KR100911365B1 - Laser trimming apparatus and method using image processing - Google Patents

Abstract

The present invention relates to a laser trimming apparatus and method thereof using image information processing, and more particularly, to an apparatus and method for laser trimming a register of an embedded printed circuit board.

The laser trimming apparatus using the image information processing according to the present invention includes an optical system for generating a laser beam and irradiating a register, an image information generator for generating image information of a register and an electrode pattern connected to the register, and a resistance value of the register. And a controller for controlling the optical system based on the image information generated by the image information generation unit and the resistance value measured by the resistance measurement unit.

Laser Trimming, Embedded Printed Circuit Boards

Description

LASER TRIMMING APPARATUS AND METHOD USING IMAGE PROCESSING

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser trimming apparatus and method thereof using image processing, and more particularly, to an apparatus and method for laser trimming a resistor formed in the form of a resistor of an embedded printed circuit board.

As electronic devices become smaller and denser, the surface area of the printed circuit board itself decreases, and as the number of chips mounted on the surface increases, a lot of difficulties arise in surface mounting of the chip. As a solution to this, an embedding method for embedding a chip in a printed circuit board has been developed, and a printed circuit board made using the embedding method is an embedded printed circuit board.

Embedded printed circuit boards are printed circuit boards that reduce area and eliminate signal interference by incorporating passive components such as resistors and capacitors and integrated circuits (ICs) into the printed circuit board instead of embedding the functions in the board itself.

These embedded printed circuit boards are more expensive than conventional printed circuit boards, but they can be cost-effective by eliminating surface mounts and placing other components in locations where resistors are to be planted, making boards more efficient to use.

In the embedded printed circuit boards mentioned, the resistors are generally formed of film resistors such as thin film resistors and thick film resistors, It is mainly used as a resistor connecting the electrode patterns and the electrode patterns formed to be spaced apart on the printed circuit board. Here, the resistance includes a carbon paste including carbon (C) and silver (Ag), and is formed by performing screen printing.

However, since the resistor is formed through the screen printing process, it is not easy to form a resistor having an accurate resistance value. Therefore, when a target resistance value of the resistor is to be formed within a range of 10 ± 1% error, a typical screen printing resistor is formed in a range of 8 Ω to 8.9 Ω, and then the resistance value of the resistor is within the error range. Laser trimming is performed to adjust the set resistance to.

Such laser trimming mainly uses a laser beam having a Gaussian profile. That is, after the resistor is formed on the printed circuit board, a portion of the resistor is removed by using a laser beam having a Gaussian profile to adjust the resistance value of the resistor to a resistance value within an error range. This is based on the property that the cross-sectional area of the resistance is inversely proportional to the resistance value.

In addition, as described above, since the register is formed through the screen printing process, the position where each register is formed is not always constant, and the position is changed by a deviation of approximately 200 μm.

Conventionally, laser trimming is started at the outermost part, i.e., on the same line as the edge of the electrode pattern, by CAD data when machining a register using a laser beam due to the changing position of the register.

1 is a diagram illustrating a register that is a target of laser trimming according to the related art.

The electrode pattern 10 is formed on the printed circuit board protective layer 50, and a resistor 20 is formed between the two electrode patterns 10 through a screen printing process. As described above, the resistor 20 is formed so that the resistor 20 is in a range of resistance values smaller than the target resistance value, and then the laser trimming 30 is performed on the resistor 20 to reach the target resistance value. Until the resistance value is increased.

On the other hand, the position where the register 20 is formed is not always constant and has a deviation of approximately 200 μm. Therefore, since the position at which the register 20 is formed cannot be precisely specified, the laser trimming 30 must start the laser trimming from the outermost line 40 by the CAD data, that is, the edge of the electrode pattern 10.

Therefore, when the actual register 20 is located apart from the outermost line 40 with a deviation, there is a problem that the time required for the entire trimming increases.

In addition, the laser trimming 30 may start from an area where the register 20 is not printed due to the positional deviation of the register 20, wherein the laser is used to protect the printed circuit board protection layer on which the register 20 is not printed. The problem is that the printed circuit board protective layer is damaged by being removed together.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and by determining a position where a register is formed and starting laser trimming from the position, a laser trimming apparatus and method which can prevent the time required for trimming the register and damage to the printed circuit board are prevented. To provide.

