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Component ( Connector ) drop during secondary reflow

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#81542

Component ( Connector ) drop during secondary reflow | 3 December, 2018

Hi ,

Observed component drop during second reflow.

Component : Image attached Perimeter : 0.15 to 0.025 cm No of leads : 22

Solder Alloy : Sn63/Pb37

As per component adhesion calculation the component should not fall. ( Excel Attached )

Profile :

first Side : RSS

Second Side : RTS and RSS both tried .

Please provide your valuable feedback.

Regards, Ameen

Attachments:

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dwl

#81546

Component ( Connector ) drop during secondary reflow | 3 December, 2018

I can't open your spread sheet to see how you calculate this, but usually this sort of calculation assumes the leads are spaced symmetrically on both sides of the part and the center of mass is between them. Gravity pulls the part down, while the wetting force of the molten solder pulls up. As long as the force of the solder exceeds that of gravity, your part will stay put.

In your case, the component has leads only on one side so the center of mass is off set. The force of gravity creates a torque so it takes a lot less force for the part to fall off.

options include running the connector side second so it won't fall off, or dispensing a small dot of adhesive under the component to hold it down durng second side reflow.

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#81552

Component ( Connector ) drop during secondary reflow | 4 December, 2018

Hi,

Thanks for the valuable feedback.

Agree with you.

1. We have similar component on both the side of the board.

2. The component fall was random like 4 out of 100 components.But last build it has increased.

3. Applying glue dot is option , but our customer need a valid reason to approve for glue application.Since it was not falling before.

Any technical way we can explain this phenomenon is not under our control. It may fall in few PCBA and few it wont.

Regards,

Ameen

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#81553

Component ( Connector ) drop during secondary reflow | 4 December, 2018

I would guess then that it is either variation in paste volume (unless you are using an inline SPI), or potentially a damaged chain or sprocket causing a small jump. The second one is easy as you can watch the chain do a full rotation, the first a bit tougher if you don't have the tools.

Out of interest is it consistent with all operators?

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#81554

Component ( Connector ) drop during secondary reflow | 4 December, 2018

Hi Rob,

Thanks.

We have inline SPI. Suspecting small jump in the reflow conveyor. We are checking on it.

Thanks for the feedback. Will update after the reflow conveyor analysis.

Yes its same with all operators.

Regards, Ameen

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#81561

Component ( Connector ) drop during secondary reflow | 5 December, 2018

You can also consider the very old simple method with decreasing the reflow zones on the bottom side with 10C. Sometimes when it is marginal issue like yours....you could be surprised.

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#81563

Component ( Connector ) drop during secondary reflow | 6 December, 2018

Hey,

What would be the peak temp. ?

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#81564

Component ( Connector ) drop during secondary reflow | 6 December, 2018

Hi Betty ,

Its around. 215 to 220 deg C

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#81565

Component ( Connector ) drop during secondary reflow | 6 December, 2018

Hi Evtimov,

Thanks for the feedback.

Will definitely try it.

Regards, Ameen

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#81566

Component ( Connector ) drop during secondary reflow | 6 December, 2018

Hi Rob,

We used different Reflow Oven and noticed the component drop is less 1 out of 24 components.

But not able to analyze, why its falling more in other reflow oven. Our maintenance team is assuring there is no vibration in any of the oven. And visually we are not able to see any jump or vibration.

Any good method to check the vibration source.Please help.

Regards, Ameen

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#81567

Component ( Connector ) drop during secondary reflow | 6 December, 2018

If you go this route vibration will not be your focus. there is something that is called pressure inside an oven. Some ovens have separate parameter to control that. Other will have the blower speed control. You should decrease the pressure(your convection should get a little lower)to secure the component stay there. After all that said

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#81570

Component ( Connector ) drop during secondary reflow | 6 December, 2018

63/37 is eutectic. It's either a liquid or a solid at a specific temperature. There is no in between.

Lowering the temperature will do nothing except make the temperature lower.

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#81571

Component ( Connector ) drop during secondary reflow | 6 December, 2018

Sr. Tech it is not as simple as that. Viscosity of material is changing with temperature. So it is liquidus but it makes difference.

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#81575

Component ( Connector ) drop during secondary reflow | 7 December, 2018

63/37 goes from solid to liquid. It melts and solidifies at a single temperature.

You can add a percentage of silver and get a slight "pasty range" for a couple seconds.

I have never seen a temperature change in a profile keep this from happening with 63/37.

This issue is a matter of a faulty oven or incorrect geometry 99.9% of the time.

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#81585

Component ( Connector ) drop during secondary reflow | 10 December, 2018

Thanks, Ameen

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#81587

Component ( Connector ) drop during secondary reflow | 11 December, 2018

What is the difference of the components that fall and the ones that don't fall?

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#81676

Component ( Connector ) drop during secondary reflow | 3 January, 2019

Hi ,

There is no difference as such in the component. So we are also confused. While few components are dropping.

Regards, Ameen

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Reflow Oven

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