How to ensure program quality in IC burning production? What are the treatment methods?

Date：2021-12-28 13:42:00Views：1234

Not all ICs can be burned, only memory can be burned. But now many single-chip computers have integrated program memory, so single-chip computers can also burn. The principle of the burner is to change the internal 010101 structure of the chip by powering up the chip within the allowable timing range for the programmable chip, so as to achieve the expected effect. It is mainly used for programming (or brush writing) of chips such as single chip microcomputer (including embedded) / memory (including BIOS). As the core component of a product, once its internal program is stolen, the whole product will face the risk of cracking. This paper will introduce the production method of IC burning to ensure quality and safety.

About security

To achieve safety in production, we must first ensure the security of burning files. Burning documents is the crystallization of R & D projects, and its safety is extremely important. Especially for the agent burning factory, the staffing is uneven. If the documents are directly distributed to the factory for production, it is easy to cause document leakage.

It provides the programmer with engineering encryption function. The burning project is made by R & D, encrypts the sensitive file data, and sends it to the factory for production in the form of encryption project, which not only solves the risk of factory contacting files, but also avoids the cumbersome operation of workers establishing and configuring the burning project, and improves the production efficiency.

Engineering Encryption ensures the security of files, but can it ensure the security of chip programs?

We know that the chip can not only burn (program), but also have a reading interface to facilitate chip debugging and verify the integrity of data, that is, the burned program can also be completely read out. Even if you don't contact the file, you can get the file content, which eventually leads to the burning file being stolen indirectly. Of course, this problem will also be considered in the design of the chip. Each chip basically has its own set of encryption methods. As long as we encrypt the chip in time after burning, we can ensure the security of the code to a certain extent.

About engineering encryption

However, the double encryption of files and chips seems unbreakable. In fact, there is still a certain vulnerability, which mainly appears in the burning process. Erasure, burning, verification and encryption are the traditional burning process, which is adopted by most programmers on the market. We know that the protection of the chip lies in encryption. In this process, encryption is implemented at the end. If the chip is removed after burning and before encryption, the chip is in the state of burning but not encrypted, resulting in the program being read and stolen.

In order to solve this problem, we can put encryption before burning, so that the burning process becomes erasure, encryption, burning and verification. Even if the chip is removed in the verification stage, the chip has been encrypted and cannot read its internal data. Can the chip burn and verify after encryption? In fact, for most chips, encryption needs to be restarted to take effect, that is, the chip can still be burned and verified normally as long as it does not lose power and reset in the burning process. When the chip is removed, the encryption will take effect immediately to protect the internal program of the chip in time.

In the process of chip burning, there are always various problems. Look at the following questions. Have you ever encountered them?

1. The writer driver is incorrect;

2. The chip is burned once, and the verification of secondary burning fails;

3. Programmer failure during burning;

4. The chip program cannot be burned;

5. There are no problems in the R & D and testing stage, and problems occur frequently after mass production;

6. After correctly burning the program, the chip program did not run;

7. When burning files, the programmer prompts pass in the whole process, but the product cannot be used normally after the chip is pasted;

8. MPLAB can detect the chip, but the burning program always fails;

9. The MCU download program failed to erase the program, and the data cannot be burned;

10. Why there is no program after chip burning;

11. Burning encryption cannot be erased and repeated burning;

12. Unknown interruption during chip burning;

We can analyze the above problems from many aspects. First, if engineers want to investigate the causes of burning failure, they must first start according to the tools and methods used in burning. Different burning methods have different burning obstacles, and the solutions are also different. For example, if it is online burning, first focus on checking the chip for faulty soldering, poor reading, etc; In the process of chip recording, check whether there is incomplete burning, interruption, etc.

Processing method of off-line burning

The so-called off-line burning is a production method in which the chip is burned off-line and then installed on the board through various special adapter seats. Due to the low universality of adapter and fixture, this kind of burning method is stable, but the cost is high.

