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Not all solder pastes are created equal

John AE5X
 

I started on my SB II last night - or tried to, only to find that the paste I ordered is too paste-like and not "liquidy" enough to be applied to the board. Instead, it pulls away with the syringe rather than adhering to the pad I try applying it to. FWIW, this is the paste I ordered:
https://www.ebay.com/itm/Kester-EP256-Lead-Solder-Paste-63-37-Syringe-Dispenser-w-additional-tips/201842021162?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

There must be something out there with a bit less viscosity. The one part currently on the board is Q2, put there with standard soldering methods (a small-tipped iron).

dyerhard1972
 

Viscosity is temperature dependant.  Try putting the solder paste in a container with warm water. The hotter the paste the thinner it will get.
Thanks jeff ke4fwe 

Steven Weber
 

If the paste is too cold it doesn’t flow very well. My paste starts out at about 50 degrees due to the fact I don’t heat the room until I need to work in it. So I hold it over the electric space heater for a little bit as I warm the room up enough to work in. Then my hand keeps it warm enough as it put down the paste.

 

I also find I have to poke a wire up into the syringe once in a while to get the flux to mix back up into the lead/tin balls.

 

Try that and see if it helps.

73, Steve KD1JV

 

 

I started on my SB II last night - or tried to, only to find that the paste I ordered is too paste-like and not "liquidy" enough to be applied to the board. Instead, it pulls away with the syringe rather than adhering to the pad I try applying it to. FWIW, this is the paste I ordered:
https://www.ebay.com/itm/Kester-EP256-Lead-Solder-Paste-63-37-Syringe-Dispenser-w-additional-tips/201842021162?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

There must be something out there with a bit less viscosity. The one part currently on the board is Q2, put there with standard soldering methods (a small-tipped iron).

 

John N0TA
 

I have tried a lot of different solder pastes, and have been most happy with what I got from Chip Quik. Currently, I'm using a syringe of SMD291AX (Sn63/Pb37 No-Clean T3 Solder Paste)

On 2/16/2019 10:13 AM, Steven Weber wrote:

If the paste is too cold it doesn’t flow very well. My paste starts out at about 50 degrees due to the fact I don’t heat the room until I need to work in it. So I hold it over the electric space heater for a little bit as I warm the room up enough to work in. Then my hand keeps it warm enough as it put down the paste.

 

I also find I have to poke a wire up into the syringe once in a while to get the flux to mix back up into the lead/tin balls.

 

Try that and see if it helps.

73, Steve KD1JV

 

 

I started on my SB II last night - or tried to, only to find that the paste I ordered is too paste-like and not "liquidy" enough to be applied to the board. Instead, it pulls away with the syringe rather than adhering to the pad I try applying it to. FWIW, this is the paste I ordered:
https://www.ebay.com/itm/Kester-EP256-Lead-Solder-Paste-63-37-Syringe-Dispenser-w-additional-tips/201842021162?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

There must be something out there with a bit less viscosity. The one part currently on the board is Q2, put there with standard soldering methods (a small-tipped iron).

 


Dennis Shubitowski
 

No problems here with Kester paste. It gets thinner when warmer.

Dennis NS8H 

On Sat, Feb 16, 2019, 10:46 AM John AE5X <ae5x@... wrote:
I started on my SB II last night - or tried to, only to find that the paste I ordered is too paste-like and not "liquidy" enough to be applied to the board. Instead, it pulls away with the syringe rather than adhering to the pad I try applying it to. FWIW, this is the paste I ordered:
https://www.ebay.com/itm/Kester-EP256-Lead-Solder-Paste-63-37-Syringe-Dispenser-w-additional-tips/201842021162?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

There must be something out there with a bit less viscosity. The one part currently on the board is Q2, put there with standard soldering methods (a small-tipped iron).

John AE5X
 

OK, gonna try again after a warm Saturday night bath (for the solder paste that is!) to thin it a bit.

ohwenzelph
 

Kester R276 has a viscosity of 650 poise. I think that’s thinner than most.
aa1of

ohwenzelph
 

Kester EP256 is 1400 poise

ohwenzelph
 

The eBay deal for EP256 looks pretty good. Ideally if you could transfer some of the paste to a one cc syringe, the hydraulics would make it much easier to dispense, also the 14G needles supplied are, like 14G wire, really big, Short(& not sharp) 20g or 22g would be better for the pads on Steve’s board. Got to get the paste into the smaller syringe without a lot of air bubbles mixed in, air will act like a spring and paste will still ooz out after you have stopped pressing on the plunger.
j t aa1of

Gwen Patton
 

I got some smaller nozzle tips, but if your want to transfer between syringes, look up "Luer lock coupler" on Amazon. It's a plastic gizmo you connect two strings nose to nose and it lets you transfer it easier from one to another without air bubbles.

Gwen Patton
 

Two *syringes* nose to nose. Curse you, Auto correct!

