Homebrew PCBs

I have made some printed circuit boards using common components
requiring drilling. I would like to start using some simple surface
mount resistors, capacitors, and transistors to reduce drilling and
reduce space. I am wondering about the best techinque to use these
devices on boards.

I did a bit of experimenting with a board using some 1206 size
resistors and it seems that using these components will be quite a
useful addition to board construction.

One recommendation I heard was to use just a small bit of glue to hold
the components in place, then once all places come back and solder
them all. I tried this and it did work, but I have some concern about
the stability of the glue over time and how this might impact long
term reliablity.

I also tried just holding a resistor in place with some tweezers and
soldering them. This also worked but obviously requires an extra hand.

I would like to know what sort of techniques people use to place
these. I also see mention of using flux paste and I am wondering if
this is solder bearing paste. Does this hold a component in place such
that it won't simply adhear to the tip of the soldering iron?

Dale Mosby wrote:

>I would like to know what sort of techniques people use to place
>these. I also see mention of using flux paste and I am wondering if
>this is solder bearing paste. Does this hold a component in place such
>that it won't simply adhear to the tip of the soldering iron?
>
>  
>
  The tip on Sparkfun is pretty useful.  Use tape, pick the component up 
with one side sticking out and tape it down.  Solder that side then take 
off the tape and do the rest of the pins.

  Just don't do it on anything super static sensitive, peeling tape can 
generate sizable static voltages, great for all the small resistors and 
caps though..

Alan

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

From: "Dale Mosby" <dale@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, January 29, 2006 4:50 AM
Subject: [Homebrew_PCBs] Question: using surface mount resistors/caps ?


>I have made some printed circuit boards using common components
> requiring drilling. I would like to start using some simple surface
> mount resistors, capacitors, and transistors to reduce drilling and
> reduce space. I am wondering about the best techinque to use these
> devices on boards.
>
> I did a bit of experimenting with a board using some 1206 size
> resistors and it seems that using these components will be quite a
> useful addition to board construction.
>
> One recommendation I heard was to use just a small bit of glue to hold
> the components in place, then once all places come back and solder
> them all. I tried this and it did work, but I have some concern about
> the stability of the glue over time and how this might impact long
> term reliablity.
>
> I also tried just holding a resistor in place with some tweezers and
> soldering them. This also worked but obviously requires an extra hand.

Put a little solder on one of the pads, place the part with the tweezers and 
apply the soldering iron to tack down that end. Solder the other end and 
then the first end, properly.

Leon

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

From: "Dale Mosby" <dale@...>

> I would like to know what sort of techniques people use to place
> these. I also see mention of using flux paste and I am wondering if
> this is solder bearing paste. Does this hold a component in place such
> that it won't simply adhear to the tip of the soldering iron?

Solder paste. Run a bead along the pads, and stuff the chip in place. The 
paste holds the part until reflowed. Heat the board and the part with hot 
air, by stir frying, or by toasting in an oven. Reflowing cooks the flux and 
melts the solder. As the solder melts, the surface tension centers the part 
on the pads. Hand soldering is as crude as hammering in comparison. No 
matter how nimble and deft your fingers and how fine your solder, there is 
very little else you can do that is as harsh and damaging as heating the 
parts unevenly with an iron.

You already know most of it through reasoning.

The glue thing is done industrially sometimes esp. for bottom side wave  
soldering. I don't think it is practical at home.

Hand soldering can be done in two simple ways:

Tin one pad, place component with tweezers and tack this pad, solder other  
pad, return to do first pad properly.
Same works for ICs and stuff, start with diagonal pads.

Version two, take a wood board, and attach a piece of steel wire to one  
corner (maybe 2mm dia, if nothing else is at hand coathanger should work)  
Bend the wire around in a upside-down U so the other end presses down  
about in the center of the board. This will be your third hand that holds  
the compoent in place while you solder. Sounds a bit awkward to use, but  
it's surprisingly easy.

