How can I find a 1 um size vacancy under 150 um brass?

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Discussion Overview

The discussion revolves around methods for detecting small voids, specifically a 1 micrometer size vacancy, in solder joints between brass and copper tape. The context includes considerations of non-destructive testing (NDT) techniques and the implications of such voids in practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about devices capable of detecting small voids in solder, specifically between brass and copper tape.
  • Another participant suggests that the detectability of voids depends on their size, noting that larger voids can be identified using standard NDT methods like X-ray and ultrasound, while smaller voids may require measuring electrical resistance variations.
  • Acoustic time domain reflectometry and ultrasonic thickness gauges are proposed as potential methods for detecting voids due to acoustic impedance mismatches.
  • Several participants express curiosity about the significance of detecting a 1 micrometer void, questioning its impact on the application and suggesting that understanding the application could aid in detection strategies.
  • One participant emphasizes the importance of preventing voids in solder and discusses the potential problems that voids could cause in applications.

Areas of Agreement / Disagreement

Participants express varying opinions on the methods for detecting voids and the significance of the void size, indicating that multiple competing views remain regarding the best approach and the implications of voids in solder.

Contextual Notes

Limitations include the dependence on the size of the voids for detection methods and the unresolved nature of how voids specifically affect the application in question.

rain2air
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I have soldered a pair of brass tape on the both side of a copper tape.
The thickness of each metal tape is about 150 um(micrometer).
The thickness of solder is about 2~20 um.
I want to know what device can find the small vacancy of solder between the brass and the copper tape.
 
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Depends on the area of the void . Very small voids will be difficult to detect by any method but larger voids that occur in normal soldered joints can be detected by a variety of standard NDT procedures . X ray and ultrasound detection are commonly used .

With these very thin layers you might be able to locate larger voids by measuring the through thickness electrical resistance at numerous points and detecting local variations .
 
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Curious to know why you need to know if there is a 1u void? Presumably it makes a difference to some something? so can you use that "something" to help locate it?
 
You should be able to use acoustic time domain reflectometry, or an ultrasonic thickness gauge. There will be a significant reflection from the acoustic impedance mismatch where there is air between the laminated metals.
 
CWatters said:
Curious to know why you need to know if there is a 1u void? Presumably it makes a difference to some something? so can you use that "something" to help locate it?
I want to prevent the void from being created in the solder.
 
rain2air said:
I want to prevent the void from being created in the solder.

Why does it matter? What will the void do? CWatters asked because if your application is X and you will get Y problem then in your test setup you could do a bit of X and try to detect Y. If you see a bit of Y then you have the void. That may not be true of your application but if it is then you have a good way of measuring it.

BoB
 
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