Homebrew PCBs

For regular SMT assembly I use commercial stencils to screen print the
solder paste but I am having problems dispensing solder paste by hand in
small amounts for rework or prototypes.  

I have seen somewhere that individual stencils are sold but that adds the
requirement to accurately align the stencil which will be very difficult on
a rework board.

Using a syringe and placing a single long bead across all the IC pin pads
work fine on wider pitch ICs but as the pitch is getting smaller I am having
trouble getting the line thin enough.  In other words, there is too much
solder so when I reflow there are solder bridging.

 

If I use a finer tip on the syringe I cannot squeeze it hard enough for the
paste to come out.  If I add some flux it gets thinner but too runny.  I
like the normal consistency since it helps to keep the ICs in place with its
stickiness.  My current smallest bead diameter is 0.5mm (20mils).  I like to
be able to get about half of that size.

 

I am basically looking for a solder paste with less solder and more thick
flux material so I can squeeze out a reasonably sized bead but after reflow
there is less solder than a normal paste.

Any suggestions on a paste like that?

 

Any other suggestions on how to place a very small amount of solder on the
IC pads?

Thanks in advance for suggestions.

Bertho

 

 



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

Something like this may be what you need:

http://cgi.ebay.com/SMT-SMD-Solder-Paste-Adhesive-Glue-Liquid-Dispenser-EFD-/220767109957?pt=LH_DefaultDomain_0&hash=item3366bec345#ht_1230wt_907

I have no experience with that specific product or seller...

-Pete

On May 7, 2011, at 1:05 PM, Boman33 wrote:

> For regular SMT assembly I use commercial stencils to screen print the
> solder paste but I am having problems dispensing solder paste by hand in
> small amounts for rework or prototypes.  
> 
> I have seen somewhere that individual stencils are sold but that adds the
> requirement to accurately align the stencil which will be very difficult on
> a rework board.
> 
> Using a syringe and placing a single long bead across all the IC pin pads
> work fine on wider pitch ICs but as the pitch is getting smaller I am having
> trouble getting the line thin enough.  In other words, there is too much
> solder so when I reflow there are solder bridging.
> 
> 
> 
> If I use a finer tip on the syringe I cannot squeeze it hard enough for the
> paste to come out.  If I add some flux it gets thinner but too runny.  I
> like the normal consistency since it helps to keep the ICs in place with its
> stickiness.  My current smallest bead diameter is 0.5mm (20mils).  I like to
> be able to get about half of that size.
> 
> 
> 
> I am basically looking for a solder paste with less solder and more thick
> flux material so I can squeeze out a reasonably sized bead but after reflow
> there is less solder than a normal paste.
> 
> Any suggestions on a paste like that?
> 
> 
> 
> Any other suggestions on how to place a very small amount of solder on the
> IC pads?
> 
> Thanks in advance for suggestions.
> 
> Bertho
> 
> 
> 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> ------------------------------------
> 
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
> 
> 
> 



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

Thanks Peter for a very fast reply.

Actually I have an equivalent USA made unit that I paid about three times
more for.  

This is a very good price and I will buy an extra one for adhesive
dispensing.

Unfortunately it will not help since when I put a small enough tip on the
syringe, the paste is too sticky to come out.

Bertho

+++++++++++++++++++++++++++++++++++++++++++++++

From Peter Loron   Sent: Saturday, May 07, 2011 16:18
Something like this may be what you need:

http://cgi.ebay.com/SMT-SMD-Solder-Paste-Adhesive-Glue-Liquid-Dispenser-EFD-
/220767109957?pt=LH_DefaultDomain_0
<http://cgi.ebay.com/SMT-SMD-Solder-Paste-Adhesive-Glue-Liquid-Dispenser-EFD
-/220767109957?pt=LH_DefaultDomain_0&hash=item3366bec345#ht_1230wt_907>
&hash=item3366bec345#ht_1230wt_907

I have no experience with that specific product or seller...

-Pete

On May 7, 2011, at 1:05 PM, Boman33 wrote:

> For regular SMT assembly I use commercial stencils to screen print the
> solder paste but I am having problems dispensing solder paste by hand in
> small amounts for rework or prototypes. 
> 
> I have seen somewhere that individual stencils are sold but that adds the
> requirement to accurately align the stencil which will be very difficult
on
> a rework board.
> 
> Using a syringe and placing a single long bead across all the IC pin pads
> work fine on wider pitch ICs but as the pitch is getting smaller I am
having
> trouble getting the line thin enough. In other words, there is too much
> solder so when I reflow there are solder bridging.