In order to achieve the above technical problem, a first aspect of the present invention provides an optical system for generating a laser beam and irradiating a resistor, an image information generator for generating image information of a resistor and an electrode pattern connected to the resistor, and a resistance of the register. It provides a laser trimming device including a resistance measuring unit for measuring a value and a control unit for controlling the optical system based on the resistance value measured by the image information and the resistance measuring unit generated by the image information generating unit.

In addition, a second aspect of the present invention is to (a) measuring the resistance value of the resistor, (b) generating image information of the resistor and the electrode pattern connected to the resistor, and (c) the image information and the resistance It provides a laser trimming method comprising the step of controlling the laser irradiated to the register through the optical system based on the value.

According to one of the problem solving means of the present invention described above, since the laser trimming is performed only on the resistor formed on the printed circuit board, it is possible to minimize the damage of the protective layer of the printed circuit board by the laser.

According to one of the problem solving means of the present invention described above, the laser trimming is performed only in the area where the laser trimming is required, thereby reducing the time required for laser trimming compared to the prior art.

According to one of the problem solving means of the present invention described above, the abnormal register can be determined before and after the laser trimming and during the laser trimming based on the image information of the register.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

2 is a block diagram illustrating a configuration of a laser trimming apparatus according to an embodiment of the present invention.

Laser trimming apparatus according to an embodiment of the present invention includes an optical system 110, the image information generating unit 120, the resistance measuring unit 130 and the control unit 140.

The optical system 110 generates a laser beam and irradiates a register. The optical system 110 performs laser trimming by focusing and / or diverging the laser beam irradiated with the register.

The laser beam generated by the optical system 110 may be a laser beam having a Gaussian profile. However, this is only an example of a laser beam, and the type of the laser beam does not form part of the present invention as long as laser trimming is possible.

In addition, the optical system 110 needs to change the path of the laser beam in some cases in order to irradiate the laser beam to the register, and may include reflecting means for this purpose. In addition, the optical system 110 may include various means such as a galvanometer scanner or one or more lenses to focus and / or diverge the laser beam.

The image information generator 120 generates image information of a register and an electrode pattern, and transmits the generated image information to the controller 140. The image information generator 120 may generate image information of the register and the electrode pattern before the laser trimming is performed and image information of the register in the process of the laser trimming. The image information before the laser trimming may be used to set the start line of the laser trimming, and the image information during the laser trimming may be used to determine whether or not the laser trimming is normally performed.

The resistance measuring unit 130 measures the resistance value of the resistor that changes as the laser trimming proceeds, and transmits the measured resistance value to the controller 140. The resistance value transmitted by the resistance measuring unit 130 may be used to determine whether the laser trimming is in progress. The resistance value measurement by the resistance measuring unit 130 may be performed by contacting the resistance measuring unit 130 with an electrode pattern connected to the resistor.

The controller 140 controls the generation of the laser beam of the optical system 110, the irradiation, and the path change of the laser beam.

The controller 140 receives image information of a register and an electrode pattern from the image information generator 120, and determines and sets a start line of laser trimming based on the received image information. The start line of laser trimming is any point of the register, not the substrate, and can be set at or within the register edge.

If the start line of laser trimming is set to the edge of the register, the laser trimming starts from the edge of the register.

The control unit 140 receives the resistance value of the resistor from the resistance measuring unit 130 to control the laser irradiation.

That is, when the initial resistance value measured before the laser trimming is larger than the target resistance value, the controller 140 does not change the resistance value to the target resistance value even if the laser trimming is performed. The laser irradiation of the optical system 110 is controlled to stop the laser trimming when the measured resistance value during the laser trimming reaches the set target resistance value.

The controller 140 stops laser trimming when the resistance value of the resistor reaches the set target resistance value, and then controls the positions of the optical system 110, the image information generation unit 120, and the resistance measurement unit 130. The register to be laser trimmed is moved to the position where the laser can be trimmed.

In addition, the controller 140 may determine an abnormally formed register by comparing the image information received from the image information generating unit 120 before and after the laser trimming and during the laser trimming with the set image information. Production of the substrate can be prevented in advance.