Or you can use solder paste, you need special SMD solder paste which is  
solder bearing and stays gel like even when heated. Plumbing paste doesn't  
work. You apply small dabs of it on the pads, and roughly place the  
component (it will self-center). Then you heat the thing with hot air  
(good heat gun), or in a small oven, or on a hotplate like a skillet if it  
is single-sided. For ICs you can make beads of paste that go right across  
the pins, it will be pulled to the pins by surface tension.

ST

On Sun, 29 Jan 2006 05:50:31 +0100, Dale Mosby <dale@...> wrote:

> I have made some printed circuit boards using common components
>
> requiring drilling. I would like to start using some simple surface
>
> mount resistors, capacitors, and transistors to reduce drilling and
>
> reduce space. I am wondering about the best techinque to use these
>
> devices on boards.
>
>
> I did a bit of experimenting with a board using some 1206 size
>
> resistors and it seems that using these components will be quite a
>
> useful addition to board construction.
>
>
> One recommendation I heard was to use just a small bit of glue to hold
>
> the components in place, then once all places come back and solder
>
> them all. I tried this and it did work, but I have some concern about
>
> the stability of the glue over time and how this might impact long
>
> term reliablity.
>
>
> I also tried just holding a resistor in place with some tweezers and
>
> soldering them. This also worked but obviously requires an extra hand.
>
>
> I would like to know what sort of techniques people use to place
>
> these. I also see mention of using flux paste and I am wondering if
>
> this is solder bearing paste. Does this hold a component in place such
>
> that it won't simply adhear to the tip of the soldering iron?

The method I use is to tin the pad, and then use Solder Wick to remove
all the solder, leaving a nicely tinned pad. I then place the
component in position with tweasers, and use a wooden toothpick to
gentle push down vertically at the center of the component.
With a 'Dry' soldering iron tip I gently heat the pad and metalising
on the component end. There is then sufficient solder adhesion to get
one end of the  component to remain in place whilst I solder the other
end. I get good results using this method without extra flux or glue.

regards
Stewart

 
--- In Homebrew_PCBs@yahoogroups.com, "Dale Mosby" <dale@a...> wrote:

>
> I have made some printed circuit boards using common components
> requiring drilling. I would like to start using some simple surface
> mount resistors, capacitors, and transistors to reduce drilling and
> reduce space. I am wondering about the best techinque to use these
> devices on boards.
> 
> I did a bit of experimenting with a board using some 1206 size
> resistors and it seems that using these components will be quite a
> useful addition to board construction.
> 
> One recommendation I heard was to use just a small bit of glue to hold
> the components in place, then once all places come back and solder
> them all. I tried this and it did work, but I have some concern about
> the stability of the glue over time and how this might impact long
> term reliablity.
> 
> I also tried just holding a resistor in place with some tweezers and
> soldering them. This also worked but obviously requires an extra hand.
> 
> I would like to know what sort of techniques people use to place
> these. I also see mention of using flux paste and I am wondering if
> this is solder bearing paste. Does this hold a component in place such
> that it won't simply adhear to the tip of the soldering iron?
>

--- In Homebrew_PCBs@yahoogroups.com, "Dale Mosby" <dale@a...> wrote:
>
> I have made some printed circuit boards using common components
> requiring drilling. I would like to start using some simple surface
> mount resistors, capacitors, and transistors to reduce drilling and
> reduce space. I am wondering about the best techinque to use these
> devices on boards.
> 
> I did a bit of experimenting with a board using some 1206 size
> resistors and it seems that using these components will be quite a
> useful addition to board construction.
> 
> One recommendation I heard was to use just a small bit of glue to hold
> the components in place, then once all places come back and solder
> them all. I tried this and it did work, but I have some concern about
> the stability of the glue over time and how this might impact long
> term reliablity.
> 
> I also tried just holding a resistor in place with some tweezers and
> soldering them. This also worked but obviously requires an extra hand.
> 
> I would like to know what sort of techniques people use to place
> these. I also see mention of using flux paste and I am wondering if
> this is solder bearing paste. Does this hold a component in place such
> that it won't simply adhear to the tip of the soldering iron?
>

I've had no luck with tweezers.  My choice is to place smt's using a
tooth pick with a pin head size ball of Blu Tack or Office Depot All
Stick, part number 323-609.

