CN103491698B - A kind of micro-focal X-ray source dynamic focus control method - Google Patents

Abstract

The invention discloses a dynamic focus control method of a micro-focus X-ray source. The method monitors the X-ray focus in real time through a detection device, and decides whether to reset the focus size according to the monitoring data. When the focus is greater than 6 μm, the ARM lower computer searches The built-in focus and output power correspondence table obtains the corresponding tube voltage and tube current parameters, and sends them to the high-frequency high-voltage generator, and the high-frequency high-voltage generator adjusts the tube voltage and current according to the received data to achieve focusing , Finally, the dynamic range of the focus is stabilized at 2-6 μm, and it is difficult to break through the closed micro-focus X-ray problem below 5 μm. The invention can control the X-ray focus to be stable below 6 μm, and is especially suitable for precision detection systems requiring high-resolution X-ray images.

Description

A Dynamic Focus Control Method of Microfocus X-ray Source

technical field

The invention relates to the field of non-destructive testing in the IC packaging process, in particular to a dynamic focus control method of a micro-focus X-ray source.

Background technique

As electronic components are becoming smaller and more complex, high-resolution nondestructive testing technology has been widely used in product quality testing in the electronics manufacturing industry, and X-ray machines are one of the main ray devices. As one of the important performance indicators of the X-ray machine, the size of the focus of the X-ray tube determines the quality of the image to a large extent. The smaller the focal point, the higher the image definition of the captured object, and the more accurate the non-destructive testing in the IC packaging process. It can be seen that the X-ray tube is the core component of the X-ray imaging equipment.

The X-ray tube is a high-voltage diode with a special structure, which is composed of a cathode, an anode and a vacuum-sealed casing. Under the action of a high-voltage electric field, the hot electrons generated by the spiral filament in the cathode bombard the anode target surface at high speed to generate the required X-rays. The area on the anode target surface hit by the high-speed electron beam is the actual focal spot, and X-rays are emitted from this area to the hemispherical space. However, as the X-ray tube ages, the focal spot size of the X-ray machine will change. The factors causing the change mainly include the change of the cathode filament and focusing performance of the ray tube, and the damage of the anode target. When the shape and focusing performance of the cathode filament change, the impact area of the electron beam on the anode target changes, resulting in a change in the focal spot size; in addition, as the X-ray tube’s service time increases, the damage of the anode target increases, and the surface of the anode Becoming bumpy, causing diffuse lines to increase, causing focal spot size to change.

In order to determine the focal point size of X-ray machines, scholars have successively proposed different focal point size measurement methods. These methods can be roughly divided into three categories: scanning methods, imaging methods, and computational methods. The scanning method directly adopts a mechanical scanning method to measure the radiation intensity distribution of the focal point by radiation counting, so as to determine the focal point size. The typical imaging methods are the pinhole method and the slit method. First, the radiographic image of the focus is obtained, and the size of the focus is directly determined from the image. Calculation methods include star card method, boundary method, etc., using high-absorbing materials to obtain radiographic images, measuring image intensity and then calculating or converting to determine the focus size. The scope of application, applicable objects, and focal points of different measurement methods are different. Even with the same measurement method, when the purpose and application of the test are different, the test conditions and procedures are slightly different. Therefore, when measuring the focal spot size, it is necessary to select the appropriate measurement method according to the specific X-ray machine parameters, test purpose and relevant regulations.

In the X-ray detection system for the packaging process of very large scale integrated circuits, the dynamic change of the focus of the X-ray machine has adverse effects on the quality of the X-ray image and the detection results. How to stably control the focus size so that it is in a suitable size range has become the focus and difficulty of X-ray imaging detection for the IC packaging process, and is also the main problem to be solved by the present invention.

At present, the minimum focus of the closed micro-focus X-ray tube can be as low as several microns, so it is widely used in X-ray inspection systems. However, the fact that the focal point of the X-ray tube changes dynamically is ignored in many practical applications, resulting in sometimes unsatisfactory X-ray images and detection results. In order to ensure the stability of the focus size, it is necessary to invent a method to adjust the focus to an appropriate size in time after the focus changes, so as to improve the detection accuracy.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a reasonable and reliable micro-focus X-ray source dynamic focus control method oriented to the IC packaging process.

