Hi Genny,

You want your pad sizes to be the same size as the pad on the particular
package.  This pad size is ALWAYS smaller than the ball diameter.  The pad
size is usually not called out on most manufactures spec sheets, so you will
have to do some research and ask questions.  If you can't find the pad size
for a specific BGA, a good rule of thumb is the 20% smaller than the ball
diameter rule given by MoonMan.

When you get down to 0.5mm pitch, other special rules will apply because the
pads can become so small that the risk of pads not adhering to the board
becomes a concern.

Kind Regards

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Genny Gibbard [SMTP:[log in to unmask]]
> Sent: Tuesday, November 06, 2001 8:25 AM
> To:   [log in to unmask]
> Subject:      [TN] BGA's in design
>
> OK, in the next few months we will probably design our first board that
> uses
> a BGA, and we are jumping in with both feet.  This board will have a 304
> ball 1.27mm pitch, a 432 ball 1.27mm pitch, a 196 ball 1.00mm pitch and a
> 256 ball 1.00mm pitch.
> Are there any resources for free land patterns for these babies?  Or how
> do
> you determine the pad size knowing the ball diameter and pitch?  Almost
> every place I found on the web with BGA patterns was selling them.  I was
> looking at the table of contents for the SM-782A standard and it only
> mentioned 1.27pitch.  Is the information in the standard easily scalable
> to
> smaller pitch?  It could be a hard sell to convince my company to buy
> patterns, which means we will probably make our own which doesn't always
> make for very good DFM.
> Secondly, (I hesitate to ask this, because I may get a bunch of
> solicitations, but) does anyone have some recommendations for board
> fabricators in Canada that can handle the BGA requirements?  We have had
> questionable quality from most or all of our current board vendors at some
> time or another (remember the switched inner layers?)  and I am looking
> for
> some new sources.
>
> Regards.
>
> Genny Gibbard (mailto:[log in to unmask])
>
> --------------------------------------------------------------------------
> -------
> Technet 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 Technet
> To temporarily halt delivery of Technet send the following message: SET
> Technet NOMAIL
> Search previous postings at: www.ipc.org > On-Line Resources & Databases >
> E-mail Archives
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> ext.5315
> --------------------------------------------------------------------------
> -------

---------------------------------------------------------------------------------
Technet 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 Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------