The pain of vias, isn’t it just a window opened in the via, how can it cause a short circuit?

yvonneGan

The pain of vias, isn’t it just a window opened in the via, how can it cause a short circuit? [Copy link]

Mr. Gaosu's original article | Wang Huidong

The senior brother often said that in the board factory, drilling is the soul of the circuit board, and the via is the soul of the soul. There are many stories about vias, so many that it would take three days and three nights to tell them all. Let's talk about one of them today.

The via is the cinnabar mole on the chest of the design engineer, and the bright moonlight in front of the window.

The function of the via on the circuit board is not just as simple as conduction, it also has other functions, such as heat dissipation.

——Preface

The most important thing in life is to have a beautiful dream and a good way to realize it.

Lin Ruyan has always wanted to be a big cow in the PCB design industry. In order to prevent the goddess in his heart from looking down on him, Zhao Ligong is also working hard to catch up.

In order to realize this dream, in addition to strengthening their own learning and participating in more project designs, constantly summarizing, they also have to visit and study on-site at the circuit board factory from time to time. Maybe some things are puzzled when designing, but you can understand many truths by taking a look at the factory.

Today is Saturday, and it is rare to have some free time. The senior brother led a team to visit and study at his own circuit board factory.

Ruyan and Zhao Ligong followed the senior brother, listening carefully, stopping to watch from time to time, and taking notes from time to time.

In the quality workshop of the solder mask process, Zhao Ligong suddenly saw a girl, a beautiful girl wearing a dust-proof coat, sitting at the table, tapping something on the board seriously.

She lowered her head and stared at the board with a pair of phoenix eyes, her long eyelashes shaking from time to time, and the highlight light under the magnifying glass shone on her fair face, revealing a charming light. She was beautiful and extraordinary, pure and innocent, independent, noble and holy, just like a fairy in a painting.

Zhao Ligong followed the senior brother to the girl and finally saw it clearly. She took a toothpick and dipped it in solder mask ink on the vias of the board, gently smearing it, smearing it...

Zhao Ligong whispered to the senior brother, the board was done, and ink was still applied on the vias. Can it be handled?

The senior brother said that the via pads should be covered with ink. If the number of vias is relatively small, it can be reworked.

Why do we need to cover the via pads now? Why didn’t we consider directly filling the vias with oil when designing it?

The girl seemed to have heard the question raised by Ligong Zhao. She stopped filling the oil, looked up at Ligong Zhao and the others, and then told a story.

She said that she was a PCB design engineer for a product company and came to the PCB factory to help with rework and cover the windows of the via pads with ink.

At the beginning, she received a product project from the company, which was a small power amplifier board.

Taking into account the power consumption and heat dissipation of the power amplifier board.

She deliberately used 16mil vias on the entire board, and they were the kind of vias with windows.

The following figure shows the package design of the vias:

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The structural engineer also took the heat dissipation of the board into consideration when designing it. A stainless steel casting was specially added under the amplifier template.

One is the full-board via opening, and the other is to add a heat sink on the window area.

When these two objects are put together, it is possible to really create sparks.
It is really a coincidence that when the actual board was made, there were indeed windows for vias of different networks in the same area of the board.

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Then install the metal heat sink. When you power on the test , there is no doubt that something is wrong here. The picture below shows the PCB board after mounting.
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The board is unusable now, but the project is urgent and we cannot remake the board. We can only put ink on the area where the vias are opened, let it pass the test first, and then find a way to rework the vias on other boards.

Usually, when you have quality problems, your leader not only educates you ideologically, but also warns you in other ways. In order to make her have a deeper impression and remember it for life, and also for the delivery of the board, let her go to the front line of the factory and rework it herself, which is very hard on her mind and body. The picture below shows the appearance of the vias after coating.
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Ligong Zhao listened in a daze, staring at the beauty, lost in thought...

In Ruyan's eyes at this time, Ligong Zhao looked like a fangirl, so she gently approached Ligong Zhao.

Ruyan came gently, she did not bring clouds, but brought a jar of jealousy.

"What are you looking at, handsome boy?" Ruyan asked softly.

"If you haven't learned enough, you can help the beauty here and add oil to the via window."

As she spoke, she put her hand on the soft flesh on Ligong Zhao's waist, and then said:

"Ligong Zhao, look at that multimeter, it can measure resistance and voltage. I haven't tested it for a long time."

Then she pinched the fat on Ligong Zhao's waist and made a rotating shape, first measuring the resistance value by turning three circles, then testing the current by turning two circles. Should I test the voltage again? The little witch was still debugging with relish.

Zhao Ligong was sweating profusely from the pain and shouted, "No more testing, Ruyan. Let's go and visit the next process."

Zhao Ligong pulled Ruyan and ran away desperately...
This is exactly:

Don't panic when designing vias,
confirm the plugging of holes and the opening of windows.
It is difficult to rework the finished product, and
the slightest mistake will lead to tears.

This content is originally created by yvonneGan , a netizen of EEWORLD forum . If you want to reprint or use it for commercial purposes, you must obtain the author's consent and indicate the source