Sometimes they look much worse from the outside of the package than they actually are due to the limited solderability of the vertical termination edges (no plating on the no-lead). The actual connection is at the bottom of the termination under the component.
You will find acceptability criteria in the new IPC-A-610D for these popular components.
Mel
Mel Parrish
Director of Training Materials and Resources
Soldering Technology International Inc.
102 Tribble Drive
Madison, AL 35758
256 705 5530
256 461 9566 Fax
[log in to unmask]
www.solderingtech.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Guy Ramsey
Sent: Wednesday, December 01, 2004 12:38 PM
To: [log in to unmask]
Subject: Re: [TN] Help, Help, I have a QFN Package I don't know what to
do !
The QFN package can be hard to heat. Did you profile the part in question?
You may find that the max temp under the component (where the solder melts)
was 10 to 15 degrees cooler than the leads of a near by QFP, and the dwell
above reflow substantially shorter than you think. This package and those
"Land Grid Arrays" drive me nuts.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kevin Jaworenko
Sent: Wednesday, December 01, 2004 12:34 PM
To: [log in to unmask]
Subject: Re: [TN] Help, Help, I have a QFN Package I don't know what to
do !
In our facility we try to limit the max temperature during reflow to 220C.
Some of the components we use have max temperature ratings of 230C, so we
prefer to have little process variation within our facility. One profile
spec for all products. That may indeed change if/when we go lead-free, but
for now it works for us.
-----Original Message-----
From: Joyce Koo [mailto:[log in to unmask]]
Sent: December 1, 2004 11:11 AM
To: [log in to unmask]
Subject: Re: [TN] Help, Help, I have a QFN Package I don't know what to
do !
what is the reason to prohibit you go to 235C?
jk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kevin Jaworenko
Sent: Wednesday, December 01, 2004 11:29 AM
To: [log in to unmask]
Subject: Re: [TN] Help, Help, I have a QFN Package I don't know what to
do !
Thanks for the good questions back.
To answer the questions:
What is the lead finish of the QFN package? It is 85SN/15PB.
What is the component dimensions? They are 5.0mm by 5.0mm by 0.9mm
What paste am I using? We are using Kester easy profile 256.
How many layers in the PCB? This is a 4 layer PCB.
What is the PCB thickness? The PCB is 1.6mm thick.
Is this the only component that is not reflowing well? Yes
Thanks in advance.
-----Original Message-----
From: Morse, Carrie [mailto:[log in to unmask]]
Sent: December 1, 2004 9:32 AM
To: [log in to unmask]
Subject: Re: [TN] Help, Help, I have a QFN Package I don't know what to
do!
Good Questions.
Also...What type of solder paste are you using?
What does your recipe/profile look like? Ramp, Soak, Reflow times and
temps?
What is the thermal mass of the board? Ex: # Layers, Thickness, Type of
Layers?
Is this the only component that did not reflow well?
-Carrie
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Wednesday, December 01, 2004 10:06 AM
To: [log in to unmask]
Subject: Re: [TN] Help, Help, I have a QFN Package I don't know what to
do!
Hi Kevin! What is the lead finish of the QFN package? Having that
information will helpful to the TechNetee's in assisting you. Also, what
are the package dimensions?
Dave Hillman
Rockwell Collins
[log in to unmask]
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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