[SI-LIST] Re: Right Angle Bends
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Vinu Arumugham" <vinu@xxxxxxxxx>
- Date: Fri, 15 Jul 2011 12:15:21 -0700
That is another urban legend. Never been true. I've seen fabricators say
this and then etch outer layers with all sorts of surface mount pads that
have traces entering them that result in right angle corners and never
complain!
We'll probably all go to our graves before we flush out all this
misinformation!
--------------------------------------------------
From: "Vinu Arumugham" <vinu@xxxxxxxxx>
Sent: Friday, July 15, 2011 11:28 AM
To: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
Cc: "Moreira, Jose" <jose.moreira@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: Right Angle Bends
> Are 90 degree turns not an "acid trap" problem especially for 3-4 mil
> wide traces?
> Lee Ritchey wrote:
>> There is a paper on my web site authored by Doug Brooks using lab
>> measurements performed by Todd Hubing when he was at UMR as part of the
>> EMI
>> department that clearly shows that right angle bends in signal traces are
>> not detectable out to something like 20 GHz.
>>
>> You can download it from www.speedingedge.com. It is titled "90 Degree
>> Corners, The Final Turn".
>>
>> This article has the info you are looking for. I'm sure Doug would not
>> object to you sending it around. Anything to stop the crazy rumors about
>> this topic.
>>
>> It is truly amazing the stories I hear about how evil things happen at
>> right
>> angle bends. In every case, the author of the rumor has no data to back
>> it
>> up or makes a statement such as "I measured this at my last company and
>> cannot share it without their permission". Doesn't that sound a little
>> fishy?
>>
>>
>> --------------------------------------------------
>> From: "Moreira, Jose" <jose.moreira@xxxxxxxxxx>
>> Sent: Friday, July 15, 2011 9:48 AM
>> To: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
>> Subject: [SI-LIST] Re: Right Angle Bends
>>
>>
>>> From my experience (I also get that statement from my customers) it
>>> comes
>>> from the thinking that on a right angle bend the signal would "see" a
>>> larger trace width when crossing "the bend" and because of this
>>> different
>>> trace width it will have a different impedance at that point so there is
>>> a
>>> discontinuity that is bad for the signal.
>>>
>>> I remember an old conference paper showing no measureable effects to 10
>>> Ghz but I cannot find it again.
>>>
>>> I would be interested if anyone know of a good up to date reference
>>> (with
>>> measurements) that I can also send to my customers when they have the
>>> same
>>> statement.
>>>
>>> Jose
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>>> On Behalf Of Lee Ritchey
>>> Sent: Friday, July 15, 2011 6:33 PM
>>> To: si-list@xxxxxxxxxxxxx
>>> Subject: [SI-LIST] Re: Right Angle Bends
>>>
>>> Does anyone know the origin of the myth that right angle bends cause
>>> signal integrity problems?
>>>
>>> I though this myth had died a long time ago, but had a conversation last
>>> week with a well known fabricator who was told by a customer that right
>>> angle bends were a no no.
>>>
>>> This was a customer who should know better.
>>>
>>> Lee Ritchey
>>> Speeding Edge
>>>
>>>
>>>
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