When You Really, Really Want to Upgrade a Tiny Notebook 104
Benz145 writes "The famous Sony VAIO UX UMPC may have been cancelled a few years back by Sony, but the community at Micro PC Talk won't let it die. Modder Anh has carefully removed the relatively slow 1.33Ghz Core Solo CPU and installed a much faster Intel Core 2 Duo U7700 (a process which involves reballing the entire CPU). On top of this, he managed to install an incredibly small 4-port USB hub into the unit which allowed for the further instillation of a Huawei E172 modem for 3G data/voice/SMS, a GPS receiver, and a Pinnacle HD TV receiver. All of this was done without modifying the device's tiny external case. Great high-res pictures of the motherboard with the modded hardware can be seen through the link."
Re:Reballed? (Score:3, Interesting)
I guess the rest of the process is to very carefully drop the chip package where you want it to go, and convince the solder to melt. How do you do that? You mentioned a "reflow oven"? I Googled that, and there are lots of different ovens out there.
If you're using old-fashioned lead/tin solder you don't have to be all that careful about the alignment: if you have 10% overlap between the ball and the solderpad on most all the pads, the capillary action of the solder will cause the bga to self-align. (I do this on a regular basis with smaller but similar chips.) Now, if you're using modern no-lead solder it's more difficult. With a BGA you can do an okay job of alignment with a boom microscope set at an angle so you can see under the edge of the chip to the first row of balls: if you have opposite corners on the pads you're good.
And I use a hotplate and a thermocouple taped adjacent to the chip with the tip touching one of the pads. You don't want to overheat the chip itself -- no higher than 260C if you can possibly manage it. A lab hotplate is faster than a toaster oven, and you need to get the heat up fast enough the flux doesn't boil off before the solder reflows. Ideally you'd like it to reflow and hold above the liquidus of the solder (which is about 220C for lead and about 240C for no-lead) for 30 seconds, but managing that without going over 260C is pretty difficult. Then you cool it down pretty quickly. I use a hairdryer with the heat turned off so it's just blowing scads of cool air.
Likewise, by the way, I use a hotplate for adhering the balls to the BGA, rather than a hot air gun -- it's more predictable, temperature-wise.
Well, okay, all the above should be put in the past tense since as of a week ago we now have an OKI bga rework station, with a vision system that aligns the chip/board and places it, and a controllable temp profiler, and it's awesome. But I do have three years' experience hand-placing leadless chips and micro-SMD's, so I know a thing or two about it.