JP5781894B2 - Method for adjusting resistance value of chip resistor - Google Patents

Description

  The present invention relates to a resistance value adjusting method that is performed by performing laser trimming on a large number of resistors printed on a collective substrate in a manufacturing process of chip resistors obtained by dividing a collective substrate into a large number. .

  The chip resistor includes a rectangular parallelepiped ceramic substrate, electrodes provided at both ends in the longitudinal direction of the ceramic substrate, a resistor provided between the electrodes, and an insulating material that covers the resistor. It is mainly composed of a protective layer and the like. Generally, when manufacturing a chip resistor, a large number of electrodes, resistors, protective layers, etc. are collectively formed on a large-sized collective substrate, and then the collective substrate is divided into vertical and horizontal dividing grooves. A large number of chip resistors are obtained by dividing the chip resistors.

  In the process of manufacturing such chip resistors, a large number of resistors (chip resistors) are printed in a matrix on the surface of the collective substrate. Due to the influence of unevenness, the resistance value of each resistor tends to vary. Therefore, when manufacturing a chip resistor, it is necessary to adjust the resistance value by performing laser trimming on each resistor in the state of the collective substrate.

  Specifically, a trimming groove is formed by sequentially irradiating a laser beam to a large number of resistors printed in a matrix on a collective substrate while measuring resistance values. Irradiation of the laser beam starts from a position before the resistor to be trimmed, and when the laser beam reaches the edge of the resistor, a trimming groove is formed. Since the resistance value increases as the trimming groove becomes longer, the laser beam irradiation is turned off when the resistance value of the resistor to be trimmed reaches a desired value. In this way, the resistors arranged in the same row are laser trimmed in order, the resistors arranged in the next row are sequentially laser trimmed, and thereafter, the laser trimming for all the resistors is completed in the same manner. Note that the resistance value of the resistor is measured using a probe or the like during laser trimming.

  By the way, since recent chip resistors are being miniaturized and automation of manufacturing is being promoted, there is an increased risk that chip resistors will be commercialized at the stage of the collective substrate even though the resistors have a trimming defect. . For example, when a trimming defect called “halfway cut” occurs in which the trimming groove is formed slightly from the edge of the resistor, the resistance value of the manufactured chip resistor is reduced during use. There is a risk of sudden change, and the reliability is significantly reduced. In addition, when the laser beam irradiation start position is shifted to the trimmed resistor side and a trimming defect called “both ends” occurs in this resistor, the resistance value of the manufactured chip resistor is It will be different from the design value. Therefore, it is desired to detect such a trimming failure promptly so that a defective chip resistor is not commercialized.

  Conventionally, as a measure for preventing a chip resistor having a poor trimming from being commercialized, an appearance inspection of a collective substrate after laser trimming has been often performed visually. However, in the inspection method of visually confirming the appearance, there is a possibility that a trimming defect may be overlooked, and there is a possibility that a defective chip resistor is manufactured in large quantities. In addition, a conventional technique is known in which a resistor during laser trimming is photographed with a CCD camera or the like, image-processed, and the position and shape of the trimming groove can be determined based on the image data. Since this method requires expensive trimming equipment, the manufacturing cost of the chip resistor increases as a result.

  Therefore, in the resistance value adjusting method in which the trimming of each resistor existing in the next row is performed in the same manner after the trimming of each resistor existing in the first row of the collective substrate is finished, The edge position of each resistor is detected and stored from the change start point of the resistance value at the time of trimming the resistor, and the irradiation start position of the laser beam to each resistor existing in the (N + 1) th column is set to the adjacent Nth column. Conventionally, a resistance value adjusting method determined from the edge position of the resistor has been proposed (see, for example, Patent Document 1). According to such a resistance value adjusting method, even when the position shift of the resistor gradually accumulates as the row to be trimmed advances, the irradiation start position of the laser beam is automatically corrected for the position shift. Therefore, it is possible to avoid the trimming failure of the chip resistor as much as possible while suppressing the increase in equipment.

JP-A-4-71203

  By the way, the resistance value adjusting method disclosed in Patent Document 1 refers to the edge position of the resistor in the front row based on the premise that the relative displacement between the resistors in the adjacent row is slight. The laser beam irradiation start position for each resistor in the next row is determined, but the relative displacement between the resistors in the adjacent row is not necessarily slight, It is also predicted that the temperature will increase beyond the allowable value due to uneven temperature during firing. In that case, the irradiation start position of the next row with reference to the edge position of the resistor in the previous row is not properly corrected, and there is a possibility that the above-described trimming failure referred to as “end cutting” may occur. If it is not detected, a defective chip resistor will be commercialized.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to provide a resistance adjustment method for a chip resistor that can quickly and accurately detect the occurrence of a trimming defect in the manufacturing process of the chip resistor. Is to provide.

