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October 2005

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Subject:
From:
Frank Kimmey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Frank Kimmey <[log in to unmask]>
Date:
Mon, 10 Oct 2005 13:58:13 -0700
Content-Type:
text/plain
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text/plain (152 lines)
John,
Your assy can probably be reflowed.
I would suggest using ENIG as the finish for your bars and PCB.
You should then be able to solder using Sn97Ag3 in either a convection with modified profile or a conduction oven.
Make sure you are using high Tg/Td materials for the PCB (will need to with stand multiple excursions to ~245C).
You will likely need to fixture for second RoHS reflow of components, but this should be the easy part.
Call me if you want to discuss off line.
Hope it helps,
FNK

Frank N Kimmey CID+
Principal PCB Designer
Powerwave Technologies Inc
Office 916-941-3159
Fax 916-941-3195
Cellular 916-804-2491


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of John Bauer
Sent: Monday, October 10, 2005 1:43 PM
To: [log in to unmask]
Subject: Re: [TN] Buss Bar Attachment Method


Hi Franklin,

1.      Does it need to be plated or can it be attached with nut-bolt?

The current design which I have been asked to duplicate as close as possible
has the buss bars as plated. There are a total of three bars. There are two
on the input end and one on the output end of the board. On the input end
there is one bar on top and one on the bottom and are offset from each
other. These bars can have up to 450V between them.

2.      Are there standoffs or other protrusions that can be inserted into
the pcb?

None.

3.      Is this a solid bar or are there holes? Do the holes align with any
holes on the board (i.e. tooling, contact, etc)

The bars are solid with the exception to the two large treaded holes for
aligning the bars in an assembly fixture and for attaching the lug from the
end of a very heavy gauge wire when the assembly is complete.

4.      Is this being attached at the beginning of the process, middle, end?

Currently it is being attached in the beginning before anything else using a
250W hand-held soldering iron.

5.      As for plating options, is there any reason it cannot remain bare
copper? What is the environment it will be used in? heat, humidity,
corrosive, neutral, sealed?

The end application for this PCBA is to drive the motor of an electric car.
This assembly does get warm. It is mounted on a large heatsink which is
mounted in an enclosure with other PCBA's.

Personally I would love to be able to attach these things with regular
hardware but one of the engineers here says that this assembly is very
sensitive and any added inductance can actually impact the way this assembly
performs.

I failed to mention in my earlier email that this PCB is fabricated with
10oz of copper. So not only do I have to deal with the bars being a big
heatsink but the board is too.


Best,

~John

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Bauer
Sent: Monday, October 10, 2005 12:24 PM
To: [log in to unmask]
Subject: [TN] Buss Bar Attachment Method

Greetings,

We have an application where we will be attaching a buss bar that is 6
inches in length X .50 inch wide X .125 inch thick to the surface of our
PCBA. The buss bar material is currently spec'd as full hard copper and is
tin-lead plated.

The .50 inch width side of the buss bar will be the surface soldered to
the PCBA.

My questions to you are

1) What process would be used to solder this bar to surface of the PCBA?

2) What plating options would be recommended other than tin-lead for this
buss bar?

The end use application for this will require that it handle 1000A of
current in a worst case scenario.

Thanks in advance,

John Bauer

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