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multilayer PCB resoldering causes more problems?

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PrescottDan

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When you resolder a multi layer PCB board it can cause more problems

Because an older multi layer PCB can have cold solder joints in the layers or fracture solder in the layers, so you have to reflow the solder again to fix it

How can you reflow the solder again? without cause more problems

When using a DVM meter in Continuity to check the Continuity of each layer to input and output test points or pins, it will check or BEEP. But when you apply or inject a logic signal to test and check each layers input and output test point it's flaky or distortion. Why doesn't the continuity checker work but when injecting a signal it's different?
 

When using a DVM meter in Continuity to check the Continuity of each layer to input and output test points or pins, it will check or BEEP. But when you apply or inject a logic signal to test and check each layers input and output test point it's flaky or distortion. Why doesn't the continuity checker work but when injecting a signal it's different?

When using a DVM on BEEP mode to test for continuity, any flick contact due to manual handling could be filtered for our hearing, which can be modeled as a logarithmic function and therefore has no ability to detect few changes on level amplitude.

Concerning to signal injection you mentioned above, you´re presumably viewing by a scope, which has a sample rate able to detect the slightest variation on signal.



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How would you re-solder each node on a multi layer board without getting cold solder joint in between the layers?

What frequency, amplitude and waveform shape would you choose to inject to test each layers input and output test points or vias?
 

How would you re-solder each node on a multi layer board without getting cold solder joint in between the layers?

Problems related to electric bad contact on a board which previously worked fine, happens not only due to resoldering process, but is aggravated if the PCB board was not well manufactured by application of enough coating tin over copper, and even if this board operated beyond recommended temperature limits for long.

Weld reinforcement by application of flux is able repair in such cases, but performing this procedure on a massive scale is no assured success if the board was subjected to the conditions above.

What frequency, amplitude and waveform shape would you choose to inject to test each layers input and output test points or vias?

Current limits depends on components expected to assemble, but you can adopt standard PCB specifications which are usually stated by manufacturers. Frequency limits also concerns to circuitry nature, but are also strongly related to layout design, so that there is no precise answer for that without knowing more details.



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