> If I use a finer tip on the syringe I cannot squeeze it hard enough for
the
> paste to come out. If I add some flux it gets thinner but too runny. I
> like the normal consistency since it helps to keep the ICs in place with
its
> stickiness. My current smallest bead diameter is 0.5mm (20mils). I like to
> be able to get about half of that size.
> 
> I am basically looking for a solder paste with less solder and more thick
> flux material so I can squeeze out a reasonably sized bead but after
reflow
> there is less solder than a normal paste.
> 
> Any suggestions on a paste like that?

> Any other suggestions on how to place a very small amount of solder on the
> IC pads?
> 
> Thanks in advance for suggestions. 
> Bertho

,___



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

Why don't you mix a 50%/50% bactch and try it with a smaller needle,

Tom

For those interested in a youtube videos of my Homebrewed Printed Circuit Board
fabrication, PIC chip experiments, High powered LED projects, Arduino
applications, QRP kit builds, and Electronics Tourism, Please take at look and
subscribe to my new improved youtube channel "Hamradio2008"

link...
http://www.youtube.com/user/HamRadio2008

heres a current video; Back from Silicon Valley:
Back from Silicon Valley _ LeCroy WaveAce 112
http://www.youtube.com/watch?v=MQ2-a1oB57Q





________________________________

From: Boman33 <boman33@...>
To: Homebrew_PCBs@yahoogroups.com
Sent: Sat, May 7, 2011 4:05:41 PM
Subject: [Homebrew_PCBs] Controlled solder paste dispensing

  
For regular SMT assembly I use commercial stencils to screen print the
solder paste but I am having problems dispensing solder paste by hand in
small amounts for rework or prototypes. 

I have seen somewhere that individual stencils are sold but that adds the
requirement to accurately align the stencil which will be very difficult on
a rework board.

Using a syringe and placing a single long bead across all the IC pin pads
work fine on wider pitch ICs but as the pitch is getting smaller I am having
trouble getting the line thin enough. In other words, there is too much
solder so when I reflow there are solder bridging.

If I use a finer tip on the syringe I cannot squeeze it hard enough for the
paste to come out. If I add some flux it gets thinner but too runny. I
like the normal consistency since it helps to keep the ICs in place with its
stickiness. My current smallest bead diameter is 0.5mm (20mils). I like to
be able to get about half of that size.

I am basically looking for a solder paste with less solder and more thick
flux material so I can squeeze out a reasonably sized bead but after reflow
there is less solder than a normal paste.

Any suggestions on a paste like that?

Any other suggestions on how to place a very small amount of solder on the
IC pads?

Thanks in advance for suggestions.

Bertho

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




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

Hi Tom,

I already did that but adding 50 % liquid flux to the solder paste I get a very liquid runny mixture that does not stay on the pads.  I am hoping to find paste flux and mix it with the solder paste.

What do other people do?

I know I can remove the extra solder afterwards with solder braid but I rather do it correctly in the first place.

Bertho

From: Tom Biery    Sent: Saturday, May 07, 2011 17:29



Why don't you mix a 50%/50% bactch and try it with a smaller needle,

Tom

For those interested in a youtube videos of my Homebrewed Printed Circuit Board
fabrication, PIC chip experiments, High powered LED projects, Arduino
applications, QRP kit builds, and Electronics Tourism, Please take at look and
subscribe to my new improved youtube channel "Hamradio2008"

link...
http://www.youtube.com/user/HamRadio2008

heres a current video; Back from Silicon Valley:
Back from Silicon Valley _ LeCroy WaveAce 112
http://www.youtube.com/watch?v=MQ2-a1oB57Q

________________________________
From: Boman33 <boman33@... <mailto:boman33%40vinland.com> >
To: Homebrew_PCBs@yahoogroups.com <mailto:Homebrew_PCBs%40yahoogroups.com> 
Sent: Sat, May 7, 2011 4:05:41 PM
Subject: [Homebrew_PCBs] Controlled solder paste dispensing

  
For regular SMT assembly I use commercial stencils to screen print the
solder paste but I am having problems dispensing solder paste by hand in
small amounts for rework or prototypes. 

I have seen somewhere that individual stencils are sold but that adds the
requirement to accurately align the stencil which will be very difficult on
a rework board.

Using a syringe and placing a single long bead across all the IC pin pads
work fine on wider pitch ICs but as the pitch is getting smaller I am having
trouble getting the line thin enough. In other words, there is too much
solder so when I reflow there are solder bridging.

