I've done whatever I want

Chapter 140 Abnormal cracks in wafer cutting
The sun is just right, the breeze is not dry.

Jiang Hua walked straight to the smoking area with the steps of disowning his relatives, leaned against the white wall, bit a cigarette with his teeth, put his hands in his trouser pockets, shook his head from time to time, and looked around, looking around. He looks so handsome.

The largest team in this factory is the production department. As the former supervisor, he is the second child in the production department.

The second child will look like the second child. Recently, he has developed the habit of not recognizing his relatives when walking. When smoking, he doesn't bother to use his hands, so he keeps smoking with his teeth. When the cigarette burns to the edge of his mouth, he will Pulling back his lips, revealing a row of yellowed teeth.

"Old classmate, what's the matter?" Jiang Hua asked, tilting his head.

"Yesterday, engineers and technicians were arranged to use fake films for process verification. I don't know what's going on?" Xin Tong flicked the soot with his fingers and said.

"Let's go to the workshop together later!"

"I have a vague feeling that this project is not simple. We must not take Motorola's project lightly." Xin Tong raised his head and looked up at the blue sky.

"The customer will come to the wafer next week. It's a donkey or a horse. You can tell after pulling it out for a walk."

After smoking, the two went straight to the wafer thinning workshop.

There was only one process technician present at the scene, and Jiang Hua grabbed him immediately: "Yesterday, I arranged for your process to be verified. Have you done 150μm thinning verification?"

"Boss Jiang, we made a slice yesterday, and found no problem with thinning, but I heard that there was a crack during cutting. Gaogong Luo found Boss Xie, and they are discussing the solution to the problem."

"Really?" Xin Tong's heart tightened.

In the past, the thinning in the workshop was only 220μm, but that was for consumer electronics. The MPC5200 is an automotive-grade product with high reliability requirements. The thinner it is, the easier it is to dissipate heat. I didn’t expect that there would be a problem with the 150μm thinning.

Fortunately, this is just a fake verification. If you directly use the customer's experimental film for verification, it is estimated that the experimental film will be used up soon, and the process of re-applying for the experimental film will be delayed by at least a month.

"Let's go, Xie Gong must be in the engineering department. Go to the engineering department to find him!" Jiang Hua said.

Xin Tong nodded.

In the conference room of the Engineering Department, Luo Gaogong was indeed discussing technical issues.

"Manager Xin, you came at the right time. We are discussing the crack cutting of the Motorola project." Luo Gaogong waved to Xin Tong.

Xin Tong nodded and found a seat to sit down.

"We have changed to two-knife cutting, and the stress on the chip has been reduced to the lowest level. Unexpectedly, cracks still appeared in the wafer." WS King Xie Jianfeng was a little disappointed.

"Xie Gong, is the two-knife cutting process mature?" Luo Gaogong asked.

"We use this process to cut 220μm wafers, and there is no problem at all. Comparative experiments show that it is still related to the thickness of the wafer, and has nothing to do with the cutting process." Xie Jianfeng said.

Xin Tong raised his head and glanced at him, thinking that the thank-you homework was done solidly, and he deserved to be a technical expert at the level of a heavenly king.

"So, the stress still comes from the thinning process, so I want to ask you, have you ever measured the warpage of the wafer after thinning?" asked Luo Gaogong.

Xin Tong cast a reverent gaze, Luo Gaogong's logical reasoning ability is really too strong, because after the wafer is stressed, there will definitely be clues to be traced, and a slight deformation will definitely not escape.

"Boss, we have measured the warpage of the wafer to be almost 400μm!" Xie Gong replied.

Xin Tong secretly sighed. He really didn't expect Xie Gong to have considered the stress of thinning. The king is the king, but isn't 400μm a bit too big?
"Have you measured the warpage of the 220μm wafer after thinning?" Xin Tong raised his head and asked.

"To tell you the truth, we have also measured the 220μm wafer, and the warpage is around 200μm!" Xie Gong replied.

