DIY smd reflow

[mkr5000]

I need to quit watching damn youtube videos and listening to 100 different answers. All I want to do, once in a while, is solder some SMD parts.

I'm ordering a hot air gun but --

also playing around with a toaster oven today and need to know --

do you preheat the oven? (I mean, after all you don't preheat when you solder using an air gun)

is it that big a deal to go through all this shit of going through different stages or can I --

(1)just preheat, put the board in.

or
(2)just put the board in (cold), set the temp and let it come up to temp, which takes only a few minutes.

no in depth science please, can I just do 1 or 2 and which is better?

 

mkr5000 <mikerbgr@gmail.com> wrote in
news:9693256d-faa7-4acd-9352-0845d068deb7@googlegroups.com:

I need to quit watching damn youtube videos and listening to 100
different answers. All I want to do, once in a while, is solder
some SMD parts.

I'm ordering a hot air gun but --

also playing around with a toaster oven today and need to know --

do you preheat the oven? (I mean, after all you don't preheat when
you solder using an air gun)

is it that big a deal to go through all this shit of going through
different stages or can I --

(1)just preheat, put the board in.

or
(2)just put the board in (cold), set the temp and let it come up
to temp, which takes only a few minutes.

no in depth science please, can I just do 1 or 2 and which is
better?

The idea here is that you do not want the temp difference to be so
high that the thermal shock introduced causes a mechanical break
inside a chip or the end of a cap. So you bring the entire board
temp up to near reflow temp, and then you can perform single chip
adds or removals with the heat gun. That makes the transistion
between reflowing solder and the board itself so small that there is
not as much mechanical stress placed on things. if you are doing a
new board and are trying to reflow the whole board, you would use the
oven, but must be a very good process monitor to catch when it gets
to reflow temps. If you are doing a single repair or part add, the
heat gun works, but you still want the whole board brought up so that
you do not do the thermo-mechanical shock thing.

 

[Don Kuenz]

DecadentLinuxUserNumeroUno@decadence.org wrote:

<snip>

The idea here is that you do not want the temp difference to be so
high that the thermal shock introduced causes a mechanical break
inside a chip or the end of a cap. So you bring the entire board
temp up to near reflow temp, and then you can perform single chip
adds or removals with the heat gun. That makes the transistion
between reflowing solder and the board itself so small that there is
not as much mechanical stress placed on things. if you are doing a
new board and are trying to reflow the whole board, you would use the
oven, but must be a very good process monitor to catch when it gets
to reflow temps. If you are doing a single repair or part add, the
heat gun works, but you still want the whole board brought up so that
you do not do the thermo-mechanical shock thing.

That's good to know. How does a thermal profile impact IR preheat? It
seems to me that excessive exposure to preheat may damage components.
Yet my limited, undisciplined use of preheat with an air gun to remove
components has yet to damage a component.
Practical experience indicates that hot air and preheat melts solder
at a lower temperature than an soldering iron. Any insight into why
that's true is appreciated.

Thank you,

--
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

 

[Dave Platt]

In article <9693256d-faa7-4acd-9352-0845d068deb7@googlegroups.com>,
mkr5000 <mikerbgr@gmail.com> wrote:

do you preheat the oven? (I mean, after all you don't preheat when you solder using an air gun)

is it that big a deal to go through all this shit of going through different stages or can I --

(1)just preheat, put the board in.

or
(2)just put the board in (cold), set the temp and let it come up to temp, which takes only a few minutes.

The approach recommended by the solder folks (and a lot of the
component folks) involves a ramp up to a preheat temperature, a soak
at that temperature for a while, another ramp up to above the solder's
liquidus temperature, a short wait, then a fairly rapid cool-down.

The ramp-and-soak preheating process helps get the solder "ready to
melt" properly, in that it allows the solder to gradually evaporate
(and out-gas) whatever paste-solvent is still present. It also allows
the components to warm up properly... slowly enough to avoid physical
stress from too-rapid expansion, and thoroughly enough that all of the
pads and pins are warm.

