CN104320965A - Screening method of space LMCCD surveying and mapping camera imaging circuit - Google Patents

Abstract

The screening method of the imaging circuit of the aerospace LMCCD surveying and mapping camera involves an imaging technology of the aerospace CCD, which solves the problem that the focal plane structure size of the three-line array surveying and mapping camera of the LMCCD is compact, and it is difficult to place additional connectors to connect industrial-grade CCD devices for circuit board screening. The problem. In the present invention, after the socket is welded at the CCD position of the circuit board, an industrial-grade CCD is used to screen the circuit board. After the screening is passed, the CCD socket is removed, and an aerospace-grade CCD device is finally welded on. Aiming at the fault model of the disassembly process of the CCD socket, the CCD pins are divided into two categories, and the static resistance value and level value before and after the socket is removed are used to judge whether it is possible to weld the aerospace-grade CCD. The invention adopts multiple screening and testing steps to eliminate defective circuit boards, thereby reducing production costs and shortening the development period.

Description

Screening method for imaging circuit of aerospace LMCCD surveying and mapping camera

technical field

The invention relates to an imaging technology of an aerospace CCD, in particular to a screening method for an imaging circuit of an aerospace LMCCD surveying and mapping camera.

Background technique

As the main load of small satellites, the LMCCD stereoscopic mapping camera has strict requirements on volume and weight, and usually uses a long lens barrel refractive optical system. For the focal plane circuit board, in order to facilitate focusing and meet the requirements of stereoscopic mapping applications, the focal plane circuit board is installed in the lens barrel and connected to the post-processing circuit through the flexible belt of the rigid-flex board, so the size of the focal plane circuit board is smaller than that of the lens barrel size. Especially for front-facing cameras, there are five CCD devices on the focal plane of the small size. Due to the high price of aerospace-grade CCD devices, the reliability of the circuit board using the rigid-flex structure is low, and the layout and wiring of the circuit board are demanding. Place additional connectors to connect industrial-grade CCD devices for board screening. Therefore, after soldering the socket at the CCD position of the circuit board, use an industrial-grade CCD to screen the circuit board. After the screening is passed, remove the CCD socket, and finally solder the aerospace-grade CCD device. Due to the risk of damage to the circuit board during the disassembly of the CCD socket, the entire process needs to be carefully inspected.

Contents of the invention

The present invention provides an aerospace LMCCD surveying and mapping camera for imaging in order to solve the problem that it is difficult to place additional connectors to connect industrial-grade CCD devices and screen circuit boards due to the compact size of the focal plane structure of the existing LMCCD three-line array surveying and mapping camera. Circuit screening methods.

The screening method of the imaging circuit of the aerospace LMCCD surveying and mapping camera, the method is realized by the following steps:

Step 1. Design the PCB circuit board and add test points to the drive pins without outgoing signals;

Step 2. Produce and process the PCB circuit board designed in step 1, and then test the connectivity of the flex strip in the rigid-flex board of each PCB circuit board. If no defect is found in the test result, perform step 3. If the test result finds If there is a defect, repeat step 2;

Step 3. Solder and assemble the PCB circuit boards described in step 2, and then perform an imaging test. At the same time, record the connection resistance of the CCD drive pin under the single board and the ground resistance of the non-drive pin, and record each The waveform of each pin of the CCD when the PCB circuit board is connected; if the test result is abnormal, perform maintenance until the imaging test is normal; perform step 4, if the test result is normal, perform step 4;

Step 4. Disassemble the CCD socket, and test the connection resistance of the CCD drive pins and the ground resistance of the non-drive pins in an environment where the temperature is lower than or equal to -25 degrees, and perform waveform testing after assembling each PCB circuit board again. , record the waveforms of each pin of the CCD when each PCB circuit board is connected, and compare the test results with the test results in step 3. If the difference between the two results is less than or equal to 5%, the PCB circuit board and each CCD tube are completed. The detection of the foot realizes the screening of the imaging circuit of the aerospace LMCCD surveying and mapping camera; otherwise, return to step one.

Beneficial effects of the present invention: 1. The present invention adopts multiple screening and testing steps to eliminate defective circuit boards, thereby reducing production costs and shortening the development cycle;

2. According to the test connectivity model, the pins of the CCD are divided into two types: ground resistance and connection resistance. During PCB design, test points are added at positions where it is inconvenient to test the connection resistance, so as to avoid damage to the conformal coating in later tests. ;

3. After disassembling the CCD socket, test the static resistance value at a low temperature such as -25 degrees, and you can check that there is no abnormality in the connection of solder joints at room temperature; after disassembling the CCD socket, test the waveforms of each pin to further check the rest of the circuit board. status is normal.

