Homebrew_PCBs

As I continue to assemble my SMT tools, supplies and processes, I was looking at acquiring some solder paste. Unfortunately, there are several kinds of solder paste? What are the pros and cons?  Should I consider water soluble paste? Does the tin vs lead vs copper mixture have a significant impact on my selection?It looks like shelf-life is limited, should that be a factor in my selection?Any input on this matter would be greatly appreciated.Thanks.FP

I'll try to make some sense out of your choices.  Basically Solder has a solidus and liqudus point.  63/37 solder is cool because they are the same.  So, for a process using lead this is almost mandatory for SMT work and it's really easy to work with.  It tends not to form bridges like 60/40.


60/40, again a lead process; when you heat the joint, it stays liguid for a while.  Remember c=soldering wires and having to hold it steady?

The other class is the Sn96.x variety.  This significantly increased the temperature.  Tin does have the tendency to form wiskers. 


I'm a novice in SMT work, but my first removal was a 64 pin processor and I used 63/37.  I used the cut and remove method and soldered it upside down.  Meaning the chip was facing down while I was soldering with the iron effectively over my head.

My first SMT paste was the Bismuth alloys of Bi58/something and I like it.  It's low temperature.  It needs to be stored in the fridge and warmed up when you want to use it.  I havn't done any stencil stuff yet.  I would consider lifetime to be important to be if you are using it with a stencil.

Another reminder is that the paste is usuallly shipped in a cold pack and 2nd day or so, so don't make the package heavy.

You should look at www.chipquick.com.  Digikey has the chipquick Bi58 allow, but I didn;t see it on chipquick's website.


I too have a solder/de-solder/hot air station from circuitspecialists.com and an over the head LED lighted magnified visor.  I can see the advantage of a bifocal microscope with a 5" or so working distance since I used them at work.

Cleaning the flux residue has always been an issue.  Water is easier than solvents.

On Monday, August 18, 2014 6:16 PM, "qz9090@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:

As I continue to assemble my SMT tools, supplies and processes, I was looking at acquiring some solder paste. Unfortunately, there are several kinds of solder paste? What are the pros and cons?  Should I consider water soluble paste? Does the tin vs lead vs copper mixture have a significant impact on my selection?It looks like shelf-life is limited, should that be a factor in my selection?Any input on this matter would be greatly appreciated.Thanks.FP
                    

Leaded paste has a higher process window than leadfree, so I would recommend that.

Use no-clean rather than water soluble. The fluxes in water soluble can be more problematic if not removed completely (which is difficult).

Shelf life is indeed limited, more so with some pastes than other. Refrigeration is recommended.

I have found that I like Amtech paste.
<http://www.amtechsolder.com/pastes.html>

The reason is simple, it works as good as any and I can get it at Farnell (re-badged under the chipquick brand).
Unlike other pastes they carry it seems to be fresh (enough turnover) and doesn't require refrigerated shipping.
The syringes have more air bubbles than high end brands (such as Martin SMT), but the cheap price and cheap shipping make up for that.

ST

On Tue, Aug 19, 2014 at 12:16 AM, qz9090@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

As I continue to assemble my SMT tools, supplies and processes, I was looking at acquiring some solder paste. Unfortunately, there are several kinds of solder paste? What are the pros and cons?  Should I consider water soluble paste? Does the tin vs lead vs copper mixture have a significant impact on my selection?It looks like shelf-life is limited, should that be a factor in my selection?Any input on this matter would be greatly appreciated.Thanks.FP

Some interesting articles about solder paste:

http://blogs.indium.com/blog/eric-bastow/solder-paste-expirationshelf-life
http://blogs.indium.com/blog/eric-bastow/solder-paste-and-summer-heathot-stuff

Mitch.

Stefan,>Leaded paste has a higher process window than leadfree, so I would recommend that.

When you say "higher process window", do you mean that there is more time to position the SMT before the solder hardens?

>Use

no-clean rather than water soluble. The fluxes in water soluble can be more problematic if not removed >completely (which is difficult).

