A specific PCB bad practise, term for it ?

N

N_Cook

Guest
Where holes are drilled for thru-board components but of diameter far too
big , thru-hole plated , but no eyelet/inserts used to fill the gap. So
1N4001 size leads in holes twice their diameter and 1N4148 in holes twice
their diameter. So not a case of only one drill size for all. So in area
terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper
solder but with PbF, ring cracks starting all over.
Is it to avoid mutiny by the by-hand board populators ?
 
In article <iouqr0$pl0$1@dont-email.me>, "N_Cook" <diverse@tcp.co.uk>
wrote:

Where holes are drilled for thru-board components but of diameter far too
big , thru-hole plated , but no eyelet/inserts used to fill the gap. So
1N4001 size leads in holes twice their diameter and 1N4148 in holes twice
their diameter. So not a case of only one drill size for all. So in area
terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper
solder but with PbF, ring cracks starting all over.
Is it to avoid mutiny by the by-hand board populators ?
Click to expand...
It's just careless design. As a contract assembly house, I see stuff
like that all the time. Surface mount footprints the wrong size for the
component, radial through holes for axial components, etc. ad infinitum.
Quoted a one-off prototype board last week at 3 hours, took 17, due to
documentation (and a slew of other) problems.

EEs should be allowed a pencil and a paper napkin to sketch out the
schematic, but after that, the board layout and overall product design
should be turned over to someone who's actually familiar with
manufacturing practices.
 
"N_Cook" <diverse@tcp.co.uk> wrote in news:iouqr0$pl0$1@dont-email.me:

Where holes are drilled for thru-board components but of diameter far
too big , thru-hole plated , but no eyelet/inserts used to fill the
gap. So 1N4001 size leads in holes twice their diameter and 1N4148 in
holes twice their diameter. So not a case of only one drill size for
all. So in area terms about 1 to 4 ratio of lead to solder. Bad
enough practise with proper solder but with PbF, ring cracks starting
all over. Is it to avoid mutiny by the by-hand board populators ?
Click to expand...
perhaps PCBs designed for machine parts insertion have those sort of
"oversize" thru-holes? Perhaps the insertion machine prefers big holes and
besides,they crimp over the leads anyways. Maybe it's too much trouble to
drill PCBs for different size thru-holes,and/or not worth the effort.

certainly stocking and inserting eyelets would be an additional,unnecessary
expense.

--
Jim Yanik
jyanik
at
localnet
dot com
 
Smitty Two wrote:
In article <iouqr0$pl0$1@dont-email.me>, "N_Cook" <diverse@tcp.co.uk
wrote:

Where holes are drilled for thru-board components but of diameter far too
big , thru-hole plated , but no eyelet/inserts used to fill the gap. So
1N4001 size leads in holes twice their diameter and 1N4148 in holes twice
their diameter. So not a case of only one drill size for all. So in area
terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper
solder but with PbF, ring cracks starting all over.
Is it to avoid mutiny by the by-hand board populators ?

It's just careless design. As a contract assembly house, I see stuff
like that all the time. Surface mount footprints the wrong size for the
component, radial through holes for axial components, etc. ad infinitum.
Quoted a one-off prototype board last week at 3 hours, took 17, due to
documentation (and a slew of other) problems.

EEs should be allowed a pencil and a paper napkin to sketch out the
schematic, but after that, the board layout and overall product design
should be turned over to someone who's actually familiar with
manufacturing practices.
Click to expand...

We had a board house add 'thermal rings' to the mounting holes in a
500 MHz synthesizer. It played hell with the modules and sent the phase
noise through the roof but they said that they would no longer make them
the way we needed them. it also dropped the center frequency by about
100 MHz. I had to take some of the copper foil we used to seal the
shields on the modules and cover them, then solder them to the surface
and the plated through holes, till we could get the boards from another
supplier. They routinely made a couple dozen different boards for us,
prior to that. When they decided to change our layouts without
permission, we dropped them.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.
 
