>>> "Mike Fenner" <[log in to unmask]> 09/17/01 10:08AM >>>

When you say "same formulation" do you mean the same generic type: OA water
washable flux. Or do you mean solder free solder paste/solderpaste vehicle
as supplied by the exact same supplier as your solderpaste?
What you have done is OK as a diagnostic but suggest no more than that. (I
wouldn't be too happy with it as its unlikely you have the same mixing
equipment, QC procedures and documentation as a regular paste supplier:)

Can I ask what happened when you did a "back to as it should ideally be
test". That is do some runs with a brand new paste on a clean stencil. Clean
means no dried out paste and no residual stencil cleaning chemical in the
openings (especially IPA and similar).

Some water wash pastes are quite vulnerable to moisture pickup and premature
ageing leading to spitting and clogging, the addition of fresh flux will
restore the activity somewhat and reduce the incidence of beading/balling,
(but will add variables to everything else such as print, tack, tack life
etc)

Best regards
Mike Fenner
Applications Engineer, European Operations
Indium Corporation
 T: + 44 1908 580 400
M: + 44 7810 526 317
 F: + 44 1908 580 411
 E: [log in to unmask] 
W: www.indium.com 
Leadfree: http://Pb-Free.com 
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jack Crawford
Sent: Monday, September 17, 2001 3:15 PM
To: [log in to unmask] 
Subject: [TN] solder beads




>>> "Marsico, James" <[log in to unmask]> 09/17/01 07:51AM >>>

We've been struggling with solder beads recently, which, after an aggressive
aqueous cleaning, have been found under some chip capacitors.  We've
probably had this problem all along, but we just got a new inspector who
decided to look under components.  Anyway, Our SMT operator decided to do
some experimenting and added liquid flux to the solder paste (Why?  Beats
me!).  The water soluble flux he added is the same formulation as the flux
in the paste.  Low and behold, the solder beads seem to have been
significantly reduced.  The only explanation I can think of is that the
extra flux results in smaller beads which wash away and don't get stuck
under the components.  Any comments?

Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879

---------------------------------------------------------------------------------
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
---------------------------------------------------------------------------------