What is the correct temperature for the iron tip?

Thread Starter

rambomhtri

Joined Nov 9, 2015
481
Hi, for the past almost 10 years I've been soldering with a soldering station that had a knob to regulate the temperature, your average cheap $30 one. With practice and experience I learned the "sweet spot" of the knob to work comfy and nicely, which was about 300-350ºC according to the sticker, which might be lower or way lower at the tip.

Recently I purchased an awesome station that uses tips that tell you the temperature of the tip, so now I know "exactly" the temperature I'm working with. My solder alloy is:

1650454501713.png

Which according to Wikipedia it melts at 183ºC (solidus) or 190ºC (liquidus). Now that's new, I always thought the melting point is the temperature at which the substance or alloy starts to change state from solid to liquid, of course at standard pressure. So having 2 melting points, I don't know what that means.
May be it's the range?
Like at 182ºC or below we are "99.99%" certain it's solid and above 190ºC is liquid? And between those we have a mix of liquid/solid?

Anyways, the question is... should I look at the specific melting point of the solder I'm working with and put the soldering station at that temperature? Or may be a little higher to make the process quick?

I see most solder alloys melt between 180ºC and 250ºC, so if you are working with these alloys, when is the 350ºC temperature recommended? When desoldering? It's better to have the tip at 350ºC because that means you reach way faster the melting point and put less stress in the components?

Thank you!
 

ericgibbs

Joined Jan 29, 2010
15,542
hi ram,
I prefer a 350C tip temperature, it is not a matter of just melting the solder, but heating the complete 'joint' point, on the component.
Some 'larger' solder joints require lots of quick heat transfer.
E
 

Ya’akov

Joined Jan 27, 2019
5,676
Hi, for the past almost 10 years I've been soldering with a soldering station that had a knob to regulate the temperature, your average cheap $30 one. With practice and experience I learned the "sweet spot" of the knob to work comfy and nicely, which was about 300-350ºC according to the sticker, which might be lower or way lower at the tip.

Recently I purchased an awesome station that uses tips that tell you the temperature of the tip, so now I know "exactly" the temperature I'm working with. My solder alloy is:

View attachment 265491

Which according to Wikipedia it melts at 183ºC (solidus) or 190ºC (liquidus). Now that's new, I always thought the melting point is the temperature at which the substance or alloy starts to change state from solid to liquid, of course at standard pressure. So having 2 melting points, I don't know what that means.
May be it's the range?
Like at 182ºC or below we are "99.99%" certain it's solid and above 190ºC is liquid? And between those we have a mix of liquid/solid?

Anyways, the question is... should I look at the specific melting point of the solder I'm working with and put the soldering station at that temperature? Or may be a little higher to make the process quick?

I see most solder alloys melt between 180ºC and 250ºC, so if you are working with these alloys, when is the 350ºC temperature recommended? When desoldering? It's better to have the tip at 350ºC because that means you reach way faster the melting point and put less stress in the components?

Thank you!
Why are you using lead free?
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
481
hi ram,
I prefer a 350C tip temperature, it is not a matter of just melting the solder, but heating the complete 'joint' point, on the component.
Some 'larger' solder joints require lots of quick heat transfer.
E
Yeah, so one can't be "too lab scientific" and set the tip to 190ºC to just melt the solder, right?
I was guessing that you had to go way higher (350ºC?) to rise the temperature of all the metal parts fast and evenly so the solder runs fine.
 

ericgibbs

Joined Jan 29, 2010
15,542
hi ram.
When using a 350C bit, you will quickly learn the best method of soldering the jointed components.
Getting the heat quickly into the joint is the best method I have found.

Also, applying the correct tip pressure to suit the pads/components is important.

Use the correct tip shape/profile for the joint being soldered, solder flux is essential to avoid dry joints.

E
 

Ian0

Joined Aug 7, 2020
5,169
My solder supplier says that the iron should be 120°C hotter than the melting point of the solder, but I have always found that a #7 Weller bit (700°F, 370°C) is ideal for leaded solder.
By far the most important thing is to avoid oxidising the solder.
 

Ya’akov

Joined Jan 27, 2019
5,676
Yeah, so one can't be "too lab scientific" and set the tip to 190ºC to just melt the solder, right?
I was guessing that you had to go way higher (350ºC?) to rise the temperature of all the metal parts fast and evenly so the solder runs fine.
Sorry, I misread. In any case you should be using a eutectic alloy, 63Sn/37Pb. I has the lowest melting point and it has no plastic region (it goes directly from liquid to solid, so no “cold” joints).

I always refer to the datasheet. The Kester 63Sn/37Pb I use says to use a tip temperature of 315°C. I leave it at that and it works well. But, I also change tips for more thermal mass if I need it. Normally, the tip scales pretty much perfectly to the joint.

[EDIT: Apparently I responded to the wrong post, it was about the lead free, not the quoted one.]
 
Last edited:

MrChips

Joined Oct 2, 2009
26,145
There is no single answer.
It depends on the solder alloy, the size of the soldering tip, the size of the component and the size of the copper traces, and of course, the length of time you take applying the soldering tip to the joint.