SMD291AX10: CHIPQUIK, INC: Test, Tools & Supplies

 

SMD291SNL10: CHIPQUIK, INC: Test, Tools & Supplies

 

http://www.dispensetips.com/xcart/LF-4300-DISPENSE-SAC305-solder-paste-35-g-SYRINGE.html?page=1


I was originally looking at the first two items above but was considering the third item based on your comments. Any thoughts?

>Shelf life is indeed limited, more so with some pastes than other. Refrigeration is recommended.

Since I would not be using the paste daily or maybe even weekly, I need it to have a reasonable shelf life (hopefully a couple of years) but I'm not sure I am going to find that.

>I have found that I like Amtech paste.

<http://www.amtechsolder.com/pastes.html>

>The reason is simple, it works as good as any and I can get it at Farnell (re-badged under the chipquick >brand).
>Unlike other pastes they carry it seems to be fresh (enough turnover) and doesn't require refrigerated >shipping.
>The syringes have more air bubbles than high end brands (such as

Martin SMT), but the cheap price and >cheap shipping make up for that.

>
>ST

Thanks for the input, always good to hear/read your comments.

FP

,I sounds like I should be looking at 63/37 paste with lead. Until I get more adept at SMT components, solder bridges are to be avoided.

I'll take a look at chipquick Bi58 at Digikey.com when I get the chance; sounds like a good option.

In looking at the specs for some of the pastes, I noticed that there is an inhalation warning. How do you avoid exposure to the fumes?  Are there other hazards to consider?

I appreciate your input on the hot air rework station and LED headlight, I am trying to decide on which items to order.

Thanks.

FP

On 19 Aug 2014 10:12:01 -0700, you wrote:

>KeepIt SimpleStupid
>,I sounds like I should be looking at 63/37 paste with lead. Until I get more adept at SMT components, solder bridges are to be avoided.

Get some solder wick to remove bridges, that seems to work better than
anything else. You can sometimes use a vacuum desoldering system, but
that is often very bulky and unable to hit just a few pins.
Mechanically cutting the solder out will stress the pads and pins way
too much. Occasionally, lots of flux and reheating the joint will
work, but you run the risk of the solder migrating up the leads to the
package itself.

Harvey

>
>I'll take a look at chipquick Bi58 at Digikey.com when I get the chance; sounds like a good option.
>
>In looking at the specs for some of the pastes, I noticed that there is an inhalation warning. How do you avoid exposure to the fumes? Are there other hazards to consider?
>
>I appreciate your input on the hot air rework station and LED headlight, I am trying to decide on which items to order.
>
>Thanks.
>
>FP

Just open the window and you will be fine.
SMD soldering doesn't release more fumes than regular soldering, just all at once during reflow.

There are again significant differences between the pastes, the Syntech from Amtech (SMD291 from Chipquick) smells much less offensive than the paste from Martin SMT.

There is of course the lead, to be taken seriously because the lead is finely ground up into a powder (actually small balls).
This makes it somewhat easier to ingest, possibly even inhale if you dry the paste and let the dust get around.

With a couple of simple rules you can eliminate the lead hazard completely.
Keep track of the paste. Anything you dispense either goes on the PCB, or on a scrap board (say to clear the dispensing nozzle).
Just reflow the scrap board too when you are done and the solder powder is bound up safe as a solid.

Don't put any paste anywhere else, not on a piece of paper, not on your bench, not on a rag, your hands, etc..
Anything that does get contaminated for whatever reason should be washed without delay or discarded properly so you don't forget.

Compared to the solder and oxide dust that accumulates under your soldering iron sponge this is nothing.
Regular good housekeeping will take care of it just fine.



As Harvey says you will get bridging and defects no matter what.
The nicer you work, the fewer the defects, but personally I rather spend a little time checking and reworking the boards than a lot of time getting it just right before the reflow.

ST

>Stefan,>Leaded paste has a higher process window than leadfree, so I
>would recommend that.
>
>When you say "higher process window", do you mean that there is more
>time to position the SMT before the solder hardens?