If I use a finer tip on the syringe I cannot squeeze it hard enough for the
paste to come out. If I add some flux it gets thinner but too runny. I
like the normal consistency since it helps to keep the ICs in place with its
stickiness. My current smallest bead diameter is 0.5mm (20mils). I like to
be able to get about half of that size.

I am basically looking for a solder paste with less solder and more thick
flux material so I can squeeze out a reasonably sized bead but after reflow
there is less solder than a normal paste.

Any suggestions on a paste like that?

Any other suggestions on how to place a very small amount of solder on the
IC pads?

Thanks in advance for suggestions.

Bertho

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

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





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

Chipquik sells a tack flux as part of their rework product line -- you might want to try using it as the additive to decrease the viscosity of your paste.

Haven't used it myself, but it's obviously thicker than standard flux from the videos of its use that I've seen.

http://www.chipquikinc.com/store/flux.htm

-e

--- In Homebrew_PCBs@yahoogroups.com, "Boman33" <boman33@...> wrote:

>
> Hi Tom,
> 
> I already did that but adding 50 % liquid flux to the solder paste I get a very liquid runny mixture that does not stay on the pads.  I am hoping to find paste flux and mix it with the solder paste.

I solder the majority of my boards by hand.  Giving the joint a good
fluxing and then zip soldering does the trick.

I have used one of those air powered dispensers before.  They are good
for some applications but not for fine pitch.

I have also tinned the pads, sat the chip ontop and hit it with a hot
air rework tool.  This usually works but can still lead to lots of
bridging.  That's why if it's only a few parts I stick with hand
soldering.

-- 
Erik L. Knise
Seattle, WA

On Sat, May 7, 2011 at 11:35 PM, Boman33 <boman33@...> wrote:
> Hi Tom,
>
> I already did that but adding 50 % liquid flux to the solder paste I get a very liquid runny mixture that does not stay on the pads.  I am hoping to find paste flux and mix it with the solder paste.
>
> What do other people do?
>
> I know I can remove the extra solder afterwards with solder braid but I rather do it correctly in the first place.
>
> Bertho
>

For prototyping you can make your own solder stencils using a 3-4 mil copper gasket material from a good hardware store.  I use toner transfer to apply the solder mask and then etch as you normally would a board.  Very fast, clean, and simple.

For fine pitch parts in prototyping or rework I always tin the pads with a solder, wick up any bridges and then use a hot air rework tool to solder the part in place.  Much easier than hand soldering the fine pitch leads and then trying to wick up the bridges.

Using a 3-4 to 1 solder paste/flux mix ratio usually thins the solder paste enough to apply on very small pads.

--- In Homebrew_PCBs@yahoogroups.com, "Boman33" <boman33@...> wrote:

>
> For regular SMT assembly I use commercial stencils to screen print the
> solder paste but I am having problems dispensing solder paste by hand in
> small amounts for rework or prototypes.  
> 
> I have seen somewhere that individual stencils are sold but that adds the
> requirement to accurately align the stencil which will be very difficult on
> a rework board.
> 
> Using a syringe and placing a single long bead across all the IC pin pads
> work fine on wider pitch ICs but as the pitch is getting smaller I am having
> trouble getting the line thin enough.  In other words, there is too much
> solder so when I reflow there are solder bridging.
> 
>  
> 
> If I use a finer tip on the syringe I cannot squeeze it hard enough for the
> paste to come out.  If I add some flux it gets thinner but too runny.  I
> like the normal consistency since it helps to keep the ICs in place with its
> stickiness.  My current smallest bead diameter is 0.5mm (20mils).  I like to
> be able to get about half of that size.
> 
>  
> 
> I am basically looking for a solder paste with less solder and more thick
> flux material so I can squeeze out a reasonably sized bead but after reflow
> there is less solder than a normal paste.
> 
> Any suggestions on a paste like that?
> 
>  
> 
> Any other suggestions on how to place a very small amount of solder on the
> IC pads?
> 
> Thanks in advance for suggestions.
> 
> Bertho
> 
>  
> 
>  
> 
> 
> 
> [Non-text portions of this message have been removed]
>

Using Zeph paste and a 25 gauge plastic syringe + hot air gun , I can solder
a 128 pin .5mm pitch QFP in under 10 seconds (including the pasting time)
with no bridging.

I cannot usually solder .4mm pitch devices without some bridging.  However,
I just use kester flux in a syringe and a wide soldering iron and drag it
across the pins and this moves 99% of bridges as long as I made my pcb pads
big enough.
Syringes have no cleanup.

