Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


BGA warpage

Robert Noory

#12865

BGA warpage | 20 January, 1999

I have received prototype PBGA (256 pins) devices from Motorola (actual part number = KXPC850ZT50). These parts seemed very warped on the edges. When I put the part on a plain surface, it rocks quite a bit when I press lightly on a corner. I have had intermittent problems with the pins on the corners. How can I mesure if the level of warpage is acceptable ? What measures can I take to minimize the effect of this warpage.

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Tony A

#12866

Re: BGA warpage | 20 January, 1999

| I have received prototype PBGA (256 pins) devices from | Motorola (actual part number = KXPC850ZT50). These parts seemed very warped on the edges. When I put the part on a plain surface, it rocks quite a bit when I press lightly on a corner. I have had intermittent problems with the pins on the corners. How can I mesure if the level of warpage is acceptable ? What measures can I take to minimize the effect of this warpage. | Have you tried to bake the parts? I believe that these parts are humidity sensitive.

Now are you placing the BGA using a rework station or you will be sending it through the normal process.

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Terry Burnette

#12867

Re: BGA warpage | 21 January, 1999

| I have received prototype PBGA (256 pins) devices from | Motorola (actual part number = KXPC850ZT50). These parts seemed very warped on the edges. When I put the part on a plain surface, it rocks quite a bit when I press lightly on a corner. I have had intermittent problems with the pins on the corners. How can I mesure if the level of warpage is acceptable ? What measures can I take to minimize the effect of this warpage. | The industry standard for PBGA warpage is .008". Warpage is measured by allowing the PBGA to sit flat (balls down) on a level surface, and measuring to the highest ball without pushing down on the package. This measurement is typically performed with automated laser scanning machines. Since the PBGA substrate is made with a BT resin, it's glass transition temperature is 170�. PBGA substrates will relax at temperatures above 170�, and be flat during soldering. The most common causes of open solder joints on PBGA's are secondary wave solder opens, due to the PBGA spheres remelting during the wave process, and intermetallic separation when BGA's are soldered on to electroless nickel/gold plated board pads, due to phosphorus which is used in the nickel plating bath. Motorola has a group dedicated to resolving interconnect problems with all semiconductor packages. If you'll email me your phone number, I'd be glad to call you and see if we can fix the intermittent problems you've been experiencing.

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