Self-adaptive quantitative control method for heat-conducting grease based on machine vision

Abstract

The invention discloses a heat-conducting grease self-adaptive quantitative control method based on machine vision, which can adaptively determine the brushing volume according to a printed board and a structural member to realize quantitative control in the heat-conducting grease brushing process. The method mainly comprises the following steps: determining a to-be-measured position through machine vision detection, and constructing a theoretical filling gap thickness model according to five-point measurement results of a displacement sensor; the relation between the brushing speed of the mechanism and the grease outlet speed of the nozzle is calculated by analyzing the rectangular strip-shaped heat-conducting grease; and spot coating and lineation coating paths are formulated according to the area of the boss to be coated and the total volume of the coated heat-conducting grease, so that the filling amount of the heat-conducting grease is quantitatively controlled, and self-adaptive coating of the heat-conducting grease is realized. The method can effectively solve the problems that a manual brushing mode cannot accurately control the brushing thickness according to the printed board assembly, the filling condition is judged by experience through repeated trial assembly, the heat-conducting grease filling consistency is poor, and the efficiency is low.

Description

Technical Field

[0001] The invention belongs to the field of printed circuit boards, and relates to a method for adaptively applying thermal grease, in particular to a method for adaptively quantitatively controlling thermal grease based on machine vision. Background Art

[0002] At present, with the advancement of aerospace electronic product technology, printed circuit boards are widely used in electronic complete products. Printed circuit boards reduce wiring and assembly errors, and are conducive to the miniaturization of electronic equipment, with better bending resistance and precision. The development of electrical products tends to be miniaturized and dense. The size of integrated circuit chips and electronic components continues to shrink, and the integration and assembly density continue to increase. The power and heat dissipation requirements of electronic devices also increase accordingly. The power of high-power CPU chips and power modules is as high as 200W. If the heat emitted by electronic devices during operation cannot be discharged in time, it is easy to cause local high temperature, which will affect the service life of electronic devices at the least, and even affect the working performance of the devices at the worst. At present, thermal conductive materials represented by thermal grease are widely used on heating devices. The purpose is to fill the gap between the structural parts and the heat dissipation surface of the device to avoid the influence of high temperature on the device. At present, thermal grease is still applied manually, which has the following shortcomings:

[0003] 1. As Figure 1 As shown, products widely use heat sinks (devices) to increase the heat dissipation area. The heat sinks (devices) are designed according to the height of the components of the printed circuit board assembly, and the gaps between the high-heat-generating components and the heat sinks (devices) are filled with thermal conductive materials to increase heat flow or reduce thermal resistance, thereby enhancing the heat dissipation effect. Due to various production factors such as poor consistency in the height of component welding and heat sink processing tolerances, the manual brushing method cannot be adaptively and evenly applied according to the printed circuit board assembly, and the brushing thickness cannot be accurately controlled. The consistency of thermal grease filling is poor, resulting in a decrease in the heat dissipation effect.

[0004] 2. For different products, blind installation is still used, such as Figure 2 As shown, the filling condition of the thermal conductive material can only be determined by repeated manual disassembly and assembly, and the filling condition is judged by manual visual observation based on experience. After the thermal conductive material is applied, the printed circuit board is fastened with screws for trial assembly. After the trial assembly, it is observed whether the thermal conductive material completely covers the surface of the heat dissipation chip, and then the excess thermal grease that overflows is cleaned with absorbent cotton, which is inefficient. Summary of the invention

[0005] The purpose of the present invention is to provide a method for adaptive quantitative control of thermal grease based on machine vision, so as to solve the problem that the amount of thermal grease applied cannot be quantified and the production efficiency of the manual repeated trial assembly process is low. At the same time, a fast adaptive thermal grease application amount calculation and control method is provided for different products. According to the adaptive measurement of the structural dimensions of the printed circuit board and the structural parts, the application area and volume are determined, and the application process parameters are formulated, which can effectively reduce the low production efficiency caused by manual repeated trial assembly, and improve the efficiency and product quality of the final assembly of high-performance and high-density printed circuit board components.

[0006] The present invention comprises the following steps:

[0007] Step 1: Load the printed circuit board and the structural parts to the positioning and clamping device, position and clamp the printed circuit board and the structural parts, detect the positions of the heating chip surface and the convex surface of the structural parts by machine vision, automatically measure the actual heights of the heating chip surface and the convex surface of the structural parts by laser displacement sensor, and optimize and correct the filling height of the thermal grease;

[0008] Step 2, calculating the relationship between the brushing speed of the brushing mechanism and the grease output speed;

[0009] Step 3: Select the dot coating or line coating method according to the area to be coated, calculate the coating trajectory, and realize adaptive coating of thermal grease.

