Shielding Case: 5 Expensive Mistakes

Shielding Case: 5 Expensive Mistakes

Common protection against EMI at a PCB level. Be careful to make the right technical choices for your shielding cases.

Today, we are sharing the worst and most expensive mistakes made on different projects we worked on. We concentrate on the choice of EMI shielding at a PCB level: shielding case.

Some of these mistakes are the origin of project abandonment.

Our goal is to make you aware of these problematics met by other companies so you will not do the same.

Let go!

Mistake N°1: Short vision on prototyping

Choosing a standard and common shielding case for prototyping is a good idea: You get low costs, short delivery, small quantities, no tooling costs.

Then when switching to mass production, surprise: the price still high. At least too high comparing to what you could get, I explain.

Standard shielding case sold in small quantities are made using deep drawing.

You can recognize it with the round corner around the part and a completely closed shape. These standards are made in really high quantity and sold on all the online shops. Deep drawing is perfect to get a low unit cost and big volumes. However the tooling for deep drawing is really expensive.

Problems:

• The manufacturers know that you cannot produce your own tooling. So you cannot look for a cheaper alternative with the same design. Then he can keep higher unit prices even for mass production.
• You have no flexibility on the design. You need to choose a part with fixed dimensions. Even if there is 5mm between 2 close references. You do not choose the dimensions it is imposed.

How to avoid to be trapped without extra costs?

Instead of deep drawing, choose cut and fold parts.

Pros:

• You are free to choose the exact dimensions of your shielding case
• The shielding performance are strictly identical
• You have more flexibility about the general design
• You can prototype without a mass production tooling. Prototypes are made using a “soft tooling”. You can modify the design after your first tests without extra costs.
• No End of Life
• You are the owner of your design

Cons:

• You need a tooling for mass production (still much cheaper than a deep drawing tool)
• Price for few unit is higher than standard parts sold online.

Mistake N°2: Choose the cheapest material

The choice of the material used for the shielding case will determine the life time of your product. You don’t want to hear about an unhappy customer in few years because your equipment is Out of Order. Why would it happened?

Because of oxydation.

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Of course you will choose at least stainless steel as raw material. However during manufacturing or transport, the plated may be damaged. If there is any scratch or surface that is not covered with the plated: it is a door opened for oxydation.

There is an easy way to avoid this: use Nickel Silver instead of Stainless Steel.

Why? Nickel Silver is a material which is not subject to oxydation (at least corrosive oxydation). The part will not be damaged, and will not change along the years. The integrity of your whole product is ensured.

Even if this material is a little bit more expensive. The impact of the raw material cost is much less than a maintenance operation few months or years later.

Mistake N°3: Forget thinking about maintenance

The durability of your product is a main subject. The maintenance of your equipment must be as easy as possible. Thinking about maintenance is thinking about how you can access to the components covered by the shielding cases.

There is 3 ways to integrate a shielding case:

Direct wielding on the PCB:

• Maintenance is not easy even impossible
• Preferred solution for military onboard equipment for example

Fixation with clips

• First the clips are welded on the PCB (assembled by Pick and Place)
• Then the shielding case is fixed on the clips
• It can be easily disassembled and maintained

Fixation a frame

• The frame is useful for multi-cavities configuration (instead of clips)
• The cover can be easily disassembled

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Mistake N°4: Underestimate mass-production optimization

You should optimize all of your production. Including the shielding of your PCB. The best way is pick and place automation. Depending the size and the volume of your shielding cases, you have different possibilities:

• Tray conditioning, for bigger parts
• Roll conditioning, only for smaller shielding cases

In both case the part must get a central tip for the pick and place suction.

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Mistake N°5: Limit your design

You will earn more time and flexibility using your own shielding case. Starting costs might be a little bit higher depending on your design. However, this investment will be quickly amortized with the time earned by reducing the mechanical constraints in your setup.

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What about you?

• Did you recognized yourself on some of these points?
• Do you have other blocking points on your project?

You can answer directly using the tchat box, I will be happy to bring to you quick and concrete answers.