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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


SRT BGA Rework

Mr Mariscal

#13240

SRT BGA Rework | 18 December, 1998

I have developing a BGA Process and having problems with 310 IO PBGA reflowing. I am achieving good wetting exept 2 to 5 balls on the outer perimeter I have a good profile my air flow is set per mfg spec, the stange thing is that it does not happen every time I reflow a part the damm thing is inconsistant.

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phillip hunter

#13241

Re: SRT BGA Rework | 18 December, 1998

| I have developing a BGA Process and having problems with | 310 IO PBGA reflowing. I am achieving good wetting exept | 2 to 5 balls on the outer perimeter I have a good profile | my air flow is set per mfg spec, the stange thing is that | it does not happen every time I reflow a part the damm thing is inconsistant. | | | | Can you give some specs on your profile: # of T/C's and location Peak temps. Max time above 183 C Process temps and times. Aproximate mass of board (in grams) Height of core above PCB

I have an SRT Summit 2000 which I dearly love. Here are some tips: Verify the PCB is perpendicular to the pickup tube. Use the plate and machinest square method. Verify the pickup tube is not bent. The manual describes how to do this. Verify the break-away sensor is working properly. Are you using place with "Zero-force" or are you using a programable force? Describe your part accurately in the software. Especially Z axis. Pre-heat your core and lower heater with conditional statements in your process sequences. The first PCB will have a different profile when the machine starts from room temp vs. the second board which has the heaters/machine heated up. I can email you a copy of my sequences if you like. Verify the lower heater plate is parallel to the PCB fixture rails. Simply use a ruller. If you try to use the support pins on an uneven heater - it will tilt your PCB. Even the simplest board can cause complex problems. Verify site preperation and solder masking with a microscope prior to pasting. Make sure your site is cleanly prepaired - that is remove all solder bumps. Otherwise your paste deposition will vary greatly. If your PCB is warped all bets are off! Its a crap shoot. Be consistent. Follow procedure. BGA's are sometimes called the most foregiveable copmponent to place. Wanna bet! Accuracy is a function of process capability. Run the calibration reticle. It couldn't hurt. I hold my machine to +/- 0.002 in. at 3 sigma. I verify calibration every 4 weeks. The optics do drift especially since their mounted over the heaters! Also, if you have the split mirror verify that cal., too. Don't be in a hurry. Even the simplest BGA will require between 4 to 6 minutes for a total reflow process. Even longer if your process defines a longer solidify sequence. Watch large array plastic BGA;s They tend to "Flex" when heated too rapidly. If you want more info call SRT. Ernie or Rey LaFleur in Tech support. These guys are experts and can work magic (black magic I suspect). Enjoy.

Phillip Hunter Engineering Support Technician Laughlin Wilt Group Inc.

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Miguel Mariscal

#13242

Re: SRT BGA Rework | 20 December, 1998

I would love to send a copy of my profile thanks, our machine is also a Summit 2000.

| | I have developing a BGA Process and having problems with | | 310 IO PBGA reflowing. I am achieving good wetting exept | | 2 to 5 balls on the outer perimeter I have a good profile | | my air flow is set per mfg spec, the stange thing is that | | it does not happen every time I reflow a part the damm thing is inconsistant. | | | | | | | | Can you give some specs on your profile: | # of T/C's and location | Peak temps. | Max time above 183 C | Process temps and times. | Aproximate mass of board (in grams) | Height of core above PCB | | I have an SRT Summit 2000 which I dearly love. Here are some tips: | Verify the PCB is perpendicular to the pickup tube. Use the plate and machinest square method. | Verify the pickup tube is not bent. The manual describes how to do this. | Verify the break-away sensor is working properly. | Are you using place with "Zero-force" or are you using a programable force? | Describe your part accurately in the software. Especially Z axis. | Pre-heat your core and lower heater with conditional statements in your process sequences. The first PCB will have a different profile when the machine starts from room temp vs. the second board which has the heaters/machine heated up. I can email you a copy of my sequences if you like. | Verify the lower heater plate is parallel to the PCB fixture rails. Simply use a ruller. If you try to use the support pins on an uneven heater - it will tilt your PCB. | Even the simplest board can cause complex problems. Verify site preperation and solder masking with a microscope prior to pasting. Make sure your site is cleanly prepaired - that is remove all solder bumps. Otherwise your paste deposition will vary greatly. | If your PCB is warped all bets are off! Its a crap shoot. | Be consistent. Follow procedure. BGA's are sometimes called the most foregiveable copmponent to place. Wanna bet! Accuracy is a function of process capability. | Run the calibration reticle. It couldn't hurt. I hold my machine to +/- 0.002 in. at 3 sigma. I verify calibration every 4 weeks. The optics do drift especially since their mounted over the heaters! Also, if you have the split mirror verify that cal., too. | Don't be in a hurry. Even the simplest BGA will require between 4 to 6 minutes for a total reflow process. Even longer if your process defines a longer solidify sequence. Watch large array plastic BGA;s They tend to "Flex" when heated too rapidly. | If you want more info call SRT. Ernie or Rey LaFleur in Tech support. These guys are experts and can work magic (black magic I suspect). | Enjoy. | | Phillip Hunter | Engineering Support Technician | Laughlin Wilt Group Inc. |

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