How do we select the dielectric material to be used in the PCB stackup. The list is long, see attachment. How we can do price wise comparison.

I just have a look at some typical stackups for standard PCBs. They have used 18 um (0,5 oz) on outer layers and 35 um (1 oz). Any reason for thinner copper layers on top and bottom. I guess a 10 mil trace can carry more current in inner thick layers compared to outer thin layers. Is that correct ?

Regarding the dielectric, we are working with standard PCB with typical heights 1.6 mm or 2.4 mm which are not flex PCBs.

In the picture I shared, there are many FR4 dielectric in the list. What is the difference between high Tg, low Tg and mid Tg ? What is low CTEz and inorganic filters ? I would like to understand the consequences of these parameters while selecting the FR4.

Rogers is a name of the company or dielectric material ?

There is list of Rogers dielectric in the picture. Which one is better for high speed signals for example 10 Gbps Ethernet, USB 3.0 and PCI 3.0 in the design.

 

What is your application where these things matter? They have never been a concern to me, except the max current capability of traces on occasion.

 

For low speed signals for example 100 MHz, it does not matters which dielectric material we use in the stakup but for 10 Gbps signals we really need to consider. I have mentioned target application in the first post. Please if any one can answer the asked questions. Thanks in advance.

 

Unfortunately the question is a complex one that interacts with the actual parameters of your project.

The application is not described in the original post (naming interface standards is just too theoretical to be useful in this highly practical question), and just what signals you are dealing with is important to determine what you should do. Worse, there are interactive parameters such as impedance, copper weight, trace width, and budget among others that will ultimately determine your best options.

What you are asking for in your question is free consulting by an expert in a field where expertise is very expensive. Then, you are hobbling an expert from being able to advise you properly by naïvely constraining the question to a narrow part of the entire relevant problem space.

If you can describe you application beyond “10GHz” you might find some help. But it is much more likely you just need to learn a lot more yourself to get this done. There is advice on this topic from Intel (among others) that is free and instructive but not general, per se.

For example, they provide information for board stack in applications involving high speed Altera FPGAs. It contains a lot of generally useful information along with the application specific suggestions. As a rule, manufacturer’s application notes are an excellent source of information but they will not tell you which options to select from a menu that has you baffled.

You are almost certainly going to have to either hire a consultant or spend a lot of time learning things.

Good luck with the project, I wish you success without too much stress.

 

I am wondering if there exist a "online material selector” which can classify the dielectric materials for the following applications.

• Dielectic materials suitable for low/medium range frequency (0 to 10 GHz)
• Dielectric materials suitable for high frequency (10 GHz to 30 GHz)
• Dielectric materials suitable for very high frequencies (20 GHz to 60 GHz)

 

RE:<<There is list of Rogers dielectric in the picture. Which one is better for high speed signals?>>
Answer: those having the least tan delta, yet being thick enough to carry the applied voltage. And this moment I dont know ANY other materials beating better than Rogers. The record is 0.00003. I have tested 4 different materials and all are good. Here is excerpt of my article about it use, sorry until it is published I may give it to read only privately. You may ask it to me at JANIS_59@INBOX.LV

material name	thick (mm)	pF/cm2	diel ε	DF @ 1 MHz	DF@ 10 GHz	Q-factor	A3 size price	f(max)***	notes	refer
how obtained	meas.	meas.	calc.	meas.	meas.	calc.		producer
traditional FR4 glass textol **	1.5	2.8	4.7	0.015	na	75-95	50	50 MHz	cheap but not enough good	[13]
capacitor pcb 3M	1.5	3100	22	0.01	na	100		1 kHz	frequency far too low huge loss	[14]
Duroid TC350	1.5	2.0	3.5	0.0015	0.002	667	115	10 GHz	matt cladding to alter natural cooling but larger Focault loss	[15]
Duroid-6035HTC*	1.5	2.2	3.6	0.0013	0.0015	770	240	40 GHz	high-T⁰ material, conduc. 1.44 W/m/K, glossy cladding	[16]
Duroid-5880*	1.5	1.7	2.2	0.0004	0.0005	2500	325	40 GHz	0.72 W/m/K	[15]
CuClad-217*	3.17		2.2	0.0009	0.0012	1100		30 GHz	45 kV/mm	[15]
DiClad-880*	3.17		2.2	0.0009	0.0010	1100		27 GHz	45 kV/mm	[15]

(*) The plastic film glued on the surface provides the advantage that even without silver-coating the capacitor surface will not oxidize too soon to lose a penetration depth over time. Better to keep that film intact.


(**) Guess the FR4 and 3M materials suffer from multiple scattering between threads with ε=10 to best case 3.7 into the epoxy having ε=3.6. Loss is dramatic there.

 

I have mentioned target application in the first post.

Not that I can see.

 

Look like this fourm is only for Experts. Please let me know if there is any way to remove this post. Thanks in advance.

 

Look like this fourm is only for Experts. Please let me know if there is any way to remove this post. Thanks in advance.

[Moderation]
@engr_david_ee AAC is not only for experts. There is no reason to remove the post, but if you want it can be closed to further replies (locked).

On the other hand, I would encourage you to persist and consider why the replies are not what you want. You need help to solve a problem about which you say yourself you are not an expert. From an expert point of view, your question requires more and different information than what you are constraining people trying to help to.

The answer to your question isn’t a simple one, but you are asking for a simple answer to a complicated question. I strongly suggest you read application notes from manufacturers on PCB stackup for high speed signaling. App notes are very practical in focus and while they may also speak from the point of view of a particular device that you are not using, they also provide the background needed to generalize the advice they contain.

If you read through a few of them I suspect you will find your questions change and are more amenable to being answered usefully. People on AAC, many who are experts with long careers and a lot of specialized experience, are often ready to provide a great deal of valuable device free of charge.

But that doesn’t mean they don’t expect something in return—by and large, this is that the person they are helping learn something and get more expert themselves. There is a lot of satisfaction in seeing someone understand something that was previously a mystery, and see them pass this on to others.

But, when you constrain the ”help” to what you think is “helpful”, and reject answers that fall outside this naïvely contrived domain, you make actually helping impossible. And, unfortunately you aren’t going to be the first or last person that will do this which can lead to a kind of cynicism on the part of your advisor that might seem short tempered or intolerant.

In any case, as TS you can always request to have the thread locked so no replies can be added, but as a rule we don’t delete threads unless there is a problem that merits it. There is nothing in this thread requiring it to be removed. I hope you work out your problem with the stackup, good luck.