[SI-LIST] Re: NELCO N-13ep HiTg > 170C

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: Richard Jungert <r_jungert@xxxxxxxxxxx>
  • Date: Sat, 06 Sep 2008 18:19:47 -0700

Oops!  Posted the signs wrong for the single termination case after 
bouncing off the driver.  Corrected table:

Z Line   One Term   Two Term
80%      +11.1%      +1.2%
85%      +8.1%       +0.7%
90%      +5.3%       +0.2%
95%      +2.6%       +0.1%
98%      +1.0%       +0.0%
102%     -1.0%       +0.0%
105%     -2.4%       +0.1%
110%     -5.8%       +0.2%
115%     -7.0%       +0.5%
120%     -9.1%       +0.8%

Steve
steve weir wrote:
> Richard, VSWR causes ISI ( as does frequency dependent loss ): Signal 
> energy reflects first off the receiver back up the line to the 
> transmitter where it distorts currently transmitted data.  Since the 
> distortion depends on prior data patterns it manifest as ISI.  A simple 
> chart for line impedances:
>
> Reflected amplitude:  ( Zline - Zload ) / ( Zline + Zload )
> One term pessimistically assumes 0 Ohm driver
> Z Line   One term   Two term
> 80%      -11.1%     +1.2%
> 85%      -8.1%      +0.7%
> 90%      -5.3%      +0.2%
> 95%      -2.6%      +0.1%
> 98%      -1.0%      +0.0%
> 102%     +1.0%      +0.0%
> 105%     +2.4%      +0.1%
> 110%     +5.8%      +0.2%
> 115%     +7.0%      +0.5%
> 120%     +9.1%      +0.8%
>
> In older signaling topologies with just one termination, tightening up 
> tolerances buys ISI margin.   In double terminated topologies there is 
> little to gain ISI wise with matches better than 15%.  This has some 
> nice implications: 
>
> 1. We can get away with skinnier traces and thinner dielectrics without 
> worrying too much about etch tolerance for Z control, and
> 2. We also don't need to be concerned about placing etch across prepreg 
> from return planes for Z control.  That makes putting the top power 
> cavity on layers 2/3, and the bottom one on N-1/N-2 where they perform 
> best and reduce the number of bypass caps needed a no-brainer.  With 
> older singly-terminated signaling schemes there was an argument for 
> putting signal on one side of a core and plane on the other for low-cost 
> Z control.  Typically that put Gnd on layer 2, signals on layers 3 and 
> 4, and the first power cavity down on layers 5/6, which really hurts Z 
> axis inductance for both bypass caps and the ICs.  It is also 
> incompatible with thin core dielectrics for power delivery.
>
> If you are making a piece of measurement equipment then depending on 
> what you want to see the extra precision may be justified.
>
> Best Regards,
>
>
>
> Steve.
>
> Richard Jungert wrote:
>   
>> Steve.
>>
>> Its not about ISI, ( intersymbol interference) as I recall. Its all 
>> about test equipment, accuracy and precision results in smaller 
>> reflections and better VSWR within the bandwidth of interest.. Good 
>> quality test equipment is all about precision, but precision costs 
>> money as we all know.  We were making a tester box that connected to 
>> multi channel wide bandwidth cable ( single ended 50 ohms ) and tested 
>> with 35ps risetime signaling from Tek equipment. It worked but was 
>> expensive to make.
>>
>> Richard Jungert
>>
>>
>>
>>
>>     
>>> Date: Sat, 6 Sep 2008 14:44:39 -0700
>>> From: weirsi@xxxxxxxxxx
>>> To: r_jungert@xxxxxxxxxxx
>>> CC: wftinghi@xxxxxxxxxxxxxx; bdempsey85@xxxxxxxxx; 
>>>       
>> costel_t@xxxxxxxxx; si-list@xxxxxxxxxxxxx
>>     
>>> Subject: Re: [SI-LIST] Re: NELCO N-13ep HiTg > 170C
>>>
>>> We're not in Kansas anymore. ( Well Eric is but that's only because he
>>> likes watching cows spin in tornadoes. ) The days of TTL/CMOS signaling
>>> with one end terminated at speed are long gone. So, why the drive for
>>> such tight Z control as +/-5%? The difference in ISI energy at the
>>> receiver between a +/-10% match and a +/-5% match for both ends
>>> terminated signaling standards is less than 1%. Why throw any time or
>>> money at such a small improvement?
>>>
>>> Steve
>>>
>>> Richard Jungert wrote:
>>>       
>>>> Steve.
>>>>
>>>> Yes, +/- 5% is higher, how much depends on your fab house. I would 
>>>>         
>> have to shop around if we needed lower cost. At the time 3 years ago I 
>> was building test equipment and yes the board was expensive. The 
>> application we were working on demanded tight impedance control.
>>     
>>>> BTW.
>>>>
>>>> This guy..
>>>> Vince BeusanMEI Inc(949)460-9500www.mei4pcbs.comTells me in a 
>>>>         
>> recent email that his fab shop can do +/-5% all day long no problem 
>> but I have not worked with them in the past. Maybe these guys have an 
>> updated fab process set up where they can do tighter tolerance at 
>> lower cost. Only way to find out is to try it.
>>     
