| Yuichi Aoki, Ichisaku Tsujie |
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Technical Development Headquarters |
| Takayuki Nagai |
|
Espec Test Center Corp. |
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To date, the effect of ramp rate on solder joints during solder joint testing has not been thoroughly researched. This report is a follow-up to our article in Espec Technology Report No.25 (September 15, 2007) titled, "The effect of ramp rate on temperature cycle fatigue in solder joints." For our current report, we have tested ramp rates from market environment conditions at 15oC/min (IEC standard 60749-25) up to the liquid bath thermal shock range, and we have investigated the correlation between ramp rates and the effect on solder joints.
Because stress in thermal fatigue tests is not defined consistently throughout Japan, we used the following definitions from the IPC-SM-785 standard.
| Thermal fatigue: |
Thermal expansion of a section or the entirety of parts bundled together leading to degradation or cracking of materials caused by repeated heating and cooling.
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| Thermal shock: |
Abrupt temperature change causing sudden temperature gradient and stress on the specimen. As a rule, the ramp rate exceeds 30oC/min.
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| Temperature cycle (thermal cycle): |
Slower temperature change insufficient to produce thermal shock in the specimen. The ramp rate used is less than 20oC/min.
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This report is a follow-up to the previous report titled "The effect of ramp rate on temperature cycle fatigue in solder joints," but the title has been changed from "temperature cycle fatigue" to "thermal fatigue testing." In accordance with the unification of terms described above, we have decided to use the name "thermal fatigue testing." |