 

I keep my solder paste in a zip lock bag, in the fridge.  It keeps much longer...
Your mileage may vary,
Jim

ohwenzelph
 

 keep my solder paste in a zip lock bag, in the fridge”
Me too, small syringe in the fridge, the really big one has been sitting in a freezer
the double lure lock adapter, female x female, is ideal but I don’t need 25 which makes the price on amazon ludicrus. I’d be tempted to take two of those 14g’s, cut them short, line em up with some wire down the center, sealit some how and then encapsulate the thing in epoxy to make one. Might work.

Stephen Wandling
 

Yes, I too stored my paste in the fridge. Never thought to warm it up.

One thought: possibly some folks think the paste is supposed to come out of the syringe as drops? I would touch the syringe tip to the pad, eject the paste, lift the syringe and then admire the 'Hershey Kiss" look.

72
Stephen
VE7NSD

On Sun, Feb 17, 2019, 6:47 AM Jim Reagan <jimreagans@... wrote:
I keep my solder paste in a zip lock bag, in the fridge.  It keeps much longer...
Your mileage may vary,
Jim

ajparent1/kb1gmx
 

I have liquid rosin.  Its pour-able but still has a bit of tack to it.  A small paint
brush puts down a film rather than a puddle.  I don't use it all that much.

Generally I use my Kester 44 rosin 63/37 and the SMT parts I find my larger (1/4")
tip Weller easier but there is a lot of technique and experience.  Been doing SMT
for a few decades.  I do hate the 0402 parts though, I wear a dust mask so I
don't accidentally blow them away breathing.

Biggest thing I see keep the iron tip clean, do not clean it before replacing it in
the stand, clean when you go to use it, and put it back dirty.  Putting it in the stand
clean allows it to sit there and oxidize, it will be harder to clean then.  I've told people
that and then videoed them doing exactly the opposite.

Allison

Joe Street
 

My two cents is use a chisel tip iron with a solder well in the tip and heed Alison's advice to clean it and freshen the well before each use, not after.  After experimentation with hand application of paste, initially thinking it was great and then being alarmed by the number of parts flipping on end (the term is "tombstoning") on me I realized that the paste process is really that, a process, which was developed in conjunction with the use of stencils and a squeegee which makes for a uniform application of the paste, and there's no point going to all that trouble for onesies and twosies.  Yes you can learn to get fairly consistent with a given batch of paste and develop a somewhat consistent dispense technique but my guess is that the inconsistency there is the cause of the tombstoning I witnessed.  Having a screen printer and an RTC belt furnace in my lab at work I am not just talking out of my hat here.  Anyways, for hobby projects I realized it is actually faster and less rework to solder SMD's with an iron.  I built an mchf with over 500 SMD's in about a week of evenings a few hours per night and it worked off the bat. Yeah it's pretty cool to place a board on a hotplate and watch the paste do its thing when all goes right, but for me at least, I'm leaving the paste for the kind of equipment it was designed for.  Your mileage may vary.

On Sun, Feb 17, 2019 at 11:36 AM ajparent1/kb1gmx <kb1gmx@...> wrote:
I have liquid rosin.  Its pour-able but still has a bit of tack to it.  A small paint
brush puts down a film rather than a puddle.  I don't use it all that much.

Generally I use my Kester 44 rosin 63/37 and the SMT parts I find my larger (1/4")
tip Weller easier but there is a lot of technique and experience.  Been doing SMT
for a few decades.  I do hate the 0402 parts though, I wear a dust mask so I
don't accidentally blow them away breathing.

Biggest thing I see keep the iron tip clean, do not clean it before replacing it in
the stand, clean when you go to use it, and put it back dirty.  Putting it in the stand
clean allows it to sit there and oxidize, it will be harder to clean then.  I've told people
that and then videoed them doing exactly the opposite.

Allison

dyerhard1972
 

Just my nickel tomb stones are caused by surface tension if one pad melts before the other it wets one side first and the surface tension of the puddle pulls the part tomb stone. I work in an electronics plant for 15 years 5 of which I repaired in process pcbs. It takes practice but the best way I found to put chip parts on is to use 2 soldering irons. Put solder on both pads place part close to where it's needed use soldering iron like chop sticks only one in each hand move part on pads with irons same time melt both pads pull away surface tension pulls part center. Sounds more complicated than it is but does take practice. 
Jeff ke4fwe 



Sent from my Samsung Galaxy smartphone.

-------- Original message --------
From: Joe Street <racingtheclouds@...>
Date: 2/17/19 12:12 PM (GMT-05:00)
To: kd1jvdesigns@groups.io
Subject: Re: [kd1jvdesigns] Not all solder pastes are created equal

My two cents is use a chisel tip iron with a solder well in the tip and heed Alison's advice to clean it and freshen the well before each use, not after.  After experimentation with hand application of paste, initially thinking it was great and then being alarmed by the number of parts flipping on end (the term is "tombstoning") on me I realized that the paste process is really that, a process, which was developed in conjunction with the use of stencils and a squeegee which makes for a uniform application of the paste, and there's no point going to all that trouble for onesies and twosies.  Yes you can learn to get fairly consistent with a given batch of paste and develop a somewhat consistent dispense technique but my guess is that the inconsistency there is the cause of the tombstoning I witnessed.  Having a screen printer and an RTC belt furnace in my lab at work I am not just talking out of my hat here.  Anyways, for hobby projects I realized it is actually faster and less rework to solder SMD's with an iron.  I built an mchf with over 500 SMD's in about a week of evenings a few hours per night and it worked off the bat. Yeah it's pretty cool to place a board on a hotplate and watch the paste do its thing when all goes right, but for me at least, I'm leaving the paste for the kind of equipment it was designed for.  Your mileage may vary.