Then, as the temperature rises further, the flux becomes active
(typically melting, I believe, and actively reducing oxides and
lifting off other contaminants). A bit higher temperature and the
solder alloy itself melts, and its surface tension helps pull the
parts into proper orientation on the pads. Once that's happened (and
it doesn't take long) you cool down the board.

Too-rapid heating can have several bad effects. It can damage parts
by thermal stress (some parts expand faster than others). It can
result in the flux and solder boiling (residual alcohol coming out
rapidly rather than evaporating slowly and gently) and this can push
parts around or even off of their pads. The flux may not have enough
time to "clean" the pads and pins. You may get "cold" solder joints
if some parts of the chip (e.g. the under-chip thermal pads) haven't
warmed up enough to melt and bond solder before you start cooling down
the board again.

So, there are benefits to warming up the oven at something resembling the
recommended rate, with a soak/preheat period partway up. You can do this
with a commercial temperature controller, or do it manually by watching
a stopwatch and thermometer, and turning the switch/thermostat manually.

A quickie version would be to preheat the oven to a temperature a bit above
the "soak" temperature, pop in the board, wait a couple of minutes, then
turn the temperature up to the recommended liquidus temperature and keep
your eye on the board. Once you see the solder melt all the way across
the board, turn the heat off and open the oven door.

 

[John Larkin]

On Fri, 31 Jan 2020 08:19:08 -0800 (PST), mkr5000 <mikerbgr@gmail.com>
wrote:

I need to quit watching damn youtube videos and listening to 100 different answers. All I want to do, once in a while, is solder some SMD parts.

I'm ordering a hot air gun but --

also playing around with a toaster oven today and need to know --

do you preheat the oven? (I mean, after all you don't preheat when you solder using an air gun)

is it that big a deal to go through all this shit of going through different stages or can I --

(1)just preheat, put the board in.

or
(2)just put the board in (cold), set the temp and let it come up to temp, which takes only a few minutes.

no in depth science please, can I just do 1 or 2 and which is better?

Some ovens (I speak from bad experience) have a heater element in the
top that blasts parts with IR and destroys them. A toaster oven could
well do that. Mine sure scorches muffins.

In theory SMD parts need a carefully controlled temperature-vs-time
profile, but you can probably get away with 2 or three steps up and
down. Preheat, put the board in, soak a few minutes, raise temp to
melt the solder, turn heat off.

You can't just hand solder?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Lasse Langwadt Christense]

fredag den 31. januar 2020 kl. 21.31.34 UTC+1 skrev John Larkin:

On Fri, 31 Jan 2020 08:19:08 -0800 (PST), mkr5000 <mikerbgr@gmail.com
wrote:

I need to quit watching damn youtube videos and listening to 100 different answers. All I want to do, once in a while, is solder some SMD parts.

I'm ordering a hot air gun but --

also playing around with a toaster oven today and need to know --

do you preheat the oven? (I mean, after all you don't preheat when you solder using an air gun)

is it that big a deal to go through all this shit of going through different stages or can I --

(1)just preheat, put the board in.

or
(2)just put the board in (cold), set the temp and let it come up to temp, which takes only a few minutes.

no in depth science please, can I just do 1 or 2 and which is better?

Some ovens (I speak from bad experience) have a heater element in the
top that blasts parts with IR and destroys them. A toaster oven could
well do that. Mine sure scorches muffins.