In order to achieve the above object, the technical solution provided by the present invention is: a dynamic focus control method of a micro-focus X-ray source, comprising the following steps:

(1) The focus detection device monitors the focus size in real time, and decides whether to reset the focus size according to the monitoring data;

(2) If the focus size is less than 6 μm, do not do any processing, otherwise go to step (3);

(3) When the focus size is greater than 6 μm, the PC host computer sends an instruction to adjust the X-ray source focus to below 6 μm to the ARM lower computer. After receiving the instruction, the ARM lower computer searches the built-in focus and output power correspondence table to obtain the focus adjustment It is necessary to output the power parameter value and the corresponding tube voltage and current value, and then send the voltage and current value to the high frequency and high voltage generator;

(4) The high-frequency and high-voltage generator adjusts the power of the X-ray tube to a specified value according to the received data, so that the focus size is below 6 μm.

In step (1), the focus detection device acquires the current focus size and sends it to the ARM lower computer, and the ARM lower computer displays it on the PC upper computer interface through a data transmission channel, thereby realizing real-time focus monitoring.

The focus detection device indirectly measures the focus size by measuring the geometric unsharpness of the image, and includes the following equipment: a test object, a radiography device, and an image processing device; the test object adopts a metal cross wire, and its intersection angle is 90°±3 °, the metal cross wire should be fixed on the fixed frame through a circular hole, the passing point is located at the center of the hole, the fixed frame will make the test object very close to the window of the X-ray tube, the image processing The device should be capable of producing linearly enhanced contours of X-ray images in mutually orthogonal directions and capable of measuring distances.

In step (2), the PC upper computer receives the current focus size from the ARM lower computer, and judges whether it is larger than 6 μm. If it is smaller than 6 μm, it does not perform any processing and continues to monitor the focus.

In step (4), the high-frequency high-voltage generator adjusts the power of the X-ray tube to a specified value according to the received data, including the following steps:

1) The high-frequency and high-voltage generator receives the tube voltage and current parameters from the ARM lower computer;

2) After receiving the data, the high-frequency and high-voltage generator directly generates the corresponding voltage and current and acts on the X-ray tube;

3) The X-ray tube forms a corresponding focus under the drive of the voltage and current, and realizes the stability of the dynamic focus within the range of 2-6 μm.

Compared with the prior art, the present invention has the following advantages and beneficial effects: through self-adaptive focusing after measuring and monitoring the focus, the dynamic range of the focus can be stably controlled within 2-6 μm, and it is difficult to break through the closed micro-focusing X-rays below 5 μm problem.

Description of drawings

Fig. 1 is a functional structural diagram of the present invention.

Fig. 2 is a block diagram of the focus detection principle of the present invention.

Fig. 3 is a flow chart of the method of the present invention.

detailed description

The present invention will be further described below in conjunction with specific examples.

As shown in Figure 1, the micro-focus X-ray source dynamic focus control method described in this embodiment adopts the following equipment: X-ray tube, PC upper computer, ARM lower computer, high frequency and high voltage generator, focus detection device, power supply, Wherein, the high-frequency high-voltage generator is respectively connected with the X-ray tube, the ARM lower computer, and the power supply, and the focus detection device is connected with the X-ray tube and the ARM lower computer respectively, and the ARM lower computer is connected with the power supply, and connected with the PC upper computer. are connected via Ethernet. The focus detection device is to indirectly measure the focus size by measuring the geometric unsharpness of the image, and includes the following equipment: a test object, a radiography device, and an image processing device; the test object adopts a metal cross wire, and its intersection angle is 90°± 3°, the metal cross wire should be fixed through a circular hole on the fixing frame, and the passing point is located at the center of the hole. The fixing frame should make the test object very close to the window of the X-ray tube, and the image The processing equipment should be able to produce linear enhancement contours of X-ray images in mutually orthogonal directions and be able to measure distances. As shown in Figure 2, it is the principle block diagram of the focus detection device. In the figure, 1 is the anode of the X-ray tube, 2 is the test object, 3 is the imaging plane, M is the magnification number and M=(a+b)/a , a is the distance between the test object and the anode of the X-ray tube, b is the distance between the test object and the imaging plane.

