effect of electrical bias on solder cracked

[alec_t]

what is the best temperature cycle to crack a eutectic solder?

What are the highest and lowest temperatures you can apply? Going down to absolute zero would probably do it .

 

[kubeek]

For example heting it up to melting point and then dumping it into liquid nitrogen should do it nicely.
I don´t really see what is the point of your question.

 

[cinderella1]

i mean for the thermal cycle (such as ramp and dwell time) until the solder is cracked. BTW, the melting point for eutectic solder is 183C

 

[alec_t]

Ramp and dwell time, however you define them, would vary enormously according to the thermal mass you are dealing with.

 

[cinderella1]

thermal mass? how about if i use muffle furnace to crack my solder.. what temperature cycle would u suggest?

 

[kubeek]

What are you trying to achieve? The thermal stress will need to be repetitive to get the solder joints to crack. Also there will be a big difference between through hole, smd, and bga packages in what amount of stress makes them fail.

 

[cinderella1]

i am using through hole. i want to crack the solder n later want to test the bias of the crack. thats what i want to achieved. any suggestion what temperature cycle should be used?

 

[kubeek]

no idea, but the general rule would be to get ramp it up and down as fast as you can.
You think that the cracked joint will have some bias voltage on its own? I don´t really see what you´re trying to find.

 

[cinderella1]

nvm, the bias part i will figure out later. btw, hw to ensure if the solder is cracked? can we just see it by naked eye or need magnifier? SEM is only used when the solder is confirmed cracked

 

[alec_t]

You may be lucky and spot a crack by eye or by sensing a change in electrical resistance between nominally connected parts.

 

[cinderella1]

electrical resistance by using multimeter? if im using diode, the how cn we know?

 

[alec_t]

if im using diode, the how cn we know?

?? Are you trying to detect a defective solder joint inside a diode, or between a diode leg and some other circuit part?

 

[cinderella1]

between a diode leg and pcb. how should i detect the crack? (using eutectic solder)

 

[alec_t]

between a diode leg and pcb

Then the fact that it's a diode makes no difference. Try a DMM on the Ohms range, with probes on that leg and the pcb.

 

[cinderella1]

can give any reference? like a website

 

[alec_t]

I suggest you do an experiment yourself, with a scrap circuit board. Use some solder wick to remove solder from a component joint then put the DMM across the joint and check resistance/volts.

 

[KeepItSimpleStupid]

Cracks in solder joints show up real easy using freeze spray.

 

[DerStrom8]

I don't have the slightest idea what you're on about?, there's no relation between dry joints and bias?.

That's exactly what I told him/her in chat but he/she refused to listen.

EDIT: Ha, now she's started the revenge game--I disliked her post, she disliked mine. How mature...

 

[DerStrom8]

cinderella1, as mentioned already a broken solder joint has no practical effect on a diode's bias. When you have a bad joint, the connection is intermittent (like I told you in chat). When it's intermittent, that means sometimes it acts like the diode is there, sometimes it acts like it's not there at all. When the joint is connected, the diode behaves as it normally would. When it's not connected, it's like the diode isn't even there, so there is no component to have a bias. Do you see now what I was trying to tell you in chat?

Let's say you have a diode in a series circuit with a resistor and an LED. The diode is forward biased, so current will flow normally. When the diode is joined properly, the LED will light. When the diode joint is broken, the circuit is broken, so the LED does not light. If there is just a crack in the joint but it is still electrically connected, the LED will still light.
An intermittent joint means it can connect and disconnect many times a second, or maybe once every few years. If it is disconnected, the LED will not light. If it is connected, the LED will light. It's as simple as that.

Don't over-think it.

 

[cinderella1]

Cracks in solder joints show up real easy using freeze spray.

good idea..but will it affect the solder performance?