YLOD, Theories, and an X-Ray Inspection –
So, I've spent the last couple of weeks trying to investigate why the YLOD happens to the PS3. I've been to many forums, read multiple threads, and really wanted to get to where the actual root cause was.
Now I've read many theories regarding solder opens, solder cracks, voiding, and solder bridging on the RSX. I wanted to see which one of these theories were true, and I wanted to see if the YLOD issue was something the folks over at SONY could fix during manufacturing.
So, I decided to buy a YLOD PS3 (80 gig, CECHK01) to test some of these theories, and because I wanted to X-Ray the motherboard. FYI, in the manufacturing process, the X-ray is used to inspect BGA components, like the RSX to find defects. If there is net access to the chip, boundary scan could also be run on the part through a JTAG TAP to ensure further reliability.
With the heatsink on top of the RSX, I wasn't able to get a good look look at the RSX through the X-Ray. The heatsink would shadow the RSX's pins and would make it look dark through the X-Ray. So, I decided to take off the heatsink on top of the RSX. The results are attached below.
You could see significant amount of pins had solder voids within each ball. While solder voids aren't necessarily defects, the voiding that was witnessed within each solder ball was less than 25%, which most manufacturers pass as acceptable.
There was some evidence of insufficient reflow in a few pins, and you could identify this with the "jagged" perimeter of the solder ball. Again, this isn't necessarily bad, as the pin could still be soldered and deemed acceptable.
Also, in the other picture, you could see some real small solder cracks, which could be characterized as a defect.
Unfortunately, even after the X-Ray inspection, what I found was quite inconclusive. BGA components are difficult to inspect and I don't think SONY could've caught many defects even with a trained X-Ray operator. YLOD's are most likely caused by insufficient reflow on the pins, solder cracks, or some other reason. I see no evidence of bridging or shorting between any of the pins.
Let me know what your thoughts are and if you all would like more pictures!
PS3 - CECHA01 60GB 3.55 CFW Kmeaw
PS3 - CECHH01 40GB OFW
PS3 - CECHK01 80GB YLOD/Research
PS2 - SCPH-30001 - FreeMCBoot
PSX - SCPH 5501 (Repaired lens and fuse)
PSP-1000 - DA 5.00 M33-6