That is, the controller 140 performs laser irradiation to prevent laser trimming when it is determined that the measured initial resistance value of the resistor is larger than the target resistance value or the generated image information is not normal compared to the set image information. After controlling, the abnormally formed register is recovered through a separate repair device or the like, and laser trimming is performed.

In addition, the controller 140 may be distributed in other components and is not necessarily limited to physically separate components.

The process of determining the start line of the laser trimming and the abnormally formed register by comparing the received image information and the set image information by the control unit 140 is performed by a conventional image processing technique. It is self-explanatory and does not explain separately.

As such, the laser trimming apparatus according to the exemplary embodiment of the present invention generates image information of the register by the image information generating unit 120 to determine the edge of the register and starts laser trimming from the edge.

Therefore, the laser trimming is performed only on the register which is the object of laser trimming, which shortens the laser trimming execution time, and the printed circuit board protective layer and the like on which the register is formed are not damaged by the laser trimming.

3 is a diagram illustrating in detail a laser trimming apparatus according to an embodiment of the present invention.

The laser trimming apparatus according to another embodiment of the present invention includes a laser generator 200, an image information generator 205, a first reflection mirror 210, a second reflection mirror 215, and a galvanometer scanner 220. , A focusing lens 225 and a resistance measuring unit 245.

The laser generator 200 generates a laser and irradiates the generated laser beam to the first reflection mirror 210. The laser beam generated and irradiated by the laser generator 200 may be a laser beam having a Gaussian profile having a high energy density at the center portion and a low energy density at the edge.

As such, the laser generator 200 may include a solid state laser oscillator capable of generating a laser beam using a solid state laser. For example, the laser generator 200 may include an Nd: YAG laser generator, an Nd: YLF laser generator, an Nd-YVO ₄ laser generator, and the like.

The image information generation unit 205 receives the visible light reflected from the register 230 and the electrode pattern 235 connected to the register 230 and outputs the image information of the register 230 and the electrode pattern 235 of the portion to be laser trimmed. Create

The image information generated by the image information generator 205 is transmitted to a controller (not shown) and used as a basis for determining the edge of the register 230.

The image information generator 205 may include a camera module. For example, a camera module using a charge coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, or the like may be used as the camera module. . CCD image sensor uses charge-coupled device (CCD) to accumulate and transfer charge generated by light energy and store image information as digital data in storage media. CMOS image sensor is an image sensor manufactured by CMOS process. The charge generated by the energy is read by a semiconductor switch to convert image information into digital data.

Accordingly, the image information generator 205 transmits the generated image information to the controller (shown in FIG. 2).

The axis of visible light transmitted to the image information generation unit 205 is preferably the same as the axis of the path of the laser beam. Thus, more accurate image information of the register 230 and the electrode pattern 235 can be generated.

The first reflection mirror 210 reflects the laser beam irradiated from the laser generator 200 to change the path of the laser beam such that the traveling direction of the laser beam is directed to the second reflection mirror 215.

The second reflection mirror 215 is composed of a semi-transparent mirror that reflects the laser beam reflected by the first reflection mirror 210 to the galvanometer scanner 220 and transmits visible light transmitted to the image information generator 205. Thus, the axis of the laser beam reflected by the second reflection mirror 215 and the axis of visible light transmitted to the image information generator 205 may be coaxially aligned.

Accordingly, the second reflecting mirror 215 reflects the laser beam reflected from the first reflecting mirror 210 to the galvanometer scanner 220, passes the visible light from the galvanometer scanner 220, and transmits the visible light. The image information generator 205 enters the image information generator 205.

In another embodiment of the present invention, only the first reflection mirror 210 and the second reflection mirror 215 are applied to the reflection mirror, but this is only an example, and in some cases, a plurality of reflection mirrors may be used.

The galvanometer scanner 220 guides the path of the laser beam reflected from the second reflection mirror 215 to irradiate the laser beam to the target area of the register 230 formed on the printed circuit board 240. In other words, the galvanometer scanner 220 adjusts the path of the laser beam to irradiate the laser beam to the target area of the register 230 to be processed.

In addition, the galvanometer scanner 220 guides the visible light from the register 230 and the electrode pattern 235 to the image information generator 205.

The focusing lens 225 focuses the laser beam guided by the galvanometer scanner 220 to the target area of the register 230. For example, the focusing lens 225 may use an f-theta lens, a telecentric lens, or the like.

