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'[EE] Going with SMT'
2006\01\10@072111 by olin piclist

face picon face
Tag changed to EE as it clearly should have been in the first place.  How is
this not engineering and even electrical engineering related!!?

While it's obviously bad to post off topic on PIC or EE, it's just as
important to use those topics when relevant.  If people did that reliably,
some of us wouldn't feel the need to subscribe to OT and there'd be less
complaining about Russell's excesses and all the IT related posts.  (I am
not an admin so this is my personal opinion.)

Rolf wrote:
> My intention with this project is to etch my own board as well...

With a lot of effort and mucking about with nasty chemicals that have to
disposed of properly, you might end up with something that's half as good as
a commercial PCB.  You won't have plated thru holes.  Unless you value your
time at a small fraction of minimum wage, etching your own PCBs just doesn't
make sense anymore.  Commercial prototype services are relatively cheap and
available and of good quality.

> So, given that I have some small successful hobby projects behind me,
> and that I am interested in persuing many more projects, I figure it is
> time to get more "professional" and compact in my execution.

Why?  Unless you really need the space, SMD in your situation is only useful
for showing off to your friends.  You can make well constructed and reliable
circuits in a variety of ways.  Using SMD parts is neither a necessary nor
sufficient condition.

> In order to go ahead with the SMT process though, I will have to
> re-stock all the components I have with SMT equivalents,

I would go with what you've got.  There is absolutely nothing wrong with a
1/4W thru hole resistor.  If you want to transition to SMD (that may be a
good idea long term), use up the old thru hole parts and buy new SMD parts.
The main attraction to SMD is lower assembly cost, but this is irrelevant
when building singles by hand.

> and a I will
> have to manually solder them to a home-brewed PCB.

I think it's actually easier to solder 2 pin 0805 parts than the equivalent
thru hole.  You don't have to flip the board over and snip off the extra
lead length.

> Is this something that is feasable with limited resources/budget?

Feasible, yes.  SMD parts are generally cheaper and more available, but the
parts already in your cabinet are the cheapest and most available of all.
Again, I would use up the old thru hole parts but replace them with SMD
parts as appropriate.

> There are some things I will have to do through-hole as well (sockets
> and connectors)....

Absolutely.  Anything that takes mechanical stress should be thru hole.

> I need to know whether it
> would be possible to do so with the same equipment that would be used
> for pure through-hole projects. Would I need any special tools?

I find messing with 0805 resistors/capacitors easier than their thru hole
counterparts.  You might want a thinner pointier tip for your soldering
iron, and you definitely want a pair of tweezers.  I like the kind where the
last inch or so is bent at an angle.  You might also want to get a spool of
smaller diameter solder, depending on what you already have.

> Is this something that is within reach of a beginner-to-intermediate
> hobbyist?

Definitely.


******************************************************************
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consultant in 2004 program year.  http://www.embedinc.com/products

2006\01\10@094604 by Rolf

face picon face
Thanks Olin...

Olin Lathrop wrote:
> Tag changed to EE as it clearly should have been in the first place.  How is
> this not engineering and even electrical engineering related!!?
>
> While it's obviously bad to post off topic on PIC or EE, it's just as
> important to use those topics when relevant.  If people did that reliably,
> some of us wouldn't feel the need to subscribe to OT and there'd be less
> complaining about Russell's excesses and all the IT related posts.  (I am
> not an admin so this is my personal opinion.)
>
>  
Point taken....
{Quote hidden}

I have seriously considered this. There are what I feel good reasons for
doing it myself.. (at least at first).
1. This is a hobby, and honestly, the time/minimum wage does not
feature. I am looking forward to doing it.
2. I have already found a hazardous waste facility near home, and
confirmed that they will dispose of the etchant properly.
3. I will no-double make mistakes, and require multiple versions of the
first board, making it pretty expensive for each mistake
4. At least in the short term, there will never be more than one or two
"final products".
5. I can say... "look, I did it all myself!".

If I were expecting multiple products, was bored of etching my own
boards, and I had reasonable certainty that I could get the board right
first time, then the prototyping is a very good idea. In a year or so I
imagine I will "be there".


{Quote hidden}

Actually, space is part of the problem. The current project is to link
in to my camera and provide an "enhanced functionality" shutter release
mechanism.
All it really does is something similar to the
http://www.amazon.com/gp/product/B00009XVA3/104-8543778-5032726?v=glance&n=502394
except my camera is a Nikon...

Also, showing off to my friends is a big part of it! ;-)

Also, common components are much cheaper as SM. Other components are
only available as SM.
{Quote hidden}

While what you say is true, it misses one of the "critical steps" in my
development. I can not design a board without playing with the
components first. I do not have the education/experience to be able to
put together a complete system before "bread-boarding" it. I still need
the Through-hole components for that. In essence I will need to keep a
re-usable library of through-hole parts for further experiments. I just
don't want to keep restocking that library unless I need to. If it would
be beneficial to go SMT, which it appears it is, then the sooner I get
on the band-wagon the more I stand to gain.

Once I have it working on the bread-board, I do the schematic/layout
using equivalent SM parts, and re-file the bread-board parts in the
through-hole library. I see this as being cheaper than having to
replenish the through-hole parts.
>> and a I will
>> have to manually solder them to a home-brewed PCB.
>>    
>
> I think it's actually easier to solder 2 pin 0805 parts than the equivalent
> thru hole.  You don't have to flip the board over and snip off the extra
> lead length.
>
>  
That's great news.
>> Is this something that is feasable with limited resources/budget?
>>    
>
> Feasible, yes.  SMD parts are generally cheaper and more available, but the
> parts already in your cabinet are the cheapest and most available of all.
> Again, I would use up the old thru hole parts but replace them with SMD
> parts as appropriate.
>
>  
My cabinet is small.... (like very small, like I have fewer than 100
resistors, like I sort them in to 6 "drawers" where each draw is an
order-of-magnitude.... last-stripe=black in this draw, last-stripe=red
in the next, orange the next, and so on....)
{Quote hidden}

Based on responses to the solder paste question, I will go for regular
"thin" solder. Tweezers, magnifier, and good light seem to be the order
of the day.
{Quote hidden}

I think my fisrt sub-project is to reproduce your RSLink device. Nice
and simple, portable, and immensely useful....

Thanks for the response.

Rolf

2006\01\10@100602 by Brian Clewer

flavicon
face
Rolf,

One thing I might add.  When you are etching your own PCB
take note of the tracks that go under other SM components
like resistors etc.  If your component is not exactly on
the pad, you can short the component to the track underneath
it without ever knowing.

Brian.

2006\01\10@143626 by Gerhard Fiedler

picon face
Brian Clewer wrote:

> One thing I might add.  When you are etching your own PCB take note of
> the tracks that go under other SM components like resistors etc.  If
> your component is not exactly on the pad, you can short the component to
> the track underneath it without ever knowing.

Yes... Without a solder mask, I wouldn't run any traces between the pads of
a 0805 or smaller component. Probably also not between the pads of slightly
bigger components -- don't know where exactly my limit would be, I use
prototyping services with solder mask :)

Consider that the contact area of the component may not be completely on
top of the pads. And as Brian says, you can't see whether it shorts down
there.

Gerhard

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