When he says "higher process window" he means that HE is the more
knowledgeable, "IN" person in this conversation. He understands what
he is saying and he is using the "in" words to show this superiority.
If you, the outsider who dares to ask for clarification, he is going
to make you ask more questions to show your "ignorance".

The truth of the matter is he is the ignorant one: ignorant of any
knowledge of how to properly explain technical matters in a manner
that can be easily understood.

I am also an outsider here, in spite of about 50 years in the
electronics field, and have never heard that expression before. From
the context I believe he means it has a longer period or time for
which it remains usable for the intended purpose; AKA: shelf life.

I apologize if I seem harsh here, but I firmly believe that we need
less "tech speak", not more of it.

Hi Paul,

On Thu, Aug 21, 2014 at 2:37 AM, Paul Alciatore palciatore@...
[Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

>
>>Stefan,>Leaded paste has a higher process window than leadfree, so I
>>would recommend that.
>
> I apologize if I seem harsh here, but I firmly believe that we need
> less "tech speak", not more of it.

It's likely that Stefan's first language is not English. Just saying.

Mitch.

Sorry I missed your question, still can't find it in fact, but this
troll response caught my eye at least, so that's good.

What I mean is that leaded solder is more forgiving.

Leadfree has a higher melting point, but the maximum workable
temperature is limited by components and the PCB.
So your workable range between the minimum and maximum temperature is
much wider for leaded solder.
Also you can have much longer soldering times if you stick to a lower
temperature, again opening up the process so it will still work fine
even if you deviate from ideal parameters.

There are several other aspects in which leadfree is more troublesome,
for example the flux needs to be more aggressive, so shelf live might
suffer, but this is not universally true for all pastes.

The time you mentioned for positioning the parts is called "tack
time", after that it will dry out.
Sometimes a value called "stencil life" is given instead, which is
interchangeable for our purposes even if we might not use a stencil.
Usually this is at least three hours, plenty of time to get all the
parts done, but you should not let a half done board sit for a day.

It does pay to learn the terms, despite what some people claim,
otherwise you might not even understand the datasheets, and there is
nothing more useful than manufacturer information.

ST




On Wed, Aug 20, 2014 at 6:37 PM, Paul Alciatore palciatore@...
[Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

>
>>Stefan,>Leaded paste has a higher process window than leadfree, so I
>>would recommend that.
>>
>>When you say "higher process window", do you mean that there is more
>>time to position the SMT before the solder hardens?
>
> When he says "higher process window" he means that HE is the more
> knowledgeable, "IN" person in this conversation. He understands what
> he is saying and he is using the "in" words to show this superiority.
> If you, the outsider who dares to ask for clarification, he is going
> to make you ask more questions to show your "ignorance".
>
> The truth of the matter is he is the ignorant one: ignorant of any
> knowledge of how to properly explain technical matters in a manner
> that can be easily understood.
>
> I am also an outsider here, in spite of about 50 years in the
> electronics field, and have never heard that expression before. From
> the context I believe he means it has a longer period or time for
> which it remains usable for the intended purpose; AKA: shelf life.
>
> I apologize if I seem harsh here, but I firmly believe that we need
> less "tech speak", not more of it.
>
>
>
> ------------------------------------
> Posted by: Paul Alciatore <PAlciatore@...>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
> ------------------------------------
>
> Yahoo Groups Links
>
>
>

I have to disagree. I think it is important to learn the terms. If you don't know what someone means, don't be shy about Googling for it, or just asking. That's how you learn.

The Process Window Index (PWI™) is a quantifiable, reproducible, statistical measure of how well a profile performs relative to critical process limits. Every thermal profile is ranked on the basis of how it “fits” within the process window. The center of the process window is defined as zero, and the extreme edge of the process window as 99%. A PWI of 100% or more indicates that the profile will not process product within specification. A PWI of 99% indicates that the profile will process product within spec, but it is running at the very edge of the process window. A PWI of 70% indicates a profile is using 70% of the process spec.

