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Is it possible to rework this BGA socket?

Steve Gregory

#13084

Is it possible to rework this BGA socket? | 6 January, 1999

Hey All you Einsteins out there!!

I gotta' problem...('course you do Steve, or you wouldn't be bugging the TechNet now would you?) I had a phone call from a acquaintance of mine wanting to bring two prototype boards over to rework a BGA socket, (actually there's two on each board). No problem I said, bring em' on over. BOY O' BOY! Did I ever open my big yap this time! These sockets aren't like anything I've ever reworked before.

They're from a company called CTI, and they're called "Z-Lok" sockets, and they're surface mount. They've got this big beefy plastic housing that goes all the way down almost to the surface of the PCB, and has a little metal handle off to one side that actuates some little "arms" inside the socket that grab each ball on the BGA for good contact, but won't deform the balls so you can still use the BGA directly on a board after being in the socket if you wanted to.

The problem is that the socket has two locating pins on the bottom, which are used to accurately locate the socket (into holes drilled in the fab) when the board was first built.

There was a big time screw-up by either the fab vendor, the board lay-out person, or the dimensional drawing for the socket itself, but what has happened is that the BGA's contact pins are now soldered one row off! I'm being asked if I can pull this socket up, clip the plastic pins off, and put it back down on the board the way it's supposed to go...sounds like fun huh? This board is 12.5" X 18.5" and .065" thick...and the sockets are in the middle of the board.

I called back to CTI (They're in Indiana, but closed now) to talk with somebody there to find out how to rework one of these monsters...if it's possible.

I personally think that the socket is not meant to be reworked, it's a test socket and has to cost at least a hundred bucks or so. I think that once they're soldered down that's it. But I thought I'd ask ya'll to see if any of you have ever had to attempt something like this. There's only two of these boards, I don't wanna take a chance turning em' into scrap if I can help it...

Thanks youse' guys!!

-Steve Gregory-

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Dave F

#13085

Re: Is it possible to rework this BGA socket? | 6 January, 1999

| Hey All you Einsteins out there!! | | I gotta' problem...('course you do Steve, or you wouldn't be bugging the TechNet now would you?) I had a phone call from a acquaintance of mine wanting to bring two prototype boards over to rework a BGA socket, (actually there's two on each board). No problem I said, bring em' on over. BOY O' BOY! Did I ever open my big yap this time! These sockets aren't like anything I've ever reworked before. | | They're from a company called CTI, and they're called "Z-Lok" sockets, and they're surface mount. They've got this big beefy plastic housing that goes all the way down almost to the surface of the PCB, and has a little metal handle off to one side that actuates some little "arms" inside the socket that grab each ball on the BGA for good contact, but won't deform the balls so you can still use the BGA directly on a board after being in the socket if you wanted to. | | The problem is that the socket has two locating pins on the bottom, which are used to accurately locate the socket (into holes drilled in the fab) when the board was first built. | | There was a big time screw-up by either the fab vendor, the board lay-out person, or the dimensional drawing for the socket itself, but what has happened is that the BGA's contact pins are now soldered one row off! I'm being asked if I can pull this socket up, clip the plastic pins off, and put it back down on the board the way it's supposed to go...sounds like fun huh? This board is 12.5" X 18.5" and .065" thick...and the sockets are in the middle of the board. | | I called back to CTI (They're in Indiana, but closed now) to talk with somebody there to find out how to rework one of these monsters...if it's possible. | | I personally think that the socket is not meant to be reworked, it's a test socket and has to cost at least a hundred bucks or so. I think that once they're soldered down that's it. But I thought I'd ask ya'll to see if any of you have ever had to attempt something like this. There's only two of these boards, I don't wanna take a chance turning em' into scrap if I can help it... | | Thanks youse' guys!! | | -Steve Gregory- | Youse: This is SMTnet Steve. Sacrifice the socket. By the time you finish putzing-around removing the balls to get the socket off the board, replacing the lifted pads on the board, and reballing the socket; you've burnt the $100 that the socket costs. Good Luck bud. TTYL Dave F

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Steve Gregory

#13086

Re: Is it possible to rework this BGA socket? | 6 January, 1999

| Youse: This is SMTnet Steve. Sacrifice the socket. By the time you finish putzing-around removing the balls to get the socket off the board, replacing the lifted pads on the board, and reballing the socket; you've burnt the $100 that the socket costs. Good Luck bud. TTYL Dave F | Hey ya' Dave!

