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|December 18, 2014
Circulation Over 51,000
|Delamination Causing Scrap |
|We have been experiencing delamination on our printed board assemblies causing scrap. Is there a way to definitively determine that the delamination is being caused by moisture vs. some other type of defect? Is it possible to repair delamination in printed board assemblies?|
The #1 cause of delamination is moisture. And by-far. While
other failure modes exist (e.g., inadequate bonding layer cure) they do not
appear in the Book of Usual Suspects.
The repair of delaminated PCBs cannot be recommended.
The IPC-1601 PRINTED BOARD HANDLING AND STORAGE
GUIDELINES can be recommended.
Robert "Bob" Lazzara
Circuit Connect, Inc.
Bob has been in PCB design and fabrication since 1976. He has held elected positions with the SMTA, is a member of the MSD Council, has served as a committee member for various IPC standards and is a Certified IPC Trainer.
The easiest way to determine if moisture is the problem is to
bake your bare PCBs immediately prior to assembly and reflow. I would
recommend 2-4 hours at 250 F and then process IMMEDIATELY!! Don't let
them sit so that they can reabsorb moisture. If the problem goes
away, you have your culprit.
by thermal excursion would not be re-workable in my opinion. Really the
only possible rework would require re-pressing (which I do NOT
recommend). Since the delamination is occurring after assembly, I assume
that you also have components on it. You cannot re-press a board with
components on it.
Senior Applications Engineer
Flexible Circuit Technologies
Mark Finstad has over 30 years in the flex circuit industry in both design and manufacturing. He is a regular speaker at IPC APEX (Professional development courses) and PCB West (flex circuit design courses). He is also vice chair of IPC-2223 and active member of IPC-6013. Finstad has extensive experience with both domestic and off-shore manufacturing.
Really, here are some broad suggestions to address your
problems: (a) determine
delamination caused by moisture vs. others - by isolating
the causes of
delamination, appropriate sensors could be built into the
pcb. Example, a
capacitive inner layer sensor for change in moisture
content. Is this a viable
option economically? If not, determine and list the types
of environments to
which the pcb exposed, rank the causes and work your way
down. You will have to
start all the way back from the pcb fabrication..
(b) repair of delaminated pcb may not be possible,
collateral damage (thermal,
mechanical) on components and other features will be
huge. Prevention is better
CALCE, University of Maryland
Bhanu Sood is the Laboratory Director at the Center for Advanced Life Cycle Engineering (CALCE) and actively assists companies and organizations in all aspects of electronics reliability. Sood's key focus area is in design reviews, custom tests, and failure analysis services. He has authored several articles on board and component level reliability and unique failure mechanisms in electronics.
Delamination has been a
concern since the beginning printed circuit boards and increased with the
introduction of multilayer boards. The most common cause is moisture in the
board and baking the boards prior to the wave soldering process will reduce if
not eliminate delamination due to moisture. The bake cycle should be overnight
at 225C and don't solder the boards while they are hot as this will impact the
fluxer process, wait until they reach room temperature.|
Among other things to watch
for is the plating in the holes, focusing on the thickness of the plating and
the integrity of the barrel. Many times if the barrels have voids, blow holes
in the solder joints will be evident and delamination around plated through
holes will result.
Check for oxidizing layer
on the inner layers of multilayer boards to make sure it is applied correctly
as this is the surface where the attachment is made between the layers. If this
is not done correctly during the board fabrication process delamination will be
Is it possible to repair
delamination? This all depends upon the extent of the delamination and the
technologies of the board - i.e., how many layers are in the structure and
where in the structure, i.e., what layer is the delamination located.
I would focus on the cause,
conduct a first piece inspection run and if delamination is evident on that
circuit, then I would bake all the boards from that lot. Additionally check the
storage where the boards are kept making sure they are stored in a dry box if
they are going to be stored for long periods of time.
are many more things involved, but these cover the basic elements and if more
is needed please get in touch with me and we can discuss it further.
Vice President, Technical Director
At EPTAC Corporation, Mr. Lambert oversees content of course offerings, IPC Certification programs and provides customers with expert consultation in electronics manufacturing, including RoHS/WEEE and lead free issues. Leo is also the IPC General Chairman for the Assembly/Joining Process Committee.
As I've mentioned in my answer regarding the bake before
rework question, the delamination is commonly caused by moisture ingression in
the PCB structure. |
The board manufacturer has to be able to provide you the
handling guidelines for your PCBs depending on the materials used and the potential (high or low) for moisture to get
in between the board internal layers. If you do not follow those guidelines,
then you expose the PCBs to risk.
For the other part of the question, the
delamination will usually result in scrap. I am not aware of a fix for such
issue. However, check the IPC standards (610 and 600) to determine the
acceptability of the exhibited problem.
Engineering and Operations Management
Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
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