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Answer to SMTA Certification Reflow Question

  • Indium Corporation
  • Folks:

    A while ago I posed the following as a typical type of question an SMTA Certified Process Engineer should be able to answer:

    A 7 zone oven has a heated tunnel length (TL) of 250 cm.  A 20 cm PCB (PCB Length =PL) needs to be in the heated part of the oven for 4 minutes.  What is the maximum throughput (TP) in PCBs per minute that this oven can support?

    The answer: 

    First we need to establish the belt speed, if the PCB needs to be in the 250 cm heated part of the oven for 4 minutes (t), the the belt speed BS = TL/t   or 250 cm/4 minutes or 62.5 cm/min.   So every minute the belt presents 62.5 cm new space for PCBs.  So  

    TP = BS/PL = (62.5cm/min)/(20 cm/PCB) = 3.125 PCBs/ min,  since a little spacing would be desired between PCBs, about 3 per minute is  a practical maximum.

    Golf Update:  As I had mentioned early in the year, for the first time in many years I really worked on my golf game, playing about twice a week, and exercising and stretching.  My typical scores were in the high 70s to low 80s, compared to mid to high 70s in my youth.  Perhaps the most interesting thing is that with the modern clubs and balls I hit the ball about 30 to 50 yards father than when I was 20.  I don't score as well because my shot game is not as good now (due to less practice I think).

    As a result of this extra distance and interesting comparison can be made. From the time I was 10 years old until I was 60 (last year) a played about 1000 rounds, yet I scored only 4 eagles (2 under par on a hole).  Form August 2007 through August 2008 I scored 3 eagles.........the difference?  I reach many par 5s in two or drive a par 4 today, whereas when I was young it was a rare occurrence.


    Dr. Ron