Actually a "keyhole pattern" where the solder is allowed to wet out
along the trace for a very short distance outside of the ball diameter
has in fact been used for many years by the flip chip industry. The
distinct "keyhole" shape is an instant indication on x-ray that the
solder on the ball wet to the pad and flowed out a short distance.
In flip chip though, this is not done with masking, but it is done by
using an osp coating on the copper pad and trace (non solder mask
defined pad), and using a low activity flux on the flip chip ball. The
wet out is actually controlled by flux activity, and is very consistent
where the flux is applied in a consistent manner (typically half ball
depth).
John
John Burke
Senior Manager - Operations , Optichron
[log in to unmask]
W: 510 249 5233
M: 408 515 4992
http://www.optichron.com
Profile: https://www.linkedin.com/e/fps/2665502/
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Friday, April 21, 2006 1:35 PM
To: [log in to unmask]
Subject: Re: [TN] BGA and CGA pad questions.
Diamond shape because when the solder wets out to the corners of the
land
the pattern is not simply a squashed ball, but has for distinct gray
corners. I first heard this DFM guidance from Glenbrook. But, I have
also
heard it argued that these land patterns may produce stress points that
could lead to reduced service life in of the joint. I don't have data to
support the argument against the square or diamond land pattern design.
They
are not commonly used.
I will say this, a key hole pattern, that can be produced by a
non-solder
mask defined land, can give a similar result. A distinct gray pattern
where
the solder wets down the trace leaving the pad.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Scott Decker
Sent: Friday, April 21, 2006 1:40 PM
To: [log in to unmask]
Subject: [TN] BGA and CGA pad questions.
All,
I was talking with our Manufacturing engineer the other day and the
people that make the SMD re-work station tools, about the pads used for
both BGA's and CGA's. The vendor was saying that diamond pads, (square
on a 45') were better for X-Ray inspection because you can see the pad
verses the pin/ball better during the inspection of the solder joints.
The X-Ray manufacturer' says the same thing, but has anyone done it this
way yet? It sounds good to me, but does anyone have any practical
experience with the diamond pads? How do you figure size between round
to square, etc.? Is it just area calculations or flat side the same as
diameter, etc.? Paste Mask sizing, Solder Mask defined, (not my thought)
or just the standard oversize, etc.? These would be for high-reliability
applications and from what I understand, the CGA is better in that
respect. Any info would be great to hear. Thanks in advance.
Scott Decker
AKA: Padmasterson
Broad Reach Engineering CAE
Ph. 480-377-0400 Ext. 34
FAX. 480-968-4597
Tempe, AZ.
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/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
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/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
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/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
-----------------------------------------------------
|