[0010] Furthermore, the detection of the position of the heat generating chip surface and the boss surface of the structural component by machine vision in step 1 includes: after selecting the position of the heat generating chip surface and the boss surface of the structural component by machine vision detection, manually determining whether the selected position is correct; if the automatically selected position is incorrect, manually performing the selection.

[0011] Furthermore, the automatic measurement of the actual height of the heat generating chip surface and the structural component boss surface by the laser displacement sensor in step 1 includes:

[0012] The five-point method is used to obtain the PCB measurement reference surface height P1, the PCB chip heating surface height P2, the structural component measurement reference surface height S1, and the structural component boss surface height S2. The theoretical gap thickness H3 between the PCB chip heating surface and the structural component boss surface is obtained by formulas (1), (2), and (3):

[0013] H2=(S1-S2)(1)

[0014] H1=(P2-P1)(2)

[0015] H3=H2-H1=(S1-S2)-(P2-P1). (3)

[0016] Furthermore, in step 2, the brushing speed and grease discharging speed of the brushing mechanism meet the following requirements:

[0017]

[0018] Among them, v r is the brushing speed of the brushing mechanism, v q is the grease outlet speed, and W is the cross-sectional area of ​​the thermal grease.

[0019] Furthermore, in step 2, when the thermal grease is in the shape of a rectangular strip, the length is l, the width is d, and the height is h, then:

[0020]

[0021] Through machine vision inspection and calculation of the theoretical size of the boss of the structural part to be painted, the area to be painted is S, and the total volume of thermal grease to be filled is:

[0022] V=H3·S.

[0023] Furthermore, the method of selecting the dot painting or line painting method according to the area to be painted in step 3 includes:

[0024] when When applying thermal grease, a dot coating method is used. By controlling the coating height, the coating speed of the coating mechanism and the grease output speed of the intermittent nozzle, a rectangular dot matrix thermal grease is sprayed on the area to be coated, and the total volume of the thermal grease applied is controlled to achieve quantitative control of the coating amount.

[0025] when When the thermal grease is applied, a line-marking method is used to control the brushing height, the brushing speed of the brushing mechanism and the grease output speed of the continuous nozzle, and a rectangular strip of thermal grease is sprayed on the area to be applied, thereby controlling the total volume of the applied thermal grease and achieving quantitative control of the amount applied.

[0026] The beneficial effects of the present invention are: based on machine vision and laser displacement sensor measurement, the coating thickness is adaptively measured and corrected according to different products, the optimal coating volume is solved, and the coating method is planned according to the coating amount calculation result and the area to be coated, and the coating path is automatically formulated. The use of the present invention can effectively solve the problem that the manual coating method cannot accurately control the coating thickness according to the printed circuit board assembly, and the filling situation is judged by experience through repeated trial assembly, and the thermal grease filling consistency is poor and the efficiency is low. The present invention can be applied to the adaptive coating of thermal grease and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an exploded schematic diagram of the printed circuit board assembly structure;

[0028] Figure 2 This is a schematic diagram of the test installation of thermal grease filling;

[0029] Figure 3 A flowchart of a specific embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the positioning and clamping of printed circuit boards and structural parts, where: Figure 4 (a) is a schematic diagram of the printed circuit board positioning and locking mechanism. Figure 4 (b) is a schematic diagram of a vacuum adsorption device for a structural part;

[0031] Figure 5 It is a schematic diagram of the theoretical gap thickness model;

[0032] Figure 6 This is a schematic diagram for calculating standard rectangular strip thermal grease. DETAILED DESCRIPTION

[0033] In order to better understand the purpose, technical solution and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings, but the present invention can be implemented in a variety of different ways as defined and covered by the claims. The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0034] The present invention detects the positions of the heating chip and the surface to be coated by machine vision, automatically measures the actual heights of the heating chip and the surface to be coated by a laser displacement sensor, optimizes and corrects the thickness of the gap to be filled with thermal grease, adopts dot coating and marking methods according to different coating areas, calculates the coating trajectory, and realizes adaptive coating of thermal grease.

