Kevin, this type of package is not required to have solderable surfaces
on the edges of the component--only on the bottom. The "bubble" of
solder on the edges is typical.

IPC-A-610D Clause 8.2.13 will have acceptance criteria for this kind of
package. You can download and review this draft at www.ipc.org/status

Jack


Jack Crawford, IOM
IPC Director Certification and Assembly Technology 
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Jaworenko
Sent: Wednesday, December 01, 2004 8:44 AM
To: [log in to unmask]
Subject: [TN] Help, Help, I have a QFN Package I don't know what to do!

G'day Everyone.

        Well as the subject states we are currently running a prototype
assembly with a new package style to me, a QFN (Quad Flat No-lead). I
had to look that one up myself.

        The problem is when we were trying to reflow the part, the
solder joint looks very poor, with little to no solder seen on the edge
of the component lead and the pad on the PCB, or a bubble of solder seen
on end of the component between the edge of the component lead and the
pad of the PCB.

        I'm currently setting up to X-ray the components to see if the
foot actually has a good solder joint underneath the component, where
the lead has been curled around the component, but has anyone else had
any dealings with this particular component type before and would be
willing to share?

        I looked up the component manufacture's website and they show
that this component has a required peak temperature of 235 (+5/-0)
degrees C.
That seems like a lot of heat for a non lead-free component.

        Feel free to email me offline if anyone likes.

Thanks in advance.

Kevin Jaworenko
Manufacturing Engineering Technologist
Vansco Electronics LP
(204) 453 - 3339 ext. 622
(204) 453 - 3663 FAX
[log in to unmask]


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