Author Topic: PCB thickness  (Read 3859 times)

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Offline joniengr081Topic starter

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PCB thickness
« on: September 22, 2023, 07:54:49 am »
Hi, I have seen some FPGA boards in which they have 10 layers stackup that ends up to 1.6 mm thickness of the PCB. I don't think more than 10 layers are possible with 1.6 mm thickness. However, for bigger FPGA PCB designs, normally 16 layers or even 22 layers is recommended if there are many peripherals and have other components with BGA packages.

What are the advantages or disadvantages of PCB thickness if we compare 2.4 mm with1.6 mm PCB thickness. 
 

Offline forrestc

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Re: PCB thickness
« Reply #1 on: September 22, 2023, 08:35:45 am »
What are the advantages or disadvantages of PCB thickness if we compare 2.4 mm with1.6 mm PCB thickness. 

You've asked a question that has no good, definitive answer, and will vary based on the specific circumstance the PCB is used in.

Taking thermal cycling as an example, theory says that a thinner board will be more reliable as the board can flex as the components shrink and grow in relation to the board itself due to thermal expansion and contraction.   However, there is a paper floating around from a couple years ago where the authors ran test boards of varying thicknesses containing various different components through thermal cycles.   The resulting data is confusing, often contradictory, and failures often seems to be more related to the component and/or solder choice than the underlying board.   Some components and solder combinations at certain cycling ranges seemed to confirm the thicker board = less reliable theory, and others seem to contradict or at least not confirm it.

On the other hand, if you look at vibration failures the theory is that a thicker board will have less failures since it is less likely to flex under vibratory loads.   You could pick any different parameter and guess whether a thicker board will do better than a thinner one or the other way around, since it's obvious that a thicker board is bigger, less flexible, heavier, and more complex - each of which is affected by outside stimulus in a different way.

My gut feeling based on everything I've seen is that there aren't a lot of places where board thickness really matters as far as reliability goes as long as you don't push it to extremes. 

 
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Offline SiliconWizard

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Re: PCB thickness
« Reply #2 on: September 22, 2023, 11:02:59 pm »
For standard processes (nothing fancy), usually the min thickness for 10 layers is 1.2mm.
With 1.6mm you can get 12 layers again with relatively standard processes, possibly 14 with a custom stackup (cost +++).
 

Offline thm_w

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Re: PCB thickness
« Reply #3 on: September 23, 2023, 12:07:02 am »
You can have 10 layers in under 0.6mm if you really want: https://www.rocket-pcb.com/high-end-hdi-anylayer-mass-production-capacity-rocket-pcb

The disadvantage of 2.4mm is mostly additional size and weight. Maybe some component leads aren't designed for that board thickness.
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Offline Doctorandus_P

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Re: PCB thickness
« Reply #4 on: September 23, 2023, 12:08:09 am »
Thicker PCB's are mechanically stronger, stiffer and heavier then thinner PCB's. When you have 6 or more layers, then the price difference is also mostly determined by the PCB size, number of copper layers and the size of the production run (Price drops a lot when you go into manufacturing for a few hundred or or a few thousand PCB's).

As far as I know, the thickness of the PCB is not an important factor at all, except when you want very thin multi layer PCB's. If the combination of the number of layers and total thickness is such that standard prepreg is too thick, then the price very likely goes up significantly.
« Last Edit: September 23, 2023, 12:10:36 am by Doctorandus_P »
 

Offline liaifat85

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Re: PCB thickness
« Reply #5 on: September 25, 2023, 07:38:57 am »
The standard thickness of a printed circuit board (PCB) can vary depending on the specific application and requirements. However, the most commonly used standard thickness for PCBs is 1.6 millimeters (mm). This thickness is widely accepted and used in various industries, including consumer electronics, telecommunications, automotive, and industrial applications. It provides a good balance between durability, flexibility, and cost-effectiveness. It's worth noting that thinner and thicker PCBs are also available, depending on the specific needs of a project.

You can find more details here:

https://www.nextpcb.com/blog/what-is-standard-pcb-thickness
 

Offline Infraviolet

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Re: PCB thickness
« Reply #6 on: September 29, 2023, 12:11:08 am »
The first thing I can think of for advantages/disadvantages is that anything with a high current on inner-most layers of a thicker PCB will probably run hotter than it would on standard thickness.
 

Offline luudee

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Re: PCB thickness
« Reply #7 on: October 06, 2023, 09:47:57 am »
Hi, I have seen some FPGA boards in which they have 10 layers stackup that ends up to 1.6 mm thickness of the PCB. I don't think more than 10 layers are possible with 1.6 mm thickness. However, for bigger FPGA PCB designs, normally 16 layers or even 22 layers is recommended if there are many peripherals and have other components with BGA packages.

What are the advantages or disadvantages of PCB thickness if we compare 2.4 mm with1.6 mm PCB thickness.

You have opened a can of worms here, lol

PCB thickness mostly depends on the Materials you are using.

We just did a 12 Layer PCB using Megtron-6 and it came out to be 1.4 mm.

You need to choose the material first, then talk to your PCB house
and create a stack-up ...

In theory, you can make it as thick as you want. But if you want
it very thin, you need to pay attention to the PCB materials ...

Advantages & Disadvantages will depend on your use case.
BGAs are not so much of an issue, it's the FPBGA (Fine Pitch
BGA) that kill layout and require additional layers.

So I would suggest to provide a lot more information about
your project if you need help !


Good Luck,
rudi
« Last Edit: October 06, 2023, 02:19:41 pm by luudee »
 

Offline Feynman

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Re: PCB thickness
« Reply #8 on: October 15, 2023, 03:32:18 pm »
1.6 mm is the standard thickness for printed circuit boards. So it's probably easier to find off-the-shelf housings or card rails where a 1.6 mm board fits in. Apart from that there are no fundamental disadvantages of a 2.4 mm board compared to a 1.6 mm board. As always, doing something non-standard might get lost in communication.

For example many mechanical engineers blindly assume a PCB being always 1.6 mm thick, which might cause surprises when the thing is built the first time. But that's not a problem of the actual PCB construction, of course.
 


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