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BGA Warp

Robert

#9260

BGA Warp | 29 September, 1999

Hi All, Any one experince BGA-chipset warp about 10-15mil after removing from PCB? FYI, the rework temperature for preheat was 170C from room temperature about 30 seconds, & BGA was removed at temperature between 190-200C. Thankyou.

BRs, Robert

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#9261

Re: BGA Warp | 29 September, 1999

| Hi All, | Any one experince BGA-chipset warp about 10-15mil after removing | from PCB? | FYI, the rework temperature for preheat was 170C from room | temperature about 30 seconds, & BGA was removed at temperature | between 190-200C. | Thankyou. | | BRs, | Robert | Could it be a moisture problem (PBGA) ?

Wolfgang

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ROBERT

#9262

Re: BGA Warp | 29 September, 1999

| | Hi All, | | Any one experince BGA-chipset warp about 10-15mil after removing | | from PCB? | | FYI, the rework temperature for preheat was 170C from room | | temperature about 30 seconds, & BGA was removed at temperature | | between 190-200C. | | Thankyou. | | | | BRs, | | Robert | | | Could it be a moisture problem (PBGA) ? | | Wolfgang | Hi , Wolfgang, Might be moisture problem , are you suggesting that the PCB must go for baking before BGA being removed ? If yes, what's the baking condition.

Robert

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Earl Moon

#9263

Re: BGA Warp | 29 September, 1999

| | Hi All, | | Any one experince BGA-chipset warp about 10-15mil after removing | | from PCB? | | FYI, the rework temperature for preheat was 170C from room | | temperature about 30 seconds, & BGA was removed at temperature | | between 190-200C. | | Thankyou. | | | | BRs, | | Robert | | | Could it be a moisture problem (PBGA) ? | | Wolfgang

PBGA's and others are built using PCB substrates themselves, as you already know. Though using BT resin/glass systems, they are quite suceptable to warpage just as any other board - especially when subjected to thermal stress of the type applied during part removal operations. See the following for part fabrication requirements, if available: | Jedec 95-1, "Jedec Design Standard, Design Requirements for Outlines of Solid State and Related Products"

JESD22 B-108, "Coplanarity Test for Surface-Mount Semiconductor Devices"

IPC: IPC-7095, "Design and Assembly Process Implementation for BGAs" (not sure if finalized)

Earl Moon

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#9264

Re: BGA Warp | 29 September, 1999

| | | Hi All, | | | Any one experince BGA-chipset warp about 10-15mil after removing | | | from PCB? | | | FYI, the rework temperature for preheat was 170C from room | | | temperature about 30 seconds, & BGA was removed at temperature | | | between 190-200C. | | | Thankyou. | | | | | | BRs, | | | Robert | | | | | Could it be a moisture problem (PBGA) ? | | | | Wolfgang | | | Hi , Wolfgang, | Might be moisture problem , are you suggesting that the PCB | must go for baking before BGA being removed ? If yes, what's | the baking condition. | | Robert | | | | Hi Robert, due to the fact that PBGAs are known as moisture sensitive devices there�s a handling procedure recommended for rework also. As I said a couple of days ago in another thread concerning BGA there�s a hint on the motorola-page http://mot-sps.com/solutions/wired/pbga/rework.html

Here an excerpt: "If the assembled board has been exposed to "out of dry-pack" conditions for an extended period of time (24 to 96 or more hours, depending on PBGA configuration and ambient conditions) and removal is performed, "popcorning"--or die attach delamination--will occur. To avoid this, the entire assembly must be baked at 125�C for 12 hours. Since the saturation/ bake-out curves for PBGA are quite steep, baking for half to two-thirds of this time will go a long way in preventing popcorning, as long as care is taken not to use an excessive ramp-up rate (>3�C/min) or maximum temperature (~240-250�C)."

For the correct handling of moisture sensitive devices and prebaking advices see IPC-SM-786A or newer publikations. I encountered the following: A tray of sample BGAs was send to me proper packed and sealed, we opened it and the parts looked perfect ( no warpage), doing soldering tests, showing samples around etc. the tray stayed open for a couple of weeks. After that I wanted to show the good coplanarity of this devices but, surprise surprise, they looked like tiny salatbowls. Haven�t done baking those more use them as bad samples. For baking I go with the recomendations made in the IPC. In your case I guess you are gonna reuse these removed components if not why not bother about something that appears strange.

Good luck Wolfgang

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#9265

Re: BGA Warp | 29 September, 1999

| Hi All, | Any one experince BGA-chipset warp about 10-15mil after removing | from PCB? | FYI, the rework temperature for preheat was 170C from room | temperature about 30 seconds, & BGA was removed at temperature | between 190-200C. | Thankyou. | | BRs, | Robert | Robert: PBGAs heat at the corners first. One has to be patient with one's profile. Good luck. Dave F

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