So the root of the problem is the warpage of the wafer!
How to reduce warpage after wafer thinning?
In a flash of inspiration, Xin Tong suddenly thought of Zhang Kaijun from Smic Fab. This wafer engineer who graduated from Tsinghua University must know it.

He took out his Bird mobile phone, clicked a few times with his fingers, and sent a short message to Zhang Kaijun.

"After this analysis, the problem of wafer cutting cracks has been locked in the thinning process!" Luo Gaogong said.

"Yes!" Xie Gong nodded.

"Why does the thinning process bring so much stress?" Luo Gaogong asked.

"We need to investigate this from the perspective of 4M1E when we get back!" Xie Gong replied.

"Xie Gong, what is the diameter of the diamond grains of the grinding wheel you use for thinning?" Xin Tong raised his head and asked.

Diamond particle diameter?This question is so professional!Xin Tong has never done any thinning, how did he know?Luo Gaogong was extremely surprised. Could it be that Xin Tong was a craftsman genius?
Jiang Hua was also very shocked. When an old classmate discussed craft issues with a king-level master, he didn't fall behind at all.

"Currently, we grind in two steps for thinning. We use a 325# grinding wheel for rough grinding and a 900# grinding wheel for fine grinding. In conversion, the diameter of the rough grinding emery particles is 44 μm, and the diameter of the fine grinding emery particles is 15 μm." Xie Gong Be well aware of the process of controlling your own processes.

Xin Tong said "Oh", flicked his fingers on his phone, and sent the message to Zhang Kaijun.

"Manager Xin is right. I also think that the problem of thinning may be related to the choice of grinding wheel!" After Xin Tong's advice, Luo Gaogong seemed to have received some kind of enlightenment.

"I doubt it too!" Xie Jianfeng said.

"Choose 325# grinding wheel for coarse grinding, there is nothing wrong, but the damage layer formed after rough grinding is about 20μm, and the roughness is about 1.5μm. Use 900# grinding wheel for fine grinding, and the damage layer is about 5μm, and the roughness is about 0.5μm. It is about 2500μm. Such uneven lines will cause stress concentration and cause cracks in the subsequent scribing process. I suggest using a 200# grinding wheel for fine grinding. Measure the warpage after the fake film is finished. If the warpage If it is less than [-]μm, you arrange cutting verification." Xin Tong said very confidently.

This Xin Tong is really against the sky, his understanding of the thinning process is definitely higher than that of Xie Jianfeng. Luo Gaogong nodded and said, "Very good!"

"Okay, Manager Xin, we will do some fake film verification according to your request!" Xie Jianfeng nodded.

He didn't know Xin Tong before, but when he heard about this person, he always felt that Xin Tong was promoted too quickly. He really didn't expect him to be so professional. When he saw him today, he was so impressed.

Seeing the head of the engineering department and the WS king nod their heads to Xin Tong's analysis, Jiang Hua was also stunned, so the old classmate's ability has surpassed these top experts?
The key is that he has never spent a day in the wafer thinning process!

Yesterday I went to take a look at the thinning machine, and he was already self-taught?

Coming out of the conference room, Jiang Hua held Xin Tong back, and couldn't help but ask, "Old classmate, aren't you from dry bonding? How come you are so proficient in thinning?"

Xin Tong smiled. If he hadn't consulted Zhang Kaijun just now, he would have been confused.

However, he didn't want to tell Jiang Hua about this, so he casually said: "The bonding process is the king process. Once you have done the bonding and look at other processes, they are all low."

Isn’t it said that every other line is like a mountain?
To be honest, Jiang Hua is in charge of all production processes of FOL. He has also seen thinning, cutting, chip mounting and bonding, and found that the differences between different processes are actually quite big.

"Really?" Jiang Hua was doubtful.

　Thanks to Brother Wumeng for his support, and to June Beauty for her support!Today is a typhoon day, so cool!

　　
　
(End of this chapter)