In theory SMD parts need a carefully controlled temperature-vs-time
profile, but you can probably get away with 2 or three steps up and
down. Preheat, put the board in, soak a few minutes, raise temp to
melt the solder, turn heat off.

or for few dollars you buy a controller that does the temperature profile

or a real reflow oven, I think you can get one for ~$150

You can't just hand solder?

with lots of part is is a hassle

 

[John Larkin]

On Fri, 31 Jan 2020 14:27:54 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

fredag den 31. januar 2020 kl. 21.31.34 UTC+1 skrev John Larkin:
On Fri, 31 Jan 2020 08:19:08 -0800 (PST), mkr5000 <mikerbgr@gmail.com
wrote:

I need to quit watching damn youtube videos and listening to 100 different answers. All I want to do, once in a while, is solder some SMD parts.

I'm ordering a hot air gun but --

also playing around with a toaster oven today and need to know --

do you preheat the oven? (I mean, after all you don't preheat when you solder using an air gun)

is it that big a deal to go through all this shit of going through different stages or can I --

(1)just preheat, put the board in.

or
(2)just put the board in (cold), set the temp and let it come up to temp, which takes only a few minutes.

no in depth science please, can I just do 1 or 2 and which is better?

Some ovens (I speak from bad experience) have a heater element in the
top that blasts parts with IR and destroys them. A toaster oven could
well do that. Mine sure scorches muffins.

In theory SMD parts need a carefully controlled temperature-vs-time
profile, but you can probably get away with 2 or three steps up and
down. Preheat, put the board in, soak a few minutes, raise temp to
melt the solder, turn heat off.

or for few dollars you buy a controller that does the temperature profile

or a real reflow oven, I think you can get one for ~$150


You can't just hand solder?


with lots of part is is a hassle

Sure, but stencils and solder paste and toaster ovens are a hassle
too.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Neon John]

On Fri, 31 Jan 2020 19:45:58 -0500, "Tom Del Rosso"
<fizzbintuesday@that-google-mail-domain.com> wrote:

John Larkin wrote:

Some ovens (I speak from bad experience) have a heater element in the
top that blasts parts with IR and destroys them. A toaster oven could
well do that. Mine sure scorches muffins.

Foil lining the top of the oven should fix that.

Then you burn out the top element by focusing the heat back on the
element. The simple thing to do is to disconnect one lead from the
top element. That guarantees the top element will never be energized.

John

John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

 

[Tom Del Rosso]

John Larkin wrote:

Some ovens (I speak from bad experience) have a heater element in the
top that blasts parts with IR and destroys them. A toaster oven could
well do that. Mine sure scorches muffins.

Foil lining the top of the oven should fix that.

 

[Peabody]

mkr5000 says...

I need to quit watching damn youtube videos and
listening to 100 different answers. All I want to do,
once in a while, is solder some SMD parts.

This one may be useful:

https://www.youtube.com/watch?v=hqwbDlXcs_I

It's a hot plate instead of a toaster oven. But you still
have to deal with paste and stencils.

 

"Don Kuenz" <g@crcomp.net> wrote in news:20200131b@crcomp.net:

Practical experience indicates that hot air and preheat melts
solder
at a lower temperature than an soldering iron. Any insight into
why that's true is appreciated.

It isn't a lower temp. It is about thermal mass.

A solder iron can only sink so much heat into a single joint and on
a cold board that offset means the tip either has to be a meaty one
or the tip heater has to be feeding heat to it all the time you are
sinking it away. So the thermal mass of a solder tip matters too.
Fine pitch tip puts down a part real well, but reflowing to remove it
usually calls for a bigger tip to make up for the heat the board
soaks in while you are on the joint.

On a preheated board the temp offset is only a few tens of degrees
so reflow occurs right where/when it is supposed to... the melt temp
for that solder.

A (spot) heat gun takes a spot region up to temp very fast and
damage ocuurs on surfaces of nearby succeptible parts like capacitor
shrink sleeves, which all (thru hole) EL caps have if the flow rate
is too high. Connector headers soften and deform even if you don't
spot it. Using a heat gun I use a very slow flow rate and very small
spot for anything smaller than 1cm sq. The heat soaks into the part
very well, so speedy air is not needed, just hot. But the preheat is
needed as well to make the job happen faster. You only apply the
heat for as long as you need to to pull the chip/part etc.

