getting rid of "Hook" and hidden capacitance

[subolg123]

Came across this little nugget recently. Co-authored by Tektronix, it is certainly interesting from back in the day when circuit board materials ( dielectrics, etc) were not super repeatable or reliable for Tek's critical requirements. It's an interesting read for those who want a historical and technical perspective on what was deemed "hook" and hidden capacitance and it is still there lurking as a potential gotcha for EEs young and old.

Enjoy! 

PS: I had to link the article to my public dropbox folder since it is larger than the 1MB file attachment limit allowed on the forum

https://dl.dropboxusercontent.com/u/6757916/_Hook%20and%20hidden%20pc-board%20capacitance.pdf

[retrolefty]

Very interesting document. But as it's dated 1978 I wonder if the PCB material manufactures have 'solved' this variation in production products?

P.S. Please don't pass this on to any of the 'golden ear' crowd, we will never hear the end of it. 

[jucole]

thanks! ;-)

[Vgkid]

Interesting read, thanks for uploading it.

[T3sl4co1l]

Cool!

Wonder how applicable it is today.  FR-4 with controlled impedances is standard today, but that's also at much higher frequencies than the article is concerned with.  Probably, bargain-basement Chinese suppliers use whatever snotty resin they have available, too.

Tim

[Ian.M]

Dropbox link expired, document reposted here:
https://www.eevblog.com/forum/beginners/isolated-usb-adapter-or-differential-probe-for-testing-non-floating/?action=dlattach;attach=1006694

[srb1954]

Tek used special circuit board laminates in their oscilloscope input circuits to get round the 'hook' problem. These special laminates were somewhat delicate compared to FR4 and there were warnings in the service manuals not to apply excessive heat or any type of solvent on these circuit boards.

[TheUnnamedNewbie]

So am I correct in understanding that this 'hook' was due to the very long dipole resonance nature of the polymer chains in the resins? This is pretty cool, interesting read, thanks!