Tuesday, January 7, 2014


I couldn't resist getting a toaster oven today to see how hard it would be to profile.  I found a Black and Decker TO1675W at a local retailer.  The first order of business was to drop in a few thermocouple probes and see just how hot this oven can get:

With the oven set to 11 it reached 250C in around 12 minutes.  This is 15C beyond the typical maximum safe temperature for lead-free parts and certainly well beyond the liquidous temperature (219C) of most lead-free solders:

I then attempted a manually controlled profile.  I plan to automate my profile, but for now I'll just close the control loop myself to build a few boards.  I placed a bityExpress rev A card in the oven with a thermocouple placed near the center of the PCB:

My initial profile attempt was the following:

  • Set the oven to 180C and turn it on
  • After the temperature has been above 150C for 60 seconds, turn the oven up to its maximum temperature
  • After the temperature has been above 220C for 30 seconds, turn the oven off

Comparing this to Altera's SMT Board Assembly Process Recommendations (AN-353-4.0):

  • Time preheating (between Ts1 and Ts2): 143 seconds
    • spec:  60-120 seconds
  • Time above 219C (Ta): 102 seconds
    • spec: 60-120 seconds
  • Time from ambient to peak temperature: just over 8 minutes
    • spec: 8 minutes

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