Well, maybe, maybe not. A Pb-free paste may need a more stringent
requirement because it needs to hold together for a longer time to
liquidus. So it would make sense if the Pb-free paste was required to
maintain a brick for up to a minute or even longer.
The problem is that when you change the paste rheology to accomplish one
thing, you usually sacrifice another. If you decrease the tack to reduce
slumping, you decrease the ability of the paste to retain the part when
they are being placed in a high-speed turret-type shooter. So
essentially different pastes work better for different applications.
A paste such as Kester R562 may be great for a production line with a
gantry-style placer such as the Mydata, but it may be a disaster for a
high-speed turret chipshooter like the Fuji.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Richard Kraszewski
Sent: Thursday, February 19, 2009 3:02 PM
To: [log in to unmask]
Subject: Re: [TN] Hot Slump
No. The negative effects of solder balls transcends both Pb-free and
Sn/Pb.
Rich Kraszewski
Plexus
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Thursday, February 19, 2009 2:41 PM
To: [log in to unmask]
Subject: [TN] Hot Slump
Technetters,
I would like your opinion on this.
IPC-TM-650, Method 2.4.35 Solder Paste - Slump Test--1/95 states that
hot slump is measured after exposure to 150C for 10 to 15 minutes. Do
you think this should be changed for lead free solder pastes?
Bev
RIM
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