Soldering Iron Temperature

Discussion in 'Homebrew and Kit Projects' started by KD2NOM, Jan 11, 2018.

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  1. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Good afternoon,

    I have recently begun assembling my own kits and have a question about the correct temperature for small board applications.

    I have a new adjustable temperature iron with a pencil tip that I have been using to assemble a QRPGuys CW Trainer. I initially set the temperature on the iron to 450 C - but I'm finding that I am not getting great flow and tend to get blobs on the component leads. Additionally it is taking a long time (20 seconds) of iron application before the solder will begin to flow - so I am worried that I might be damaging the board or the components.

    So my questions are: a) what temperature do you set your irons to for small PCB work and b) how long should it take for solder to flow properly?

    Thank you for taking the time to read this and responding.

    Best regards,

    Mark Steele
  2. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    That seems too hot. Start at about 350C (600F) and see if that is adequate. If not, increase in increments. You want to use around the lowest temperature that will still give good flow and uniform heating throughout the joint. The setting will also be somewhat different depending on the type and size of the tip.

    The main problem with too high a temperature is that the flux gets vaporized too quickly to do much good so the solder has trouble wetting the joint.
    Last edited: Jan 11, 2018
    N2SUB likes this.
  3. N2SUB

    N2SUB Premium Subscriber QRZ Page

    I remember somewhere between 650-700F was the sweet spot on my iron. You also might want to change the tip on the iron (if it's old), and make sure you are using quality solder that's not too thick. Sorry, without looking at my old spools I cannot give a recommendation on that, but I'm sure someone on here can.
  4. N5RFX

    N5RFX Ham Member QRZ Page

    Are you sure it is 450C? That is 842F. Even with a pencil tip on a ground plane 450C should work fine, but is probably too hot for non ground plane or other connections that do not act as a heat sink.

    Mark N5RFX
  5. SM0XHJ

    SM0XHJ Ham Member QRZ Page

    350 - 370 C for leaded solder. Around 410 C for lead free. If 450 C is barely enough, there is something wrong.
    Either the temperature control is way off, or your tip is not tinned properly so the heat isn't transferred to the pin/pcb efficiently.

    As N0TZU wrote, a too hot tip will create issues with standard flux. You will see that as excessive smoke from the solder. It is better to use a larger tip/iron on larger components than raising the temperature.
    Last edited: Jan 11, 2018
    KB0MNM likes this.
  6. KF5FEI

    KF5FEI Ham Member QRZ Page

    Umm.... What diameter of solder are you using? .031" it typical for thru-hole, and 0.020" or 0.015" is good for surface mount.

    What does the label on the solder say?

    Either you have crap solder, your tip is too small, the wattage of the iron is too low, or the temp control on the iron is crappo.
  7. W9GB

    W9GB Ham Member QRZ Page

    Using 450° C (842° F) is TOO HOT for typical PC Board soldering.
    Adjustable Temperature solder stations permit Novices and Beginners to Learn Bad Soldering Habits. Soldering is a Skill that requires Practice and Hands-On education.
    While Videos may be useful ... Direct feedback (correction) from a Master or Certified instructor causes you to learn FASTER.

    How many Sports are learned by reading a book or watching a video?

    1.) Use a QUALITY solder, such as Kester “44” 63/37 alloy with a diameter 0.020” to 0.031”.
    2.) Plenty of cheap soldering “junk” on market, that produces bad solder joints.
    3.) Soldering Iron Tip : CHISEL or SCREWDRIVER Profile; 1.6 to 2.4mm width (1/16” to 3/32”)

    Kester Pocket Paks® are an inexpensive way to learn about different solders (alloys, No Lead, Silver).
    I suggest this for Novices, just learning the skill.
    Last edited: Jan 11, 2018
  8. KD0CAC

    KD0CAC Ham Member QRZ Page

    Not enough info in your post - what iron , make & model ?
    What solder lead , leadfree , flux in solder or not , diameter ?
    You mention pencil tip - size , its rare that a pencil tip would be recommended , most common is a chisel tip , and in a variety of sizes - generally the chisel tip should match the surface area of the part being soldered .
    And no mention of flux & type ?
    So I would recommend finding used , old electronics to take apart , and put back together for learning & practice .
    Also , are your talking about surface mount or through hole ?
  9. SM0XHJ

    SM0XHJ Ham Member QRZ Page

    Yes, the type of solder used is very important. Use good quality solder like W9GB suggested.

    When soldering components, it takes me something like 2 seconds per pin. One second preheating the pad/pin, one second to add solder and let it flow out nicely. Maybe a second or two longer for really large pins or pins connected to heat sinks or similar. 20 seconds is way too long anyway.
    WA7PRC likes this.
  10. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Thanks for all the replies - let me see if I can answer all the questions in a single reply:

    Iron: Aven Tools #17405 Soldering Station (
    Solder: lead free unknown manufacturer (came with a solder training kit) - I have several spools of Kester '44' however I did not use it as it's diameter seemed large
    Tip: Standard tip according to the website - long and pointy - not a chisel tip - new and clean
    Flux: in the solder as far as I can tell
    PCB type: thru-hole - no SMC on this one

    I'm thinking it may have been too hot and the flux is vaporizing - I'll try some experiments on a practice PCB I have.

    Thank you!

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