KR100585203B1 - Method of manufacturing a buried resistor for printed circuit board - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of printed circuit boards (PCBs), and more particularly to embedding resistors, which can reduce errors and simplify the trimming process in the step of fine tuning resistors formed by laser trimming in the manufacture of printed circuit boards having embedded resistors. It relates to manufacturing technology. The present invention is to control the resistance variation in only one direction by increasing the ratio of length and width among the mask shape of the buried resistor applied to the printed circuit board, as a result of performing the laser trimming process in only one direction as well as laser trimming By omitting the resistance check step before and after the process, the working yield can be improved.

Printed circuit board, buried resistor, laser trimming.

Description

METHODS OF MANUFACTURING A BURIED RESISTOR FOR PRINTED CIRCUIT BOARD

1A-1D illustrate one embodiment of a process for manufacturing a buried resistor in accordance with the prior art;

2A and 2B are characteristic views showing the shape of a mask pattern for manufacturing a buried resistor according to the prior art and the present invention, respectively.

3A and 3B are views illustrating a process of performing laser trimming after fabricating a buried resistor according to the prior art and the present invention, respectively.

<Explanation of symbols for the main parts of the drawings>

10: substrate

20: resistance metal

30: conductive metal

40: photoresist

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of printed circuit boards (PCBs), and in particular, in the manufacture of printed circuit boards having buried resistors, the error reduction and trimming in the step of fine tuning the resistor formed through laser trimming It relates to a buried resistor manufacturing technology that can simplify the process.

A printed circuit board is a board on which electronic circuit components such as transistors and semiconductor integrated circuit chips are mounted, and an external resistor must be used for signal coupling of each component. However, in recent years, as the signal processing use frequency of electronic circuits used in printed circuit boards is increased, the above-described external resistors have a technical limitation in meeting the technical trend of requiring high density mounting.

In order to solve this problem, a buried resistor is used in a printed circuit board. A buried resistor is a technology in which a conductive pattern between a contact and a contact is formed by directly filling an upper portion of an insulating layer of a printed circuit board with a resistance pattern of a corresponding resistive capacitance, and a buried resistor technique is Omega-Ply. ) Is disclosed in Japanese Patent Application Laid-Open No. 2000-36300.

1A to 1D illustrate an embodiment of a process of manufacturing a buried resistor according to the prior art. Referring to FIG. 1A, a resistive metal 20 thermocompressed under high temperature and high pressure on a substrate 10 and a conductive metal (for example, copper) 30 are formed thereon. Here, the photoresist 40 is applied to the entire surface of the substrate to form a pattern for forming a buried resistor.

Subsequently, by filling the photoresist 40, a buried resistance pattern having a width of W and a length of L is formed. Subsequently, in FIG. 1C, the conductive metal 30 is etched to have a width of W and a length of L by using the patterned photoresist film 40 as a mask.

As a result, a buried resistor is formed between the contact and the contact. However, in the process of etching the conductive metal 30 using the patterned photoresist film 40 as a mask, the copper film 30 is often etched using copper sulfate corrosion solution (CuSO ₄ · 5H ₂ O). The copper film 30 may be overetched to have the shape of the cross section A shown in FIG. 1C.

In another case, when the copper conductive metal 30 is underetched as shown in FIG. 1D, a cross-section B as shown in FIG. 1D may be shown. As a result, the resistance value of the buried resistor produced as a result of the above-described manufacturing process may cause an error more than the tolerance due to the deviation of the width W and the length L of the formed buried resistor.

In order to solve such a problem, the prior art uses a laser after forming the buried resistor (FIGS. 1C and 1D), and the conductive metal 30 remains in the width (W) and length (L) directions of the buried resistor. The step of correcting the resistance value is further performed by trimming the edge of the?

However, in the case where there may be a deviation in the material constant of the resistor of the buried resistor itself, the magnitude of the error generated when the buried resistor is bidirectionally laser trimmed in the width (W) direction and the length (L) direction is Δx △ Increased to y, the laser trimming process is complicated, there is a technical problem that the production yield is lowered and the manufacturing cost is increased.

Accordingly, a first object of the present invention is to provide a manufacturing method that can simplify a laser trimming process for tuning the resistance value of a buried resistor in a buried resistor manufacturing step for a printed circuit board.

A second object of the present invention is to provide a manufacturing method that can easily produce a buried resistor within an allowable error in manufacturing a printed circuit board in addition to the first object.