Solder paste is expensive with a short life.

I use a 15 watt iron with a fine tip, a head magnifier, a flux pen,
and .020 diameter solder.

Flux solves a multitude of sins.  I even have good luck smearing flux
from a Radio Shack tube on the pads before soldering.  But a flux pen
is cleaner.

Apply flux to the pads before soldering and let it dry.  

With a small bead of solder tin one of the pads.  

Place the component with the toothpick, hold in place, and heat to
tack it in place.  Use a bead of solder to mount the other end. 
Repeat on the tacked end. It only takes a second to solder each end.
With small components I put the bead on the tip.  The solder roll
doesn't come near the chip.  

If the components are old, reluctant to accept solder, I'll flux the
ends after tacking. 

This is the low budget approach to simple smt's.  I use it for 0805's,
SOIC, and SOT-23 packages. If you get smaller than SOIC packages you
might need more sophistication.

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

From: "Alan King" <alan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, January 29, 2006 5:58 AM
Subject: Re: [Homebrew_PCBs] Question: using surface mount resistors/caps ?


> Dale Mosby wrote:
>
>>I would like to know what sort of techniques people use to place
>>these. I also see mention of using flux paste and I am wondering if
>>this is solder bearing paste. Does this hold a component in place such
>>that it won't simply adhear to the tip of the soldering iron?
>>
>>
>>
>  The tip on Sparkfun is pretty useful.  Use tape, pick the component up
> with one side sticking out and tape it down.  Solder that side then take
> off the tape and do the rest of the pins.

I sometimes use a piece of BluTak to hold the chip down on one side, or a 
small piece can be placed under the chip.

Leon

> Use tape, pick the component up

Another great thing about tape is that the part can be nudged into 
alignment after it's held in place due to the nature of tape. The 
method (if any) chosen to hold the component in place while soldering 
really depends a lot on taste and the expectations of the individual. 
If you can get away with misalignment (usually the case with 
resistors and caps) and don't care how things look then the tweezers 
approach works well.

However, if you want pick and place alignment then expect to take 
more time just aligning the component then arrive at some method of 
temporarily fixing the part while soldering. I've tried glue, tape 
etc. but the most efficient way IMO for holding parts on a relatively 
small board is by using a reverse action tweezers like this;

http://rocky.digikey.com/WebLib/Cooper%20Tools/Web%20Photo/XHT412.jpg

The non-component side of the board should be covered to prevent 
minor scratching and the order in which components are soldered 
becomes important. You should be able to figure out the rest.

--- In Homebrew_PCBs@yahoogroups.com, Alan King <alan@n...> wrote:
>
>   The tip on Sparkfun is pretty useful.  Use tape, pick the 
component up 
> with one side sticking out and tape it down.  Solder that side then 
take 
> off the tape and do the rest of the pins.
> 
>   Just don't do it on anything super static sensitive, peeling tape 
can 
> generate sizable static voltages, great for all the small resistors 
and 

> caps though..
> 
> Alan
>

On Tue, 31 Jan 2006 16:27:58 +0100, derekhawkins <eldata@...> wrote:

>
>
> However, if you want pick and place alignment then expect to take
>
> more time just aligning the component then arrive at some method of
>
> temporarily fixing the part while soldering. I've tried glue, tape
>
> etc. but the most efficient way IMO for holding parts on a relatively
>
> small board is by using a reverse action tweezers like this;


You could also use paste and reflow if appearance is an issue, it  
self-centers exactly due to surface tension and looks perfect.

ST

> You could also use paste and reflow if appearance is an issue, it
> self-centers exactly due to surface tension and looks perfect.