Nevertheless, some engineers choose such burning. Once there is a burning problem in this burning method, it should be investigated from two aspects——

1. At the hardware level

(1) First, check whether the contact between the burner and the test seat is insensitive and the reading is slow due to too long and frequent use;

(2) Check whether there is a burning option supporting this model in the burning Library of the burner. If so, confirm whether the model of IC and software is consistent;

(3) Check whether the USB cable connected to the burning tool is incompatible or unreadable;

(4) Whether the selected burner is domestic or self-made simulator, engineers need to consider whether the burner is compatible with the chip model;

(5) Pay attention to the service life of the chip burning fixture. Generally speaking, the chip burning fixture has service times, that is, the service life limit. Many small faults such as poor contact originate from the burning base.

2. At the software level

(1) Check whether the computer has installed the program files that affect the computer, resulting in unstable burning;

(2) Check whether the format of the chip program is inconsistent with the format specified by the chip;

(3) Check whether the drive of the burning tool is compatible;

(4) Check whether the certification of the burning drive has expired;

(5) Check whether the installed program belongs to a different brand from the burner. If it is a different brand, check whether there is a compatibility problem.

After eliminating the above hardware and software problems, the rest is the problem of personnel operation. For the chip with burning error, the ID detection function can be removed manually, and read or erase, programming and verification can be performed to see whether it can succeed.

Processing method of online collection

Online recording is a mass operation, efficient and high-cost burning method. It is burned directly after pasting the board, and then PCBA is sent to the testing machine for testing. The whole production process is fully automated, which is convenient for the online simulation of the product program at the immature stage and the appropriate adjustment of the program.

Although the cost of online recording is relatively low, the technical requirements for operators are high, and professional engineers are needed to burn, which ordinary workers can't complete.Then, when there is a burning problem in this burning method, we can start from these aspects.

(1) In case of unknown interruption during chip burning, the watchdog count shall be cleared in time, and the watchdog will generate a reset signal to reset the target chip to avoid accidental interruption of current chip burning due to chip program flying or entering the dead cycle state, resulting in burning failure;

(2) When the burning program is correct and the chip program does not run, it may be because the device with battery needs to be reset after the chip code erasure programming verification is passed, so that the chip can start to work for subsequent product testing;

(3) Reasons for line length, speed and stability - the communication quality between programmer and target board is related to the length and speed of communication cable. Generally, the longer the cable, the higher the communication rate, which will reduce the communication quality and affect the burning stability. In order to burn fast and stably, it is necessary to select the line length suitable for the target board according to the specific situation, and set the appropriate communication rate according to the line length.

(4) Surge effect - some use the programmer to supply power to the target board. At the moment of starting to supply power to the target board, due to the placement of more capacitors in some equipment, there will be an instantaneous super large charging current, that is, surge effect, which will easily promote the overcurrent protection of the programmer. At this time, it is best to use external direct power supply for the target board to achieve the operation effect of controlling power supply.

(5) When burning files, the programmer prompts pass in the whole process, but the product cannot be used normally after the chip is pasted.

① Verify the burning file. If the file is not verified, it is likely that it will not run normally after burning. Therefore, it is recommended that users must make a small batch trial production before mass production to verify the correctness of the burning file;

② Set the "configuration parameters" and manually modify the configuration parameters in the chip. If the parameters are not set according to the specifications, the chip will not operate normally.

③ Avoid irreversible losses caused by abnormal operation. If there is illegal operation in the burning process, it will inevitably lead to the failure of normal use of batch chips, damage to chips and irreversible consequences.

(6) When it cannot be burned again after burning error, determine whether it is a disposable chip, and the configuration bit is whether the OTP area can only be burned once.

The above is the related content of "IC burning quality assurance" brought by the core creation test. I hope it can be helpful to you. We will bring more wonderful content in the later stage. The company's testing services cover: electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, function testing, factory incoming material inspection, tape braiding and other testing items. Welcome to call Chuangxin testing, we will serve you wholeheartedly.