And that definition really clarifies things. I rest my case. Thanks!

"Higher Process Window” is absolutely meaningless. The proper term should have been “wider process window” as the "process window” term is used in statical process control.
And this is again not very relevant to hand soldering, where operator skill plays a huge role.

Jean-Paul
AC9GH
over 40 years of Electronic Manufacturing Engineering experience

On Aug 22, 2014, at 3:19 PM, palciatore@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

> And that definition really clarifies things. I rest my case. Thanks!
>
>
>
> ---In Homebrew_PCBs@yahoogroups.com, <alienrelics@...> wrote :
>
> I have to disagree. I think it is important to learn the terms. If you don't know what someone means, don't be shy about Googling for it, or just asking. That's how you learn.
> Process Window Index | Kicthermal.com
>
> Process Window Index | Kicthermal.com
> PWI datasheet – click here PWI datasheet – A4 size – click here A Method for Quantifying Thermal Profile Performance The Process
> View on kicthermal.com
> Preview by Yahoo
>
>
> "The Process Window Index
> The Process Window Index (PWI™) is a quantifiable, reproducible, statistical measure of how well a profile performs relative to critical process limits. Every thermal profile is ranked on the basis of how it “fits” within the process window. The center of the process window is defined as zero, and the extreme edge of the process window as 99%. A PWI of 100% or more indicates that the profile will not process product within specification. A PWI of 99% indicates that the profile will process product within spec, but it is running at the very edge of the process window. A PWI of 70% indicates a profile is using 70% of the process spec.
>
> The PWI tells you exactly how much of your process window a given profile uses, and thus how robust that profile is. The lower the PWI, the better the profile. The thermal process can now be reliably measured, analyzed, compared and tracked with the same level of SPC and Quality Control available to other manufacturing processes."
>
> http://www.isixsigma.com/dictionary/process-window-index-pwi/
>
>
> "Process Window Index (PWI)
> A statistical measure that quantifies the robustness of a thermal process. PWI measures how well a process fits into a user-defined process limit known as the specification limit. PWI is used in the electronics manufacturing industry, particularly the soldering industry, where the scale and rankings were developed for various thermal processes."
>
> If I say eutectic solder, I may parenthetically define it. Or I may not. Either way, it is not an attempt to make anyone else feel like an outsider.
>
> Steve Greenfield AE7HD
>
>
> ---In Homebrew_PCBs@yahoogroups.com, <palciatore@...> wrote :
>
> >Stefan,>Leaded paste has a higher process window than leadfree, so I
> >would recommend that.
> >
> >When you say "higher process window", do you mean that there is more
> >time to position the SMT before the solder hardens?
>
> When he says "higher process window" he means that HE is the more
> knowledgeable, "IN" person in this conversation. He understands what
> he is saying and he is using the "in" words to show this superiority.
> If you, the outsider who dares to ask for clarification, he is going
> to make you ask more questions to show your "ignorance".
>
>
>
>
>

So a wider process window of leaded paste (if you prefer, although it
is a two-dimensional thing, and I thought about the vertical,
conventionally temperature, axis) will not make hand soldering easier?

Besides, I would not call the reflow process hand soldering, even if
done in a manually controlled fashion with a hotplate or pizza oven.

But instead of discussing semantics, how about you two Pauls share
your combined century of experience to actually _help_ people?

ST

On Fri, Aug 22, 2014 at 10:26 PM, Jean-Paul Louis louijp@...
[Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

