TECHNET Archives

August 2009

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Thu, 6 Aug 2009 13:19:43 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (165 lines)
Bev, I think this looks good to me.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Thursday, August 06, 2009 11:35 AM
To: [log in to unmask]
Subject: [TN] Let's try this again - Underfill Workmanship

TechNetters, 
I put out to you last week a newer version of the document we had put
together on the above titled subject. I did not receive a single comment
back, either on or off line from TechNetters.  :(  I am trying again.

There are some additions but also some changes because I had had some
grief that what was being asked for in the previous version was not
always attainable.  Changes are in capitals, since TechNet can't show
colors or italics.

The creep of solder into connecting voids has been argued to not be a
high level concern where:
1) the product use temperature is less than 50C
2) the product has a practical lifetime of about two years
3) The solder used is SAC305, not the lower melting SnPb eutectic.

Hope this sparks a good technical discussion. It is not Friday yet.

Bev
RIM

Workmanship Standards for BGA and CSP Underfills

For general inspection of all circuit packs coming down a production
line, apply only the portions of this document that can be performed
visually to underfilled, uncovered CSPs and BGAs or those same types of
components under fence and lid RF shields. The visual inspection rules
do not apply to CSPs and BGAs for general production under single piece
RF cans. This would require destruction of all product.

However, all the rules apply for process development/product
qualification where one is willing to sacrifice finished circuit packs
to gain knowledge of the acceptability of the overall quality.


Target - Class 1,2,3
*	Component requiring underfill completely underfilled with a good
fillet all the way around, the fillet just approaching the maximum
component body height, completely cured, no encroachment onto other
components and no voiding whatsoever

Acceptable - Class 3
*	At least 50% fillet height up the side of the component body

*	Small pin holes and voids are permissible provided they do not
exceed 5% of fillet surface area and have a maximum diameter of 0.5 mm
(0.020 inches).

Acceptable - Class 1,2
*	Component requiring underfill underfilled such that all balls
are covered, but no evidence of an exterior fillet, no encroachment onto
other components and no voiding whatsoever.

*	Component requiring underfill underfilled such that all balls
are covered, with or without an exterior fillet, no encroachment onto
other components and only small voids, not touching any solder joints.

*	Component requiring underfill underfilled such that all balls
are covered, with or without an exterior fillet, no encroachment onto
other components and even large voiding, but not touching any solder
joints.

*	TOTAL VOID AREA, IRRESPECTIVE OF LOCATION, AS A PERCENTAGE OF
COMPONENT AREA SHALL BE EQUAL TO OR LESS THAN 10%.
*	A VOID OR VOIDS LESS THAN OR EQUAL TO 50% AROUND THE PERIMETER
OF ONE OR MORE SOLDER JOINTS, INCLUDING IN AN OUTER ROW.

*	VOIDS GREATER THAN 50% AROUND INNER ROW SOLDER JOINTS.

*	SOLDER JOINTS WITH VOIDS COMPLETELY SURROUNDING INDIVIDUAL
SOLDER JOINTS AND/OR VOIDS CONNECTING TWO SOLDER JOINTS MAKE UP LESS
THAN 10% OF THE TOTAL NUMBER OF SOLDER JOINTS OF THE COMPONENT.  THIS
RULE ONLY APPLIES TO INNER ROW SOLDER JOINTS (E).

Defect - Class 3
*	LESS THAN 50% FILLET HEIGHT UP THE SIDE OF THE COMPONENT BODY

*	SMALL PIN HOLES AND VOIDS EXCEEDING 5% OF FILLET SURFACE AREA
AND/OR HAVE A MAXIMUM DIAMETER OF GREATER THAN 0.5 MM (0.020 INCHES).

Defect - Class 1,2,3
*	Underfill completely missing from components where it is
required

*	Underfill not completely covering all the peripheral solder
joints

*	Voiding such that a void traverses the distance between two or
more OUTER ROW solder joints (DELETE under the array device requiring
underfill)

*	A void or voids more than 50% around the perimeter of one or
more OUTER ROW solder joints

*	Material extending on to the top of the BGA or CSP

*	Uncured material

*	Underfill interfering with proper placement of a heatsink or
other mounted or mechanical devices or would interfere with the assembly

*	There should be no evidence of underfill flowing out through
holes under the device.

*	After curing there should be no visual evidence of cracks
between the device surface, underfill or board.

*	There should be no evidence of damage to the board or device
caused by contact with the dispensing needle or height sensor.

*	Underfill filler shows evidence of separation

Special Conditions - Class 1,2
*	Encroachment onto other components, but meeting all other
criteria above for target or acceptable conditions will be dealt with as
a pass/fail on a case-by-case basis



---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential
information, privileged material (including material protected by the
solicitor-client or other applicable privileges), or constitute
non-public information. Any use of this information by anyone other than
the intended recipient is prohibited. If you have received this
transmission in error, please immediately reply to the sender and delete
this information from your system. Use, dissemination, distribution, or
reproduction of this transmission by unintended recipients is not
authorized and may be unlawful.

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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 15.0
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
-----------------------------------------------------

ATOM RSS1 RSS2