 

dplatt@coop.radagast.org (Dave Platt) wrote in
news:s1aegg-es7.ln1@coop.radagast.org:

In article
9693256d-faa7-4acd-9352-0845d068deb7@googlegroups.com>, mkr5000
mikerbgr@gmail.com> wrote:

do you preheat the oven? (I mean, after all you don't preheat when
you solder using an air gun)

is it that big a deal to go through all this shit of going through
different stages or can I --

(1)just preheat, put the board in.

or
(2)just put the board in (cold), set the temp and let it come up
to temp, which takes only a few minutes.

The approach recommended by the solder folks (and a lot of the
component folks) involves a ramp up to a preheat temperature, a
soak at that temperature for a while, another ramp up to above the
solder's liquidus temperature, a short wait, then a fairly rapid
cool-down.

The ramp-and-soak preheating process helps get the solder "ready
to melt" properly, in that it allows the solder to gradually
evaporate (and out-gas) whatever paste-solvent is still present.
It also allows the components to warm up properly... slowly enough
to avoid physical stress from too-rapid expansion, and thoroughly
enough that all of the pads and pins are warm.

Then, as the temperature rises further, the flux becomes active
(typically melting, I believe, and actively reducing oxides and
lifting off other contaminants). A bit higher temperature and the
solder alloy itself melts, and its surface tension helps pull the
parts into proper orientation on the pads. Once that's happened
(and it doesn't take long) you cool down the board.

Too-rapid heating can have several bad effects. It can damage
parts by thermal stress (some parts expand faster than others).
It can result in the flux and solder boiling (residual alcohol
coming out rapidly rather than evaporating slowly and gently) and
this can push parts around or even off of their pads. The flux
may not have enough time to "clean" the pads and pins. You may
get "cold" solder joints if some parts of the chip (e.g. the
under-chip thermal pads) haven't warmed up enough to melt and bond
solder before you start cooling down the board again.

So, there are benefits to warming up the oven at something
resembling the recommended rate, with a soak/preheat period
partway up. You can do this with a commercial temperature
controller, or do it manually by watching a stopwatch and
thermometer, and turning the switch/thermostat manually.

A quickie version would be to preheat the oven to a temperature a
bit above the "soak" temperature, pop in the board, wait a couple
of minutes, then turn the temperature up to the recommended
liquidus temperature and keep your eye on the board. Once you see
the solder melt all the way across the board, turn the heat off
and open the oven door.

+1

Top info. Very good, accurate and very well stated.

 

[Tom Gardner]

On 01/02/20 05:37, Peabody wrote:

mkr5000 says...

I need to quit watching damn youtube videos and
listening to 100 different answers. All I want to do,
once in a while, is solder some SMD parts.

This one may be useful:

https://www.youtube.com/watch?v=hqwbDlXcs_I

It's a hot plate instead of a toaster oven. But you still
have to deal with paste and stencils.

I've been known to use:
- saucepan with glass lid which keeps the heat in
- gas hob so heat input and temperature is rapidly variable
- thin layer of sand to act as a thermal buffer
- non-contact IR temperature "gun"
- wire through mounting holes to lift board out to cool down
- watch progress through lid

No burning, have to brush sand off, no components
on bottom side.

That's surprisingly successful, but I'd be somewhat reluctant
to recommend it for professional use

 

Neon John <no@never.com> wrote in
news:u1k93fd705donpkldtturechj5ra27gbmd@4ax.com:

On Fri, 31 Jan 2020 19:45:58 -0500, "Tom Del Rosso"
fizzbintuesday@that-google-mail-domain.com> wrote:

John Larkin wrote:

Some ovens (I speak from bad experience) have a heater element
in the top that blasts parts with IR and destroys them. A
toaster oven could well do that. Mine sure scorches muffins.

