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How to prevent Bluetooth Module BGA short anybody?

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#38005

How to prevent Bluetooth Module BGA short anybody? | 20 November, 2005

Hi guys!! Just want to ask regarding the Bluetooth Module. The module has BGA inside shield before production we checked Raw materials no short probems. But after Passing N2 Reflow during normal production the BGA inside module tend to get shorted.. Any experiences on this? I already check profile still within specs of peak temp of 215 deg C at body using Leaded process.

I also checked X-ray if shield have direct contact w/ BGA but do not have it has around 0.75mm gap from top of BGA to shield. Can anybody suggest how to prevent it from getting short we only encounter random qty.

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Amol

#38011

How to prevent Bluetooth Module BGA short anybody? | 21 November, 2005

With a BGA, how much solder paste are you putting on the pads? sometimes, bridging occurs when there is more solder paste than needed during reflow.....just a thought

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#38013

How to prevent Bluetooth Module BGA short anybody? | 21 November, 2005

He's not talking about the balls. He's talking about the sheilding. As soon as I saw the data sheet and all it's warnings, I thought o crap. Anyways the customer had checked all 5 before giveing them to us. After 4 failed. MuRata said the profile we sent looked good. When I heard they had failed, my opinion was, the profile was good, if the profile was the problem don't buy those parts they will be too low a yeild. I know that is not a real option but what I was really saying was put pressure on MuRata. I wish there was someway to have everybody who has tried to reflow them, all talk to each other. I "knew" we weren't the only ones that had problems.

And we used leadfree reflow and no N2.

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#38028

How to prevent Bluetooth Module BGA short anybody? | 22 November, 2005

Have you complained yet to MuRata? You are talking about the same bluetooth module, aren't you. I hope everybody having trouble with module complains to them. I don't believe they put all the cautions and warnings about reducing the deltaT on the data sheet for fun. I beleive they had problems soldering them on boards when they were testing them. If we run them again I will make adjustments to the recipe, and see if we can get a better yeild.

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URL

#38043

How to prevent Bluetooth Module BGA short anybody? | 23 November, 2005

Shorted to the sheild or the BGA balls are shorted? Sheilds move a lot during reflow. If this is the case, place some adhesive or peelable solder mask on either side of the shield and baords to stop it from moving.

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#38079

How to prevent Bluetooth Module BGA short anybody? | 25 November, 2005

Nope actually the whole bluetooth component is a raw part comprising of BGA and chip components in one small PCB wherein this whole assembly is encased in a shield. So basically when we recieve the part we can only see the shield and some minor chip components outside the shield. This whole bluetooth module is now mounted in our normal mainboard PCB at SMT line. Prior to mounting I already used X-ray to check contents inside the shield and so i can see the some micro BGA and other chip comps encased by the shield so far no short. Now after mounting this whole unit in our mainboard and run down in reflow I again checked the module using x-ray and found out that BGA encased in the shield was already shorted not with the shield but the balls itself. I confirmed body temp of shield during reflow and the profile reads only 215C. So guy's any opinion on this. By the way supplier of the bluetooth is Actiontec.

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Amol

#38080

How to prevent Bluetooth Module BGA short anybody? | 25 November, 2005

cookson has something they call "cool caps" that reduces the delta T across the component top surface, something you might wanna explore to reduce the delta T even further....FYI, I am not associated with cookson in any way

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#38081

How to prevent Bluetooth Module BGA short anybody? | 25 November, 2005

pyramus,

First, search the fine SMTnet Archives for previous discussions on BGA shorts.

Second, we're still not clear on the issue. * Is the problem with a BGA? If so, please describe the BGA, including any heat spreader * Is the problem with a uBGA? If so, please describe the uBGA, including any encapsulant

Third, tell us about the controls that you use to limit the moisture absorption of the module prior to board attach.

Forth, the temperature of the shield on the module is interesting, but the temperature of the component solder ball that is bridging is more meaningful. Continuing, what is the actual temperature measured on the solder balls?

Finally, what does Actiontec suggest as the temperature for proper reflow?

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bwet

#38238

How to prevent Bluetooth Module BGA short anybody? | 6 December, 2005

Try using some of those new polyimide stencils. They are 8mils thick and can prevent shorting if it is due to solder mask problems or too much paste. http://www.solder.net/technical/tips.asp

BWET

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