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'[OT] Pcb VIAS'
1999\04\15@084527 by Barry King

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> When you get you design back from the electronics shop, do you
> have to put solder in the vias also?
> I had the pcb drilled and tinned in the shop already, but I
> get the feeling that there is no solder (through) in the vias !!
Normally, all the holes on double sided PCB are plated through,
connecting the top and bottom side traces.  However, some simple,
cheap prototyping systems, including the popular home PCB systems
don't provide this, so you have to solder through all the vias.

Its easy to tell:  Use your ohmmeter (you do have an ohmmeter, I
hope) to see if an example trace is connected top to bottom.

If not, don't panic.  Two things to do on these kind of boards.

1) First solder a piece of wire into every via (the ones that do not
get a component lead) and make sure it is soldered top and bottom.
You won't automatically get good flow through, so check it on both
sides.  Then trim them a flat as practical before adding components.

2) Make sure that you solder the top and bottom of the component
leads.  If a lead has a trace to only the solder side, you don't
have to solder the top, but I usually do anyhow.  There are some
components where its hard to reach the top side pads.  Examples:
Radial lead capacitors, and metal can transistors.  I usually leave
them slighty up off the PCB so I can readch under with the
soldering iron.

Hope this helps.

Barry.
------------
Barry King, KA1NLH
Engineering Manager
NRG Systems "Measuring the Wind's Energy"
Hinesburg, Vermont, USA
spam_OUTbarryTakeThisOuTspamnrgsystems.com
"The witty saying has been deleted due to limited EPROM space"


'[OT] PCB vias'
1999\12\31@212834 by Jinx
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Hi, wonder if there's someone who can give me an idea of PCB
assembly. Being the holiday season I can't get a hold of any local
mftrs to sound them out, and I'd like to be using the time to move
ahead as far as possible with the layout.

I'm working on a board that has DIP on one side and some SMT
memory on the other. Consequently I need to route many address
lines from counters and data lines to the PICs. I've persisted with it
for a few days as a single-sided board but the time has come when
I realise this is not practical. Too many links and flying leads. So
the only choice I have is to go double-sided. I'm looking at an initial
run of probably 50 and don't want to get bogged down for days
snipping little bits of wire.

The cost of the board is important in that more money will have to
paid up front for the mftr but, as the items are leased and not sold,
in the long run it won't make a lot of difference. What I'm trying to
find out is more along the lines of easy of assembly.

The layout I've got has 250 conventional component holes but many
links and wires (=time). If I used vias or PTH the holes wouldn't go
down by much but the assembly time would. As a rough idea I'd say
there could be 50 vias. A few via connections will be accounted for
by component leads.

Is a via necessarily a PTH (which I know can be expensive) ?

If not, how is one side connected to the other using a via ? I've
seen boards that are obviously PTH and others that have a flat
pad of solder each end of the via, but I can't tell if those too are
PTH or whether they've somehow been filled with solder.

Any suggestions ?

Jinx

1999\12\31@222246 by Mark Willis

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Jinx wrote:
{Quote hidden}

Makes sense to me.

A via doesn't have to be a PTH, but - if it's not - you'd have to solder
a piece of wire in there, so you want PTH here as otherwise the VIAs
don't gain you much <G>

Those vias that have solder fills, were probably wave soldered or
soldered by dipping in a solder pot.  They're probably PTH, and then
"wicked" themselves full of solder.  Unless someone soldered a wire in
there, lots of work.

Hand-soldering jumpers is good for small or slow production runs, hard
work for fast production.  It's a tradeoff.

 Mark

--
I re-ship for small US & overseas businesses, world-wide.
(For private individuals at cost; ask.)


'[OT] PCB vias'
2000\01\01@022238 by ShadeDemon
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 Don't forget you have another option, that may be viable
since you described it as a lot of address/data lines.  Old
useless chips (or maybe even the blank test ones some places
sell for soldering practice) make good via makers if you
have a bit of flexibility in layout and can align your
holes.  Put them on .1" centers, bend the leads straight out
from the chip so they'll be easier to cut, and solder in.
Solder both sides and cut off the rest of the leads and
chip.  Is a heck of a lot faster than placing single wires
by hand.  Can use header etc what ever you have on hand, I
just usually have junk chips.  50 is a bit much, but if you
can lay it out so you have 2 rows of 20 and use an old 40
pin chip it can be managed..

