V-Scoring

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Below is information on how to implement the V-Scoring technique to panelize printed circuit boards.

V-Scoring is one of the tried and tested methods of panelization. The other main considerations are routing with rat-bites or breakaways... and the method where the board outline is cut with hard tooling and then the board pressed back into the panel.

Each method has its pros and cons. One of the main benefits from V-Scoring is that is used less pcb real estate as compared to the routing technique that requires the width of the routing bit. This may enable a better panel utilization.

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Choosing a depth that will provide a sturdy work-piece and still separate with light to moderate pressure after assembly, is an important element in profitable manufacturing.

Most score depth specifications make use of one of the following conventions:

1. V-depth measured from one or both sides of the PCB surface. Or, the more appropriate...
2. Cross-sectional view, indicating the distance between Vees. This residual material is called the Web.

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Understanding the variables that determine score width along with the associated process tolerances, will help you identify problematic specifications, and aid greatly in laying out a manufacturable product.
Knowing what your score width will be is essential to design and planning. Understanding the variables that determine score line width is, once again, quite straightforward.

Variables.

Score line width is determined by a combination of two elements; blade angle and blade wear. Simply stated, a blade of a larger angle will cut a wider path than a blade of a narrower angle, at the same depth. Also, the deeper the blade penetrates the surface of the board, the wider the path will be. Also, as the blade wears, the tip essentially "moves up" the width of the blade, resulting in a wider score path for the same given web.

http://www.pcbstandards.com/pic/vscore12.gif

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Optimum Web Thickness.

Determining the thickness of this uniform core of material for each individual project is really very simple.
We need only consider the needs of the subsequent assembly operations. In the assembly area we are looking for the following performance criteria:

1. Overall part planarity, not only for component placement, but also for solder reflow and/or wave processes.
2. Ease of de-paneling. After component attachment is complete, the individual boards should break apart with only moderate pressure.

Notice how the web gets thinner as the individual board size gets smaller. The smaller the part, the less leverage that you can apply to the score line.

One of the great features of most modern CNC scoring equipment, is the ability to easily program the web thickness from line to line and axis to axis.
One popular application for this feature of varying web thickness is called "Deep Cut" or Framing. This is where the outside border of the array is cut to a relatively thin web of down to .006". This allows for an easy break off of the scrap frame.
This is also commonly used to easily separate multiple arrays from a production panel, without the worry of breaking the wrong line.

These are GENERAL guidelines. The final decision on
web thickness should be made only after careful consideration
of future process and handling requirements...

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One technique for strength is to add some is to offset the V-scores that are opposite from each other, typically with about a .012-.013 delta.

Keep in mind you need to have adequate clearance for the cutting tool and loss of board material.

Attached is an AutoCad file with the V-Score detail with an offset.

[randychase]

Here is an AutoCad detail drawing for a simple V-Score (non-offset). Easily modify to your dimensions as required.