Jim Yanik wrote:
"N_Cook" <diverse@tcp.co.uk> wrote in news:iouqr0$pl0$1@dont-email.me:

Where holes are drilled for thru-board components but of diameter far
too big , thru-hole plated , but no eyelet/inserts used to fill the
gap. So 1N4001 size leads in holes twice their diameter and 1N4148 in
holes twice their diameter. So not a case of only one drill size for
all. So in area terms about 1 to 4 ratio of lead to solder. Bad
enough practise with proper solder but with PbF, ring cracks starting
all over. Is it to avoid mutiny by the by-hand board populators ?




perhaps PCBs designed for machine parts insertion have those sort of
"oversize" thru-holes? Perhaps the insertion machine prefers big holes and
besides,they crimp over the leads anyways.
Click to expand...

Microdyne stopped bending the leads or using the special cutters that
cripmed the leads back in the '80s to reduced damage to the PTH.


Maybe it's too much trouble to
drill PCBs for different size thru-holes,and/or not worth the effort.
Click to expand...

It's more likely that there was no design review, or the cad operator
was too lazy to verify the hole sizes.


certainly stocking and inserting eyelets would be an additional,unnecessary
expense.
Click to expand...

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.
 
Michael A. Terrell <mike.terrell@earthlink.net> wrote in message
news:A8qdnSGUA-9Vfy7QnZ2dnUVZ_radnZ2d@earthlink.com...
Jim Yanik wrote:

"N_Cook" <diverse@tcp.co.uk> wrote in news:iouqr0$pl0$1@dont-email.me:

Where holes are drilled for thru-board components but of diameter far
too big , thru-hole plated , but no eyelet/inserts used to fill the
gap. So 1N4001 size leads in holes twice their diameter and 1N4148 in
holes twice their diameter. So not a case of only one drill size for
all. So in area terms about 1 to 4 ratio of lead to solder. Bad
enough practise with proper solder but with PbF, ring cracks starting
all over. Is it to avoid mutiny by the by-hand board populators ?




perhaps PCBs designed for machine parts insertion have those sort of
"oversize" thru-holes? Perhaps the insertion machine prefers big holes
and
besides,they crimp over the leads anyways.


Microdyne stopped bending the leads or using the special cutters that
cripmed the leads back in the '80s to reduced damage to the PTH.


Maybe it's too much trouble to
drill PCBs for different size thru-holes,and/or not worth the effort.


It's more likely that there was no design review, or the cad operator
was too lazy to verify the hole sizes.


certainly stocking and inserting eyelets would be an
additional,unnecessary
expense.


--
You can't fix stupid. You can't even put a Band-AidT on it, because it's
Teflon coated.
Click to expand...

As the drill bits tend to be very brittle carbide rather than HSS I imagine
doubling the drill bit diameter drops the breakage rate by 1/10 or so,
reduced bit replacement costs, plus reduced down-time manual intervention
to rectify stoppages, due to such breakages.
 
N_Cook wrote:
Michael A. Terrell <mike.terrell@earthlink.net> wrote in message
news:A8qdnSGUA-9Vfy7QnZ2dnUVZ_radnZ2d@earthlink.com...

Jim Yanik wrote:

"N_Cook" <diverse@tcp.co.uk> wrote in news:iouqr0$pl0$1@dont-email.me:

Where holes are drilled for thru-board components but of diameter far
too big , thru-hole plated , but no eyelet/inserts used to fill the
gap. So 1N4001 size leads in holes twice their diameter and 1N4148 in
holes twice their diameter. So not a case of only one drill size for
all. So in area terms about 1 to 4 ratio of lead to solder. Bad
enough practise with proper solder but with PbF, ring cracks starting
all over. Is it to avoid mutiny by the by-hand board populators ?




perhaps PCBs designed for machine parts insertion have those sort of
"oversize" thru-holes? Perhaps the insertion machine prefers big holes
and
besides,they crimp over the leads anyways.


