I'd start with a temperature profile with the Thermocouple on couple of pads
that are bad and couple that are good to determine if the thermals are doing
their job.
The wetting or flux system seems to be suspect. I would imagine this is the
result of the second pass, but he solder never made it to the edges, and
these are huge pads for this part design.
The finish will dictate the wetting properties, but for starters the temp
profile and flux I think is the culprit.
The grainy structure give the appearance of rapid cooling or possible
movement during Apha stage, so it could be disturbed, but aren't we all...
Rodney
-----Original Message-----
From: Howard Watson [mailto:[log in to unmask]]
Sent: Tuesday, September 02, 2003 5:08 PM
Subject: Re: pic's
Hi all,
I work with Lance and he just signed on to the TechNet. I guess that
means he gets a "free" attachment pass. The odd thing about what we are
seeing with these diodes is that:
1) The problem occurs with diodes only from ON Semiconductor.
2) On some diodes, the solder joint on one lead is nice and shiny, like
all the others on the board, but the other lead will have the "disturbed"
look. It occurs inconsistently among the 9 ON diodes on the board.
Several different reel lots were evaluated, with no difference. A reel
was sent to ON for solderability testing, and not surprisingly, the
results came back with no solderability problem (they only tested 5
components).
If this were disturbed soldering, how could this show up only on a diode
and only from one manufacturer (there are several diodes from other
Mfg'rs)?
Some other points to note: this is the 2nd side of reflow with 300
components, it's on a chain conveyor, there are two cooling zones in the
10 zone oven. Thanks for the feedback.
Howard Watson
SMT Manufacturing Engineer
AMETEK/Dixson
Carlr Ray <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
09/02/03 02:18 PM
Please respond to "TechNet E-Mail Forum."; Please respond to Carlr Ray
To: [log in to unmask]
cc:
Subject: Re: [TN] pic's
Lance,
Couple of questions for you.
1. Does the product ride through the oven on a conveyor (grid or belt),
or is it a rail system?
2. Has anyone checked to make sure the transport method (grid/belt or
rail) is operating correctly and not jerking or causing movement of the
product during reflow?
3. Does you reflow oven have a cooling section? If so is it possible
that it is cooling the units to quickly?
Sorry I don't have any suggestions but I do agree with a previous email
that is appears as though the components were disturbed during the
reflow process. I do not see any solder defects but I do think that this
could lead to defects if the problem is not corrected.
>>> [log in to unmask] 9/2/2003 2:16:06 PM >>>
I have attached some pictures of components that always seem to have
one
joint that is not soldered as the other end. These happed mainly with
this component at various sites on the board. Is this a contamination
a
disturbed joint or a cold joint. This is an SMT process and the
problems
vary
on the runs. I would like to know if this is a defect for class 2 or
not.
Thanks in advance for your time.
P. Lance Mayes
Mfg. Trainer
----- Forwarded by Lance Mayes/CO-GRA/Ametek on 09/02/03 01:07 PM
-----
Howard Watson
08/27/03 05:33 PM
To: Lance Mayes/CO-GRA/Ametek@Ametek
cc:
Subject: pic's
Howard Watson
SMT Manufacturing Engineer
AMETEK/Dixson
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