reflow the solder, apply a temperature profile according to
the IC data sheet. So as not to damage neighbouring
components, it may be necessary to reduce some
temperatures and times.
More Information
For more information on how to handle BGA devices, visit this
URL: www.atyourservice.ce.philips.com (needs subscription,
not available for all regions) ). After login, select "Magazine",
then go to "Workshop Information". Here you will find
Information on how to deal with BGA-ICs.
2.3.4
Lead Free Solder
Some PWBs in this chassis are "lead-free prepared". This is
indicated on the PWB by the PHILIPS lead-free logo (either by
a service-printing or by a sticker). It does not mean that lead-
free solder is actually used!
Figure 2-3 Lead-free logo
Due to this fact, some rules have to be respected by the
workshop during a repair:
•
Use only lead-free soldering tin Philips SAC305 with order
code 0622 149 00106. If lead-free solder paste is required,
please contact the manufacturer of your soldering
equipment.
Safety Instructions, Warnings, and Notes
P
b
L04E AB
•
Use only adequate solder tools applicable for lead-free
soldering tin.
•
Adjust your solder tool so that a temperature around 217 -
220 deg. C is reached at the solder joint.
•
Do not mix lead-free soldering tin with leaded soldering tin;
this will lead to unreliable solder joints!
•
Use only original spare parts listed in this manual. These
are lead-free parts!
•
On the website www.atyourservice.ce.philips.com
subscription, not available for all regions) you can find
more information on:
–
Aspects of lead-free technology.
–
BGA (de-)soldering, heating-profiles of BGAs used in
Philips sets, and others.
2.3.5
Practical Service Precautions
•
It makes sense to avoid exposure to electrical shock.
While some sources are expected to have a possible
dangerous impact, others of quite high potential are of
limited current and are sometimes held in less regard.
•
Always respect voltages. While some may not be
dangerous in themselves, they can cause unexpected
reactions - reactions that are best avoided. Before reaching
into a powered TV set, it is best to test the high voltage
insulation. It is easy to do, and is a good service precaution.
2. EN 5
(needs