1.6mm versus 0.8mm PCB from an EMC perspective - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: March 30, 2020, 01:23:53 pm
content: I am designing a filter. This means that given the simplicity in the layout with most components sitting between two rail simply making each rail a plane on either side of the board joins all parts together with low impedance connections. The pairing of the layers so will also aid in reducing emissions. But something obvious to wonder about is how much effect dose the distance between the planes make. Would halving it really make much difference?

author: Simon
author_rank: Unknown
timestamp: March 30, 2020, 01:54:29 pm
content: I will probably get 0.8mm if I can but there are other considerations like what copper thickness they offer on 0.8mm and the mechanical rigidity that can screw you with larger package ceramics which is this case I can only put near an edge.Most boards are as standard one layer either side rather than on one side in 4 layer style.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 30, 2020, 03:55:32 pm
content: Unless you have ultra-specific requirements (which you may have, we don't know any detail about your circuit), integration and mechanical rigidity are the main decision factors for board thickness IMO. If impedances are a stringent concern, just calculate them according to layer spacing whatever thickness you choose.blueskull made a very good point: absolutely not all 4-layer stackups for a given board thickness are the same, so check that as well. If that really matters in your application.

author: Simon
author_rank: Unknown
timestamp: March 30, 2020, 04:04:04 pm
content: Well I am doing 2 layer so they will be opposite sides of the PCB. I will be potting the PCB so it just has to be stiff enough for assembly.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 30, 2020, 04:07:31 pm
content: Quote from: Simon on March 30, 2020, 04:04:04 pmIs there any ground plane on either side?

author: Simon
author_rank: Unknown
timestamp: March 30, 2020, 09:09:53 pm
content: well one of the rails is ground as it's power supply to a fan being filtered.

author: Whales
author_rank: Super Contributor
timestamp: March 30, 2020, 11:55:45 pm
content: Quote from: Simon on March 30, 2020, 09:09:53 pmWait, filtering for a power rail for a fan? Don't even bother optimising PCB thickness, the effect (on conducted EMC) will be negligible at these current draw levels (pF?). EDIT: and I suspect the emitted EMC side of things will be dominated by the unshielded fan coils.(I was reading this topic as signal filtering)

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 31, 2020, 12:40:22 am
content: Quote from: Simon on March 30, 2020, 01:23:53 pmfor low frequency low voltage, no difference electrically. mechanically it will be more easier to bend/flex/break. for high frequency, trace impedance will change. for high lethal KV voltage, you may check CAT rating compliance. EMC wise, having ground plane is much better than nothing at all, if full metal/conductive enclosure (faraday cage) is more expensive or not feasible. i'll go for thinner pcb when space is constraint such as in miniature device, i'll go for thicker one if rigidity/durability is more important or space is not a constraint. seeedstudio only offer 1mm minimum at $5 package. ymmv.