[SI-LIST] Re: AW: Control Impedance testing
- From: Istvan Novak <istvan.novak@xxxxxxx>
- To: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
- Date: Sat, 12 Sep 2009 22:50:18 -0400
Lee and All,
If I interpret the question in the original post correctly, one aspect
of the issue/concern here is whether we can take the test coupon result
and apply it to the entire board. In other words: assuming that there
is a test coupon inside our board with traces on all layers and for all
different geometries/impedances, AND all of these traces are found to be
within spec, does this guarantee that all of the other similar traces on
the board are within spec? The answer is NO. This is why on demanding
boards a periodical full-board scan is a good idea to find out the
distribution of trace impedances over the various layers.
Regards,
Istvan Novak
SUN Microsystems
Lee Ritchey wrote:
> It's much more reliable to build test traces right into the PCB. That way,
> impedance can be checked anytime. Very easy to do.
>
> Lee Ritchey
>
>
>
>> [Original Message]
>> From: Salkow, Steven <steven.salkow@xxxxxxxx>
>> To: Havermann, Gert <Gert.Havermann@xxxxxxxxxxx>; si-list@xxxxxxxxxxxxx
>>
> <si-list@xxxxxxxxxxxxx>
>
>> Date: 9/11/2009 5:39:54 PM
>> Subject: [SI-LIST] Re: AW: Control Impedance testing
>>
>> Coupons are a practical way to audit Trace impedance. There should be
>>
> test coupons for every signal layer and every different type: i.e.
> differential and single ended as required. Most fabricators can now
> generate the test coupons too. If going this way, have them serialised same
> as board and note lot codes for tracking. See IPC 2221/2222 for more info.
> Your fabricator knows all about this - ask for a run down.
>
>> Steven Salkow
>> Lockheed Martin
>>
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>>
> On Behalf Of Havermann, Gert
>
>> Sent: Sunday, August 30, 2009 11:54 PM
>> To: si-list@xxxxxxxxxxxxx
>> Subject: [SI-LIST] AW: Control Impedance testing
>>
>> Dear Liao,
>>
>> there are some PCB maker out there with the capability and willingness to
>>
> test all, or selected traces of your board. Of coarse you have to pay for
> this service, as well as you have to pay for very tight impedance control.
> For mass production this is not the way to go. You have to make shure that
> the design works within all production variations. For special test cards,
> thats another story. We found a PCB maker in Germany for such test boards,
> and they guaratee a 6% tolerance for prototype volumes and test most of the
> traces. Unfortunately, they can only test single ended, thus you have to
> specify both impedances, and they will only guaratee the single ended to
> come out right.
>
>> Let me know if you would like the contact data.
>>
>> BR
>> Gert
>>
>>
>> --------------------------------------------------------------------------
>> Absender ist HARTING Electronics GmbH & Co. KG; Sitz der Gesellschaft:
>>
> Espelkamp; Registergericht: Bad Oeynhausen; Register-Nr.: HRA 5596;
> persönlich haftende Gesellschafterin: HARTING Electronics Management GmbH;
> Sitz der Komplementär-GmbH: Espelkamp; Registergericht der
> Komplementär-GmbH: Bad Oeynhausen; Register-Nr. der Komplementär-GmbH: HRB
> 8808; Geschäftsführer: Torsten Ratzmann
>
>> -----Ursprüngliche Nachricht-----
>>
>> Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>>
> Im Auftrag von BO-LIAO
>
>> Gesendet: Sonntag, 30. August 2009 14:09
>> An: si-list@xxxxxxxxxxxxx
>> Betreff: [SI-LIST] Control Impedance testing
>>
>> Dear Sir,
>>
>> My PCB supplier doesn't test control impedance on actual board. They said
>>
> control impedance is measured on test coupon.
>
>>
>> Please advice if it is realistic and reliable to use the test coupon
>>
> measured impedance?
>
>>
>> Is this an industry norm, or standard?
>>
>> Thank you.
>>
>> Best regards,
>> Liao Bo
>>
>>
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