HI Alain,
Regarding your damaged PTH. Assuming that the lands,
and any circuitry connected to the lands, are still
good ---- jumper wires are not needed to insure a
reliable electrical connection.
That said. During the repair, first the lands should
be tinned with solder, and once the “correctly sized”
eyelet is installed, the eyelet flanges must be
soldered to the lands.
The forming of the eyelets will create a “mechanical”
connection to the lands, but it is the solder joint
that makes the reliable electrical connection.
OOPs, the technicians at CAE damaged the circuitry
connected to the land, or the land is missing. Now
you use a jumper wire. A flat, ribbon of wire
(Circuit Track material) makes a nicer looking repair.
To make this type of repair: 1. remove the solder
mask from a portion of the existing circuitry and tin
with solder. 2. Clean and tin a jumper
wire/conductor, or ribbon, and lap solder this to the
newly tinned existing circuitry. Note the minimum
over lap requirement of the IPC-7721 procedure 5.1 3.
Insert the other end of the jumper wire/conductor, or
ribbon into the prepared PTH. 4. Insert the
“correctly sized” eyelet into the prepared PTH, such
that the “factory flange” of the eyelet will “trap”
the jumper wire/conductor that is in the PTH. (
Looking at IPC-7721, procedure 5.1, Figure 2. Can you
see the “trapped conductor” coming from the upper left
corner of the figure, and being held by the factory
flange of the eyelet?) Let the jumper wire/conductor
enter the prepared PTH at least 50% of the PCB
thickness. But not so far as to interfere with the
forming of the flange on the opposite side of the PCB.
5. Form the eyelet, and solder the flanges to the
circuitry. 6. Coat the jumper wire/conductor with
epoxy to insulate it, and secure it to the PCB.
Regarding the reliability of the repair. I direct you
back to IPC-7721, page 2. section 1.4.3 “levels of
conformance”. Read the paragraph that starts with,
“Class 3 Products must use procedures rated Higest
level-------.” Note that Procedure 5.1 is rated as
Highest level of conformance.
I do hope that this will help you. You may contact me
off line if you want to kick this around some more:
978-264-0078
Thanx
Bill Butman
**************************************
--- Alain Savard <[log in to unmask]> wrote:
> Hi Netters,
>
> This is a question about assemblies being repaired
> because through holes are
> damaged.
>
> In IPC 7721, method 5.1 (no inner layer connection):
>
> Should a jumper (or jumpers)be used to insure
> reliable electrical
> conductivity for class 2 assemblies?
> How about class 3?
>
> How about for method 5.2 (with inner layer
> connection)?
>
> Thanks in advance for all answers,
>
> Alain Savard
> QA - PCB
> CAE Inc.
>
>
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=====
Bill Butman
Circuit Technology Center
45 Research Drive
Haverhill, MA 01832
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