No kidding! How many of us are reflowing on boards without solder 
masks?

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@g...> wrote:
>
> On Tue, 31 Jan 2006 16:27:58 +0100, derekhawkins <eldata@m...> 
wrote:
> 
> >
> >
> > However, if you want pick and place alignment then expect to take
> >
> > more time just aligning the component then arrive at some method 
of
> >
> > temporarily fixing the part while soldering. I've tried glue, tape
> >
> > etc. but the most efficient way IMO for holding parts on a 
relatively

> >
> > small board is by using a reverse action tweezers like this;
> 
> 
> You could also use paste and reflow if appearance is an issue, it  
> self-centers exactly due to surface tension and looks perfect.
> 
> ST
>

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

From: "derekhawkins" <eldata@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, January 31, 2006 4:20 PM
Subject: [Homebrew_PCBs] Re: Question: using surface mount resistors/caps ?


>> You could also use paste and reflow if appearance is an issue, it
>> self-centers exactly due to surface tension and looks perfect.
>
> No kidding! How many of us are reflowing on boards without solder
> masks?

Everyone making their own PCBs, probably. I don't think that anyone has got 
a solder-mask technique for homebrew boards.

Leon 

---
[This E-mail has been scanned for viruses but it is your responsibility 
to maintain up to date anti virus software on the device that you are
currently using to read this email. ]

> Everyone making their own PCBs, probably.

Perhaps you misread my question...How many of us is using solder 
paste to solder SMD components to their **homemade boards**? I'm not 
referring to reflowing plumber's paste for tinning. I'm not referring 
to melting solder with a soldering iron. The answer couldn't be 
everyone.

--- In Homebrew_PCBs@yahoogroups.com, "Leon Heller" 
<leon.heller@b...> wrote:
>
> 
> Everyone making their own PCBs, probably. I don't think that anyone 
has got 
> a solder-mask technique for homebrew boards.
> 
> Leon 
> 
> ---
> [This E-mail has been scanned for viruses but it is your 
responsibility 
> to maintain up to date anti virus software on the device that you 
are
> currently using to read this email. ]
>

On Tue, 31 Jan 2006 17:20:01 +0100, derekhawkins <eldata@...> wrote:

>> You could also use paste and reflow if appearance is an issue, it
>
>> self-centers exactly due to surface tension and looks perfect.
>
>
> No kidding! How many of us are reflowing on boards without solder
>
> masks?


Most of us, actually, i guess ;-)

Of those that using smd paste that is.

Why would you think you need soldermask?

ST

On Tue, 31 Jan 2006 18:34:23 +0100, derekhawkins <eldata@...> wrote:

> Perhaps you misread my question...How many of us is using solder
>
> paste to solder SMD components to their **homemade boards**? I'm not
>
> referring to reflowing plumber's paste for tinning. I'm not referring
>
> to melting solder with a soldering iron. The answer couldn't be
>
> everyone.


The answer is still _a lot_.

ST

> Why would you think you need soldermask?

Exposed tracks leading to the pads will cause unpredictable imbalances 
as the solder "wicks" away on them. Self centering is not one of the 
benefits of solder paste in the absence of solder mask. 

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

>
> Most of us, actually, i guess ;-)
> 
> Of those that using smd paste that is.
> 
> Why would you think you need soldermask?
> 
> ST
>

> The answer is still _a lot_.

I'm impressed.


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

>
> 
> The answer is still _a lot_.
> 
> ST
>

I think he might mean stencils. The answer is still the same: few of us and 
it doesn't make much difference. The stencil's job is to mask the paste into 
an even thickness only where it's needed. Typically, the stencil is 3 to 5 
mil thick. Adding the solder mask thickness, it leaves about 8 mil of paste 
on the pads after troweling off.

Why might you not need a stencil? Conversely, why are they used if you can 
do without? Very briefly: surface tension, and manual application versus 
automated production line. Apply the paste where it's needed, not too much 
and not too little. Bridging isn't a concern. Experiment a little. Prove it 
to yourself.