[0035] like Figure 3 As shown, in a specific embodiment of the present invention, the following steps are included:

[0036] Step 1: Load the printed circuit board (PCB) and structural parts into the positioning clamping device.

[0037] After the printed circuit board and structural parts are loaded, the printed circuit board is positioned using a movable slide rail and clamped by a locking fixture. The fixture locking head is equipped with a buffer rubber block to protect the printed circuit board from damage and can be adjusted up and down. The locking connecting rod can be telescopic and rotated, and can be adjusted in all directions with the locking head. After the debugging cylinder is pressed down, each locking head is adjusted to the appropriate position (up, down, left, and right), and the locking cylinder is pressed and clamped (the pressure can be precisely adjusted) to achieve the locking of the printed circuit board. Figure 4 (a) As shown; the structural parts are positioned and fixed by vacuum adsorption, such as Figure 4 (b) is shown to facilitate the measurement of the boss height of the structural part and the adaptive coating of the thermal conductive material.

[0038] After the printed circuit board and the structural parts are positioned and clamped, the positions of the heating chip surface to be inspected and the convex surface of the structural parts (i.e. the surface to be painted) are automatically framed by machine vision, and the frame selection position is manually determined to be correct. If the automatic frame selection position is incorrect, the frame selection is performed manually. The positions to be measured (heating chip surface and structural part convex surface) are positioned and measured by laser ranging, and the printed circuit board measurement reference surface height P1, printed circuit board chip heating surface height P2, structural part measurement reference surface height S1 and structural part convex surface height S2 are calculated by the five-point method (i.e. after measuring the height of the center and diagonal points, the average value is taken as the measured height).

[0039] When the printed circuit board is assembled on the structural part and fastened, it can be known that the measurement reference surface of the printed circuit board and the measurement reference surface of the structural part are in contact, so a theoretical gap thickness model can be established, such as Figure 5 As shown in the figure, the theoretical gap thickness H3 between the heating surface of the printed circuit board chip and the convex surface of the structural component is calculated by formulas (1), (2) and (3):

[0040] H2=(S1-S2)(1)

[0041] H1=(P2-P1)(2)

[0042] H3=H2-H1=(S1-S2)-(P2-P1)(3)

[0043] Step 2: Calculate the relationship between the brushing speed of the brushing mechanism (i.e. the moving speed of the brushing mechanism) and the grease output speed (i.e. the grease output speed of the nozzle).

[0044] The shape of thermal grease brushing (i.e. filling) is generally cylindrical, long strip, etc. Rectangular strip is a typical long strip, such as Figure 6 shown.

[0045] In a specific embodiment of the present invention, rectangular strip-shaped thermal grease is used.

[0046] The screw valve coating method is set to a standard rectangular strip design, and a rectangular nozzle is used to apply thermal grease. The length of the rectangular strip thermal grease is l, the width is d, and the height is h, so the spraying volume is:

[0047] V l = l·d·h

[0048] Set the brushing speed of the brushing mechanism to v r , then the painting time t1 of the painting mechanism is:

[0049] t1=l / v r

[0050] Set the total amount of thermal grease applied to C and the nozzle grease discharge speed to v q , so the nozzle grease discharge time t2 is:

[0051] t2=C / v q

[0052] Because the total volume of the coating is theoretically equal to the total amount of thermal grease applied, that is: V l =C, and the brushing time of the brushing mechanism is consistent with the nozzle spraying time, that is: t1 = t2, so the relationship between the brushing speed of the brushing mechanism and the grease output speed of the nozzle can be calculated as:

[0053]

[0054] Taking rectangular strip thermal grease as the analysis object, the relationship between the brushing speed of the brushing mechanism and the grease discharge speed of the nozzle is established. This relationship is used to describe the relationship between the brushing speed of the brushing mechanism, the grease discharge speed of the nozzle, and the grease coating length and width.

[0055] Through the above analysis, it can be concluded that under normal circumstances, the matching rule between the brushing speed of the brushing mechanism and the grease discharge speed of the nozzle is:

[0056]

[0057] Wherein, W is the cross-sectional area of ​​the thermal grease, that is, the cross-sectional area of ​​the nozzle opening.

[0058] In practical applications, the total volume of thermal grease to be applied and the area to be applied in step three are combined, and the application speed range of the application mechanism is set, and then the matching nozzle grease delivery speed can be calculated.

