What CEM-x laminate material could replace FR-4?

Thread Starter

Younes Thabet

Joined Jan 9, 2019
71
Hello,

I didn't know which topic is approbriate for this question so I posted it here ..
I am trying to save some money by choosing a different laminate material for my PCBs. I am currently using FR-4 tg135 and I have been advised to use CEM (Composite epoxy material) ..
Could anyone tell which of the CEM 1-5 is a good replacement for FR4 in terms of electrical, mechanical, physical, and thermal properties and of course in terms of cost!?
Also are there any other CEM variants other than CEM 1-5? which ones are more common in the PCB industry?

Thanks,
 

MrSalts

Joined Apr 2, 2020
1,762
I see that CEM-3 is cheaper than FR-4, but how cheap !? is it worth changing PCB material from FR-4 to CEM-3?
I would really appreciate it if you could give a price comparison between FR-4 and CEM-3 for a 100*50mm 2-layer board !?

Thanks in advance,
Sometimes, the shear volume that a product is manufactured at will make a better product cheaper than an inferior product. FR4 has become dirt cheap. If you are making one, use FR4. If you plan to make millions of pieces, your question may make sense. Jlcpcb will make five pieces of your circuit up to 100 x 100mm for $5. If you "panelize" two on each board, you'll get 10 total pieces (both circuits on the panel must be identical or they will charge you a panelization fee).
How many pieces do you plan to make or have made?
 

Thread Starter

Younes Thabet

Joined Jan 9, 2019
71
Sometimes, the shear volume that a product is manufactured at will make a better product cheaper than an inferior product. FR4 has become dirt cheap. If you are making one, use FR4. If you plan to make millions of pieces, your question may make sense. Jlcpcb will make five pieces of your circuit up to 100 x 100mm for $5. If you "panelize" two on each board, you'll get 10 total pieces (both circuits on the panel must be identical or they will charge you a panelization fee).
How many pieces do you plan to make or have made?
The estimated yearly production might reach up to 25000 pieces..
So even if CEM-3 is slightly cheaper than FR-4, it will make a big difference in total!
For now we are studying this possiblity, but we still have to check mechanical, thermal, and electrical properties of CEM if it really can substitute FR-4 ...
 

MrSalts

Joined Apr 2, 2020
1,762
if CEM-3 is slightly cheaper than FR-4, it will make a big difference in total!
it will make a cost difference but not a big difference. CEM-3 is the same resin as FR-4, it is simply glass mat instead of woven glass cloth. The very uniform non-woven mat is almost the same price as cloth. The cost advantage comes from drilling and cutting - there is less wear on bits and blades. Your order will likely come in at $7500 to $12500 range plus shipping if made in China (w/FR4). You'll be lucky to save $500. You may waste more time (and time is money) discussing why CEM-3 was used instead of FR-4 and consume any savings with internal discussions or customer debate than you may may get from your vendor.

EDIT: I just texted a friend about CEM-3, he said, a board vendor asked him if CEM-3 could be used instead of FR-4 on a project - no price reduction, just a shift towards CEM-3 at some board houses as an internal cost savings on tooling that are not passed in to the customer.
 

Thread Starter

Younes Thabet

Joined Jan 9, 2019
71
it will make a cost difference but not a big difference. CEM-3 is the same resin as FR-4, it is simply glass mat instead of woven glass cloth. The very uniform non-woven mat is almost the same price as cloth. The cost advantage comes from drilling and cutting - there is less wear on bits and blades. Your order will likely come in at $7500 to $12500 range plus shipping if made in China (w/FR4). You'll be lucky to save $500. You may waste more time (and time is money) discussing why CEM-3 was used instead of FR-4 and consume any savings with internal discussions or customer debate than you may may get from your vendor.

EDIT: I just texted a friend about CEM-3, he said, a board vendor asked him if CEM-3 could be used instead of FR-4 on a project - no price reduction, just a shift towards CEM-3 at some board houses as an internal cost savings on tooling that are not passed in to the customer.
Understood, your information were very much valuable..
Thank you, i really appreciate your help..
 

drjohsmith

Joined Dec 13, 2021
394
check which approvals your board needs,
UL , CE , Ce, Uv etc.

Double check why your being asked to change and by who

Check any board impedances / rack size needs as well as any drilling / via pad requirements,
 

drjohsmith

Joined Dec 13, 2021
394
Nobody asked the OP to change anything. Read the story again.
I understood the OP had been looking to save costs,
and " I have been advised to use CEM "

as opposed to FR4.

All I am saying is, ask why the person suggested they change to CEM,
as opposed to say looking for a cheaper production house .

And whilst I'm on

https://en.wikipedia.org/wiki/Compo...ials (CEM) are,used in printed circuit boards.

Check what CEM they are offering, and what your board designers think,
 
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