I know, I know...I messed-up and forgot to change that first part before I posted here. I posted to the TechNet first, and then did a copy and paste in here 'cause I was too lazy to type it all out again...I knew I was gonna take some hits for that one! (GRIN)

You're right about the socket...but this one's weird. It doesn't have balls on for the contacts on the board, they're little "L" shaped leads that come outta the bottom of the socket and solder to the pads on the board... strange huh? I'm not so sure I can get the damn thing off without putting a big divot or whoop-de-doo around where the socket is from the heat.

The leads that solder to the board go up inside the socket and is surrounded by the socket body plastic through a grid pattern of holes in the socket...so there's really not any exposed area on the leads for any heat to get to. Plus, like I said the plastic body goes down till it's almost flush with the surface of the PCB, so that's going to block any heat from getting towards the pins in the center...I was hoping that maybe if I directed the heat at the top of the socket at the contact points where the BGA balls mate with the pins, that I might get enough heat transfer down through the pins to reflow the joints enough where I could pull the socket up. But I don't think that's gonna work too good because there's some sort of mechanical linkage on the pins at the top that allow it to open and close to grip the BGA balls when the part is put in the socket. So that means that I won't get the kind of thermal transfer that you would get from a solid lead.

But here's the quandry, there's ONLY two of these boards. If I can't get them off and back on again without dusting the boards, that means he's gotta go out and order two more fabs and re-build them again...and you probably know how much each board costs when you only want a few.

But, that may be his only choice...I've never had to try and rework something like this before...and I still have this gut feeling that the socket was never meant to be reworked, but I won't know that for sure until I talk to somebody at CTI.

But hey, thanks anyway pardner!!

Sorry 'bout my little faux pax in my last post!!

-Steve "I don't like sockets" Gregory-

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Dave F

#13087

Re: Is it possible to rework this BGA socket? | 6 January, 1999

| | Youse: This is SMTnet Steve. Sacrifice the socket. By the time you finish putzing-around removing the balls to get the socket off the board, replacing the lifted pads on the board, and reballing the socket; you've burnt the $100 that the socket costs. Good Luck bud. TTYL Dave F | | | Hey ya' Dave! | | I know, I know...I messed-up and forgot to change that first part before I posted here. I posted to the TechNet first, and then did a copy and paste in here 'cause I was too lazy to type it all out again...I knew I was gonna take some hits for that one! (GRIN) | | You're right about the socket...but this one's weird. It doesn't have balls on for the contacts on the board, they're little "L" shaped leads that come outta the bottom of the socket and solder to the pads on the board... strange huh? I'm not so sure I can get the damn thing off without putting a big divot or whoop-de-doo around where the socket is from the heat. | | The leads that solder to the board go up inside the socket and is surrounded by the socket body plastic through a grid pattern of holes in the socket...so there's really not any exposed area on the leads for any heat to get to. Plus, like I said the plastic body goes down till it's almost flush with the surface of the PCB, so that's going to block any heat from getting towards the pins in the center...I was hoping that maybe if I directed the heat at the top of the socket at the contact points where the BGA balls mate with the pins, that I might get enough heat transfer down through the pins to reflow the joints enough where I could pull the socket up. But I don't think that's gonna work too good because there's some sort of mechanical linkage on the pins at the top that allow it to open and close to grip the BGA balls when the part is put in the socket. So that means that I won't get the kind of thermal transfer that you would get from a solid lead. | | But here's the quandry, there's ONLY two of these boards. If I can't get them off and back on again without dusting the boards, that means he's gotta go out and order two more fabs and re-build them again...and you probably know how much each board costs when you only want a few. | | But, that may be his only choice...I've never had to try and rework something like this before...and I still have this gut feeling that the socket was never meant to be reworked, but I won't know that for sure until I talk to somebody at CTI. | | But hey, thanks anyway pardner!! | | Sorry 'bout my little faux pax in my last post!! | | -Steve "I don't like sockets" Gregory- | | Steve: Hey there's no mercy out here in the big time!!! Yer right, it sounds like one weird socket. Hey when I say sacrifce that dude, I'm not thinkin' solderin' iron pard. I'm talkin' drummel tool ... cut the plastic away so that you can see and get at the solder connections and clean-up the board without torturing it too much. Push on. TTYL Dave F

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Chris G.