Foil lining the top of the oven should fix that.

Then you burn out the top element by focusing the heat back on the
element.

You don't put it up next to the element. You put it down in the
cavity, but above the work product. It homogenizes the temp of the
cavity area below it at that point.

"burn out"? What kind of cheap chinese toaster oven brands are you
cheaping out on?

The simple thing to do is to disconnect one lead from
the top element. That guarantees the top element will never be
energized.

Using only the lower element works, IF you also place a foil shield
OVER it. MUST be between it and the reflow target surface.

The goal is to stop directly radiated IR and homogenization of the
cavity temp. Makes for a better, slower ramp up too.

 

[Phil Hobbs]

On 2020-01-31 15:31, John Larkin wrote:

On Fri, 31 Jan 2020 08:19:08 -0800 (PST), mkr5000 <mikerbgr@gmail.com
wrote:

I need to quit watching damn youtube videos and listening to 100 different answers. All I want to do, once in a while, is solder some SMD parts.

I'm ordering a hot air gun but --

also playing around with a toaster oven today and need to know --

do you preheat the oven? (I mean, after all you don't preheat when you solder using an air gun)

is it that big a deal to go through all this shit of going through different stages or can I --

(1)just preheat, put the board in.

or
(2)just put the board in (cold), set the temp and let it come up to temp, which takes only a few minutes.

no in depth science please, can I just do 1 or 2 and which is better?

Some ovens (I speak from bad experience) have a heater element in the
top that blasts parts with IR and destroys them. A toaster oven could
well do that. Mine sure scorches muffins.

In theory SMD parts need a carefully controlled temperature-vs-time
profile, but you can probably get away with 2 or three steps up and
down. Preheat, put the board in, soak a few minutes, raise temp to
melt the solder, turn heat off.

You can't just hand solder?

The hotplate method is the bomb for things with, say, 100 parts. Ours
is an old Corning ceramic-top hot plate, with a 10-inch square piece of
half-inch aluminum jig plate on top. (We ordered the plate from
McMaster-Carr for a few bucks.) We also got a nice Extech SD200
triple-thermocouple data logger to get the reflow temperature right.

You get a stainless or Kapton stencil for cheap (PCBway sends them
epoxied to these Godzilla aluminum weldments, for amazing cheap), plunk
it over the board, shim the edges so the stencil lies flat on the board,
squeegee on some paste, remove the stencil, place the parts, and them
reflow them on the hot plate.

It takes a couple of tries to get the temperature right, but for protos
we've had good luck with the hotplate method.

Nowadays we usually pay to have PCBway or Screaming Circuits or
Pentalogix do the assembly of first articles. It isn't that cheap, but
overall it makes economic sense unless you have lots of technicians
and/or assembly folks on board.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Don Kuenz]

DecadentLinuxUserNumeroUno@decadence.org wrote:

"Don Kuenz" <g@crcomp.net> wrote in news:20200131b@crcomp.net:

Practical experience indicates that hot air and preheat melts
solder
at a lower temperature than an soldering iron. Any insight into
why that's true is appreciated.

It isn't a lower temp. It is about thermal mass.

A solder iron can only sink so much heat into a single joint and on
a cold board that offset means the tip either has to be a meaty one
or the tip heater has to be feeding heat to it all the time you are
sinking it away. So the thermal mass of a solder tip matters too.
Fine pitch tip puts down a part real well, but reflowing to remove it
usually calls for a bigger tip to make up for the heat the board
soaks in while you are on the joint.

On a preheated board the temp offset is only a few tens of degrees
so reflow occurs right where/when it is supposed to... the melt temp
for that solder.

