No lead solder needs an 85 watt soldering iron

[willwatts]

why do you have to use an 85 watt soldering iron for no lead solder? it won't work with a 60watt soldering iron

 

[hevans1944]

Lead-free solder alloys melt at a higher temperature than lead-tin alloys. The amount of power needed depends on the mass and dimensions of the soldering iron tip. There is no "magic" in 60 watt versus 85 watt soldering irons. The higher wattage provides more power than the lower wattage, but the tip temperature is a complex function of heat losses from the soldering tip. You can try a temperature-controlled tip, but success depends on matching the power available, tip mass, and size to the task at hand. It takes more power to transfer heat, at any given temperature, to a larger mass than is required for a smaller mass.

 

[willwatts]

Well The fine pitch IC and SMT 402, 603 are cold solder joints at random fine pitch IC pins
It's really hard to troubleshoot cold solder joints at random places

The PCB go through a oven with solder paste
Does the solder paste need to be frozen or cold before using it?

Lead free solder creates more cold solder joints? compared to lead tin solder it seems

With high temps and air flow the 402 and 603 get off aligned in the oven to melt the lead free solder

 

[hevans1944]

Yeah, keeping those little SMT devices in place while blowing hot air over the board is a real PITA. No, the solder paste is usually at room temperature. I think even a perfect lead-free solder joint looks like a cold solder joint, which is why I exclusively use 63% Sn 37% Pb flux-cored solder. I might try a toaster oven without air flow if I ever need to mass assemble a bunch of SMT parts for my VNA project.

 

[willwatts]

The solder paste for the soldering ovens is different then the solder paste used for "reworking" SMT/SMD

When the Solder paste is new its soft but after a couple of days it gets hard

How do you hold down the 402 components when soldering? i have tried tweezers or a tooth pick

Also when I'm reworking boards that have SMT components next to Plastic connection, how do you prevent the Hot Air gun from melting those Plastic connects or other plastic surrounding the components? what type of shields do you use?

 

[willwatts]

I use the 85 watt soldering iron but ground planes because the 65 watt doesn't do well with ground planes even those they are both set to 800F or 900F

I'm not sure why 85 watts at 800F is different then 65 watts at 800F

 

[KrisBlueNZ]

User willwatts has started five threads within the past few hours. I am closing all of them temporarily.