The resistor 230 is formed through a screen printing process between the electrode patterns 235 formed to face each other. The resistor 230 may be formed of a carbon paste including carbon (C) and silver (Ag). As such, the register 230 is formed between the electrode patterns 235 on the printed circuit board 240 in a solution state, whereby the position where the resistor 230 is formed is inevitably changed with a predetermined deviation for each register. do.

The resistor 230 is formed of a film resistor such as a thin film resistor and a thick film resistor.

The electrode pattern 235 is formed to face each other on the printed circuit board 240 and may include one or more of copper or aluminum. As described above, the resistor 230 is formed between the electrode patterns 235 formed to face each other.

The resistance measuring unit 245 measures the resistance of the resistor 230 that is the object of laser trimming. In this case, the resistance measuring unit 245 may measure the resistance value of the resistor 230 by contacting the electrode pattern 235. . The resistance measuring unit 245 transmits the measured resistance value to a controller (not shown). As described above, the resistance measuring unit 245 may measure the resistance by contacting the electrode pattern 235 while the laser trimming is performed.

4 is a diagram illustrating a register to be processed by the laser trimming apparatus according to another embodiment of the present invention.

The electrode patterns 310 are formed to face each other on the printed circuit board protection layer 350, and a resistor 320 is formed between the formed electrode patterns 310 through a screen printing process.

In one embodiment of the present invention, laser trimming 330 starts from the start line 340 of laser trimming. The start line of the laser trimming may be set at any point of the register 320 where the substrate is not damaged by the irradiated laser, and in this embodiment, the boundary between the register 320 and the printed circuit board protective layer 350. That is, the edge of the register 320 is set to the start line 340 of the laser trimming.

The edge of the register 320 may be determined based on the image information of the register 320 generated by the image information generator (not shown) and the electrode pattern 310 connected to the register 320.

The laser trimming region 360 is formed only in the resistor 320 because the laser trimming 330 starts at or around the edge of the resistor 320.

Therefore, since the laser trimming is not performed on the printed circuit board protective layer 350, the printed circuit board protective layer 350 may not be damaged by laser trimming. In addition, since the laser trimming is performed only for the area where the laser trimming is required, the time required for laser trimming is relatively small as compared with the conventional technology in which the start position of the laser trimming is collectively determined.

As a result, the laser trimming time for one resistor is reduced, ensuring higher yields.

5 is a flow chart showing the flow of a laser trimming method according to another embodiment of the present invention.

In step S110, CAD data is read to determine a laser trimming object, that is, a position of a register. A plurality of resistors are formed on one embedded printed circuit board. Therefore, whenever the laser trimming is performed for each register, it is low in efficiency to manually grasp the position where the register is formed, that is, the position where the electrode pattern is formed, and to move the laser trimming apparatus to the position. Therefore, the position where each register is formed from the CAD data is determined, and whenever the laser trimming for one register is completed, the laser trimming device is automatically moved to the position of the next trimming target.

In step S120, the initial resistance value for the register at the position according to the CAD data read in step S110 is measured. More specifically, the resistance measuring unit measures the initial resistance value of the resistor by contacting the electrode pattern formed at the position according to the CAD data.

If the initial resistance value of the resistor measured in step S120 is larger than the set target resistance value, it is impossible to set the resistance value to the target resistance value by laser trimming, so that the resistor is repaired through the repair equipment or printing is not possible. The circuit board itself can be discarded.

In operation S130, image information of a register to be laser trimmed and an electrode pattern connected to the register is generated. As described above, the image information of the register and the electrode pattern may be generated by the image information generator, and the image information generator may include a camera module including a CCD image sensor or a CMOS image sensor.

If it is determined that the register is defective by comparing the image information of the register with the set image information based on the generated image information in step S130, the register is repaired through a repair apparatus, or if this is impossible, the printed circuit board itself is discarded. You can.

Steps S120 and S130 described above are not limited to the temporal order and may be performed simultaneously. When step S120 and step S130 are performed at the same time, the time required for laser trimming of the register may be shortened.

In step S140, the start line of laser trimming is determined using the image information generated in step S130. As described above, the start line of the laser trimming may be set to an edge of the register 320 or any point therein, and the laser trimming is started by comparing and analyzing the set image information and the generated image information with an image processing technique. You can set the line.