#13088

Re: Is it possible to rework this BGA socket? | 6 January, 1999

| Hey All you Einsteins out there!! | | I gotta' problem...('course you do Steve, or you wouldn't be bugging the TechNet now would you?) I had a phone call from a acquaintance of mine wanting to bring two prototype boards over to rework a BGA socket, (actually there's two on each board). No problem I said, bring em' on over. BOY O' BOY! Did I ever open my big yap this time! These sockets aren't like anything I've ever reworked before. | | They're from a company called CTI, and they're called "Z-Lok" sockets, and they're surface mount. They've got this big beefy plastic housing that goes all the way down almost to the surface of the PCB, and has a little metal handle off to one side that actuates some little "arms" inside the socket that grab each ball on the BGA for good contact, but won't deform the balls so you can still use the BGA directly on a board after being in the socket if you wanted to. | | The problem is that the socket has two locating pins on the bottom, which are used to accurately locate the socket (into holes drilled in the fab) when the board was first built. | | There was a big time screw-up by either the fab vendor, the board lay-out person, or the dimensional drawing for the socket itself, but what has happened is that the BGA's contact pins are now soldered one row off! I'm being asked if I can pull this socket up, clip the plastic pins off, and put it back down on the board the way it's supposed to go...sounds like fun huh? This board is 12.5" X 18.5" and .065" thick...and the sockets are in the middle of the board. | | I called back to CTI (They're in Indiana, but closed now) to talk with somebody there to find out how to rework one of these monsters...if it's possible. | | I personally think that the socket is not meant to be reworked, it's a test socket and has to cost at least a hundred bucks or so. I think that once they're soldered down that's it. But I thought I'd ask ya'll to see if any of you have ever had to attempt something like this. There's only two of these boards, I don't wanna take a chance turning em' into scrap if I can help it... | | Thanks youse' guys!! | | -Steve Gregory- | Steve,

I too once opened my mouth before knowing all the facts. My story is exactly the same as yours. I was asked to build a couple of prototype boards. I was asked if I could place 16 mil pitch QFPs. I said no problem. Done it many times before.

Well, I was presented with the exact same part you are describing only the QFP style socket was for a QFP. It had the same plastic sides which covered most of the legs and had two plastic alignment pins.

Since this component was not a normal 16 mil pitch QFP and I could not spend a lot of time taking down production equipment attempting to machine place this component, I decided to hand place the socket. How difficult could this be, I only had to build a couple of boards.

I solder printed the board and went to place the QFP style socket onto the board. When I attempted to align the plastic pins into the holes in the PCB, the pins did not properly align the legs to the solder pads. They were in my case as in yours about a row off. The PCB was not designed correctly. So I cut the legs off and hand placed without the aid of the plastic pins. Since the socket has sides which cover most of the legs, it was difficult to align the socket to the solder pads.

When the two boards came out of the reflow oven, the sockets were not aligned very well and had lots of solder bridges. I guess I expected a miracle. Now how do I rework this thing. I didn't. I removed the socket and soldered the QFP which was to go into the socket directly on the board.

Now here comes the process I am not proud of. Since I did not have any good rework equipment to remove the socket, I devised an embarassing method of socket removal. I took two alligator clamps and placed them such that the areas you press with your fingers, on the clamps, were underneath the socket body between the PCB and socket body. This put upward pressure on the socket. I then placed the completely populated circuit board into the reflow oven. I watched, with a flashlight, as the board went through the oven. I really thought I would have solder pads ripped off the PCB due to one soldered down leg melting before the other. I also thought that if the socket let go it would fly off the PCB and knock other components off the board when it landed. The socket popped about 3 inches into the air and landed upsidedown directly where it was originally soldered down. It was really amazing and extremely funny. I inspected the PCB and all solder pads were intact. I ran the other boards with alligator clips jammed under the socket and it too worked out well.

Sorry for being longwinded but your story was so similar to mine that I had to share my story.

I believe you could possibly remove this socket with an AirVac DRS22 rework station. The station has a splt prism to show both the component bottom as well as the PCB. This would aid in reinstalling the socket. I believe the socket could be removed as well with the DRS22. The heat can be controlled very well as to not damage the PCB. If you do not have one of these, you will have to come up with another method.

Thanks,

Chris G.

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