> Jinx wrote:
> > run of probably 50 and don't want to get bogged down for days
> > snipping little bits of wire.
> >
> > The cost of the board is important in that more money will have to
> > paid up front for the mftr but, as the items are leased and not sold,
> > in the long run it won't make a lot of difference. What I'm trying to
> > find out is more along the lines of easy of assembly.

2000\01\01@091635 by wwl

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On Wed, 1 Dec 1999 15:23:02 +1300, you wrote:

{Quote hidden}

For 50 vias, do it properly and use a PTH board. PTH boards are made
in such numbers that they are not that much more expensive, and will
certainly be cheaper than the labour involved in soldering links, not
to mention the hassle of top-soldering components, and the
unreliability when one is missed but just happens to make contact
during test then fails in the field. Non PTH double sided PCBs are
more trouble than they're worth for anything other then one-off
prototyping.  

2000\01\01@122707 by Mark Walsh

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I would definitely go with a double sided board.  Unless the value of your
time is close to nothing, it will be much cheaper to get away from using
jumpers.  You can get a cost for your board from http://www.4pcb.com/  I
checked them this morning, but couldn't get past the main page (probably
shut down for the weekend out of fear of Y2K glitches).  You can get an
instant quote by entering board dimensions, number of layers, solder mask
preference, delivery time, etc. I think you will find the difference in
price of a double sided and single sided board is surprisingly small.

There is also the question of reliability and maintainability, which will
fall off with each jumper you install.  I assume this is a new commercial
venture for you.  You also want to think about the image you create of
yourself and your work when the customer sees the board.  The aesthetics of
a well designed double-sided PCB versus those of a single-sided PCB with a
rat's nest of jumpers may make a difference in getting future work.

By definition a via is a connection from one layer to another on a PCB.  If
there are PCB houses that do double sided boards without plating the holes,
I'm not aware of them.  I suspect it would be a special order to get the
plating omitted.

Mark Walsh

2000\01\01@130644 by p.cousens

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Jinx wrote:
SNIP
> The layout I've got has 250 conventional component holes but many
> links and wires (=time). If I used vias or PTH the holes wouldn't go
> down by much but the assembly time would. As a rough idea I'd say
> there could be 50 vias. A few via connections will be accounted for
> by component leads.

You make all the holes PTH don't worry about how many are via's.
To make a board with some holes PTH and some not will cost more
as it requires the board to be drilled twice (once before plating
and then after plating).
One size drilling will also save the PCB maker time, as will the
total number of holes

A trick I use on RF boards is to have non PTH holes included
for small decoupling caps of around 100pf.
I put surface mount caps (805) through the hole and solder it on the top
and bottom, one of which will be the ground plane.
--
Peter Cousens
email: .....p.cousensKILLspamspam@spam@cwcom.net  or  p.cousensspamKILLspamvirgin.net
smail: 48, Yarmouth Cresent, London, N179PQ, England.

2000\01\01@152330 by Ken Webster

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>Hi, wonder if there's someone who can give me an idea of PCB
>assembly. Being the holiday season I can't get a hold of any local
>mftrs to sound them out, and I'd like to be using the time to move
>ahead as far as possible with the layout.
>
-- SNIP --
>
>Any suggestions ?


I have links to my favorite PCB prototype houses and related information
(layout tips, design guides, PCB FAQ, etc.) here:
http://ken.webster.org/links/shopping.html
(in the center column under the "Electronics, technical" heading)

Most of the PCB prototype houses have online pricing calculators or very
simple pricing formulas based on total square inches, etc.  All of them
except PCB milling do plated-through holes at no additional cost.  With 50
vias per board I would definitely recommend using plated-through holes since
the cost is quite reasonable and should save you a lot of time.

Ken

2000\01\01@174303 by Jinx

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Thanks for all's suggestions re PCB mftr. I'll be sorting it out
today (4pcb seems to be working now). DS PCBs, PTH etc is
something I generally don't get involved with. 99% of the time I
etch one or two SS prototype boards for me or a customer and
that's as far as it goes. This time I'm actively involved with mftr
and I appreciate the efforts to push me up that learning curve.

Jinx

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