>>>> Richard
>>>>
>>>>
>>>>
>>>>
>>>>         
>>>>> From: wftinghi@xxxxxxxxxxxxxx
>>>>> To: r_jungert@xxxxxxxxxxx; bdempsey85@xxxxxxxxx; 
>>>>>           
>> costel_t@xxxxxxxxx; si-list@xxxxxxxxxxxxx
>>     
>>>>> Subject: RE: [SI-LIST] Re: NELCO N-13ep HiTg > 170C
>>>>> Date: Sat, 6 Sep 2008 10:22:01 +0800
>>>>>
>>>>> Richard,
>>>>>
>>>>> So how about the cost? I feel +/-5% tolerance impedance control will
>>>>> increase the PCB cost a lot.
>>>>> The most local FAB houses I worked with will increase the cost if 
>>>>>           
>> we are
>>     
>>>>> trying to specify tolerance less than 10% due to their worse 
>>>>>           
>> yield rate.
>>     
>>>>> Specifying 5% tolerance can easily double the cost according to their
>>>>> feedbacks.
>>>>>
>>>>> Steve
>>>>>
>>>>> -----Original Message-----
>>>>> From: si-list-bounce@xxxxxxxxxxxxx 
>>>>>           
>> [mailto:si-list-bounce@xxxxxxxxxxxxx] On
>>     
>>>>> Behalf Of Richard Jungert
>>>>> Sent: Saturday, September 06, 2008 5:12 AM
>>>>> To: Bill Dempsey; costel_t@xxxxxxxxx; si-list@xxxxxxxxxxxxx
>>>>> Subject: [SI-LIST] Re: NELCO N-13ep HiTg > 170C
>>>>>
>>>>> I promote Data Circuits Systems/Merix because they can spec 50 
>>>>>           
>> ohms +/- 5%
>>     
>>>>> tolerance which in my experience is rare in the high speed pcb 
>>>>>           
>> fab business.
>>     
>>>>> Or at least it was 3 years ago.. Tektronix also uses this material in
>>>>> building fast TDR test equipment last I heard.
>>>>>
>>>>> Richard
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>           
>>>>>> From: bdempsey85@xxxxxxxxx
>>>>>> To: r_jungert@xxxxxxxxxxx; costel_t@xxxxxxxxx; si-list@xxxxxxxxxxxxx
>>>>>> Subject: RE: [SI-LIST] Re: NELCO N-13ep HiTg > 170C
>>>>>> Date: Fri, 5 Sep 2008 16:02:59 -0500
>>>>>>
>>>>>> 13EP is available as 13EP-SI as well and is used for higher temp
>>>>>>
>>>>>>             
>>>>> processing
>>>>>
>>>>>           
>>>>>> used in lead-free assembly.
>>>>>> *Most* customers I deal with are moving over to EP and EP-SI for 
>>>>>>             
>> RoHS
>>     
>>>>>> products. Something to consider.
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: si-list-bounce@xxxxxxxxxxxxx 
>>>>>>             
>> [mailto:si-list-bounce@xxxxxxxxxxxxx]
>>     
>>>>> On
>>>>>
>>>>>           
>>>>>> Behalf Of Richard Jungert
>>>>>> Sent: Friday, September 05, 2008 3:58 PM
>>>>>> To: costel; si-list@xxxxxxxxxxxxx
>>>>>> Subject: [SI-LIST] Re: NELCO N-13ep HiTg > 170C
>>>>>>
>>>>>> Costel.
>>>>>>
>>>>>> I would talk to the engineers at Data Circuits in San Jose about 
>>>>>>             
>> this
>>     
>>>>>> material. Merix recently bought them out but in the old days it 
>>>>>>             
>> was Data
>>     
>>>>>> Circuits Systems Inc who built equipment with this type of material.
>>>>>>
>>>>>> Have you considered Nelco N4000-13SI ? This is also a very high
>>>>>>
>>>>>>             
>>>>> performance
>>>>>
>>>>>           
>>>>>> material and in my recent designs/projects have found this 
>>>>>>             
>> material works
>>     
>>>>>> clear up to 15Ghz bandwidth.
>>>>>>
>>>>>> I recommend calling the FAB house your working with. These folks 
>>>>>>             
>> have that
>>     
>>>>>> info readily available.
>>>>>>
>>>>>> Richard Jungert
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>             
>>>>>>> Date: Fri, 5 Sep 2008 03:31:05 -0700
>>>>>>> From: costel_t@xxxxxxxxx
>>>>>>> Subject: [SI-LIST] NELCO N-13ep HiTg > 170C
>>>>>>> To: si-list@xxxxxxxxxxxxx
>>>>>>>
>>>>>>> Can anybody tell me the prepreg thicknesses for NELCO N4000-13EP
>>>>>>> much apreciated
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>>               
>>>>>> _________________________________________________________________
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>>>>>>             
>>>>> _________________________________________________________________
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>>>>>           
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>>>> _________________________________________________________________
>>>> See how Windows Mobile brings your life together—at home, work, or 
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>>>>         
>>> --
>>> Steve Weir
>>> Teraspeed Consulting Group LLC
>>> 121 North River Drive
>>> Narragansett, RI 02882
>>>
>>> California office
>>> (866) 675-4630 Business
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>>>
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>>>
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>
>
>   


-- 
Steve Weir
Teraspeed Consulting Group LLC 
121 North River Drive 
Narragansett, RI 02882 

California office
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