In step S150, the laser trimming is performed on the registers based on the start line of the laser trimming obtained in step S140. When laser trimming is started, laser trimming is started from the start line of laser trimming obtained in step S140. The laser beam used for laser trimming can be generated using a solid state laser.

When the laser trimming is performed on the resistor as described above, the cross-sectional area of the resistor through which the charge passes is reduced by cutting the resistor by the laser beam, thereby increasing the resistance value of the resistor.

In addition, while step S150 is in progress, the resistance measurement of step S120 and the generation of image information of step S130 are continuously performed, and the measured resistance value and the generated image information determine whether to stop laser irradiation. Is the basis.

In step S160, the resistance value of the laser-trimmed resistor is compared with the set target value, and it is determined whether the resistance value of the resistor has reached the set target value. The measurement of the resistance value may be performed by contacting the resistance measurement unit with an electrode pattern connected to the resistor. This allows the resistance value of the resistor to be changed as the laser trimming proceeds.

In step S170, when it is determined in step S160 that the resistance value of the resistor has reached the set target value, the laser trimming for the corresponding resistor is stopped, and the laser trimming device and the resistor to the register as the target of the next processing according to the CAD data. Move the measurement unit.

6 is a flow chart showing the flow of a laser trimming method according to another embodiment of the present invention.

Steps S240 to S70 of the embodiment shown in FIG. 6 are substantially the same as steps S140 to S170 of the embodiment shown in FIG. 5.

In the embodiment shown in FIG. 6, the step S220 of generating image information of the electrode pattern connected to the resistor and the resistor is performed before the step S230 of measuring the initial resistance value.

In this configuration, in step S230, not only the CAD data read in step S210 but also the image information generated in step S220 may be used as a basis for determining the position of the electrode pattern to which the register is connected. That is, since the resistance measurement unit determines the position of the electrode pattern in consideration of the CAD data read out in step S210 and the image information generated in step S220 together, and then measures the initial resistance value of the resistor, accurate pad contact Initial resistance measurements are possible.

By processing the resistor in this manner, the laser trimming time can be shortened, and damage to the printed circuit board due to the laser trimming can be minimized.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a diagram showing a register subject to laser trimming according to the prior art;

2 is a block diagram showing a configuration of a laser trimming apparatus according to an embodiment of the present invention;

3 illustrates a laser trimming apparatus according to an embodiment of the present invention;

4 is a view showing a register to be processed in the laser trimming apparatus according to another embodiment of the present invention,

5 is a flowchart showing a flow of a laser trimming method according to another embodiment of the present invention;

6 is a flow chart showing the flow of a laser trimming method according to another embodiment of the present invention.

Claims (24)

delete delete delete delete delete delete delete delete delete delete delete delete In the laser trimming method of the register using the image information processing, (a) measuring the resistance of the resistor; (b) repairing the resistor when the initial resistance value of the measured resistor is greater than a set target resistance value; (c) generating image information of the register and an electrode pattern connected to the register; and (d) controlling a laser beam irradiated to a register through an optical system based on the generated image information and the measured resistance value Laser trimming method comprising a. The method of claim 13, In step (d), (d1) determining a start line of laser trimming based on the generated image information; and (d2) performing laser trimming from the start line; Laser trimming method comprising a. The method of claim 14, Step (d1), And performing the image processing comparing the generated image information with the set image information. The method of claim 14, And the start line is an edge of the register. The method of claim 14, And the start line is any point within the register. The method of claim 13, In step (d), (d3) receiving the measured resistance value and comparing the received resistance value with a set target resistance value; and (d4) if the received resistance value reaches a target resistance value, stopping the laser trimming. The method of claim 13, In step (b), Discarding the substrate on which the register is formed if repair of the register is not possible. The method of claim 13, In step (d), (d7) comparing the generated image information with the set image information to determine an abnormally formed register; and (d8) if it is determined that the register is abnormally formed, stopping the laser trimming. The method of claim 13, (A) and (c) are performed simultaneously. The method of claim 13, Step (c) is performed before step (a), Wherein step (a) is performed by determining the position of the register based on the image information generated in the step (c). The method according to any one of claims 13 to 22, And the laser beam is generated using a solid state laser. The method according to any one of claims 13 to 22, And the image information is generated using a camera module.

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