LISTSERV - DESIGNERCOUNCIL Archives

DESIGNERCOUNCIL Archives

August 2005

DesignerCouncil@IPC.ORG

	LISTSERV Archives
	DESIGNERCOUNCIL Home
	DESIGNERCOUNCIL August 2005

	Log In
	Register

	Subscribe or Unsubscribe

	Search Archives

Options:	Use Monospaced Font Show Text Part by Default Show All Mail Headers
Message:	[<< First] [< Prev] [Next >] [Last >>]
Topic:	[<< First] [< Prev] [Next >] [Last >>]
Author:	[<< First] [< Prev] [Next >] [Last >>]

Subject:	Re: .5mm pitch bga's ...
From:	"Litson, Cherie" <[log in to unmask]>
Reply To:	(Designers Council Forum)
Date:	Thu, 11 Aug 2005 10:48:44 -0700
Content-Type:	text/plain
Parts/Attachments:	text/plain (45 lines)

Frank,

How many pins in this bga and are there any "blank" rows or columns?  We have had a similar problem with a .65mm, 625pin bga with 95% of the pins used.  We were able to use 4mil micro vias in the pads and break out on layer 2. The capture pads on layer 2 can be 12 mils with the top pad being the same as the bga (11.8mils).  The outside 2 rows were routed on layer 1 (we could get a trace between the pads) and layer 2 on the next 2 rows.  This didn't totally do it.  We used some special buried vias that have caused us problems (too small) due to multiple pwr rails and poor signal placement in the bga.  Given a choice, I wouldn't do it this way again.  I would rather go with multiple stacked vias between layers 2-3 & 2-4.  Maybe more if we needed them. Run this by your fab house or OEM and see if they can do it. 

IMHO, I think multiple stacked micro vias are going to be the only way to go to get these small pitch/high pin count bga's to break out.  Especially as more controled impedance signals are added to the designs.  Gold plating on the top causes plating problems with small signal traces (even 4mils) as well.

Cherie


-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]]On Behalf Of Frank
A Bergmeister
Sent: Thursday, August 11, 2005 7:34 AM
To: [log in to unmask]
Subject: [DC] .5mm pitch bga's ...


I have a design with about 6 .5mm pitch bgas.  Only one pin inside of the
outer ring is being used.  How is everyone making the connection?  The
padstack for the bga is .0118 (per 7351).  I don't want to use via in pad
because the via is too big and ends up too close to the next pad.  I can
route .003 but it is an external layer so plating becomes an issue.  Plus
it's a class 3 design.  Love to hear what others are using for this size
bgas.

Frank

---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------

---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------

ATOM RSS1 RSS2

LISTSERV.IPC.ORG