John,

There are times when the metric system makes things seem very complicated !

The new version io IPC-A-610, (revision B) refers to solder balls of
0.13mm diameter etc.

The imperial way was a little easier to remember: (I call it the 5 ball
system!)

-  No more than 5 balls per square inch allowed
-  Solder balls cannot be greater than 5 mil (0.005in)
-  Solder balls cannot be less than 5 mil from the nearest land or trace

This is the same as the requirement in IPC-A-610B, but easier to remember.

Note: 	I have come across a few situations where people are playing  '8 ball' 
	(i.e. 8 balls/sq in, of <=8 mil diameter and >= 8 mil from conductors). 
	This is particularly the case with some companies who have been 
	struggling to come to grips with the new no-clean fluxes.


I hope that this helps...


Brendan McCormack
Senior Interconnect Engineer
AMT Ireland
Electronics Manufacturing Centre
University of Limerick
Limerick
Ireland

Ph. +353 61 331588
Fx. +353 61 330316
EM. [log in to unmask]



Origional message follows.....................



On Tue, 25 Apr 1995 [log in to unmask] wrote:

> Hi,
> 
> Does anyone have any details of specifications as to the acceptability of 
> solder balls on a finished board which details ball count per square inch, 
> maximum ball size etc.??
> 
> Thanks in anticipation.
> 
> John Burke.
> -------------------------------------
> Name: John Burke
> E-mail: [log in to unmask] (John Burke)
> Compuserve: 100575,2301
> 04/25/95
> 08:34:21
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