Unbanal way to fix hardware error
At the dawn of the era of Habrahabr I was fortunate to participate in the development of a device that was not simple at that time. It was a small 10-layer board jam-packed with electronic components.
After the production of an experimental batch revealed a serious problem. An error was found due to which the NAND memory did not work. Since NAND was the only option to boot, the device, despite the performance of the other components, turned out to be absolutely useless.
It was necessary to solve the problem. If you find errors in the program, you can infinitely apply patches to it. With hardware errors, “patches” in the form of cut tracks and jumpers do not always help to cope. What to do if two rows of conclusions are mixed up under the BGA chip?
The revision of the board takes time and money. Since, resources were limited I wanted to do without it. We had to put something under the BGA chip to fix the pinout. The thought came to my mind to make an adapter in the form of a double-sided printed circuit board installed under the BGA chip.
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It turned out to be some kind of analogue of the now widespread PoP technology. Despite its seeming simplicity, the adapter had to be manufactured to a high accuracy class, since small diameter of vias and small width of conductors are required.
There was a desire to make everything quickly, so we were looking for the production of printed circuit boards alongside. Fortunately, there was one organization that agreed, without any guarantees, to try to make this adapter.
A few days later the adapters were ready and they passed the electrical test successfully.
The appearance of the adapter:
To repair it was necessary to perform the following steps:
Top view of the repaired board:
Side view of the board:
Fortunately, after the operation was completed, all devices without exception started working. A few years later they are still working for the good of mankind.
Reliability because of this "patch" is not affected. When the device is shaken, it is not enough that they heat themselves.
After the production of an experimental batch revealed a serious problem. An error was found due to which the NAND memory did not work. Since NAND was the only option to boot, the device, despite the performance of the other components, turned out to be absolutely useless.
It was necessary to solve the problem. If you find errors in the program, you can infinitely apply patches to it. With hardware errors, “patches” in the form of cut tracks and jumpers do not always help to cope. What to do if two rows of conclusions are mixed up under the BGA chip?
The revision of the board takes time and money. Since, resources were limited I wanted to do without it. We had to put something under the BGA chip to fix the pinout. The thought came to my mind to make an adapter in the form of a double-sided printed circuit board installed under the BGA chip.
')
It turned out to be some kind of analogue of the now widespread PoP technology. Despite its seeming simplicity, the adapter had to be manufactured to a high accuracy class, since small diameter of vias and small width of conductors are required.
There was a desire to make everything quickly, so we were looking for the production of printed circuit boards alongside. Fortunately, there was one organization that agreed, without any guarantees, to try to make this adapter.
A few days later the adapters were ready and they passed the electrical test successfully.
The appearance of the adapter:
To repair it was necessary to perform the following steps:
- Using a soldering dryer, raise the BGA chip;
- Clean the board surface;
- Using the stencil to roll the balls on the underside of the adapter;
- Using a hair dryer, put the adapter on the board;
- Using the stencil to recover the balls on the BGA chip;
- Install the BGA chip on the upper side of the adapter and warm it up again with a hairdryer.
Top view of the repaired board:
Side view of the board:
Fortunately, after the operation was completed, all devices without exception started working. A few years later they are still working for the good of mankind.
Reliability because of this "patch" is not affected. When the device is shaken, it is not enough that they heat themselves.
Source: https://habr.com/ru/post/165173/
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