Delamination After V-cut

• V-cut design of the board - depth and angle
• V-cut consistency across the board
• Blade design (angle) and dimension
• Positioning of the board in the depanelization process (is the assembly leveled when you perform this)
• The humidity and the moisture content of the PCB (ideally the boards are dry) The problem of having the same board for 2 models with only one failing this process might be related to lot number, moisture content and/or operator performing the job.
• There is no silver bullet for this problem however I hope that this is giving you a starting point.

Without knowing more about the affected PCB, difficult to say for sure but a number of things that could affect this would be. Has the PCB seen high temperature during manufacture e.g. HASL - especially leaded? Are the PCB's warped in any way (this would also suggest high heat in manufacture) What is surface finish - again related to the above. Assuming a double sided PCB, CEM3 is not a homogenous material and almost always sees woven prepreg placed top and bottom of a non woven core. The non woven core has a higher rate of z axis expansion and that will create stress in the PCB. Also, how long have the PCB's sat since V Score and in what conditions? V score essentially breaks glass fibres and that on it's own will make the PCB material more likely to uptake moisture (in itself, a common culprit of delamination, even with FR4 material)