----- Original Message ----- 
From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, January 31, 2006 12:21 PM
Subject: Re: [Homebrew_PCBs] Re: Question: using surface mount 
resistors/caps ?

> On Tue, 31 Jan 2006 17:20:01 +0100, derekhawkins <eldata@...> wrote:
>
>>> You could also use paste and reflow if appearance is an issue, it
>>
>>> self-centers exactly due to surface tension and looks perfect.
>>
>>
>> No kidding! How many of us are reflowing on boards without solder
>>
>> masks?
>
>
> Most of us, actually, i guess ;-)
>
> Of those that using smd paste that is.
>
> Why would you think you need soldermask?

Solder mask has absolutely no effect there. Aside from BGA, the entire 
footprint including the pads and spaces is not masked.

It's one of those things you'll have to take on faith until you see it for 
yourself. The chips wiggle themselves into place during reflow. Not only is 
self-centering one of the benefits of solder paste, there is little you can 
do to prevent it.

There's nothing magic about paste. You don't even need paste and an oven to 
prove it to yourself. Point a heat gun at a hand soldered 0402 or SOIC and 
see.

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

From: "derekhawkins" <eldata@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, January 31, 2006 2:11 PM
Subject: [Homebrew_PCBs] Re: Question: using surface mount resistors/caps ?


>> Why would you think you need soldermask?
>
> Exposed tracks leading to the pads will cause unpredictable imbalances
> as the solder "wicks" away on them. Self centering is not one of the
> benefits of solder paste in the absence of solder mask.
>
> --- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
> <stefan_trethan@g...> wrote:
>>
>> Most of us, actually, i guess ;-)
>>
>> Of those that using smd paste that is.
>>
>> Why would you think you need soldermask?

> I think he might mean stencils.

I mean't the usually green stuff called solder mask. You cannot get 
perfect or near perfect centering of SMD components during reflow 
without it. BTW, even though stencils are more efficient, there are 
still shops that use CNC solder paste dispensers.

> Bridging isn't a concern

It is a concern if a track runs under a SMD component and there is no 
solder mask when solder paste is used. Lots of talk about solder 
paste but very few proficient in its actual use so far. Personally, 
it would be my soldering method of choice on a board done 
professionally. Doubt if I'll ever use it on something made at home. 


--- In Homebrew_PCBs@yahoogroups.com, "Mike Young" <mikewhy@s...> 
wrote:
>
> I think he might mean stencils. The answer is still the same: few 
of us and 
> it doesn't make much difference. The stencil's job is to mask the 
paste into 
> an even thickness only where it's needed. Typically, the stencil is 
3 to 5 
> mil thick. Adding the solder mask thickness, it leaves about 8 mil 
of paste 
> on the pads after troweling off.
> 
> Why might you not need a stencil? Conversely, why are they used if 
you can 
> do without? Very briefly: surface tension, and manual application 
versus 
> automated production line. Apply the paste where it's needed, not 
too much 
> and not too little. Bridging isn't a concern. Experiment a little. 
Prove it 
> to yourself.
> 
> 
> ----- Original Message ----- 
> From: "Stefan Trethan" <stefan_trethan@g...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Tuesday, January 31, 2006 12:21 PM
> Subject: Re: [Homebrew_PCBs] Re: Question: using surface mount 
> resistors/caps ?
> 
> 
> > On Tue, 31 Jan 2006 17:20:01 +0100, derekhawkins <eldata@m...> 
wrote:
> >
> >>> You could also use paste and reflow if appearance is an issue, 
it

> >>
> >>> self-centers exactly due to surface tension and looks perfect.
> >>
> >>
> >> No kidding! How many of us are reflowing on boards without solder
> >>
> >> masks?
> >
> >
> > Most of us, actually, i guess ;-)
> >
> > Of those that using smd paste that is.
> >
> > Why would you think you need soldermask?
>

> The chips wiggle themselves into place during reflow. Not only is
> self-centering one of the benefits of solder paste, there is little 
> you can do to prevent it.

