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July 2009

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Subject:
From:
Jack Olson <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jack Olson <[log in to unmask]>
Date:
Fri, 31 Jul 2009 08:36:39 -0500
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That makes perfect sense, thanks.

When reading the text, the part that wasn't apparent to me was the fact that

most designs have enough features breaking up the planes to provide those
etched areas for bonding. (maybe we could add one extra sentence somwhere
around paragraph two, but we can talk about that at IPC MidWest, right?)

Just one more question before I thoroughly annoy the other 1000 people who
don't care about this subject: During the UL certification process that you
mentioned, is it the layer to layer lamination they are worried about, or
the
mask adhesion to the surface layers, or both?

seeya in September,

Jack

On Thu, Jul 30, 2009 at 6:55 AM, Gary Ferrari <[log in to unmask]>wrote:

> Jack,
>
> Brian's reasoning is the closest. Blistering, warpage, etc. are all
> considerations. A fabricator still must qualify his ability to build large
> unbroken copper areas for his UL certification. If they normally deal with
> large copper areas in their products, they will submit an appropriate test
> vehicle to UL for approval. A little side note, if you are building products
> that must have UL certification, then you must validate that your suppliers
> have certified to your type of construction (an entirely new discussion).
>
> This all said, let's do a quick reality check with today's technologies.
>  Blistering problems, etc. are still a risk. But seriously look at today's
> boards. Circuit density is much higher using vias (holes) all over the
> place, which in turn break up large copper areas, naturally. Years ago
> component density was much less and designers took pride in designing boards
> with no vias, resulting in many areas of unbroken copper. Sometimes I think
> that today's CAD systems vie for who can place the most vias on a board.
>
> So, I believe today's high design designs naturally break up larger
> conductive areas, resulting in a general loss of the fundamental reasoning
> behind the still valid recommendation. As RF and microwave designs increase
> in demand, so does the necessity for fabricators to re-qualify with UL,
> something that is normally done outside of the designers watchful eye.
>
> On a side note, I see many instances where the reasoning for fundamental
> recommendations have been lost over time.
>
> Gary
>
> Jack Olson wrote:
>
>>  Greetings,
>>
>> I was just reading through the latest draft of IPC-2222,
>> and stumbled into the advice in section 10 regarding
>> "large conductive areas", where we are advised to
>> use some kind of etched pattern (cross-hatching)
>> for any area larger than a 25mm diameter circle.
>>
>> I have done this exactly once in the last 22 years,
>> does anyone else do this?
>>
>> Has anyone ever experienced a problem by NOT doing
>> this? (not counting soldermask over HASL)
>>
>> Jack
>>
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