I have a laser cutter and it's pretty effortless for me to make a stencil
but I don't use it unless I need to make more than 2 boards because the
cleanup time is more than my syringe time.

On Mon, May 9, 2011 at 5:27 PM, Terry <twgray2007@gmail.com> wrote:

>
>
> For prototyping you can make your own solder stencils using a 3-4 mil
> copper gasket material from a good hardware store. I use toner transfer to
> apply the solder mask and then etch as you normally would a board. Very
> fast, clean, and simple.
>
> For fine pitch parts in prototyping or rework I always tin the pads with a
> solder, wick up any bridges and then use a hot air rework tool to solder the
> part in place. Much easier than hand soldering the fine pitch leads and then
> trying to wick up the bridges.
>
> Using a 3-4 to 1 solder paste/flux mix ratio usually thins the solder paste
> enough to apply on very small pads.
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "Boman33" <boman33@...> wrote:
> >
> > For regular SMT assembly I use commercial stencils to screen print the
> > solder paste but I am having problems dispensing solder paste by hand in
> > small amounts for rework or prototypes.
> >
> > I have seen somewhere that individual stencils are sold but that adds the
> > requirement to accurately align the stencil which will be very difficult
> on
> > a rework board.
> >
> > Using a syringe and placing a single long bead across all the IC pin pads
> > work fine on wider pitch ICs but as the pitch is getting smaller I am
> having
> > trouble getting the line thin enough. In other words, there is too much
> > solder so when I reflow there are solder bridging.
> >
> >
> >
> > If I use a finer tip on the syringe I cannot squeeze it hard enough for
> the
> > paste to come out. If I add some flux it gets thinner but too runny. I
> > like the normal consistency since it helps to keep the ICs in place with
> its
> > stickiness. My current smallest bead diameter is 0.5mm (20mils). I like
> to
> > be able to get about half of that size.
> >
> >
> >
> > I am basically looking for a solder paste with less solder and more thick
> > flux material so I can squeeze out a reasonably sized bead but after
> reflow
> > there is less solder than a normal paste.
> >
> > Any suggestions on a paste like that?
> >
> >
> >
> > Any other suggestions on how to place a very small amount of solder on
> the
> > IC pads?
> >
> > Thanks in advance for suggestions.
> >
> > Bertho
> >
> >
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>  
>


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

What type of laser cutter are you using?  

And ditto on the stencil.  If I don't have several boards it's just not worth the effort/time.

--- In Homebrew_PCBs@yahoogroups.com, Henry Liu <henryjliu@...> wrote:

>
> Using Zeph paste and a 25 gauge plastic syringe + hot air gun , I can solder
> a 128 pin .5mm pitch QFP in under 10 seconds (including the pasting time)
> with no bridging.
> 
> I cannot usually solder .4mm pitch devices without some bridging.  However,
> I just use kester flux in a syringe and a wide soldering iron and drag it
> across the pins and this moves 99% of bridges as long as I made my pcb pads
> big enough.
> Syringes have no cleanup.
> 
> I have a laser cutter and it's pretty effortless for me to make a stencil
> but I don't use it unless I need to make more than 2 boards because the
> cleanup time is more than my syringe time.
> 
> On Mon, May 9, 2011 at 5:27 PM, Terry <twgray2007@...> wrote:
> 
> >
> >
> > For prototyping you can make your own solder stencils using a 3-4 mil
> > copper gasket material from a good hardware store. I use toner transfer to
> > apply the solder mask and then etch as you normally would a board. Very
> > fast, clean, and simple.
> >
> > For fine pitch parts in prototyping or rework I always tin the pads with a
> > solder, wick up any bridges and then use a hot air rework tool to solder the
> > part in place. Much easier than hand soldering the fine pitch leads and then
> > trying to wick up the bridges.
> >
> > Using a 3-4 to 1 solder paste/flux mix ratio usually thins the solder paste
> > enough to apply on very small pads.
> >
> >
> > --- In Homebrew_PCBs@...m, "Boman33" <boman33@> wrote:
> > >
> > > For regular SMT assembly I use commercial stencils to screen print the
> > > solder paste but I am having problems dispensing solder paste by hand in
> > > small amounts for rework or prototypes.
> > >
> > > I have seen somewhere that individual stencils are sold but that adds the
> > > requirement to accurately align the stencil which will be very difficult
> > on
> > > a rework board.
> > >
> > > Using a syringe and placing a single long bead across all the IC pin pads
> > > work fine on wider pitch ICs but as the pitch is getting smaller I am
> > having
> > > trouble getting the line thin enough. In other words, there is too much
> > > solder so when I reflow there are solder bridging.
> > >
> > >
> > >
> > > If I use a finer tip on the syringe I cannot squeeze it hard enough for
> > the
> > > paste to come out. If I add some flux it gets thinner but too runny. I
> > > like the normal consistency since it helps to keep the ICs in place with
> > its
> > > stickiness. My current smallest bead diameter is 0.5mm (20mils). I like
> > to
> > > be able to get about half of that size.
> > >
> > >
> > >
> > > I am basically looking for a solder paste with less solder and more thick
> > > flux material so I can squeeze out a reasonably sized bead but after
> > reflow
> > > there is less solder than a normal paste.
> > >
> > > Any suggestions on a paste like that?
> > >
> > >
> > >
> > > Any other suggestions on how to place a very small amount of solder on
> > the
> > > IC pads?
> > >
> > > Thanks in advance for suggestions.
> > >
> > > Bertho
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> >  
> >
> 
> 
> [Non-text portions of this message have been removed]
>