Description of drawings

Fig. 1 is that in the screening method of aerospace LMCCD surveying and mapping camera imaging circuit of the present invention, CCD drives the connection pin schematic diagram;

Fig. 2 is the CCD bias pin connection schematic diagram in the screening method of aerospace LMCCD surveying and mapping camera imaging circuit of the present invention;

Fig. 3 is the CCD output pin connection schematic diagram in the screening method of aerospace LMCCD surveying and mapping camera imaging circuit of the present invention;

Fig. 4 is a flow chart of the screening method of the imaging circuit of the aerospace LMCCD surveying and mapping camera according to the present invention.

Detailed ways

The present embodiment is illustrated in conjunction with Fig. 1 to Fig. 4, the screening method of aerospace LMCCD camera imaging circuit,

Combined with the circuit schematic diagram in Figure 1, the logical process of judging the connectivity by testing the resistance of the solder joints can be regarded as a series structure model of each resistor. When the original resistance is low and R _{is low} , the solder joints break, then The total resistance shows a high state R _high , from R _low to R _high , and it is easy to judge the fault; when the original resistance is high and R _high , the solder joint breaks, and the total resistance still shows a high state R _high , It is difficult to judge whether there is a malfunction. Therefore, in the connectivity comparison test, it is necessary to select a lower original test resistance value.

Combining Figure 2 and Figure 3, the CCD pins can be divided into drive pins whose input changes with time according to their functional characteristics, bias pins whose input is a fixed level, and output pins that output analog signals. Figure 1 is a schematic diagram of the CCD drive connection pins. The failure model of the CCD socket during the disassembly process is an open circuit or an increase in resistance, especially at low temperatures. Since both the drive and the drive pins are in a high-impedance state to the signal ground (ground), Therefore, it is difficult to judge whether the status is normal by testing the resistance of the drive pin to ground. You can only measure the on-resistance value between the pin and the connected signal. Since it is difficult to measure the circuit board after brushing the conformal paint, when the signal is not connected to the connection, you need to Lead out the test points in the PCB design stage and protect the test points when the conformal paint is painted; for the CCD bias pins, an external power supply and a voltage divider are usually used to provide a constant DC level, because the external power supply and the voltage divider are The ground resistance value is low, and the ground resistance of the pin can be directly measured to detect the state after the socket is disassembled; for the CCD output pin, since there is an external DC bias circuit with a low resistance value, it can also be directly measured. The ground resistance detects the state after the socket is disassembled.

The specific process of the screening method of the aerospace LMCCD camera imaging circuit described in the present embodiment is:

1. Design the PCB circuit board according to the design requirements, and add test points for the non-leading drive signal.

Second, the production and processing of PCB circuit boards are carried out in the factory.

3. Before the PCB circuit board is soldered, carry out the inspection of the PCB circuit board, especially the connectivity test of the flexible belt in the rigid-flexible board; if there is a defect (all detected connection resistances are greater than 0.1 ohms), re-produce the PCB circuit board processing.

4. If no defects are found in the test (all the detected connection resistances are less than 0.1 ohms), solder and assemble the PCB circuit board, and then perform normal temperature and pressure imaging tests, normal pressure and vacuum thermal cycle imaging tests, and record the single The connection resistance of the CCD driving pin under the board and the grounding resistance of the non-driving pin, record the waveform of each pin of the CCD under the connection state of each circuit board; The scrapped circuit board is re-produced; the abnormal situation in the test refers to: the connection resistance of the driving pin and the ground resistance of the non-driving pin, the DC level of the bias pin, the high level and low level of the driving pin , when the value of any of the above items changes by more than 5% compared with the design value.

5. Carry out the three-proof treatment of the circuit board, and protect the drive signal lead-out point and connector before the three-proof treatment;

6. After the three defenses, assemble the circuit board, and conduct thermal cycle experiments under normal pressure and vacuum; if the test is abnormal, carry out investigation and maintenance until the imaging tests are normal, otherwise the circuit board will be scrapped and re-produced.

