Figure 1 Typical thermal profile with the four traditional parameters within spec

There are other ways to look at a profile which can be helpful in determining if the profile may threaten components and showing if it is consistent, both across solder joints, and over time.

In the profile example above, the Time Above Liquidus (TAL)on solder joints 1 and 3 are within 2 seconds, yet channel 3 (from the data; plot not shown for visual clarity) had more readings at higher temperatures. This means that although this part may have the same time above 183ºC, more readings were at temperatures higher than channel 1; higher risk of damage. Also note that the peak temperatures were not far apart; 222.2ºC vs. 223.5ºC.

So we added a new measurement to the MAP software to not only show Time Above Liquidus, but also consider the temperature values during the TAL portion of the profile. This new measurement has several names: “Total Heat,” ” Area Under the Curve,” or “Stress Integral.” It combines the time element of Time Above Liquidus with the temperature measurements during that time to give the Total Heat the component experienced, expressed in degree-seconds.

Figure 2 Total Heat measurements (component 1 only shown for clarity)

In this case, even though the Time Above Liquidus values are within 2 seconds and the peak temperature is less than 2 degrees apart, the Total Heat values are 2278º-sec and 2628 º-sec which differ by 350 º-sec! This clearly points out that component 3 had to withstand more Total Heat than component 1 and this simple parameter can now be examined in an instant, using the latest; version 2.18j of MAP software.

The ECD V-MOLE with patented one button “OK” profile evaluation

(The OK Button is also available on the 20-channel MEGAM.O.L.E.™ thermal profiler, and OvenCHECKER™ )

Taking only seconds, the MOLE can tell you and your oven operators if the profile just measured is in or out of specification with the universally understood Green for good (GO!) or Red for bad (STOP!).

You get to set the specification limits for any or all of the four most popular profile parameters:

• Ramp Slope
  
• Time Between temperatures
  
• Time above Liquidous
  
• Peak Temperature
  

…and you can choose which of the MOLE’s input channels to include, up to 20 channels on the MEGAM.O.L.E.™, and three on the V-M.O.L.E.™ thermal profilers.

The Specification Table in MAP Software

Using the MAP™ Profiling software, enter your specification limits for the four profile parameters in the Upper and Lower Limits table in the “Target-10 OK” tab. These values will automatically be sent to the MOLE profiler when you use the Verify Process Wizard to confirm that a previously characterized oven recipe is still performing within specification.

MAP™ Profiling Software Target-10 OK Profile tab

Once programmed, the MOLE profiler can be used many times (up to 96 times) to Verify your oven is producing the same profile, without reconnecting to your computer. Simply run the profile and press the “OK Button” on the MOLE. No more running back to the PC software to download to see the results. One push of the OK button, and you get your answer…Go, or No-Go. It’s that simple!

*U.S. Patent Number 7653502.