  In order to achieve the above-mentioned object, the present invention measures the resistance value sequentially for a large number of resistors printed and formed in a predetermined arrangement on a collective substrate for taking a large number of chip resistors. In the resistance value adjustment method for a chip resistor, in which the resistance value is adjusted by irradiating a laser beam to form a trimming groove, the laser beam reaches the resistor and trimming from the time when the irradiation of the laser beam is started. The elapsed time t until the groove starts to be formed is measured based on the change in the measured resistance value, and only when this elapsed time t is zero or longer than the preset allowable time T (t = 0 or t> T). It was determined that a trimming failure occurred.

  In the laser trimming process that is performed to adjust the resistance value of each resistor in the state of the collective substrate, when the laser beam reaches the resistor after the irradiation of the laser beam is started, a trimming groove is formed in the resistor to be trimmed. Therefore, by comparing the measured resistor arrival time (elapsed time t) with a preset allowable time T, it is possible to detect in real time that a trimming failure has occurred. That is, when the trimming defect called “halfway cut” occurs when the irradiation start position of the laser beam is shifted to the inside of the edge of the resistor to be trimmed, the resistor arrival time t becomes zero. Based on this measured value (t = 0), the occurrence of “halfway cut” can be detected quickly and accurately. In addition, when the laser beam irradiation start position is undesirably shifted to the trimmed resistor side and a trimming defect called “both ends” occurs, the resistor arrival time t becomes longer than the allowable time T. Therefore, it is possible to quickly and accurately detect the occurrence of “end cutting” based on the measured value (t> T). Then, when a resistor that is determined to be defective in trimming is detected, after the trimming operation is interrupted, the collective substrate including the resistor is processed as a defective product, or identification marking is applied to the resistor. If this is the case, there is no possibility that a defective chip resistor will be commercialized.

  When the laser beam reaches the resistor, the measured resistance value of the resistor starts to change (increase), so that the formation start point of the trimming groove in the resistor to be trimmed can be accurately grasped. Further, since the relative moving speed of the laser beam along the surface of the collective substrate is constant from the irradiation start time to the trimming groove formation start time, based on the measured value of the elapsed time t which is the resistor arrival time, The linear distance from the irradiation start position to the edge of the resistor can also be accurately grasped.

  In the resistance value adjusting method for the chip resistor according to the present invention, the measured value of the resistor arrival time t that elapses from when the laser beam reaches the resistor from the irradiation start position is set to zero (t = 0) or preset. Since it is determined that a trimming defect has occurred only when it is longer than the allowable time T (t> T), if a trimming defect referred to as “halfway cut” or “both end cut” occurs, Can be detected quickly and accurately, and the trimming operation can be interrupted. Therefore, there is no possibility that a defective chip resistor will be commercialized, and an excellent effect is achieved that a highly reliable chip resistor can be mass-produced. Further, since a trimming failure can be detected using a normal trimming facility, the initial cost does not increase and the productivity is not adversely affected.

It is a principal part top view of the aggregate substrate which shows the state by which the chip resistor was normally laser-trimmed. It is explanatory drawing which shows the resistor arrival time corresponding to FIG. It is a principal part top view of the aggregate substrate which shows the state where the trimming defect called halfway cut occurred in the resistor for chips. It is explanatory drawing which shows the resistor arrival time when this halfway cut | disconnection occurs. It is a principal part top view of the aggregate substrate which shows the state which the trimming defect called the both-ends cutting generate | occur | produced in the resistor for chips. It is explanatory drawing which shows a resistor arrival time at the time of this both-ends cutting | disconnecting. It is sectional drawing which shows a general chip resistor typically. FIG. 8 is a schematic process diagram for explaining the manufacturing method of the chip resistor shown in FIG. 7.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A resistance value adjusting method according to an embodiment of the present invention provides resistance to a chip resistor provided on a collective substrate at the time of manufacturing a chip resistor. This is applied in a laser trimming process performed to adjust the value.

  First, a configuration of a general chip resistor and a manufacturing method thereof will be described with reference to FIGS.

  The chip resistor 1 shown in FIG. 7 includes a rectangular parallelepiped ceramic substrate 2, a pair of back electrodes 3 provided at both ends in the longitudinal direction on the lower surface of the ceramic substrate 2, and a longitudinal direction on the upper surface of the ceramic substrate 2 in the illustrated direction. A pair of surface electrodes 4 provided at both ends of the substrate, a resistor 5 provided between the surface electrodes 4, an insulating protective layer 6 covering the resistor 5, and a ceramic substrate 2 is provided with a pair of end face electrodes 9 provided on both end faces in the longitudinal direction to bridge the front face electrode 4 and the back face electrode 3. 9 and the back electrode 3 are coated with a plating layer 10.