In order to achieve the above object, the present invention provides a method for forming an embedded buried resistor in a printed circuit board, (a) is applied over a conductive metal layer formed on the resistive metal formed on the printed circuit board and the resistive metal Patterning the formed photoresist so that a resistor having a width of W and a length of L is formed, and designing a pattern (L> W) so that the length of L is longer than the width W (L> W); (b) following step (a), forming a resistor by pattern etching the exposed conductive metal using the patterned photoresist as a mask; And (c) as a result of step (b), laser trimming is performed on a resistor formed of a resistive metal having a width W and a length L (L> W) by a predetermined value only in one direction in the width direction, thereby resisting the resistor. A method of manufacturing a buried resistor in a printed circuit board comprising tuning a value.

Hereinafter, a technology for manufacturing a buried resistor according to the present invention will be described in detail with reference to FIGS. 2 and 3. In the method of manufacturing a buried resistor according to the present invention, the ratio of the width W and the length L of the buried resistor shown in FIG. 2 is relatively large, whereby the error of the resistance value due to the variation of the pad shape generated during the etching process is long. The laser trimming is performed only in the remaining direction (width W direction) by inducing it to occur less in the (L) direction, thereby reducing the resistance value checking time required before and after the laser trimming process and improving the productivity of the substrate.

2A and 2B are diagrams characteristically showing the shape of a mask pattern for manufacturing a buried resistor according to the prior art and the present invention, respectively. Comparing the buried resistance mask pattern shown in Figures 2a and 2b it can be seen that the length ratio of W: L of the buried resistance mask pattern according to the present invention is larger than the pattern shape according to the prior art. That is, it is characterized by making the longitudinal direction larger than the width direction.

According to the present invention, if the length ratio of the mask pattern W / L of the buried resistor is increased, the resistance change rate ΔL / L in the length L direction becomes smaller than the resistance change rate ΔW / W in the width direction.

Therefore, after the conductive metal 30 layer is etched by the wet etching method, the laser trimming may be performed only in the width (W) direction.

3A and 3B are views illustrating a process of performing laser trimming after fabricating a buried resistor according to the prior art and the present invention, respectively. Referring to FIG. 3A, in the prior art, after checking the resistance value of the manufactured resistor, laser trimming is performed in the X and Y directions to have a desired resistance value.

Then, the process of checking the resistance value of the resistor again is repeated. In contrast, referring to FIG. 3B, when the laser trimming is performed by a predetermined value in the width (W) direction by increasing the ratio of W: L, the resistance change rate in the W direction is zero and the etching rate is increased. The change rate of resistance as much as the change in length is the total change rate of resistance.

This is an advantage that the resistance measurement step before and after laser trimming can be omitted since the design can satisfy the error level required by the manufacturer. As a preferred embodiment of the present invention, when the resistance management range is ± 10%, the ratio of W and L may be 2.0, and when the ratio is 5%, the ratio of W and L may be 4.0.

The foregoing has outlined rather broadly the features and technical advantages of the present invention to better understand the claims of the invention which will be described later. Additional features and advantages that make up the claims of the present invention will be described below. It should be appreciated by those skilled in the art that the conception and specific embodiments of the invention disclosed can be readily used as a basis for designing or modifying other structures for carrying out similar purposes to the invention.

In addition, the inventive concepts and embodiments disclosed herein may be used by those skilled in the art as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. In addition, such modifications or altered equivalent structures by those skilled in the art may be variously changed, substituted, and changed without departing from the spirit or scope of the invention described in the claims.

As described above, the present invention controls the resistance variation in only one direction by relatively increasing the ratio of length and width of the mask shape of the buried resistor applied to the printed circuit board, and as a result, the laser trimming process is performed only in one direction. In addition, the work yield can be improved by omitting the resistance check step before and after the laser trimming process. Therefore, laser trimming, which is currently three stages, can be simplified to a one-step process without resistance check. As a result, the time required for laser trimming can be reduced by 70% or more, so that the overall process time can be shortened and productivity can be improved.

Claims (2)

In the method of forming an embedded buried resistor in a printed circuit board, (a) patterning the resistive metal formed by thermocompression bonding to the printed circuit board and the photoresist applied on the conductive metal layer formed on the resistive metal to form a resistor having a width of W and a length of L, wherein Designing and forming a pattern such that the length of L is longer than that of L (W); (b) following step (a), forming a resistor by pattern etching the exposed conductive metal using the patterned photoresist as a mask; And (c) As a result of step (b), a laser trimming is performed on a resistor formed of a resistive metal having a width W and a length L (L> W) by a predetermined value only in one direction in the width direction to thereby obtain a resistance value of the resistor. To tune A buried resistor manufacturing method of a printed circuit board comprising a. delete

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