|Ask the Experts|
March 19, 2020
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?
|Expert Panel Responses|
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.
Circuit Connect, Inc.
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.
Delamination caused 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
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 than cure!
CALCE, University of Maryland
Delamination has been a concern since the beginning printed circuit boards and increased with the introduction of multi layer 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 prevalent.
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.
There 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
As I've mentioned in my answer regarding the bake beforerework 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
I am unaware of a method for determining the specific cause of delamination. As others have stated, the most common cause is moisture entrapment in the circuit board. The IPC 7711/7721 Repair Guidebook has two procedures for the repair of delamination and we have completed both.
Procedure 3.1 Delamination/Blister Repair, Injection Method is difficult to complete but when there is a clean separation of the base board layer it can be filled completely with epoxy. When there is not a clean separation it is often easier to excavate down through the surface of the board and utilize procedure 3.5.1 Base Material Repair, Epoxy Method to correct the defect.
Circuit Technology Center
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