[PCB_FORUM] Re: BGA Fanout / Filled vias

  • From: "J Wages" <jwages@xxxxxxxxx>
  • To: <icu-pcb-forum@xxxxxxxxxxxxx>
  • Date: Thu, 16 Feb 2006 07:21:06 -0500

I'd find a new assembly house. 
We use soldermask encroached vias and fan out typical 1mm bga's that
have 21 mil pads with 20 mil vias and hold around 7.34 to 7.35 mils
spacing. The key is to encroach the vias. My 20 mil via has an 8 mil
plated hole. The soldermask opening is only 14 mils in diameter. 
Good luck.

Jim S. Wages / SR. PCB Layout Designer:  
Cary, NC - (919) 466-1596

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Mark Salberg
Sent: Thursday, February 16, 2006 4:25 AM
To: Cadence User Group
Subject: [PCB_FORUM] BGA Fanout / Filled vias

Hello all,
What BGA Ball pad to via clearance is needed for BGA fanout?
Our Assembly house is telling us that we need 10 mil copper to copper 
(15mil preferred).
On 1mm BGA's using an 18mil via with 8mil drill gets us 9.8mil via to
pad.
On our .75mm BGA this via gets us 4mil via to pad. Which also breaks the

soldermask dam.

Is epoxy filled and tented vias our best or only option at this point?

Thanks for any input.
Mark


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