Hi Matthew

No problems (I was surprised too) here .
Perhaps few quartz IR bars would help you to boost the top ;
seems the plcc's drains too much , the heat flow around square is bit
sluggish .
I found convection with touch of IR (only if you need it) ideal
combination .

Paul
>----------
>From:  Matthew Park[SMTP:[log in to unmask]]
>Sent:  Wednesday, 7 January 1998 9:29
>To:    [log in to unmask]
>Subject:       Re: [TN] Lead Solderability - second reflow -Reply
>
>Paul,
>
>Are you saying "maintaining two different temperatures" for
>top and bottom sides during the second reflow?
>
>I remember testing reflow temp profiles with the bottom
>side reflow zone set at 20'c to 30'c lower than the top side
>reflow zone.  Since the board temp on the bottom side is
>about 5 to 10'c cooler, it works quite well for preventing
>components falling off, but once in a blue moon, causes
>unsoldered joints for top side large smt components like
>PLCC's.
>
>Matthew
>
>>>> Paul Klasek <[log in to unmask]> January 6,
>1998  1:47 pm >>>
>Hi Krishna
>Apart from what Matthew recommends, if you do not want to
>go through
>glue process and do not want to reflow base again and have
>to keep chips
>on base as well at the same time ;
>with convection you have an option of "chilled" base air feed
>with up to
>a 25C temp. difference ,
>that would hold you anything.
>Tested & proven , original equipment or pending your oven
>perhaps a mod.
>Without sparking commercials , write me back on my
>address, I'd have to
>refer you to a specific solution .
>
>See you                  Paul
>
>>----------
>>From:  Krishna
>Kalyan[SMTP:[log in to unmask]]
>>Sent:  Wednesday, 7 January 1998 2:15
>>To:    [log in to unmask]
>>Subject:       [TN] Lead Soderability - second reflow
>>
>>Hello :
>>
>> Happy New Year to all of you.
>>
>> I am a process engineer trying to resolve the falling of a
>bottom side
>>surface mount component during second pass of forced
>convection reflow.
>>I am beginning to feel that the solderability of the
>component leads is
>>getting reduced after the first pass of reflow and that is
>causing the
>>part to fall. If any of you have had similar experiences, could
>you
>>please share ? Your suggestions are welcome.
>>
>>Krishna Kalyan
>>
>>
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