> "Higher Process Window” is absolutely meaningless. The proper term should have been “wider process window” as the "process window” term is used in statical process control.
> And this is again not very relevant to hand soldering, where operator skill plays a huge role.
>
> Jean-Paul
> AC9GH
> over 40 years of Electronic Manufacturing Engineering experience
>
> On Aug 22, 2014, at 3:19 PM, palciatore@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
>
>> And that definition really clarifies things. I rest my case. Thanks!
>>
>>
>>
>> ---In Homebrew_PCBs@yahoogroups.com, <alienrelics@...> wrote :
>>
>> I have to disagree. I think it is important to learn the terms. If you don't know what someone means, don't be shy about Googling for it, or just asking. That's how you learn.
>> Process Window Index | Kicthermal.com
>>
>> Process Window Index | Kicthermal.com
>> PWI datasheet – click here PWI datasheet – A4 size – click here A Method for Quantifying Thermal Profile Performance The Process
>> View on kicthermal.com
>> Preview by Yahoo
>>
>>
>> "The Process Window Index
>> The Process Window Index (PWI™) is a quantifiable, reproducible, statistical measure of how well a profile performs relative to critical process limits. Every thermal profile is ranked on the basis of how it “fits” within the process window. The center of the process window is defined as zero, and the extreme edge of the process window as 99%. A PWI of 100% or more indicates that the profile will not process product within specification. A PWI of 99% indicates that the profile will process product within spec, but it is running at the very edge of the process window. A PWI of 70% indicates a profile is using 70% of the process spec.
>>
>> The PWI tells you exactly how much of your process window a given profile uses, and thus how robust that profile is. The lower the PWI, the better the profile. The thermal process can now be reliably measured, analyzed, compared and tracked with the same level of SPC and Quality Control available to other manufacturing processes."
>>
>> http://www.isixsigma.com/dictionary/process-window-index-pwi/
>>
>>
>> "Process Window Index (PWI)
>> A statistical measure that quantifies the robustness of a thermal process. PWI measures how well a process fits into a user-defined process limit known as the specification limit. PWI is used in the electronics manufacturing industry, particularly the soldering industry, where the scale and rankings were developed for various thermal processes."
>>
>> If I say eutectic solder, I may parenthetically define it. Or I may not. Either way, it is not an attempt to make anyone else feel like an outsider.
>>
>> Steve Greenfield AE7HD
>>
>>
>> ---In Homebrew_PCBs@yahoogroups.com, <palciatore@...> wrote :
>>
>> >Stefan,>Leaded paste has a higher process window than leadfree, so I
>> >would recommend that.
>> >
>> >When you say "higher process window", do you mean that there is more
>> >time to position the SMT before the solder hardens?
>>
>> When he says "higher process window" he means that HE is the more
>> knowledgeable, "IN" person in this conversation. He understands what
>> he is saying and he is using the "in" words to show this superiority.
>> If you, the outsider who dares to ask for clarification, he is going
>> to make you ask more questions to show your "ignorance".
>>
>>
>>
>>
>>
>
>
>
> ------------------------------------
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
> ------------------------------------
>
> Yahoo Groups Links
>
>
>

The solder paste or the wire have usually the same metal composition. The difference is the flux used.

For leaded solder, the eutectic is really 63/37 as tin/lead ratio, but some manufacturer will sell you 60/40. The 63/37 is really the mix that provide the real eutectic point ( see http://en.wikipedia.org/wiki/Eutectic_system ) that has the lowest melting point (183 Celsius).
When you have a lot of SMD, the most efficient process is solder paste and reflow, while hand soldering is still a valid option.
The problem with the use of solder paste is that the flux contained in the paste has to be activated before the real reflow step. If you look at a reflow profile, you see that you need a first plateau around 130 Celsius to activate the flux, then you raise the temperature to the reflow (above 183 Celsius, usually 220 Celsius for 60 to 90 seconds), then fairly fast cooling but less than 2 degree/second.
That is why trying to implement a reflow with a hot plate or a pizza oven is not a simple thing.
With leaded solder, it is still easier than lead-free solder, as lead-free require a much higher melting point, and many component do not like the higher temperature. That’s why the control is much more critical, and that’s why we say that the lead-free process window is much narrower than the leaded process.

I hope I do not sound too pompous in my explanations.
Feel free to ask specific questions, and I will try to be helpful, as I do not like to criticize unless I can offer a good advice.