[0059] Step 3: According to the area to be coated, choose to use the dot coating or line coating method, calculate the coating trajectory, and realize adaptive coating of thermal grease.

[0060] The theoretical gap thickness model in step 1 can be used to obtain the thickness to be coated as H3. By inputting the theoretical size of the boss of the structural part to be coated, the area to be coated can be calculated as S (S = length × width). Therefore, the total volume of thermal grease to be coated can be obtained as:

[0061] V=H3·S

[0062] Select the painting method of marking and spot painting according to the area to be painted and the thickness of the paint.

[0063] When the area to be painted S is small, When applying thermal grease, a dot coating method is used. By controlling the coating height, the coating speed of the coating mechanism and the grease output speed of the intermittent nozzle, a rectangular dot matrix thermal grease is sprayed on the area to be coated, and the total volume of the thermal grease applied is controlled to achieve quantitative control of the coating amount.

[0064] When the area to be painted S is large, When the thermal grease is applied, a line-marking method is used to control the brushing height, the brushing speed of the brushing mechanism and the grease output speed of the continuous nozzle, and a rectangular strip of thermal grease is sprayed on the area to be applied, thereby controlling the total volume of the applied thermal grease and achieving quantitative control of the amount applied.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for adaptive quantitative control of thermal grease based on machine vision, characterized in that: The steps include: Step 1: Load the printed circuit board and the structural parts to the positioning and clamping device, position and clamp the printed circuit board and the structural parts, detect the positions of the heating chip surface and the convex surface of the structural parts by machine vision, automatically measure the actual heights of the heating chip surface and the convex surface of the structural parts by laser displacement sensor, and optimize and correct the filling height of the thermal grease; Step 2, calculating the relationship between the brushing speed of the brushing mechanism and the grease output speed; Step 3: Select the dot coating or line coating method according to the area to be coated, calculate the coating trajectory, and realize adaptive coating of thermal grease.

2. The method for adaptive quantitative control of thermal grease based on machine vision according to claim 1, characterized in that: The step 1 of detecting the position of the heat generating chip surface and the structural component boss surface by machine vision includes: after selecting the position of the heat generating chip surface and the structural component boss surface by machine vision detection, manually determining whether the selected position is correct; if the automatically selected position is incorrect, manually selecting the position.

3. The method for adaptive quantitative control of thermal grease based on machine vision as claimed in claim 1, characterized in that: The automatic measurement of the actual height of the heating chip surface and the structural component boss surface by the laser displacement sensor in step 1 includes: The five-point method is used to obtain the PCB measurement reference surface height P1, the PCB chip heating surface height P2, the structural component measurement reference surface height S1, and the structural component boss surface height S2. The theoretical gap thickness H3 between the PCB chip heating surface and the structural component boss surface is obtained by formulas (1), (2), and (3): H2=(S1-S2) (1) H1=(P2-P1) (2) H3=H2-H1=(S1-S2)-(P2-P1). (3).

4. The method for adaptive quantitative control of thermal grease based on machine vision as claimed in claim 3, characterized in that: In step 2, the brushing speed and grease dispensing speed of the brushing mechanism meet the following requirements: Among them, v r is the brushing speed of the brushing mechanism, v q is the grease outlet speed, and W is the cross-sectional area of ​​the thermal grease.

5. The method for adaptive quantitative control of thermal grease based on machine vision as claimed in claim 4, characterized in that: In step 2, when the thermal grease is in the shape of a rectangular strip, the length is l, the width is d, and the height is h, then: Through machine vision inspection and calculation of the theoretical size of the boss of the structural part to be painted, the area to be painted is S, and the total volume of thermal grease to be filled is: V=H3·S.

6. The method for adaptive quantitative control of thermal grease based on machine vision as claimed in claim 5, characterized in that: The method of selecting the dot coating or line coating method according to the area to be coated in step 3 includes: when When applying thermal grease, a dot coating method is used. By controlling the coating height, the coating speed of the coating mechanism and the grease output speed of the intermittent nozzle, a rectangular dot matrix thermal grease is sprayed on the area to be coated, and the total volume of the thermal grease applied is controlled to achieve quantitative control of the coating amount. when When the thermal grease is applied, a line-marking method is used to control the brushing height, the brushing speed of the brushing mechanism and the grease output speed of the continuous nozzle, and a rectangular strip of thermal grease is sprayed on the area to be applied, thereby controlling the total volume of the applied thermal grease and achieving quantitative control of the amount applied.

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