On Sun, Feb 17, 2019 at 11:36 AM ajparent1/kb1gmx <kb1gmx@...> wrote:
I have liquid rosin.  Its pour-able but still has a bit of tack to it.  A small paint
brush puts down a film rather than a puddle.  I don't use it all that much.

Generally I use my Kester 44 rosin 63/37 and the SMT parts I find my larger (1/4")
tip Weller easier but there is a lot of technique and experience.  Been doing SMT
for a few decades.  I do hate the 0402 parts though, I wear a dust mask so I
don't accidentally blow them away breathing.

Biggest thing I see keep the iron tip clean, do not clean it before replacing it in
the stand, clean when you go to use it, and put it back dirty.  Putting it in the stand
clean allows it to sit there and oxidize, it will be harder to clean then.  I've told people
that and then videoed them doing exactly the opposite.

Allison

Joe Street
 

I agree with you there Jeff. And I think if there is inconsistency in the amount of paste on each side then there is a difference in thermal mass and one side melts just befor the other.  My technique is a little different since I only have one good iron at home.  I bring the part close by its location and leave it sitting on the solder mask.  I swipe the pads with a rosin pen and then freshen the iron and put a small bump of solder on on pad then grab the part and slide it up against the bump and then re-flow the bump as I slightly slide the part into it.  Remove the iron while holding the part steady.  Now flow the solder on the other end of the part.  Finally I reflow the first end again just incase there was any slight movement of my tweezers during the crystalization phase which would be a cold joint.  It is easiest to do all the parts aligned in one direction first and then rotate the board 90 degrees and do the others.  Of course sometimes you have to plan ahead thinking of your access to things which are closely spaced with this technique.

Joe

On Sun, Feb 17, 2019 at 12:38 PM dyerhard1972 via Groups.Io <Dyerhard1972=yahoo.com@groups.io> wrote:
Just my nickel tomb stones are caused by surface tension if one pad melts before the other it wets one side first and the surface tension of the puddle pulls the part tomb stone. I work in an electronics plant for 15 years 5 of which I repaired in process pcbs. It takes practice but the best way I found to put chip parts on is to use 2 soldering irons. Put solder on both pads place part close to where it's needed use soldering iron like chop sticks only one in each hand move part on pads with irons same time melt both pads pull away surface tension pulls part center. Sounds more complicated than it is but does take practice. 
Jeff ke4fwe 


John AE5X
 

Joe Street
 

As fate would have it I am actually writing a tutorial today on the essential steps for a reliable solder connection to give to grad students in the engineering school where I work.  It might come as a shock to people on this list to learn that graduating electrical engineers these days, a shocking number of them it turns out, couldn't solder to save their lives!  The university has decided there are many cases where students lack practical skills when they leave and knowing how to solder is one of them that has been identified as an area we could improve upon. And here, I thought they were going to say spelling.   Most of our grad students come from foreign lands so apparently this lack is pretty wide spread in engineering schools.  Yikes.

On Sun, Feb 17, 2019 at 12:51 PM Joe Street via Groups.Io <racingtheclouds=gmail.com@groups.io> wrote:
I agree with you there Jeff. And I think if there is inconsistency in the amount of paste on each side then there is a difference in thermal mass and one side melts just befor the other.  My technique is a little different since I only have one good iron at home.  I bring the part close by its location and leave it sitting on the solder mask.  I swipe the pads with a rosin pen and then freshen the iron and put a small bump of solder on on pad then grab the part and slide it up against the bump and then re-flow the bump as I slightly slide the part into it.  Remove the iron while holding the part steady.  Now flow the solder on the other end of the part.  Finally I reflow the first end again just incase there was any slight movement of my tweezers during the crystalization phase which would be a cold joint.  It is easiest to do all the parts aligned in one direction first and then rotate the board 90 degrees and do the others.  Of course sometimes you have to plan ahead thinking of your access to things which are closely spaced with this technique.

Joe

On Sun, Feb 17, 2019 at 12:38 PM dyerhard1972 via Groups.Io <Dyerhard1972=yahoo.com@groups.io> wrote:
Just my nickel tomb stones are caused by surface tension if one pad melts before the other it wets one side first and the surface tension of the puddle pulls the part tomb stone. I work in an electronics plant for 15 years 5 of which I repaired in process pcbs. It takes practice but the best way I found to put chip parts on is to use 2 soldering irons. Put solder on both pads place part close to where it's needed use soldering iron like chop sticks only one in each hand move part on pads with irons same time melt both pads pull away surface tension pulls part center. Sounds more complicated than it is but does take practice. 
Jeff ke4fwe