Microdyne stopped bending the leads or using the special cutters that
cripmed the leads back in the '80s to reduced damage to the PTH.


Maybe it's too much trouble to
drill PCBs for different size thru-holes,and/or not worth the effort.


It's more likely that there was no design review, or the cad operator
was too lazy to verify the hole sizes.


certainly stocking and inserting eyelets would be an
additional,unnecessary
expense.


--
You can't fix stupid. You can't even put a Band-AidT on it, because it's
Teflon coated.

As the drill bits tend to be very brittle carbide rather than HSS I imagine
doubling the drill bit diameter drops the breakage rate by 1/10 or so,
reduced bit replacement costs, plus reduced down-time manual intervention
to rectify stoppages, due to such breakages.
Click to expand...

A properly run PCB drilling system doesn't break the bits, and they
are replaced before they are dull enough to cause a problem. If it is a
cheap, in house product, all bets are off. You can get properly made
boards, if buying the cheapest you can find is at the top of the list.
Boards with over sized holes use more chemicals to plate the PTH, and
waste solder in the hand or wave solder process. We stuffed and placed
our boards at Microdyne, but used outside PCB houses to produce the
blanks. Some of our boards were 16 layer and cost over $8,000 to
populate.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.
 
"N_Cook" <diverse@tcp.co.uk> wrote in news:ip109c$f1n$1@dont-email.me:

Michael A. Terrell <mike.terrell@earthlink.net> wrote in message
news:A8qdnSGUA-9Vfy7QnZ2dnUVZ_radnZ2d@earthlink.com...

Jim Yanik wrote:

"N_Cook" <diverse@tcp.co.uk> wrote in
news:iouqr0$pl0$1@dont-email.me:

Where holes are drilled for thru-board components but of diameter
far too big , thru-hole plated , but no eyelet/inserts used to
fill the gap. So 1N4001 size leads in holes twice their diameter
and 1N4148 in holes twice their diameter. So not a case of only
one drill size for all. So in area terms about 1 to 4 ratio of
lead to solder. Bad enough practise with proper solder but with
PbF, ring cracks starting all over. Is it to avoid mutiny by the
by-hand board populators ?




perhaps PCBs designed for machine parts insertion have those sort
of "oversize" thru-holes? Perhaps the insertion machine prefers big
holes
and
besides,they crimp over the leads anyways.


Microdyne stopped bending the leads or using the special cutters
that
cripmed the leads back in the '80s to reduced damage to the PTH.


Maybe it's too much trouble to
drill PCBs for different size thru-holes,and/or not worth the
effort.


It's more likely that there was no design review, or the cad
operator
was too lazy to verify the hole sizes.


certainly stocking and inserting eyelets would be an
additional,unnecessary
expense.


--
You can't fix stupid. You can't even put a Band-AidT on it, because
it's Teflon coated.


As the drill bits tend to be very brittle carbide rather than HSS I
imagine doubling the drill bit diameter drops the breakage rate by
1/10 or so, reduced bit replacement costs, plus reduced down-time
manual intervention to rectify stoppages, due to such breakages.
Click to expand...
Tektronix still used the crimped over leads on their TH PCBs all the way up
to conversion to SMD boards,and that didn't happen until the late 1990's.
We didn't have much trouble with damaged thru-plated holes.

--
Jim Yanik
jyanik
at
localnet
dot com
 
On Sat, 23 Apr 2011 16:24:17 +0100, "N_Cook" <diverse@tcp.co.uk>
wrote:

Where holes are drilled for thru-board components but of diameter far too
big , thru-hole plated , but no eyelet/inserts used to fill the gap. So
1N4001 size leads in holes twice their diameter and 1N4148 in holes twice
their diameter. So not a case of only one drill size for all. So in area
terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper
solder but with PbF, ring cracks starting all over.
Is it to avoid mutiny by the by-hand board populators ?
Click to expand...
It was always my understanding that the "oversized" PTH was a
deliberate choice. If significant current needs to pass to both
planes, a (proper, of course, not RoHS) solder plug enhances the
through-plating's capability.
 
