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'connectors on SMT boards'
1999\07\20@140104 by Anne Ogborn

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ok - I've gotten my board down to where
I can make it totally surface mount if not
for the connectors. The manufacturer is
encouraging me to bite the bullet and
use through hole connectors.

What's people's experience with SMT connectors?

--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\07\20@140919 by Dave VanHorn

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>
> What's people's experience with SMT connectors?


Depends on the connector. I'd be very nervous if the only mechanical support
for a large-ish connector was smd pads. I use thruhole connectors for that
reason. I also like a lot of insertion force, (my definition of "captive"
cables: If you can swing the product around your head by the cable, then
it's captive)

YMMV

1999\07\20@151738 by Adam Davis

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You'll note that the newer hard drives have surface mount connectors for the
power and signal cables.  It has been my experience that these are durbale and
reliable despite only being supported by the board, but they *look* fragile, and
I'm always afraid that the insertion or removal may cause enough stress to
fracture something.  So from a consumer standpoint, I know I would probably lean
towards a product that looks and feels sturdy rather than one that does not.

But it really does depend on the connector.  Obviously the force needed to
insert and remove a connector will generally be less than the force needed to
break the solder joints holding the connector to the board, however, is that
still going to be less than the stress needed to fracture the board or any
traces on it, or flex it enough to pop some other items off the board?  You can
always get surface mount connectors which have levers for removing the
connector, such as the DIMM memory modules for the newer motherboards.

In other words, we can't give you a good idea until you give us more detail.
What kind of board is it (multilayer, single, double sided, etc) and what kind
of connections must you provide (number of connections, amperage, etc)

-Adam

Anne Ogborn wrote:
{Quote hidden}

1999\07\20@154446 by Dave VanHorn

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> You'll note that the newer hard drives have surface mount connectors for
the
> power and signal cables.  It has been my experience that these are durbale
and
> reliable despite only being supported by the board, but they *look*
fragile, and
> I'm always afraid that the insertion or removal may cause enough stress to
> fracture something.  So from a consumer standpoint, I know I would
probably lean
> towards a product that looks and feels sturdy rather than one that does
not.

That's a good point as well, how often the connector is stressed is a key
issue.
I only deal with external connectors exposed to customers, so I overlooked
the case like a drive cable, where it gets conencted only a few times in
it's life.

1999\07\20@154650 by Mark Walsh

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>
> ok - I've gotten my board down to where
> I can make it totally surface mount if not
> for the connectors. The manufacturer is
> encouraging me to bite the bullet and
> use through hole connectors.
>
> What's people's experience with SMT connectors?
>
> --
> Anniepoo

We have prototypes out for user evaluation right now that have surface mount
screw terminal blocks.  They are designed to have screws mechanically secure
them from the opposite side of the board, but since the back of the board is
a keypad we can't use them.  We tried super glue but they broke them free
while putting wires in the screw terminals.  Now we epoxy them to the board
and have had no problem yet.

If I could, I would definitely try to use through hole connectors.  They are
always a weak link both electrically and mechanically.  The more securely
you can mount them the better.

Mark Walsh

1999\07\20@160532 by Wagner Lipnharski

picon face
Connectors... 94% of failures in mainframes and all other electronic
related equipment are related to connectors. More than 50% of the
problems related to connection, a simple unplug/replug fix them all.
People think that scale integration was a result of looking for space
savings, but great part of the energy and money invested in it was to
eliminate as much connections as possible from the circuits.  Who
remembers the TTL family in '74 and on? power hungry wires and circuits,
there was no power and cards connectors that could deal with that thing
correctly without generate lots of problems, and heat!

How many times did you checked your computer power connectors when
looking for a problem? how many times your hardisk just reset itself
because a bad contact on those black, yellow and red wires connectors?
sometimes they are lose, sometimes they are so tied you need a
screwdriver to force and unplug it.

We tried to reinforce a surface connector by drilling incomplete holes
below the connector. At the installation, epoxy drops are deposited into
the holes to glue the connector "in place", it also helps to reinforce
the connector mechanically on board.  Good connectors helps a lot.

--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\07\20@163159 by Anne Ogborn

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I have a strange situation with the connectors.

This gizmo goes under a model RR layout, and has
sensors, speaker, power, etc. hooked up to it.
These all come in from different places.

The user can field reprogram the unit, which they
might do a fair number of times while getting it
set up. Each time they do this they have to pull it
out and take it to a PC to program it.

So either they have to plug in a bunch of things,
in the dark, and possibly getting them mixed up,
(and the cables can't be given different connectors),
or they have to plug them into something and
have that something plug into the unit with a single
connector.

I'm avoiding either ugly solution by using a connector
sold as a 2 part terminal block. The header IMC mounts
to the board. The screw terminal block plugs into this,
and they can be stacked with interlocking dovetails.

So, my end user brings the wires togather, interlocks
the terminal block plugs, and plugs the whole mass into
the card.


