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August 2000

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Subject:
From:
Lee Whiteman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 23 Aug 2000 16:39:05 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (83 lines)
George,

In the IPC-A-610, Rev C., section 11.2 Jumper Wires, it reads:

Keep jumper wires as short as practical and do not route over and under
other replaceable components. Design constraints such as real estate,
availability and minimum electrical clearance, need to be taken into
consideration when routing or staking wires. Jumper wires 25 mm [0.984 in]
maximum in length whose path does not pass over conductive areas and do not
violate the designed spacing requirements may be uninsulated. Insulation,
when required on the jumper wires, needs to be compatible with conformal
coating.

Concerning your EMI question:

At frequencies above 100 MHz it can cause problems if the jumper goes over
or under a signal trace, i.e. a trace another 100 MHz or more signal on it.
You will get cross talk on the circuit. For actual radiation of power out
the board, this happens above 500 MHz. Recommend that you check the board,
and shielding of the box to determine if this is a problem.

Good Luck.

Lee Whiteman
Senior Manufacturing Engineer
ACI / EMPF
Telephone: (610) 362-1200; Ext. 208
FAX: (610) 362-1290
E-Mail: [log in to unmask] <mailto:[log in to unmask]>


> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Carroll, George
> Sent: Wednesday, August 23, 2000 3:02 PM
> To: [log in to unmask]
> Subject: [TN] Jumpers
>
>
> Ladies and Gentlemen,
> After assembly of a board, it was discovered at test that there
> was an error
> in the fab board causing a signal short.  The inner layer short
> was cut and
> a jumper installed to repair.   I request guidance regarding the allowable
> length for a jumper.  I believe the linear length of this one to
> be about 4
> inches.  Can the installation of a jumper on a board's surface cause EMI
> problems?
>
> George Carroll
> SE&A
>
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