Thanks everyone for the feedback.
I am ordering the Zeph paste and the Chipquick one and some thick flux paste
too.
Both companies have good videos and info.
My goal is to develop a foolproof procedure since we have to rework over 100
12 layer PCBs each with six 208 pin 0.5mm spacing ICs for a customer.
Stencils are not practical on a populated board so that  is why I am looking
for a controlled amount of solder paste dispensing.

Henry: What are you using for the laser cut stencil material?
Bertho

-----Original Message-----
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
On Behalf Of Henry Liu
Sent: Monday, May 09, 2011 23:04
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: Controlled solder paste dispensing

Using Zeph paste and a 25 gauge plastic syringe + hot air gun , I can solder
a 128 pin .5mm pitch QFP in under 10 seconds (including the pasting time)
with no bridging.

I cannot usually solder .4mm pitch devices without some bridging.  However,
I just use kester flux in a syringe and a wide soldering iron and drag it
across the pins and this moves 99% of bridges as long as I made my pcb pads
big enough.
Syringes have no cleanup.

I have a laser cutter and it's pretty effortless for me to make a stencil
but I don't use it unless I need to make more than 2 boards because the
cleanup time is more than my syringe time.

We make our own laser cutters + direct print software + control electronics:
www.fullspectrumengineering.com/co2laserv2-40w.html

Our 40w has 1000dpi and I can easily do stencils for my .5mm pitch devices
for around $2000.  Shameless plug: we have better vector cut quality than
even a $20,000 Epilog laser due to a superior spline trajectory algorithm
(verified side by side).

We also have pulsed fiber lasers that can do stainless steel stencils but
these are $35k+.

Laser transperency is the best material.  It is heat resistant and cheap.
Others use kapton but this is an inferior CO2 laser material.

Again take it from me if I don't make the stencil when I make the laser and
can modify the software anyway I want (I just hit File\Print from Altium and
the stencil would pop out) that the syringe is easier for one offs.

You should keep your paste up to room temperature otherwise it will get
stuck in the 25gauge tip.

Henry
On Tue, May 10, 2011 at 12:36 AM, Boman33 <boman33@...> wrote:

>
>
> Thanks everyone for the feedback.
> I am ordering the Zeph paste and the Chipquick one and some thick flux
> paste
> too.
> Both companies have good videos and info.
> My goal is to develop a foolproof procedure since we have to rework over
> 100
> 12 layer PCBs each with six 208 pin 0.5mm spacing ICs for a customer.
> Stencils are not practical on a populated board so that is why I am looking
> for a controlled amount of solder paste dispensing.
>
> Henry: What are you using for the laser cut stencil material?
> Bertho
>
> -----Original Message-----
> From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
> On Behalf Of Henry Liu
> Sent: Monday, May 09, 2011 23:04
>
> To: Homebrew_PCBs@yahoogroups.com
> Subject: Re: [Homebrew_PCBs] Re: Controlled solder paste dispensing
>
>
> Using Zeph paste and a 25 gauge plastic syringe + hot air gun , I can
> solder
> a 128 pin .5mm pitch QFP in under 10 seconds (including the pasting time)
> with no bridging.
>
> I cannot usually solder .4mm pitch devices without some bridging. However,
> I just use kester flux in a syringe and a wide soldering iron and drag it
> across the pins and this moves 99% of bridges as long as I made my pcb pads
> big enough.
> Syringes have no cleanup.
>
> I have a laser cutter and it's pretty effortless for me to make a stencil
> but I don't use it unless I need to make more than 2 boards because the
> cleanup time is more than my syringe time.
>
>  
>


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