--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\07\20@171458 by Barry King

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> What's people's experience with SMT connectors?
I've used some of each.  The pure surface mount ones are more
likely to break off the pcb if stressed.   For external connectors,
like AC jacks, I/O connectors, I would recommend paying the extra
assembly cost for through hole, for mechanical reasons.

On board-to-board or internal wiring harnesses, we've had OK luck
with SMT connectors.  The fine pitch ones are a problem because of
fine pitch, not because of being SMT, that is, they are susceptable
to shorts in soldering.  As with SOICs, the right board layout and
especially solder mask are very important.

------------
Barry King, KA1NLH
Engineering Manager
NRG Systems "Measuring the Wind's Energy"
Hinesburg, Vermont, USA
http://www.nrgsystems.com

1999\07\20@184128 by paulb

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Adam Davis wrote:

> You'll note that the newer hard drives have surface mount connectors
> for the power and signal cables.  It has been my experience that these
> are durbale and reliable despite only being supported by the board,
> but they *look* fragile,

> In other words, we can't give you a good idea until you give us more
> detail.  What kind of board is it (multilayer, single, double sided,
> etc) and what kind of connections must you provide (number of
> connections, amperage, etc)

 Something comes to mind.  My concern would be of tracks lifting from
the PCB on stress.  Presumably you could arrange a via to sit at each
end of each pad used for the termination.  Applies to the larger (power)
connections.

 O O O O
 I I I I
 O O O O

 Smaller connections; possibly a via at alternate ends of alternate
pads.

 O O O O
 IIIIIIII
  O O O O
--
 Cheers,
       Paul B.

1999\07\20@184926 by Dennis Plunkett

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At 13:01 20/07/99 -0500, you wrote:
>>
>> What's people's experience with SMT connectors?
>
>
>Depends on the connector. I'd be very nervous if the only mechanical support
>for a large-ish connector was smd pads. I use thruhole connectors for that
>reason. I also like a lot of insertion force, (my definition of "captive"
>cables: If you can swing the product around your head by the cable, then
>it's captive)
>
>YMMV
>
>


I have seem many responses to this topic and most seem to look at it from
the user point. Well perhaps we can sway that a bit.

The first point is "Why have a connector"
The second is "Who will access the connector"
The last point "How many times do you expect the connection to be made"

Of course that is only a short list and many other points are to always be
considered. The idea behind  surface mount connectors is the same as for
any other component, save space cost etc.
The connector mounted on the hard disk is a classic example, How many times
is it removed during normal service? What sort of environmental conditions
does it incur? Perhaps it is in one of the best locations.

So realy if the connector is only to mate one card to another and the
stresses placed on it are minor, then use surface mount (IDC header types
ones). However if the connector is to gain access to the outside world i.e.
through the product to provide power and signals etc, then perhaps fixed
through hole should be used.

While the last point may have thrown a spanner into the works, it really
does come down to what the connector is supposed to do who will have access
and for what purpose. By this also don't be afraid of SMT plug connectors.


Dennis

1999\07\20@194823 by Mark Walsh

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>
> I'm avoiding either ugly solution by using a connector
> sold as a 2 part terminal block. The header IMC mounts
> to the board. The screw terminal block plugs into this,
> and they can be stacked with interlocking dovetails.
>
> So, my end user brings the wires togather, interlocks
> the terminal block plugs, and plugs the whole mass into
> the card.
>
>
> --
> Anniepoo

Who is making surface mount pluggable terminal blocks?  About 18 months ago
I couldn't find any.  Several manufacturers had them in catalogs, but at
that time I couldn't get a projected cost or delivery date.

We sell oil field controls and these guys have a tendency to put cheaters
for more torque on their screw drivers when they tighten down on the wires.
If the connector isn't even attached to the board when they do it, you
shouldn't have problems with surface mount connectors.

Mark Walsh

1999\07\20@204944 by Bob Drzyzgula

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Annie,

As I read your description, it seemed to me that perhaps
what might make more sense would be a two-part PC board,
with the connector half being a relatively heavy, perhaps
even crude, all through-hole and possibly one sided
affair, that had all the terminal blocks and a card-edge
connector. That could be solidly anchored to the fram--
er, benchwork, and could easily be designed to withstand
ham-fisted screwdriver operators. Your controller board
could then be 100% surface mount, small and compact,
and simply slide in and out of the terminal-block frame.
If you have power regulation circuitry on the controller,
that could probably go on the terminal block board as well.

It probably would cost a little more, but I would imagine
that it could just about eliminate connector-related
failures of the controller board; the termination device
would be relplacable probably at lower cost and be repairable
by an amateur with any old cheap soldering iron. You might
find people wanting to have multiple controller cards that
simply slide in and out for different programming, say the
weekend schedule, the rush-hour schedule, the late-night
schedule, etc. One could also have an extra for when one
is working on an upgrade to the programming while having
a stable, known-to-work version around to use when people
want to see one's layout.

I liked the idea enough to pull up AutoCAD and
sketch out what I was talking about; take a look at
ftp://ftp.drzyzgula.org/pub/forannie.jpg -- most of it
should be fairly obvious if I've done a decent job of
drawing it. On the two long sides are card-guide slide
bearings, and on the end of the slot is a card-edge
connector that mates with the pads on the end of the
controller card.

