Carey,
thank you for your reply.
In my company we are making tests in the area of microvias.We are
investigating different processes for creating of microvias (
photovias,different types of laser drilling as well and controlled deep
mechanical drilling using flat bits). Metallisation of the holes is based on
conventional permangatate desmear followed by copper electroless process
and the final copper thickness of 20 to 25 microns is build by pulse
plating.We got good results with laser drilled holes down to 4 mills
diameter and mechanical drilled blind vias 5 mills diameter.
The question of the finishing arose during technical discussion with one of
our customers concerning test vehicle.The customer spoke about pads with
blind hole within the pad.The customer stated,that from his point of view ,
he preffers flat pad .I do not know,how essential is this request,since I
know nothing about assembly problems.From my own experience I know,that this
can be achieved using traditional additive lamination ( external layer
pre-drilled,holes plated and laminated) ,which assure the hole completly
filled with the resin and then the outer surface is again overplated
creating "no-hole".
May be now my question is more clear concerning the practice.
I does no seams to me feasible to fill such hole ( 4 mill diameter drilled
hole after metallisation it will be 2 to 2.5 mill internal diameter,less
than 2 mill deep) with LPI or any kind of fill material due to registration
problems.To fill it with electrolytic copper is may be possible,but very
problematic to achieve.
Best regards
Edward
P.S.
Following your Shana Tova I presume you are "one of ours",so I am wishing
you Gmar Hatima Tova
Edward Szpruch
Eltek , Manager of Process Engineering
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel ++972 3 9395050 , Fax ++972 3 9309581
e-mail [log in to unmask]
> -----Original Message-----
> From: Carey Pico [SMTP:[log in to unmask]]
> Sent: ד ספטמבר 15 1999 20:10
> To: TechNet E-Mail Forum.; edward Edward Szpruch
> Subject: Re: [TN] BGA micro-blind vias
>
> Edward
> There is no "common practice" for BGA's. It depends on the PWB shop and
> customer requirements. Also on the BGA density (of connnections).
> Microvias range in size from 2-8 mils diameter. Plating is typically
> electroplated copper (although the photovia process is being demonstrated
> by
> conductive inks provided by ORMET). Most don't require microvias below
> 4-5
> mils (because of the cost of manufacturing).
>
> There is much more detail to go into, but your question is vague. Do you
> need to locate a laser drill shop, board supplier, etc? Or is this
> educational?
>
> Shannah Tovah
>
>
> -----Original Message-----
> From: edward Edward Szpruch <[log in to unmask]>
> To: [log in to unmask] <[log in to unmask]>
> Date: Tuesday, September 14, 1999 5:06 AM
> Subject: [TN] BGA micro-blind vias
>
>
> >Hi,
> >What is the common practice concerning blind-microvias located on BGA
> pads:
> >a) open ? ( 2-3 mills diameter, 2 mills deep)
> >b) filled with what ( fill materials,LPI solder mask)?
> >c) filled with electroplated copper ?
> >Pls advice
> >
> >Edward Szpruch
> >Eltek , Manager of Process Engineering
> >P.O.Box 159 ; 49101 Petah Tikva Israel
> >Tel ++972 3 9395050 , Fax ++972 3 9309581
> >e-mail [log in to unmask]
> >
> >##############################################################
> >TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> >##############################################################
> >To subscribe/unsubscribe, send a message to [log in to unmask] with
> following
> text in
> >the body:
> >To subscribe: SUBSCRIBE TECHNET <your full name>
> >To unsubscribe: SIGNOFF TECHNET
> >##############################################################
> >Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> >information.
> >If you need assistance - contact Gayatri Sardeshpande at [log in to unmask]
> or
> >847-509-9700 ext.5365
> >##############################################################
> >
>
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################
|