At least two things prevent it actually;

1. Pads not designed for reflow
2. No solder mask

Again, your idea of self centering may be different from mine. All 
boils down to taste and expectations.

--- In Homebrew_PCBs@yahoogroups.com, "Mike Young" <mikewhy@s...> 
wrote:
>
> Solder mask has absolutely no effect there. Aside from BGA, the 
entire 
> footprint including the pads and spaces is not masked.
> 
> It's one of those things you'll have to take on faith until you see 
it for 
> yourself. The chips wiggle themselves into place during reflow. Not 
only is 
> self-centering one of the benefits of solder paste, there is little 
you can 
> do to prevent it.
> 
> There's nothing magic about paste. You don't even need paste and an 
oven to 
> prove it to yourself. Point a heat gun at a hand soldered 0402 or 
SOIC and 
> see.
> 
> ----- Original Message ----- 
> From: "derekhawkins" <eldata@m...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Tuesday, January 31, 2006 2:11 PM
> Subject: [Homebrew_PCBs] Re: Question: using surface mount 
resistors/caps ?
> 
> 
> >> Why would you think you need soldermask?
> >
> > Exposed tracks leading to the pads will cause unpredictable 
imbalances
> > as the solder "wicks" away on them. Self centering is not one of 
the

> > benefits of solder paste in the absence of solder mask.
> >
> > --- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
> > <stefan_trethan@g...> wrote:
> >>
> >> Most of us, actually, i guess ;-)
> >>
> >> Of those that using smd paste that is.
> >>
> >> Why would you think you need soldermask?
>

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

From: "derekhawkins" <eldata@...>


> You cannot get
> perfect or near perfect centering of SMD components during reflow
> without it.

I can and do regularly, casually. It's as for sure as marinara and white 
shirts. I would shrug it off as differing experiences, but it's entirely 
certain and obvious you haven't ever tried.

>> Bridging isn't a concern
>
> It is a concern if a track runs under a SMD component and there is no
> solder mask when solder paste is used.

Let me rephrase. I'm not concerned unless, say, a huge dust bunny falls 
under the chip as I stuff it into place. What failure mechanism are you 
imagining?

> Lots of talk about solder
> paste but very few proficient in its actual use so far. Personally,
> it would be my soldering method of choice on a board done
> professionally. Doubt if I'll ever use it on something made at home.

It's not at all complicated. There are barriers to overcome, and I suspect 
in your case, the first and final one is insurmountable.

On Tue, 31 Jan 2006 21:11:10 +0100, derekhawkins <eldata@...> wrote:

> Exposed tracks leading to the pads will cause unpredictable imbalances
>
> as the solder "wicks" away on them. Self centering is not one of the
>
> benefits of solder paste in the absence of solder mask.


Not in practice, if the traces are thin enough.
If you have that problem you can always run them in from the ends of the  
pads rather than the sides where it won't matter much.

Have you actually tried this or are you just a nay sayer?
Other people have tried, and it works perfectly for us, so forgive me if i  
can't quite see the reasons for your concern.

ST

On Tue, 31 Jan 2006 21:48:23 +0100, derekhawkins <eldata@...> wrote:

>
>
> It is a concern if a track runs under a SMD component and there is no
>
> solder mask when solder paste is used. Lots of talk about solder
>
> paste but very few proficient in its actual use so far. Personally,
>
> it would be my soldering method of choice on a board done
>
> professionally. Doubt if I'll ever use it on something made at home.


Why would it be a concern then? you don't solder the component to this  
trace so why should it be a problem?
You _can_ have bridging if you run traces between IC pins and just put a  
bead of paste across the pins, not individual portions per pin, but that  
can easily be sorted by either interrupting the bead at the trace or using  
some solder wick to clear the bridge IF it happens.

Just try it, you'll see...

ST