As shown in Figure 3, the above-mentioned micro-focus X-ray source dynamic focus control method in this embodiment, the specific conditions are as follows:

(1) The focus detection device obtains the current focus size and sends it to the ARM lower computer, and the ARM lower computer displays it on the PC upper computer interface through the data transmission channel, thereby realizing real-time focus monitoring;

(2) The PC upper computer receives the current focus size from the ARM lower computer, and judges whether it is larger than 6 μm. If it is smaller than 6 μm, it means that the current focus size meets the requirements and does not do any processing, otherwise go to step (3);

(3) When the focus size is greater than 6 μm, the PC host will issue an instruction to adjust the focus of the X-ray source to below 6 μm and transmit the instruction to the ARM lower computer through Ethernet. After receiving the instruction, the ARM lower computer will search for the built-in focus and output power The corresponding relationship table obtains the output power parameter values required for focusing and the corresponding tube voltage and current values, and then sends the voltage and current values to the high-frequency and high-voltage generator;

(4) The high-frequency and high-voltage generator adjusts the power of the X-ray tube to a specified value according to the received data, so that the focus size is below 6 μm, including the following steps:

1) The high-frequency and high-voltage generator receives the tube voltage and current parameters from the ARM lower computer;

2) After receiving the data, the high-frequency and high-voltage generator directly generates the corresponding voltage and current and acts on the X-ray tube;

3) The X-ray tube forms a corresponding focus under the drive of the voltage and current, and realizes the stability of the dynamic focus within the range of 2-6 μm.

After adopting the above scheme, the present invention monitors the X-ray focus in real time through the focus detection device, and decides whether to reset the focus size according to the monitoring data, thereby stably controlling the dynamic range of the focus within 2-6 μm, breaking through the closed micro-focus It is difficult for X-rays to break through the problem below 5 μm. Compared with the prior art, the present invention can effectively control the X-ray focus to be stable below 6 μm, and is especially suitable for precision detection systems requiring high-resolution X-ray images, and is worthy of popularization.

The implementation examples described above are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Therefore, all changes made according to the shape and principles of the present invention should be covered within the protection scope of the present invention.

Claims (3)

1. A microfocus X-ray source dynamic focus control method, is characterized in that, comprises the following steps: (1) The focus detection device monitors the focus size in real time, and decides whether to reset the focus size according to the monitoring data; (2) If the focus size is less than 6 μm, do not do any processing, otherwise go to step (3); (3) When the focus size is greater than 6 μm, the PC host computer sends an instruction to adjust the focus of the X-ray source to less than 6 μm to the ARM lower computer. After receiving the instruction, the ARM lower computer searches the built-in focus and output power correspondence table to obtain the focus adjustment. It is necessary to output the power parameter value and the corresponding tube voltage and current value, and then send the voltage and current value to the high frequency and high voltage generator; (4) The high-frequency and high-voltage generator adjusts the X-ray tube power to a specified value according to the received data, so that the focus size is below 6 μm; In step (1), the focus detection device obtains the current focus size and sends it to the ARM lower computer, and the ARM lower computer displays it on the PC upper computer interface through a data transmission channel, thereby realizing real-time focus monitoring; The focus detection device indirectly measures the focus size by measuring the geometric unsharpness of the image, and includes the following equipment: a test object, a radiography device, and an image processing device; the test object adopts a metal cross wire, and its intersection angle is 90°±3 °, the metal cross wire should be fixed on the fixed frame through a circular hole, the passing point is located at the center of the hole, the fixed frame will make the test object very close to the window of the X-ray tube, the image processing The device should be capable of producing linearly enhanced contours of X-ray images in mutually orthogonal directions and capable of measuring distances. 2. a kind of micro-focus X-ray source dynamic focus control method according to claim 1 is characterized in that: in step (2), PC upper computer receives the current focus size from ARM lower computer, judges whether it is greater than 6 μ m , if less than 6μm, do not make any treatment, continue to monitor the focus. 3. A kind of micro-focus X-ray source dynamic focus control method according to claim 1, is characterized in that: in step (4), high-frequency high-voltage generator adjusts X-ray tube power to specified value according to received data, comprises The following steps: 1) The high-frequency and high-voltage generator receives the tube voltage and current parameters from the ARM lower computer; 2) After receiving the data, the high-frequency and high-voltage generator directly generates the corresponding voltage and current and acts on the X-ray tube; 3) The X-ray tube forms a corresponding focus under the drive of the voltage and current, so as to stabilize the dynamic focus within the range of 2-6 μm.