Homebrew PCBs

I need to terminate some wires to an otherwise all SMT PCB I'm 
designing.

The wires don't naturally have any connectors on them so some sort 
of barrier or terminal strip would be preferred.

Options I've considered:

SMT connectors...haven't found any for just wires.

Terminal strips mounted on underside with pins protruding topside 
for soldering to traces.

PTHs for top mounted terminal strips.

Although the euro style terminal strips look good I haven't tried 
them and haven't seen any with SMT mounting.

Any recommendations?

tnx
jtm

One unconventional method would be to use the std. screwterms I just 
described. Simply mount them at the edge of the board, by their TH 
pins. (NOT through hole, though. Think of an edge connector. Then 
solder the pins of the screw terminal to these "edge connector" 
traces. That way the wires will exit perpendicular to the board, and 
the screw driver will be used parallel to the board. 

Will only work if your wires are at the board edge though...

Hope this helps,

Ballendo

P.S. Sounds like what you need is an smd version of a flea-clip... 
Have you looked at SMD test points?

--- In Homebrew_PCBs@yahoogroups.com, "mdgolfbum" <jim@j...> wrote:

> I need to terminate some wires to an otherwise all SMT PCB I'm 
> designing.
> 
> The wires don't naturally have any connectors on them so some sort 
> of barrier or terminal strip would be preferred.
> 
> Options I've considered:
> 
> SMT connectors...haven't found any for just wires.
> 
> Terminal strips mounted on underside with pins protruding topside 
> for soldering to traces.
> 
> PTHs for top mounted terminal strips.
> 
> Although the euro style terminal strips look good I haven't tried 
> them and haven't seen any with SMT mounting.
> 
> Any recommendations?
> 
> tnx
> jtm

On Tue, 30 Mar 2004 16:02:50 -0000, ballendo <ballendo@...> wrote:

> One unconventional method would be to use the std. screwterms I just
> described. Simply mount them at the edge of the board, by their TH
> pins. (NOT through hole, though. Think of an edge connector. Then
> solder the pins of the screw terminal to these "edge connector"
> traces. That way the wires will exit perpendicular to the board, and
> the screw driver will be used parallel to the board.
>
> Will only work if your wires are at the board edge though...
>

And only if the screw terminal doesn't lift off the trace...
I would never ever put any mechanical strain on a small pad.
It WILL LIFT off.

drill the holes and put them through, or put the wires themselves through,
and you won't have problems.

ST

Stefan,

It seems you have had at least one bad experience at some point with 
traces coming off...

With the older and/or cheaper bakelite type boards this can be a 
problem, but I sure haven't seen it with any of the glass-epoxy types.

At any rate, if this is a concern, use of some epoxy which can adhere 
to the bare parts of the board between the traces will deal with it. 
And provide a conformal coating at the same time...

Ballendo

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> On Tue, 30 Mar 2004 16:02:50 -0000, ballendo <ballendo@y...> wrote:
> 
> > One unconventional method would be to use the std. screwterms I 
just
> > described. Simply mount them at the edge of the board, by their TH
> > pins. (NOT through hole, though. Think of an edge connector. Then
> > solder the pins of the screw terminal to these "edge connector"
> > traces. That way the wires will exit perpendicular to the board, 
and
> > the screw driver will be used parallel to the board.
> >
> > Will only work if your wires are at the board edge though...
> >
> 
> And only if the screw terminal doesn't lift off the trace...
> I would never ever put any mechanical strain on a small pad.
> It WILL LIFT off.
> 
> drill the holes and put them through, or put the wires themselves 
through,

> and you won't have problems.
> 
> ST

On Tue, 30 Mar 2004 16:34:14 -0000, ballendo <ballendo@...> wrote:

> Stefan,
>
> It seems you have had at least one bad experience at some point with
> traces coming off...
>
> With the older and/or cheaper bakelite type boards this can be a
> problem, but I sure haven't seen it with any of the glass-epoxy types.
>
> At any rate, if this is a concern, use of some epoxy which can adhere
> to the bare parts of the board between the traces will deal with it.
> And provide a conformal coating at the same time...
>
> Ballendo
>

You are right, i had bad experiences with traces coming off....

It happens more often with bakelite, i agree, but it does also happen with 
FR4.

In my opinion the glue that holds the copper is simply not made for taking 
any force,
especially if heating from soldering is involved. if you look at any 
professional board
(throughhole) you will see there is always some sort of spacer etc used on 
the top side
to counter the force. the pad (on a not plated through board) is never 
allowed to take
any force which would lift it off. the only parts where this is not true 
are transistors
sometimes.
With SMD this rule is greatly loosened, because you simply don't have the 
holes.
I guess you are right, and the glue holding the copper got better over 
time, along with the
smd developement so it can take more force. however i have not seen a 
substantial connector
in SMD with no mechanical restraint to prevent lifting of the pads.
The connectors i know which do not require any mounting holes have very 
low "pull out force"
of the plug. the ones with better sitting plugs have some sort of plastic 
"rivets" or are
at the edge of the board (Around it).

