Electronics Assembly Knowledge, Vision & Wisdom
V-Score and Depanel in One Step
V-Score and Depanel in One Step
Can we score and de-panel assembled PCBs in one step to create a card edge connector on the PCB. Is there a precedence for doing this? Jim Hall and Phil Zarrow, The Assembly Brothers, answer this question.
Board Talk
Board Talk is presented by ITM Consulting

Phil Zarrow
Phil Zarrow, ITM Consulting
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.

Jim Hall
Jim Hall, ITM Consulting
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.

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Welcome to Board Talk with Phil Zarrow and Jim Hall of ITM Consulting, the Assembly Brothers. Today, we're coming to you from the ITM Elegante Ballroom high atop Mount Rialto. 

We're here to talk about electronic assembly; materials, equipment, components, practice and procedures, and who knows what else.

Jim knows what else because he's got today's question.  What is it, Jim?

It comes from B.S. I am considering scoring a PCB with a 90 degree scoring blade after SMT placement and reflow to create a card edge connector on the PCB. 

I would score it deep enough to bevel and de-panelize in one step. Is there a precedence for doing this and are there any horror stories of failures?

This is an interesting situation because we're not just talking about scoring and singulation of boards. We're talking about where an edge connector is ultimately going. 

I'm trying to contemplate your board layout and figure you probably have some sort of interconnectors, either fingers or holes or pads. So we're assuming the area is clear in the vicinity of the score of components, particularly those wonderful, very crackable ceramic capacitors.

In terms of the stress of the wheel or the pizza cutter it will probably be somewhat nominal. I would also hope that you've had these PCBS pre-scored in your fab shop to IPC-782 specifications.

However when you actually do separate the boards, what should he look out for?

Certainly you don't want to flex the board in any way that would crack solder joints. The classic ones are your ceramic chip capacitors which can be near the edge or can be anywhere on the board. 

If they're in the area and the board gets flexed, you can crack the joints. Most panels that we've seen like this are pre-scored at the fab shop before the components are placed and the solder joints are created. 

Supporting the board properly so that it doesn't flex and crack your solder joints is the horror story. There are horror stories probably around any process in SMT or electronics assembly because, we're all human and if it can go wrong, it has gone wrong.

Hopefully we've answered the question and given you the proper caveats. 

Remember, whether you agree or disagree with Board Talk, the secretary disavows any knowledge of our actions. This recording will self-destruct in ten seconds, good luck Jim. 

Whatever you do, don't solder like my brother.

And don't solder like my brother.

As an electronic contract manufacturer we work with a wide variety of PCB's and often are challenged to depanel boards without causing damage to the boards. As board size continues to shrink and density of components continue to increase it is becoming even more critical for us to be able to utilize as much of the PCB as possible. We have installed a Hylax Technology 20-Watt UV laser and a Epilog Fusion M2 40 75-Watt CO2 laser which allows us to depanel PCB's automatically and without stressing the PCB and causing damage or latent failures.
Steve Kelly, Z-Axis
The answer to the question is yes. A pizza cutter to depanel scored boards can work, but the better question should be "how much strain is being induced upon my circuit during the depaneling process?"

The cost to repair a soldered PCB is considered to be 10X that of a non soldered PCB. Choosing the right tool to accurately remove the circuit while protecting the value added investment of parts and process cost down stream is critical, and often an afterthought.

Today's lead free alloys and ultra fine components compound the issues and challenges of limiting the mechanical stress due to being less ductile and malleable.

Strain tests that we performed comparing "pizza style" devices vs routing show an exertion of mechanical strain more than 10X that of a more controlled process such as routing where the parts are mechanically secured onto the routing table, with each circuit being accurately and precisely cut to .005"; preventing any possible error due to improper handling by the operator.

Using a board router the individual circuits in the array are not induced to undue stress and vibration. Furthermore, with Servo Z control, boards with overhanging components and parts near the edge can still be singulated without special jigs or post operations. The routed board leaves a smooth fray-free edge that doesn't require any further manual operation or handling.
Patty Chonis, A-Tek Systems Group
There are always horror stories. When using V-Score cutters, the simplest machine is the open wheel with a short guide where the wheel is fixed (and rotating) and the operator moves the board. This means the operator and the adjustment of the machine, controls exactly where the cut is made. Some skill is required.

If you wish to improve your odds, use a V-Score machine that allows for fixing the board on a jig and aligns the V-Score of the board on a long fixed blade or rest for alignment. These types of V-Score cutters have a moveable cutter wheel on a slide and remove a large portion of the alignment away from the operator providing a lower defect rate and improved quality of cut.
Bruce Webster, Iridium Communications, USA
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