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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Al Carrillo

#12742

BGA PROFILE | 2 February, 1999

Hi everybody. Somebody know any consideration or special care to make a profile for BGA's.

any advice is aprecied.

thanks Al Carrillo

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Justin Medernach

#12743

Re: BGA PROFILE | 2 February, 1999

| Hi everybody. | Somebody know any consideration or special care to make a profile for BGA's. | | any advice is aprecied. | | thanks | Al Carrillo | | Hi Al, A BGA should be looked at just like any other surface mount device. However, just like any surface mount device, the different types of BGAs are going to have different thermal characteristics with relation to reflow. For example, the CBGA and SBGA (EBGA) is going to pull a lot of heat into the component and away from the substrate. These types of devices cause "cool" spots on your board. The best way to develop a profile is to phyisically insert thermocouples into the device. Drill through your substrate at a pad location. Use an .020" drill bit. Insert a thermocouple up into the substrate from underneath the board. Use #5 thermocouple wire. The total diameter is about .020". Paste up the location, populate it and run the board through your process. Record the time vs. Temperature data and adjust your profile accordingly. Watch out for overheating the PBGA packages. Also, make sure the PBGA packages stay "dry". Pay close attention to the moisture sensitivity levels and bake the components if necessary. A good indicator that something is wrong on a PBGA process, is the coplanarity of the device after it is soldered. The component should collapse evenly on the substrate. Don't be too intimidated by the BGA package. To quote the infamous Phil Zarrow, "BGAs, what's the BFD?"

Regards, Justin Medernach

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Brian Stumm

#12744

Re: BGA PROFILE | 2 February, 1999

| Hi everybody. | Somebody know any consideration or special care to make a profile for BGA's. | | any advice is aprecied. | | thanks | Al Carrillo | | | Al,

From my experience BGA's are no more difficult to profile than any other component. Like Justin said the best thing to do is to place a thermocouple under the device for profiling. I believe that Justin's instructions were for an unpopulated board. Thermocouples can also be attached to the populated board. Just drill (per Justin's advice) through the bottom of the board underneath the BGA (hopefully at the same location as a pad) insert your thermocouple and glue shut.

One thing to keep in mind is that profiling BGA's in an IR based oven can be quite a challenge. I recently had one of my customers call regarding a board they were having trouble profiling in their old IR oven. Delta's were 25 - 40 degrees. I told him to send me the board. When I received it I realized the problem, the BGA was as shiny on top as a mirror. The IR wavelengths were bouncing off. Profiling in a convection oven showed Delta's of about 10 - 12 degrees C.

Hope this helps.

Brian

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Tony

#12745

Re: BGA PROFILE | 2 February, 1999

| Hi everybody. | Somebody know any consideration or special care to make a profile for BGA's. | | any advice is aprecied. | | thanks | Al Carrillo | | | | Al, I have been using the same process as Justin recomendations. I have been verry succesful doing it that way, first I drill two or three on various locations of the land pattern of the BGA. I try to drill the hole as close to pad as possible than I attach it with a small amount of high temp solder. Once I have attach my thermal couples a cover the holes with chip bonder. Than I dispence solder paste on my board, than mount the BGA and reflow with my Data Logger.

Every time I develope a profile I X-Ray the BGA and look for any Solder Void.. Solder Void are caused by having a hotter profile.

But like I said Justin and Brian can better discrive the optimum process to profile BGAs

Thanks

Tony A

reply »

gcollier

#12746

Re: BGA PROFILE | 2 February, 1999

| | Hi everybody. | | Somebody know any consideration or special care to make a profile for BGA's. | | | | any advice is aprecied. | | | | thanks | | Al Carrillo | | | | | Hi Al, | A BGA should be looked at just like any other surface mount device. However, just like any surface mount device, the different types of BGAs are going to have different thermal characteristics with relation to reflow. For example, the CBGA and SBGA (EBGA) is going to pull a lot of heat into the component and away from the substrate. These types of devices cause "cool" spots on your board. The best way to develop a profile is to phyisically insert thermocouples into the device. Drill through your substrate at a pad location. Use an .020" drill bit. Insert a thermocouple up into the substrate from underneath the board. Use #5 thermocouple wire. The total diameter is about .020". Paste up the location, populate it and run the board through your process. Record the time vs. Temperature data and adjust your profile accordingly. | Watch out for overheating the PBGA packages. Also, make sure the PBGA packages stay "dry". Pay close attention to the moisture sensitivity levels and bake the components if necessary. A good indicator that something is wrong on a PBGA process, is the coplanarity of the device after it is soldered. The component should collapse evenly on the substrate. Don't be too intimidated by the BGA package. To quote the infamous Phil Zarrow, "BGAs, what's the BFD?" | | Regards, | Justin Medernach |

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