Jean-Paul
AC9GH

On Aug 22, 2014, at 11:22 PM, Stefan Trethan stefan_trethan@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

> So a wider process window of leaded paste (if you prefer, although it
> is a two-dimensional thing, and I thought about the vertical,
> conventionally temperature, axis) will not make hand soldering easier?
>
> Besides, I would not call the reflow process hand soldering, even if
> done in a manually controlled fashion with a hotplate or pizza oven.
>
> But instead of discussing semantics, how about you two Pauls share
> your combined century of experience to actually _help_ people?
>
> ST
>
> On Fri, Aug 22, 2014 at 10:26 PM, Jean-Paul Louislouijp@...
> [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
> > "Higher Process Window” is absolutely meaningless. The proper term should have been “wider process window” as the "process window” term is used in statical process control.
> > And this is again not very relevant to hand soldering, where operator skill plays a huge role.
> >
> > Jean-Paul
> > AC9GH
> > over 40 years of Electronic Manufacturing Engineering experience
> >
> > On Aug 22, 2014, at 3:19 PM, palciatore@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
> >
> >> And that definition really clarifies things. I rest my case. Thanks!
> >>
> >>
> >>
> >> ---In Homebrew_PCBs@yahoogroups.com, <alienrelics@...> wrote :
> >>
> >> I have to disagree. I think it is important to learn the terms. If you don't know what someone means, don't be shy about Googling for it, or just asking. That's how you learn.
> >> Process Window Index | Kicthermal.com
> >>
> >> Process Window Index | Kicthermal.com
> >> PWI datasheet – click here PWI datasheet – A4 size – click here A Method for Quantifying Thermal Profile Performance The Process
> >> View on kicthermal.com
> >> Preview by Yahoo
> >>
> >>
> >> "The Process Window Index
> >> The Process Window Index (PWI™) is a quantifiable, reproducible, statistical measure of how well a profile performs relative to critical process limits. Every thermal profile is ranked on the basis of how it “fits” within the process window. The center of the process window is defined as zero, and the extreme edge of the process window as 99%. A PWI of 100% or more indicates that the profile will not process product within specification. A PWI of 99% indicates that the profile will process product within spec, but it is running at the very edge of the process window. A PWI of 70% indicates a profile is using 70% of the process spec.
> >>
> >> The PWI tells you exactly how much of your process window a given profile uses, and thus how robust that profile is. The lower the PWI, the better the profile. The thermal process can now be reliably measured, analyzed, compared and tracked with the same level of SPC and Quality Control available to other manufacturing processes."
> >>
> >> http://www.isixsigma.com/dictionary/process-window-index-pwi/
> >>
> >>
> >> "Process Window Index (PWI)
> >> A statistical measure that quantifies the robustness of a thermal process. PWI measures how well a process fits into a user-defined process limit known as the specification limit. PWI is used in the electronics manufacturing industry, particularly the soldering industry, where the scale and rankings were developed for various thermal processes."
> >>
> >> If I say eutectic solder, I may parenthetically define it. Or I may not. Either way, it is not an attempt to make anyone else feel like an outsider.
> >>
> >> Steve Greenfield AE7HD
> >>
> >>
> >> ---In Homebrew_PCBs@yahoogroups.com, <palciatore@...> wrote :
> >>
> >> >Stefan,>Leaded paste has a higher process window than leadfree, so I
> >> >would recommend that.
> >> >
> >> >When you say "higher process window", do you mean that there is more
> >> >time to position the SMT before the solder hardens?
> >>
> >> When he says "higher process window" he means that HE is the more
> >> knowledgeable, "IN" person in this conversation. He understands what
> >> he is saying and he is using the "in" words to show this superiority.
> >> If you, the outsider who dares to ask for clarification, he is going
> >> to make you ask more questions to show your "ignorance".
> >>
> >>
> >>
> >>
> >>
> >
> >
> >
> > ------------------------------------
> >
> > ------------------------------------
> >
> > Be sure to visit the group home and check for new Links, Files, and Photos:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> > ------------------------------------
> >
> > Yahoo Groups Links
> >
> >
> >
>
>