7. Disassemble the CCD socket.

8. Test the connection resistance of the CCD drive pin and the ground resistance of the non-drive pin at a low temperature such as -25 degrees. After assembling the circuit board, perform a waveform test and compare it with the test record before the three-proof treatment to confirm whether There is an abnormality; if there is an abnormality, it cannot be repaired, and the scrapped circuit board will be re-produced.

9. After confirming that there is no abnormality, weld the aerospace-grade CCD that has been installed on the optical-mechanical structure to meet the requirements of surveying and mapping applications.

10. Assemble the circuit board and optical-mechanical structure, and conduct the whole machine test experiment.

In this embodiment, a multimeter is used to test the static resistance; an oscilloscope with a storage function is used to test the waveform of each pin of the CCD, and the CCD socket adopts a single-row socket; the CCD adopts a device of E2V Company;

According to the test connectivity model, the present invention divides the pins of CCD into two types for testing ground resistance and connection resistance. During PCB design, a test point is added at the signal position of the driving pin which is inconvenient to test the connection resistance; Test the static resistance value at low temperature, such as -25 degrees, to check whether there is no abnormality in the connection of solder joints at room temperature; after disassembling the CCD socket, test the waveform of each pin to further check whether the rest of the circuit board is in normal condition. The present invention adopts multiple screening test steps to eliminate defective circuit boards early; the screening test steps mainly include PCB design, production and processing, PCB circuit board inspection before welding, PCB welding assembly and imaging test, three-proof treatment, normal pressure and Thermal cycle experiment under vacuum, disassembly of CCD socket, resistance and waveform test, soldering CCD, whole machine test experiment.

Claims (5)

1. the screening method of aerospace LMCCD surveying and mapping camera imaging circuit, it is characterized in that, this method is realized by the following steps: Step 1. Design the PCB circuit board and add test points to the CCD drive pins without outgoing signals; Step 2. Produce and process the PCB circuit board designed in step 1, and then test the connectivity of the flex strip in the rigid-flex board of each PCB circuit board. If no defect is found in the test result, perform step 3. If the test result finds If there is a defect, repeat step 2; Step 3. Solder and assemble the PCB circuit boards described in step 2, and then perform an imaging test. At the same time, record the connection resistance of the CCD drive pin under the single board and the ground resistance of the non-drive pin, and record each The waveform of each pin of the CCD when the PCB circuit board is connected; if the test result is abnormal, perform maintenance until the imaging test is normal; perform step 4, if the test result is normal, perform step 4; Step 4. Disassemble the CCD socket, and test the connection resistance of the CCD drive pins and the ground resistance of the non-drive pins in an environment where the temperature is lower than or equal to -25 degrees, and perform waveform testing after assembling each PCB circuit board again. , record the waveforms of each pin of the CCD when each PCB circuit board is connected, and compare the test results with the test results in step 3. If the difference between the two results is less than or equal to 5%, the PCB circuit board and each CCD tube are completed. The detection of the foot realizes the screening of the imaging circuit of the aerospace LMCCD surveying and mapping camera; otherwise, return to step one. 2. the screening method of aerospace LMCCD surveying and mapping camera imaging circuit according to claim 1, is characterized in that, described in the step 3 respectively records the connected resistance value of CCD driving pin under the veneer and the grounding of non-driving pin resistance, and the non-driving pins are bias pins and output pins of the CCD. 3. The screening method of the aerospace LMCCD surveying and mapping camera imaging circuit according to claim 1 or 2, is characterized in that, if the abnormal situation occurs in the test described in step 3, it refers to: the connection resistance and the non-connection resistance of the drive pin The ground resistance of the drive pin, the DC level of the bias pin, the high level and the low level of the drive pin, when the value of any of the above changes more than 5% compared with the design value. 4. the screening method of aerospace LMCCD surveying and mapping camera imaging circuit according to claim 1, is characterized in that, between step 3 and step 4, also comprises disconnecting between described each PCB circuit board, and carries out three steps respectively Anti-treatment, protect the drive signal lead-out point and connector before the three-proof treatment; then assemble the PCB circuit boards, and conduct thermal cycle experiments under normal pressure and vacuum; if the test is abnormal, check and repair, Until each imaging test is normal, then go to step 4, if the test result is normal, go to step 4. 5. the screening method of aerospace LMCCD surveying and mapping camera imaging circuit according to claim 1, it is characterized in that, in the step 2, the connectivity of the flexible band in the rigid-flexible board of each PCB circuit board is detected, if no defect is found in the detection result It means that the connection resistance of all tests is less than 0.1 ohm to meet the test conditions.