Not if you qualify your vendor properly.  Four reflow normally should be
used for qualification.... Or 3 reflow plus one wave.... Depend upon it
is mixed or not.... (At user's location, not include HASL, plating
reflow at vendor site...).  Find open via at assembly is non-starters
(you pay 10x more than qual the board house...).
Poor ($) fellow's take on this...
                                                       jk

>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of
>Robert Tarzwell
>Sent: Tuesday, July 08, 2003 4:17 PM
>To: [log in to unmask]
>Subject: Re: [TN] Operating temperature of PCB
>
>
>Hi guys  and the answer is yes each pass through a solder temp
>cycle destoyes the board a little more. most .062 1 oz plated
>boards can only withstand 2 or 3 cycles before they start to
>crack at the via to joint. now as most things are cumilitive
>and definable it may take 4-5 to acualy open but I have and
>can easly find cracks starting as low as 2 cycles. remeber the
>board manufacturer takes two cycles away because he hot oil
>reflows and he oven cures for solder mask. I have a chart
>where I did a test of copper thickness vers's heat cycles. 1
>oz fialed in 5 to 7 cycles ( no pcb manufatures cycles)  2 oz
>survived 7 to 12 3 oz 15 to 20 4 oz threough 10 oz were not
>realy affected. it appears that the heaver copper vias are
>able to resist the push of the expansion forces happening when
>you solder. the initial question was does high temp affect a
>board and the answer is more then you think. So if you want a
>very reliable board add extra plating, this can be done quite
>easly by starting with 1/4 oz copper and use 3 or 4 mil dry
>film and plate up . The etching is faster and the line
>definition will be much better, but best of all your board
>will withstand twice the relfow solder cycles.
>Robert tarzwell   author of  high powered printed circuits and,  flex
>circuit design  Megadawn.com
>
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