I had some bad experiences and do not want to repeat that.
Of course it will work (i also tack wires to the copper side for short 
tests etc.)
but i really think a good and long-term reliable board is designed to 
prevent such things.


The epoxy is certainly a good idea, there is another occasion where it is 
useful.
Sometimes you solder wires directly to a board, just like a resistor, with 
the isolation
on the top side, stripped through the hole.
If the wire is small gauge it will break if you move it too often.
Running the wire through another hole will remove the problem (a bigger 
hole and run
it through with the isolation on) epoxy helps if ther is no other hole or 
no space.

I have had several bad experiences with trace lifting, and wire breaking, 
too often.

ST


there is another thing, if you solder on the screw terminal like you 
described the
force is on the edge of the trace, having a very good lever. it is much 
more
likely to come off than if you pull on the center of a pad.

----- Original Message ----- 

From: "mdgolfbum" <jim@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, March 30, 2004 4:28 PM
Subject: [Homebrew_PCBs] Wire connections to SMT PCBs?


> I need to terminate some wires to an otherwise all SMT PCB I'm
> designing.
>
> The wires don't naturally have any connectors on them so some sort
> of barrier or terminal strip would be preferred.
>
> Options I've considered:
>
> SMT connectors...haven't found any for just wires.
>
> Terminal strips mounted on underside with pins protruding topside
> for soldering to traces.
>
> PTHs for top mounted terminal strips.
>
> Although the euro style terminal strips look good I haven't tried
> them and haven't seen any with SMT mounting.

With my home made single-sided SMT boards I put all the SMT stuff on the
bottom and through-hole components like connectors and wire links on the
top. It looks a bit strange but works OK.

Leon

> With my home made single-sided SMT boards I put all the SMT stuff on the
> bottom and through-hole components like connectors and wire links on the
> top. It looks a bit strange but works OK.
>
> Leon
>
>

I do that too...

It's the method with the highest component density on single sided boards.
you have all the throughhole components on top, and on the bottom you have 
the smd
stuff "between their pads".

Works very well and you get a lot of parts on a very small area. parts like
connectors, potentiometers, power transistors, switches etc. are sometimes
easier and better to do throughhole, while resistors, capacitors, small 
transistors
are easier and faster to do SMD.
It's the same with ICs i only get/have throughhole. put them on top and 
the external
components needed nicely fit on the bottom layer.

Actually most of my boards look like that, because i do not like to bother 
with two layers.
I do not see any major disadvantage, and it seems quite common in the 
industry too.

It allows you to still use your standard throughhole parts stock, but 
saves a lot of work
with drilling holes for all those resistors and capacitors.

I don't exactly know why you think it looks strange...

ST

I totally agree with connectors being through hole.  there is no 
comparison.  Put pads/solder on both sides for additional strength.

I mix smt on bottom and top.  It saves vias some times.  also, bottom 
side for bypass caps is totally natural - especially for a number of 
the larger TH PICs that have power and ground on adjacent pins.


--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> 
> > With my home made single-sided SMT boards I put all the SMT stuff 
on the
> > bottom and through-hole components like connectors and wire links 
on the
> > top. It looks a bit strange but works OK.
> >
> > Leon
> >
> >
> 
> I do that too...
> 
> It's the method with the highest component density on single sided 
boards.
> you have all the throughhole components on top, and on the bottom 
you have 
> the smd
> stuff "between their pads".
> 
> Works very well and you get a lot of parts on a very small area. 
parts like
> connectors, potentiometers, power transistors, switches etc. are 
sometimes
> easier and better to do throughhole, while resistors, capacitors, 
small 
> transistors
> are easier and faster to do SMD.
> It's the same with ICs i only get/have throughhole. put them on top 
and 
> the external
> components needed nicely fit on the bottom layer.
> 
> Actually most of my boards look like that, because i do not like to 
bother 
> with two layers.
> I do not see any major disadvantage, and it seems quite common in 
the 
> industry too.
> 
> It allows you to still use your standard throughhole parts stock, 
but 

> saves a lot of work
> with drilling holes for all those resistors and capacitors.
> 
> I don't exactly know why you think it looks strange...
> 
> ST

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan
<stefan_trethan@g...> wrote:

--- Leon said: 
> > With my home made single-sided SMT boards I put all the SMT stuff
on the
> > bottom and through-hole components like connectors and wire links
on the
> > top. It looks a bit strange but works OK.
> >
> > Leon

...
> Actually most of my boards look like that, because i do not like to
bother 
> with two layers.
> I do not see any major disadvantage, and it seems quite common in the 
> industry too.

Yes, some brands of TV use that method quite extensively. I think it
it Thomson Electronics that makes it a nightmare by mixing SMT and
through-hole on doublesided boards with multiple vias and zero ohm
chip resistor jumpers. I've seen a connection cross sides 3 times and
go through several zero ohm jumpers, from what is just a line on a
schematic.

But that's the worst of it.

Steve

In a message dated 3/30/2004 9:31:13 AM Central Standard Time, 
jim@... writes:
PTHs for top mounted euro style terminal strips.

Although the euro style terminal strips look good 


[Non-text portions of this message have been removed]