Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


copper land delamination

Bob Smith

#8520

copper land delamination | 15 November, 1999

Hi,

I have a problem I've never seen before so I hope someone here can help. A recent batch of PCBs arrived where the copper lands delaminate with a small pull. Normally you have to pull pretty hard and the whole land comes off the substrate. These boards act as if the copper was put on in layers - there is shiny copper on the lifted leads and on the PCB substrate with a layer of black particulate material covering or almost covering the copper. These boards were thermally cycled and electrically tested by the manufacturer and look normal under 7X. I'm worried about the reliability of the boards and whether this apparent delamination will cause failures. Anyone have any experience with this effect?

Thanks

Bob

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#8521

Re: copper land delamination | 15 November, 1999

Bob

Bob: Fortunately, you found this before you built-up a lot of product. Some thoughs and other drivel:

1 Use IPC-TM-650, Method 2.4.8 for copper peel with a Instron machine. Typical pad peel strength requirement for FR-4, 2 oz. copper is: 6 lb/in. You didn�t talk about the type of board or copper weight, but from the sound of things from you, I doubt the pads on your boards would come anywhere near this. 2 Copper is often plated in multiple processing steps. You should take a tour of you fabricator. It�ll take a half day or so. From the sound of things from you, the two of you will be getting to know each other better, anyhow. 3 You weren�t real clear on the "black particulate material." It could be carbon used in the electroplating process. The copper on the lifted leads is probably a lot "brighter" than you�d expect. 4 You are correct to be concerned. Your fabricator should be concerned also.

my2�

Dave F

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cklau

#8522

Re: copper land delamination | 25 November, 1999

hello,

One way to prevent copper land delamination is to applied Anchoring spurs also referred to as "tie-down tabs" or "rabbit ears".These are a metal projection around a land.This features is fully captured by the cover lay (cover coat) that is normally applied on top of the flexible printed circuit.The net effect can mechanically restrain the land from being lifted from the base laminate.This is especially useful to provide resistance in pads lifting during initial assembly and field repair works,thus this techniques is primary benefits for a single-sided design.But however a word of caution is necessary on the use of this methode that is DO NOT USED anchoring spurs on gigahertz frequency design cos it can act as a miniature antennae that can transmit unwanted noise.

This artical are some of the basic fundementals regarding DFM.

Best of regards

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