[PCB_FORUM] Re: 0402 round pads

Tell those "some folks" that the cell phone industry lives on those microvias 
and cheap PWBs.  I believe that the video recorder industry is a heavy user of 
microvias and even uses ALIVH type vias.  
 
Point those "some folks" to the internet where they can do a quick search and 
read documents with words such as these: "Naturally however, economic 
considerations for or against play a significant role. A comparison of variable 
drilling costs reveals the superiority of microvia technology over mechanical 
drilling (Ø 0.3 mm) even with a relatively small number of holes. The 100x 
faster drilling speed and the tool costs approaching ZERO make laser drilling 
extremely fast and cheap. This effect becomes more pronounced as the number of 
drill holes increases"
 
Have a good day.
 
 

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of J Wages
Sent: Friday, January 05, 2007 5:37 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: 0402 round pads



Jelena,

I agree. I love using micro vias, but it's hard to convince some folks of the 
real value. Signal integrity plus high yield. What they see first in the 
initial fabrication costs. Tis a shame.

 

Jim S. Wages / SR. PCB Layout Designer:  

Cary, NC - H: 919-466-1596 Cell: 919-484-2963

 

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Jelena Larsen
Sent: Friday, January 05, 2007 8:16 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: 0402 round pads

 

Ah....the luxury of a micro via. If you get a chance look at an XBOX360 
motherboard, bottom side under the CPU. An array of 0402 bypass caps side by 
side tied to the plane with a standard via 10mil finished drill size. No 
tombstone issues. Manufacturing tested. Patented design. Most impressive for a 
4 layer board. Oh....the 0402 pads are rectangle. You can find pictures of it 
on the internet.

 

Jelena

 


  _____  


From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Unruh Barry
Sent: Friday, January 05, 2007 4:24 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] 0402 round pads

 

Gary

     I feel that the significance of this discussion has been missed.

 

The fact that you can imbed termination resistors and decoup caps into a 1mm 
BGA via grid on the back side is a very BIG DEAL!

The round pads enable you to do this. Maybe some other shape works also, but 
not square or rectangle.

For every 2 vias you can fit one 0402 component.

No vias need to be removed.

Short is better whether your talking about caps or termination resistors.

This technique may delay or reduce the need of moving to 0201 packages.

 

Build your 0402 alt symbol with 1 mm pad to pad spacing.

 

What we use is....

Pad size is .022".

Via size is .019".

Via to pad is .007 min.

Make the solder mask cover most of the via.

 

Of course I can't guarantee yield, but so far so good.

 

It would make placement easier to be using a metric database but not vital.

If your on an inch database use the rat going to the pad to enable you to place 
the part to the closest .0001 inch.

 

Barry Unruh

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