We had already seen the defective card in all its glory at Igor’s, even before I had laid a hand on it. When I then connected the card to the testbench on arrival, I could observe exactly the behavior that Igor had already reproduced before me. So, it’s time to get out the screwdriver, blank out dear Navi 21 and then pay attention to the “what happens next” principle! After dismantling the heat sink, optical inspection follows, first by eye, then by microscope. I could already determine that the card is not completely intact mechanically. Some screw heads are worn out, one SMD header for the LEDs is torn off and untraceable, the PCB itself has mechanical deformations, so it’s a bit out of shape, and also otherwise the card makes a rather suffering impression.
The next step is a closer visual inspection of the usual suspects. By the description that the card triggers different circuits when switched off, sounds to me first of all like a coil short circuit or also a defective diode. The latter should actually prevent just such a thing. Here we inspect the jumper resistors, which tend to break due to thermal stress, because they have 0 Ohm resistance:
By measuring with a multimeter, we can confirm here that the resistors conduct without problems. Next, we perform a blocking test on the power diodes and determine if they are behaving as they should. Result: All diodes perform exactly what they were installed for.
The next step takes us under the microscope to find out if perhaps PWM and controller chips have burned out on such a small area that we can’t see it with our eyes. Except for small residues of thermal pads, all ICs look completely normal. Thanks to the manufacturer’s data sheet for the mentioned components, I was able to measure a correct signal voltage and also the curve with an oscilloscope and found them to be flawless.
All the major components have no obvious fault, so the mechanical deformation of the PCB gave me the idea that maybe we have a problem with the PCB itself, because that also happens a lot. In this case, we don’t have much choice but to either selectively or automatically put the card into the reflow oven. Tensions and also cold solder joints, as well as torn balls under the chips can be restored in this way.
If we wanted to check the integrity of the traces ourselves, we would either have to take well over 10,000 measurements or hold the board under an X-ray machine with magnification. However, both are out of the question, because both are much too time-consuming for normally just under 70 Euros repair fee. To give you an idea how sensitive to mechanical stress such a high performance board with typically eight layers is, I show you here a typical layer structure with its functions:
All layers, which are orange, red and blue, have a copper thickness of only 35 µm, so you can imagine how quickly the traces can break at a width of 0.127 mm. Soldermask describes the solder mask that also gives the PCB surface its color. High speed signal layer is a dedicated copper layer as discussed and prepreg describes a textile fiber semi-finished layer to insulate and reinforce the mechanical properties of a PCB. GND-Plane means that here the common mass is distributed over a large area, which also benefits the thermal dissipation properties. Core is an aluminum core that makes the PCB insensitive to mechanical damage and greatly improves the thermal dissipation of the components.
On the next page it is then (loosely based on Tim Mälzer) “Baking is not cooking” and that’s exactly why I show after turning the page, how such a thing is done RIGHT, even if now one or the other YouTuber certainly gets moist eyes. Because for baking you also need a certain baking aid from the tube. Otherwise, with a little luck, there will be unhappy roast piglets. By the way, omitting the necessary flux also explains why so many even “cured” cards succumb to the disease again after a shorter time. You just don’t have it. New page please!
- 1 - Graphics card death, eBay and the circumstances
- 2 - Initial findings and head shaking
- 3 - Wound dressing and referral to specialist
- 4 - ELITKon who? Things that only the specialist can manage
- 5 - Disassemble, test and measure
- 6 - Flux, Reflow and the Miraculous Recovery
- 7 - Commissioning, summary and hospital address
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