Just a thought, you're probably too far along to make this
big a change, but it might solve the problem in a way that
added some new features as well.

FWIW.

--Bob

On Tue, Jul 20, 1999 at 01:29:17PM -0700, Anne Ogborn wrote:
{Quote hidden}

--
============================================================
Bob Drzyzgula                             It's not a problem
spam_OUTbobTakeThisOuTspamdrzyzgula.org                until something bad happens
============================================================

1999\07\20@220309 by Gennette Bruce
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Annie,

I think you should follow the tried-and-true solution used by most small
computers/games consoles in the past -

   You make one end of your circuit board into an edge connector.
   You make your rugged screw terminal block and matching socket on a
separate, solid piece of circuit board.
   Put both pieces into pretty plastic cases that have nice, stress
eliminating guides moulded in and thru-bolts to lock them (the cases)
together.

Use a fixed font, like courier, to view this ascii art.


               _|----------------------------------|_
              | |----------------------------------| |- Bolt
              |_|----------------------------------|_|-
                |  |-----------------------------| |
                |  | O Terminal          |---| O | |
|------------------||   Block   |---|     | O |   | |
|                  || |------|  | O |     |---|   | |
| |---------------------|    |  |---|     | O |   | |
| | O                 --|    |  | O |     |---|   | |
| |                   --|    |  |---|     | O |   | |
| |                   --|    |  | O |     |---|   | |
| |    Your           --|    |  |---|     | O |   | |
| |    programable    --|    |  | O |     |---|   | |
| |    circuit        --|    |  |---|     | O |   | |
| |    board          --|    |  | O |     |---|   | |
| |                   --|    |  |---|     | O |   | |
| |                   --|    |  | O |     |---|   | |
| | O                 --|    |  |---|     | O |   | |
| |---------------------|    |  | O |     |---|   | |
|                  || |------|  |---|     | O |   | |
|------------------|| |         | O |     |---|   | |
                |    | O       |---|           O | |
               _|    |---------------------------| |_
              | |----------------------------------| |- Bolt
              |_|----------------------------------|_|-
                |----------------------------------|


Make the terminal block case bigger, thicker and screw mountable, it stays
in place and your programable module unscrews whenever required.  These
matching modules are available, in several sizes, from several manufacturers
and I think most end users will pay the (small) extra cost for a quality
easy disconnect.

This could lead to extra sales, multiple controller boxes that the end user
plugs in as desired. (Just like changing games on a play station . . .)  A
matching socket on your programer should make the whole thing much more
professional too.

Don't re-invent the wheel when bringing your control lines to the edge
connector either, use a known arrangement like the simmstick layout, wrapped
around if necessary.

Bye.


       {Original Message removed}

1999\07\22@195837 by Anne Ogborn

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Bob Drzyzgula wrote:
>

Thanks Bob -

Actually, that was more or less our original design.
I decided to use the stackable connector basicly for
cost reasons. My 'other half' in the business didn't
like the raw PC card look.  I had an edge card connector on
the "header" board that the card plugged into, and then
connectors for all the wires.

thanks for taking the time to make a sketch - at least I know now
I'm not completely loony.


--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\07\22@200835 by Anne Ogborn

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the user point. Well perhaps we can sway that a bit.
>
> The first point is "Why have a connector"

1) It's not known until install time what sort of thing is being plugged into
the connector. The connector is a standard i/o control for any of several sensor
s/
controllers.
2) It would be extremely inconvenient to install the sensors if they were perman
ently attached
3) The unit gets removed repeatedly during the install/setup process. Each occas
ion would
mean re-running 6 cables.

> The second is "Who will access the connector"

End user, who is completely untrained.

> The last point "How many times do you expect the connection to be made"

far less than 100

>
> Of course that is only a short list and many other points are to always be
> considered.

Yes - I guess "will the cable be tugged?" should be on there - obviously it's cr
azy
to smt mount a connector whose cable is attached to a person walking around.


> The connector mounted on the hard disk is a classic example, How many times
> is it removed during normal service? What sort of environmental conditions
> does it incur? Perhaps it is in one of the best locations.

I used to telecommute 3 days, come in 2, and solved the "it's on the other compu
ter"
problem by having an external hard drive (this on a mac) that traveled with me
twice a day between SF and Cupertino.  Wonder what the design expectancy is for
DB connectors? They were originally a modem to terminal connection.


--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\07\22@201300 by Anne Ogborn

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> Who is making surface mount pluggable terminal blocks?  About 18 months ago
> I couldn't find any.  Several manufacturers had them in catalogs, but at
> that time I couldn't get a projected cost or delivery date.
>

I hadn't gotten further than asking the AMP rep if they made them SMT.
He said they did - you might check with AMP.

> We sell oil field controls and these guys have a tendency to put cheaters
> for more torque on their screw drivers when they tighten down on the wires.
> If the connector isn't even attached to the board when they do it, you
> shouldn't have problems with surface mount connectors.
>
> Mark Walsh

=8oX

--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

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