who where wrote:
On Sat, 23 Apr 2011 16:24:17 +0100, "N_Cook" <diverse@tcp.co.uk
wrote:

Where holes are drilled for thru-board components but of diameter far too
big , thru-hole plated , but no eyelet/inserts used to fill the gap. So
1N4001 size leads in holes twice their diameter and 1N4148 in holes twice
their diameter. So not a case of only one drill size for all. So in area
terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper
solder but with PbF, ring cracks starting all over.
Is it to avoid mutiny by the by-hand board populators ?

It was always my understanding that the "oversized" PTH was a
deliberate choice. If significant current needs to pass to both
planes, a (proper, of course, not RoHS) solder plug enhances the
through-plating's capability.
Click to expand...

It makes more sense to just specify a thicker plating on the PTH.
Solder his a higher resistance, and is much weaker.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.
 
In article <18j9r6lhguj9eetm312dp0694dacjqhc93@4ax.com>,
who where <noone@home.net> wrote:

On Sat, 23 Apr 2011 16:24:17 +0100, "N_Cook" <diverse@tcp.co.uk
wrote:

Where holes are drilled for thru-board components but of diameter far too
big , thru-hole plated , but no eyelet/inserts used to fill the gap. So
1N4001 size leads in holes twice their diameter and 1N4148 in holes twice
their diameter. So not a case of only one drill size for all. So in area
terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper
solder but with PbF, ring cracks starting all over.
Is it to avoid mutiny by the by-hand board populators ?

It was always my understanding that the "oversized" PTH was a
deliberate choice. If significant current needs to pass to both
planes, a (proper, of course, not RoHS) solder plug enhances the
through-plating's capability.
Click to expand...
Um, I'm not an EE, but I thought the leg of the component helped to
carry current from one side of the board to the other.
 
On Tue, 26 Apr 2011 10:05:39 -0700, Smitty Two
<prestwhich@earthlink.net> wrote:

In article <18j9r6lhguj9eetm312dp0694dacjqhc93@4ax.com>,
who where <noone@home.net> wrote:

On Sat, 23 Apr 2011 16:24:17 +0100, "N_Cook" <diverse@tcp.co.uk
wrote:

Where holes are drilled for thru-board components but of diameter far too
big , thru-hole plated , but no eyelet/inserts used to fill the gap. So
1N4001 size leads in holes twice their diameter and 1N4148 in holes twice
their diameter. So not a case of only one drill size for all. So in area
terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper
solder but with PbF, ring cracks starting all over.
Is it to avoid mutiny by the by-hand board populators ?

It was always my understanding that the "oversized" PTH was a
deliberate choice. If significant current needs to pass to both
planes, a (proper, of course, not RoHS) solder plug enhances the
through-plating's capability.

Um, I'm not an EE, but I thought the leg of the component helped to
carry current from one side of the board to the other.
Click to expand...
It does (doh!) but obviously the hole plating and the solder fill also
contribute to the overall conduction.
 
who where wrote:
On Sat, 23 Apr 2011 16:24:17 +0100, "N_Cook" <diverse@tcp.co.uk
wrote:

Where holes are drilled for thru-board components but of diameter far too
big , thru-hole plated , but no eyelet/inserts used to fill the gap. So
1N4001 size leads in holes twice their diameter and 1N4148 in holes twice
their diameter. So not a case of only one drill size for all. So in area
terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper
solder but with PbF, ring cracks starting all over.
Is it to avoid mutiny by the by-hand board populators ?

It was always my understanding that the "oversized" PTH was a
deliberate choice. If significant current needs to pass to both
planes, a (proper, of course, not RoHS) solder plug enhances the
through-plating's capability.
Click to expand...
The blob of solder has much less resistance than the
very thin copper surrounding the hole.
Mass counts here, and the copper is at a big disadvantage there.
 
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