All About Metal Clad PCB

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Hey Geeks, we all know normal Printed Circuit Board (PCB) which you see everywhere in electronics which is in green color. But there is a special Printed Circuit Board called Metal Clad PCB (MCPCB). This type of PCB have many names. We will discuss about that soon below.

Let me share my story when I came across this type of PCB (MCPCB) before I get into the main topic. I was designing a circuit which protects the Thruster from high voltage, short circuit, high starting surge current, etc. The  thruster which I was working with was T200 from Blue Robotics, which consumes maximum 30 to 35 Amps of current with 12 volts to 20 volts. So, my circuit design was completed virtually, made a prototype and tested in vero board with trace width and solder thickness accordingly with my manual calculation, estimated the thickness and the width of the track. Why I did manual calculation for this because most of the online trace width calculator works up-to only 35 Amps input. But I have designed my circuit in which the maximum load requires 105 Amps because I was using three Thrusters in parallel. My prototypes for single thrusters were totally perfect with all type of testing.

img_1098
Protection board for single T200 Thruster Prototype

After testing I was happy with my teammates juniors Arnab, Jayanth, Tony and Rahul who were worked and assisted me. Till this process I din’t think about the PCB designing process, so then started my PCB designing next day in Eagle CAD. Then I realized “OH SHIT WAIT” this board is going to carry 105 Amps and FR4 usual PCB material will be fried. That’s how ended up with Metal Clad PCB (MCPCB) after lots of research.

From my story, you might have guessed by now, where and why this Metal Clad PCB’s are widely used. Yes, it is used in where high current which dissipates high temperature heat. This type of PCB is widely used in Automobile industry where the circuitry works in high current and voltage. This also used in high powered LEds, solid state relays, motor drivers, etc. I just gave on of the main reason for using this type of PCB. I will discuss more reasons why this is used below.

And one more important thing is, this type of PCB literally having MANY name. I was confused while I was researching about it. So, don’t be confused. I ll put the other names for this type of PCB below.

  • Aluminium clad
  • Aluminum Base
  • Metal Clad Printed Circuit Board (MCPCB)
  • Insulated Metal Substrate (IMS or IMPCB)
  • Thermally Conductive PCBS

So, these are the names I came across for this type of PCBs. I love “Metal Clad PCB” name. So I will be using in this article and don’t get confused when you see these names somewhere else.

There are four types of Metal Clad PCB, they are,

  • Flexible Aluminium PCB
  • Hybrid Aluminum PCB
  • Multilayered Aluminum PCB
  • Through Hole Aluminum PCB

In this type of PCB, Aluminum is used but don’t get fooled by seeing “Aluminium” word in the names because Copper too used instead Aluminum. It might be little confusing what I am talking about. I will tell you in detail below about the design and construction of this type of PCB.

Basic Design & Construction of Metal Clad PCB :

Lets take single sided Metal Clad PCB for easy understanding. In this single sided Metal Clad PCB there will be three layers.

  • 1st layer or Top layer – Circuit layer
  • 2nd layer or Middle layer – Dielectric layer
  • 3rd layer or bottom layer – Aluminium or copper base

pcb_thermal_clad_budowa

The above image shows the three layers of Metal Clad PCB. These all three layers are put into a single piece. 1st Layer or Top layer – Circuit layer ; is a layer which is for circuit what we have designed. This circuit layer is compressed with a metal base (3rd layer or bottom layer) using a dielectric material (2nd layer or middle layer ; which won’t conduct electricity but conducts thermal heat).

The simple theory is, dissipating the heat generated in Circuit layer due to high current flow in the circuit in the PCB using metal clad or metal base (like a big heat sink to the whole PCB)  in  which the Circuit layer and metal base (Aluminium or Copper) is isolated using a dielectric material (Dielectric layer) which is very thin, highly thermal conductivity and high dielectric strength which allows to  guarantee of thermal endurance. This is the whole theory why and when this type of PCB is used. Because of the above reasons, it have high durability and more efficient.

The dielectric materials used in metal clad PCBs are mostly :

  • Polymer
  • ceramic
  • Epoxy
  • Boron Nitride
  • or combination of above

Thickness used in all three layers are mostly :

  • Circuit Layer : 35 micrometer to 140 micrometer
  • Dielectric material – 38 micrometer to 200 micrometer
  • Metal Base – 0.059 inches to 0.25 inches

One should be very careful while designing, and deciding the placement of the type of PCB because as usual PCB design ruins and makes the Metal Clad PCB fabrication complex and expensive. I will tell you what are the things one should keep in mind in detail below while designing. Placement is too important because the bottom layer will a conductive layer completely. So, one should give importance to decide the placement too, as you given to the designing.

photo-21-02-17-7-25-18-pm

Types of Metal Clad PCB in detail :

  • Flexible Aluminium PCB : In this type of PCB, flexible polymide dielectric, flexible aluminum base is used. I have never seen this in practice. This can be bent few times. This is not used in applications like flexing the PCB regularly.
  • Hybrid Aluminum PCB : This is s type in which FR material and Aluminum base is sandwiched with dielectric material.
  • Multilayered Aluminum PCB : This multilayered Metal Clad PCB is very most expensive of all types, the only interesting thing in this is the vias, the blind vias are used for signal routing. If you are not sure about this type of Vias. I will post video explaining that.
  • Through Hole Aluminum PCB : This the type of PCB, I first designed in Metal clad PCB types and gave for fabrication. This is the very most complex design of all types of MCPCB. I would like to discuss this type in my YouTube channel in very detail.

Check the Video in my YouTube channel in which I show how dielectric layer looks like inside the Metal Clad PCB and much more. 🙂

 

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