Mr Bisson,

It is a guessing game to  troubleshoot your process from sitting
at my desk.  There are many controllable and uncontrollable
factors that causes solder ball formation.  From based upon
the info you supplied, you could try a few simple tests to narrow
down causes of solder balls.

1. Use a fresh new solder paste and perform the test as you
described.
2. Use a different mfg's NC paste and perform the test as
you described.
3. Print and remove small portions of printed paste from inside
areas of homeplate pads. And perform the test.    This step
basically removes squeezing-out effect of paste into masking
area between pads when components are placed by a pick'n
place machine.  I believe this is what happened with 2 solder
balls with homeplate.  Homeplate will not completely eliminate
this squeezing-out effect of solder paste during a component
placement and the problem of solder balls gets worse with
smaller chip components.

V-design openings eliminate squeezing-out paste and at the
same time leave enough paste area for component to hold on
during placement cycles.  We got no solder balls (very close to
zero) since we started using V-design two years ago.

regards

Matthew Park
NII Norsat International Inc.

>>> Andre Bisson <[log in to unmask]> July 13,
1998  11:49 am >>>
Mr. Park

I read you article and I agree with you. I Understand that many
people use
the homeplate or equivalent shape. My question is, in the
company I work
before, I was using a reduction of 2 mils from the pad size using
Water
soluble paste and the result was no solder ball at all (really no
solder
ball).

Now here we are using NC with the homeplate opening and
sometime we still
have some solder ball, same thing if we use the water soluble
solder paste.
I did conduct a test, just for fun,  using a Topline board with (NC
paste):

- 2 rows with 1:1 (pad vs aperture)
- 4 rows with 2 mils less
- 4 rows with homeplate

we assembled 8 boards and the result was respectively 122, 58
and 2 solder
balls.

So what is confusing me is why before I did not see solder ball
and now I'm
facing the solder ball problem?

The answer is probably the placing equipment but why? Or
maybe something else!

Any others help will be appreciate.

Thank you,


At 10:18 98-07-13 -0700, Matthew Park wrote:
>Mr. Bisson
>
>Please get hold of a March issue of Circuit Assembly.  There is
>an article that might help you with solderball problem.  I am
>available to discuss  with you if you have further questions.
>
>regards
>
>matthew
>SMT Manufacturing Engineer
>NII Norsat International Inc.
>604-597-6200, ext 254
>
>>>> Andre Bisson <[log in to unmask]> July 10,
>1998  10:40 am >>>
>Hello,
>
>I need help from people who assembled board using NC
solder
>paste. I'm
>presently facing some issues with solder balling after reflow
>using NC paste.
>
>Our parameter are:
>
>NC paste
>Good standard profile
>Homeplate opening for chip (mpm printer)
>Panasonic equipment for pick and place
>
>I'm use to run board with the following parameter with any
solder
>ball
>(different company):
>
>Water paste
>Good standard profile
>Opening reduce by 0.002" than the pad size (mpm printer)
>Contact system or Fuji Cp pick and place
>
>I will like to have comment from people who use NC paste and
>don't have
>this problem. If possible can you tell me why I have solder ball. I
>take a
>close look of the board and they are built with the ipc standard.
>
>Thank you very much,
>
>
>
>________________________________
>
>Andre Bisson
>Process Engineering
>Matrox Electronic Systems
>Tel.: (514) 969-6000 Ext: 2462
>E-mail: [log in to unmask]
>________________________________
>
>################################################################
>TechNet E-Mail Forum provided as a free service by IPC using
>LISTSERV 1.8c
>################################################################
>To subscribe/unsubscribe, send a message to
>[log in to unmask] with following text in the body:
>To subscribe:   SUBSCRIBE TechNet <your full name>
>To unsubscribe:   SIGNOFF TechNet
>################################################################
>Please visit IPC's web site (http://www.ipc.org) "On-Line
>Services" section for additional information.
>For technical support contact Hugo Scaramuzza at
>[log in to unmask] or 847-509-9700 ext.312
>################################################################
>
>################################################################
>TechNet E-Mail Forum provided as a free service by IPC using
LISTSERV 1.8c
>################################################################
>To subscribe/unsubscribe, send a message to
[log in to unmask] with
following text in the body:
>To subscribe:   SUBSCRIBE TechNet <your full name>
>To unsubscribe:   SIGNOFF TechNet
>################################################################
>Please visit IPC's web site (http://www.ipc.org) "On-Line
Services"
section for additional information.
>For technical support contact Hugo Scaramuzza at
[log in to unmask] or
847-509-9700 ext.312
>################################################################
>
>
>

________________________________

Andre Bisson
Process Engineering
Matrox Electronic Systems
Tel.: (514) 969-6000 Ext: 2462
E-mail: [log in to unmask]
________________________________

################################################################
TechNet E-Mail Forum provided as a free service by IPC using
LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to
[log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line
Services" section for additional information.
For technical support contact Hugo Scaramuzza at
[log in to unmask] or 847-509-9700 ext.312
################################################################

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################