General guidelines are:
lead alloy solder: 300-370°C
lead free solder: 350-400°C

Go for the lower range that gets the job done, the higher the temperature, the shorter the life of the soldering tip.
As Ian suggests, go for 100°C higher than the melting point of the solder as a starting point. Hence if it melts at 200°C, setting the soldering station to 300°C is a good place to start.
 

sagor

Joined Mar 10, 2019
696
Hi, for the past almost 10 years I've been soldering with a soldering station that had a knob to regulate the temperature, your average cheap $30 one. With practice and experience I learned the "sweet spot" of the knob to work comfy and nicely, which was about 300-350ºC according to the sticker, which might be lower or way lower at the tip.

Recently I purchased an awesome station that uses tips that tell you the temperature of the tip, so now I know "exactly" the temperature I'm working with. My solder alloy is:

View attachment 265491

Which according to Wikipedia it melts at 183ºC (solidus) or 190ºC (liquidus). Now that's new, I always thought the melting point is the temperature at which the substance or alloy starts to change state from solid to liquid, of course at standard pressure. So having 2 melting points, I don't know what that means.
May be it's the range?
Like at 182ºC or below we are "99.99%" certain it's solid and above 190ºC is liquid? And between those we have a mix of liquid/solid?

Anyways, the question is... should I look at the specific melting point of the solder I'm working with and put the soldering station at that temperature? Or may be a little higher to make the process quick?

I see most solder alloys melt between 180ºC and 250ºC, so if you are working with these alloys, when is the 350ºC temperature recommended? When desoldering? It's better to have the tip at 350ºC because that means you reach way faster the melting point and put less stress in the components?

Thank you!
In between 183 and 190, the solder is more like a "paste". That is where the eutectic of the two alloys is in a transition state. At 182, it should be 100% solid. At 190+, it is in a liquid state, with possibility of some solid metal that has not melted fully.

eutectic.jpg
 

Ya’akov

Joined Jan 27, 2019
5,676
Just a point that is worth mentioning. While 63Sn/37Pb is the best for making solder joints because of its properties. It’s wetting action, that is, its ability to form the alloy with the metals being soldered, is not as good as 60Sn/40Pb. This is why the latter is used for tinning wires and leads in solder pots.
 

Ian0

Joined Aug 7, 2020
5,169
Just a point that is worth mentioning. While 63Sn/37Pb is the best for making solder joints because of its properties. It’s wetting action,is not as good as 60Sn/40Pb.
It’s rare that I join in any AAC discussion without learning something, and I didn’t know that, despite doing a 2nd year course at university in metallurgy, and spending what seemed like weeks on the tin-lead eutectic.
But did you know that when you tin a wire, that just after the point where the tin colour finishes and the copper colour returns, a tin-lead-copper alloy is formed that is particularly brittle? That is why regulations require that wires joined by solder must have an extra fixing.
 

Ya’akov

Joined Jan 27, 2019
5,676
It’s rare that I join in any AAC discussion without learning something, and I didn’t know that, despite doing a 2nd year course at university in metallurgy, and spending what seemed like weeks on the tin-lead eutectic.
But did you know that when you tin a wire, that just after the point where the tin colour finishes and the copper colour returns, a tin-lead-copper alloy is formed that is particularly brittle? That is why regulations require that wires joined by solder must have an extra fixing.
I did not know that, so we both get to learn something.

I have a solder pot I use when I am going to do a lot of wires or components and it is very satisfying to see how well it works. It’s also a lot faster than using the iron and does a much better job. Because you don‘t heat the wire melt back of insulation like PVC is not a problem. It tins right up to the insulation with only a slight distortion of the end of the insulation.
 

dl324

Joined Mar 30, 2015
14,484
I use a 700F conical tip for almost all of my soldering. My iron can only have 3 tip temperatures: 600F, 700F, or 800F.
 

Rich2

Joined Mar 3, 2014
241
I use 400°c for the small tip or with the big tip if it's a big joint, or 360c for big tip for smaller joints. Errr if that makes sense :)

I don't know how accurate the readout temperature is, but that's what works for me.
 

MisterBill2

Joined Jan 23, 2018
11,919
I mostly use the cheap soldering pencils, a lot like the ines RadioShack used to sell for $4.95. For more delicate work I use a longer tip turned down to a narrower cross section so that it delivers less heat, no matter what the temperature is. The soldering process is often helped along with a bit of flux. What the process actually consists of is first heating the materials to be soldered up to the solder melting point. That happens much more rapidly if a bit of solder is used to provide better than just a point contact between the iron tip and the work. Then adding a bit more solder until the joint gaps are filled , and then removing the hot iron and the solder feed, so that the joint can cool. The secrets are having a hot enough tip with an adequate thermal mass so that enough heat can transfer quickly to the work. That is where many soldering efforts go wrong. The heat must transfer quickly until an adequate temperature is reached an the solder flows. This does require being able to see the joint, and it needs the joint materials to quickly accept and become wet with the solder. Thus enough of the correct flux is vital for materials not already coated with solder. That is a prime reason for utilizing used connectors.
And thanks for letting me point out that even cheap soldering tools can produce great joints.
 
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