A (spot) heat gun takes a spot region up to temp very fast and
damage ocuurs on surfaces of nearby succeptible parts like capacitor
shrink sleeves, which all (thru hole) EL caps have if the flow rate
is too high. Connector headers soften and deform even if you don't
spot it. Using a heat gun I use a very slow flow rate and very small
spot for anything smaller than 1cm sq. The heat soaks into the part
very well, so speedy air is not needed, just hot. But the preheat is
needed as well to make the job happen faster. You only apply the
heat for as long as you need to to pull the chip/part etc.

Empirical temperature data collected by me.

Hot air apparatus:
T-8280 Preheater
Aoyue 906 Rework station
Chemical stand that vertically secures hot air nozzle
BK 630 Thermometer
Measured temperature to remove component: 220 - 230 C

Hot iron apparatus:
HOKKA 472D
Temperature setting to remove componet: 330 - 340 C

This reflow profile confirms my hot air data:
https://hobbybotics.files.wordpress.com/2012/05/kester2.png


Thank you,

--
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

 

[Robert Baer]

Don Kuenz wrote:

DecadentLinuxUserNumeroUno@decadence.org wrote:
"Don Kuenz" <g@crcomp.net> wrote in news:20200131b@crcomp.net:

Practical experience indicates that hot air and preheat melts
solder
at a lower temperature than an soldering iron. Any insight into
why that's true is appreciated.

It isn't a lower temp. It is about thermal mass.

A solder iron can only sink so much heat into a single joint and on
a cold board that offset means the tip either has to be a meaty one
or the tip heater has to be feeding heat to it all the time you are
sinking it away. So the thermal mass of a solder tip matters too.
Fine pitch tip puts down a part real well, but reflowing to remove it
usually calls for a bigger tip to make up for the heat the board
soaks in while you are on the joint.

On a preheated board the temp offset is only a few tens of degrees
so reflow occurs right where/when it is supposed to... the melt temp
for that solder.

A (spot) heat gun takes a spot region up to temp very fast and
damage ocuurs on surfaces of nearby succeptible parts like capacitor
shrink sleeves, which all (thru hole) EL caps have if the flow rate
is too high. Connector headers soften and deform even if you don't
spot it. Using a heat gun I use a very slow flow rate and very small
spot for anything smaller than 1cm sq. The heat soaks into the part
very well, so speedy air is not needed, just hot. But the preheat is
needed as well to make the job happen faster. You only apply the
heat for as long as you need to to pull the chip/part etc.

Empirical temperature data collected by me.

Hot air apparatus:
T-8280 Preheater
Aoyue 906 Rework station
Chemical stand that vertically secures hot air nozzle
BK 630 Thermometer
Measured temperature to remove component: 220 - 230 C

Hot iron apparatus:
HOKKA 472D
Temperature setting to remove componet: 330 - 340 C

This reflow profile confirms my hot air data:
https://hobbybotics.files.wordpress.com/2012/05/kester2.png


Thank you,

Thanks.

 

[Jon Elson]

On Fri, 31 Jan 2020 08:19:08 -0800, mkr5000 wrote:

All I want to do, once in a while, is solder some SMD

parts.

I'm ordering a hot air gun but --

also playing around with a toaster oven today and need to know --

do you preheat the oven? (I mean, after all you don't preheat when you
solder using an air gun)

Here's my system - I have done over 2000 boards this way.
I got a thermocouple ramp and soak temperature controller off eBay.
The ramp and soak option allows you to set temperature points and times
to go from one to the next. So, I do 3 minutes from ambient to 180 C,
2 minutes from 180 to 235 C, hold at 235 for 1 minute, 2 minute ramp to
ambient. I poke the thermocouple wire into a plated through hole in the
board, as the air temp never rises ANYWHERE NEAR the board temp. Having
the sensor measure the actual temp of the board gets you out of all the
calibration and differences between different boards.

The oven is a large GE toaster oven with a solid state relay cut in
series with the thermostat.

So, I don't preheat, the board goes in before heating starts, and I don't
disturb the board until it cools to about 100 - 120 C. I usually open
the door when in the cooldown cycle.

Jon