Hi all,

I have a circuit board which I need to replace a relayon. One of the pads seems to have over heated and left residue on the exposed copper. When I remove the relay I was looking to clean up the pads to make sure the new one is connected correctly.

What is the best way to do this without further damaging the pad? I have rosin flux but this is solid.

Thanks

Lee.

On 22/01/2024 16:48, Lee Nowell wrote:
> Hi all,
>
> I have a circuit board which I need to replace a relayon. One of the pads seems to have over heated and left residue on the exposed copper. When I remove the relay I was looking to clean up the pads to make sure the new one is connected correctly.
>
> What is the best way to do this without further damaging the pad? I have rosin flux but this is solid.
>

IPA - Isopropyl alcohol and an old toothbrush

If it's old overheated flux it should come off with IPA but usually when
a board is soldered the flux residue is washed off. This makes it more
difficult to remove components unless you add more (liquid) flux or
re-solder the connection before you try and remove the component.

If the residue is burnt carbon from the board scrubbing with IPA will
often clean up the loose bits but will not remove the burn embedded into
the PCB material.

If the board has been burnt too much it's unlikely that the copper pad
is still anchored to the board beneath. All is not lost in this case as
all you do is strengthen the connection with a bit of wire. Fit your new
relay through the pad (which may be loose), wrap a bit of wire around
the pin of the relay and solder it along the track to a bit where the
copper is still firmly attached to board. You may have to scrape off any
top layer of solder resist to expose bare copper.

Assuming abuse of the board when removing components, if the PCB is
double sided/layered and the pad is plated through you may have to get a
multi-meter to check that you still have continuity to both sides of the
pad(s).

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 22/01/2024 16:48, Lee Nowell wrote:
> Hi all,
>
> I have a circuit board which I need to replace a relay on. One of the
> pads seems to have over heated and left residue on the exposed
> copper. When I remove the relay I was looking to clean up the pads to
> make sure the new one is connected correctly.
>
> What is the best way to do this without further damaging the pad? I
> have rosin flux but this is solid.
>
IPA is generally best solvent with fibreglass brush.

But any abrasive will also clean up the board, if the pad is still
properly attached to the subtsrate

> Thanks
>
> Lee.

--
Canada is all right really, though not for the whole weekend.

"Saki"

On 22/01/2024 17:32, The Natural Philosopher wrote:
> On 22/01/2024 16:48, Lee Nowell wrote:

>> I have a circuit board which I need to replace a relay on. One of the
>> pads seems to have over heated and left residue on the exposed
>> copper. When I remove the relay I was looking to clean up the pads to
>> make sure the new one is connected correctly.
>>
>> What is the best way to do this without further damaging the pad? I
>> have rosin flux but this is solid.
>>
> IPA is generally best solvent with fibreglass brush.

Domestic meths would be a reasonable substitute if you don't have access
to IPA. I cleaned up my router board with that after spilling milk on it.

--
Max Demian

On 22/01/2024 17:56, Max Demian wrote:
> On 22/01/2024 17:32, The Natural Philosopher wrote:
>> On 22/01/2024 16:48, Lee Nowell wrote:
>
>>> I have a circuit board which I need to replace a relay on. One of the
>>> pads seems to have over heated and left residue on the exposed
>>> copper. When I remove the relay I was looking to clean up the pads to
>>> make sure the new one is connected correctly.
>>>
>>> What is the best way to do this without further damaging the pad? I
>>> have rosin flux but this is solid.
>>>
>> IPA is generally best solvent with fibreglass brush.
>
> Domestic meths would be a reasonable substitute if you don't have access
> to IPA. I cleaned up my router board with that after spilling milk on it.
>
cellulose thinners and acetone also work, but are more aggressive and
may attack components

--
"An intellectual is a person knowledgeable in one field who speaks out
only in others...”

Tom Wolfe

On 22/01/2024 18:00, The Natural Philosopher wrote:
> On 22/01/2024 17:56, Max Demian wrote:
>> On 22/01/2024 17:32, The Natural Philosopher wrote:
>>> On 22/01/2024 16:48, Lee Nowell wrote:
>>
>>>> I have a circuit board which I need to replace a relay on. One of the
>>>> pads seems to have over heated and left residue on the exposed
>>>> copper. When I remove the relay I was looking to clean up the pads to
>>>> make sure the new one is connected correctly.
>>>>
>>>> What is the best way to do this without further damaging the pad? I
>>>> have rosin flux but this is solid.
>>>>
>>> IPA is generally best solvent with fibreglass brush.
>>
>> Domestic meths would be a reasonable substitute if you don't have
>> access to IPA. I cleaned up my router board with that after spilling
>> milk on it.
>>
> cellulose thinners and acetone also work, but are more aggressive and
> may attack components
>

Water would also work for milk. Ideally de-ionised/distilled water but
cold water from the tap will do in some cases. If after using this
method it's wise to leave the board for hours in a warm place for any
water under components to dry out.

Some assembled PCB boards are also washed in water if a water soluble
flux has been used.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On Monday 22 January 2024 at 16:48:17 UTC, Lee Nowell wrote:
> Hi all,
>
> I have a circuit board which I need to replace a relayon. One of the pads seems to have over heated and left residue on the exposed copper. When I remove the relay I was looking to clean up the pads to make sure the new one is connected correctly.
>
> What is the best way to do this without further damaging the pad? I have rosin flux but this is solid.
>
> Thanks
>
> Lee.

usually quicker to scrape a blade over it

On Mon, 22 Jan 2024 20:45:07 +0000
alan_m <junk@admac.myzen.co.uk> wrote:

> On 22/01/2024 18:00, The Natural Philosopher wrote:
> > On 22/01/2024 17:56, Max Demian wrote:
> >> On 22/01/2024 17:32, The Natural Philosopher wrote:
> >>> On 22/01/2024 16:48, Lee Nowell wrote:
> >>
> >>>> I have a circuit board which I need to replace a relay on. One
> >>>> of the pads seems to have over heated and left residue on the
> >>>> exposed copper. When I remove the relay I was looking to clean
> >>>> up the pads to make sure the new one is connected correctly.
> >>>>
> >>>> What is the best way to do this without further damaging the
> >>>> pad? I have rosin flux but this is solid.
> >>>>
> >>> IPA is generally best solvent with fibreglass brush.
> >>
> >> Domestic meths would be a reasonable substitute if you don't have
> >> access to IPA. I cleaned up my router board with that after
> >> spilling milk on it.
> >>
> > cellulose thinners and acetone also work, but are more aggressive
> > and may attack components
> >
>
> Water would also work for milk. Ideally de-ionised/distilled water
> but cold water from the tap will do in some cases. If after using
> this method it's wise to leave the board for hours in a warm place
> for any water under components to dry out.
>
> Some assembled PCB boards are also washed in water if a water soluble
> flux has been used.
>

I used to use water with a small amount of detergent to remove leaked
electrolyte from failed electrolytic capacitors, then clean water to
rinse and then leave to dry. Then examine for partly-eaten tracks...

--
Joe

On Monday 22 January 2024 at 16:48:17 UTC, Lee Nowell wrote:
> Hi all,
>
> I have a circuit board which I need to replace a relayon. One of the pads seems to have over heated and left residue on the exposed copper. When I remove the relay I was looking to clean up the pads to make sure the new one is connected correctly.
>
> What is the best way to do this without further damaging the pad? I have rosin flux but this is solid.
>
> Thanks
>
> Lee.

Thanks very much all. I used some meths in the end as I had some and it worked a treat. Thanks very much all for the suggestions