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SMT electronics assembly manufacturing forum.


PCB finish for vapor phase oven

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#71829

PCB finish for vapor phase oven | 12 March, 2014

Hello,

in my SMT process I have some problems with the solderability (look like dewetting) on a PCB with finish HASL Lead Free with a composition that is melt at 230 degree Celsius. My oven is with vapor phase and the peak temperature is 230 degree Celsius. The solder paste is lead free and the melting temperature is about 217-219 degree Celsius. This problem is possible to appear because of the melting point differences between solder paste and PCB finishing? I know that the request of the solder paste is that peak temperature must be with 10 degree higher than melting point temperature (219 +10= 229), this rule must be apply also to the PCB finishing? Thank you in advance.

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#71831

PCB finish for vapor phase oven | 13 March, 2014

You're creating a new alloy on the surface of your board. The alloy will have a melting point determined by the constituent metals of the alloy. Your alloy consists of: * Lead-free HASL solderability protection on the board * Lead-free solder paste * Solderability protection on the components that can be lead-free or not * Other stuff

Your MP+10*C rule ["solder paste is that peak temperature must be with 10 degree higher than melting point temperature (219 +10= 229)"] is sketchy. You leave no room for variation. For instance: How tight can you hold that 230*C peak of your oven? I suggest "melting point + 20*C." Sounds like you have the wrong fluid in your oven. SB "HS" rather than "LS." Look here: http://www.torenko.com/pdf/Todays-Vapor-Phase-Soldering-Tech-Paper.pdf

BR davef

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