thanks Joey, I will look for him at the IPC HR forum.


-- 
Bhanu Sood


On Thu, Apr 26, 2018 at 10:26 AM, Jose A Rios <[log in to unmask]> wrote:

> Hey Bhanu, in my previous life we always discouraged etchback/3 pt. Legacy
> users/designs wouldn’t relent even in the face of reduced CITC performance
> (sometimes vastly reduced), when compared side to side under controlled
> conditions (same boards with and without 3pt). Kevin Knadle has all sorts
> of data showing this, unsure if he’s published anything or kept it under
> wraps.... Basically plasma etchback creates gauges or amplifies existing
> drill gauges in order to create the 3pt. Plating those tight without plated
> copper pinch points becomes tricky, and you know the rest. You may be able
> to pin Kevin down during the May IPC seminar in MD.... Give me a call if
> you want to discuss further.
>
> Sent from my iPhone
>
> > On Apr 26, 2018, at 9:56 AM, Bhanu Sood <[log in to unmask]> wrote:
> >
> > Good morning,
> >
> > Is there a recent peer reviewed study or presentation (reported in open
> > literature) that discusses the relative reliability of various etchback
> > conditions in context of applied stresses, processing conditions and
> > materials (high Tg 180C++ laminates, higher 10%++ elongation foil and
> > higher 15%++ elongation plating chemistries)? (I am not looking for
> > sections/paragraphs of applicable Standards)
> >
> > In some instances, the merits of positive etchback are discussed in
> context
> > of a "three point connection", but one disadvantage of this arrangement
> is
> > poor low cycle fatigue reliability.
> > Literature has reported that negative etchback "up to a certain extent"
> is
> > reliable, however one disadvantage is a possibly poor foil to barrel
> > connection in cases where process residues prevent a good connection with
> > the foil. The no etchback (only smear removed) is also shown in
> literature
> > as reliable, and the middle of the road solution to the etchback
> > requirement.
> >
> > Thanks,
> > Bhanu
> >
> > --
> > Bhanu Sood
>






-- 
Bhanu Sood
Tel: (202) 468-8449