  Explaining in detail with reference to FIG. 8, the ceramic substrate 2 of the chip resistor 1 is obtained by dividing the collective substrate 20 along the vertical and horizontal dividing grooves 21 and 22 into individual pieces. Although shown in a simplified manner in FIG. 8, a large number of dividing grooves 21 and 22 are actually formed in one collective substrate 20, and this collective substrate 20 corresponds to a large number of chip resistors 1. A large number of backside electrodes 3, front surface electrodes 4, resistors 5, protective layers 6, and the like are collectively formed. The resistance value of the chip resistor 1 is adjusted by irradiating the resistor 5 with a laser beam to form a trimming groove 11. The protective layer 6 has a two-layer structure in which an undercoat layer 7 formed before adjusting the resistance value for trimming the resistor 5 and an overcoat layer 8 formed after adjusting the resistance value are laminated. Yes. Further, the end face electrode 9 is formed on a split surface of a strip-like substrate 23 obtained by primary division of the collective substrate 20, and after the end face electrode 9 is formed, the strip-like substrate 23 is secondarily divided into individual pieces (chips alone). Thus, the plating layer 10 is applied to each chip alone. Generally, the plating layer 10 includes an innermost nickel (Ni) plating layer that is in close contact with the base electrode layer, and an outermost solder (Sn / Pb) plating layer or tin (Sn) plating layer that is exposed on the outer surface. It is the laminated structure of 2 or more layers containing these.

  The manufacturing method of the chip resistor 1 will be briefly described. First, an aggregate substrate 20 in which vertical and horizontal dividing grooves 21 and 22 are formed is prepared, and silver paste or the like is provided at substantially corresponding positions on both the front and back surfaces of the aggregate substrate 20. Are printed and fired to form a large number of back electrodes 3 and front electrodes 4 at a time. In the collective substrate 20, each of the squares divided by both the dividing grooves 21 and 22 becomes a chip area, but the back electrode 3 and the front electrode 4 are connected via the primary dividing grooves 21. It is continuously formed at one longitudinal end of one adjacent chip region and the other longitudinal end of the other chip region.

  Next, a resistor paste such as ruthenium oxide is screen-printed and fired on each chip region on the surface of the collective substrate 20 to form a large number of resistors 5 at a time. At that time, both ends in the longitudinal direction of the resistor 5 are overlapped with the surface electrode 4 respectively.

  After that, an undercoat layer corresponding to a primary protective coat covering the resistor 5 is obtained by screen-printing and baking a glass paste in a region covering each resistor 5 individually, as shown in FIG. 7 is formed. This undercoat layer 7 is for preventing the vicinity of the trimming groove 11 of the resistor 5 from being damaged by the heat of the laser beam irradiated in the next step.

  That is, as a next step, as shown in FIG. 8B, a large number of resistors 5 covered with the undercoat layer 7 are sequentially trimmed by irradiation with a laser beam while measuring resistance values. By forming the groove 11, the resistance value of each resistor 5 is adjusted. At this time, as shown in FIG. 1, irradiation of the laser beam starts from a position before the resistor 5 to be trimmed, and when the laser beam reaches the edge 5a of the resistor 5, the trimming groove 11 starts to be formed. Since the resistance value increases as the trimming groove 11 becomes longer, the laser beam irradiation is turned off when the resistance value of the resistor 5 to be trimmed reaches a desired value. During the laser trimming, the resistance value of the resistor 5 is measured using a probe or the like.

  In the resistance value adjusting method according to this embodiment, in the laser trimming step, an elapsed time t until the laser beam reaches the resistor 5 from the irradiation start position P (hereinafter referred to as a resistor arrival time). Only when the measured value of the resistor arrival time t is zero (t = 0) or longer than the preset allowable time T (t> T), the trimming failure is determined. Will be described later.

  After the laser trimming for a large number of resistors 5 printed and formed on the surface of the collective substrate 20, as shown in FIG. 8C, a resin paste (or glass paste) covering the undercoat layer 7 and the trimming groove 11 is obtained. ) Is screen printed and cured by heating to form an overcoat layer 8 corresponding to the secondary protective coat covering the resistor 5 and the undercoat layer 7. This overcoat layer 8 is for protecting the resistor 5 from the external environment. By forming the undercoat layer 7 and the overcoat layer 8 in this manner, the protective layer 6 having a two-layer structure covering the resistor 5 is obtained.

  The process so far is a batch process for the collective substrate 20, but in the next process, a primary break process is performed in which the collective substrate 20 is divided into strips along the primary division grooves 21 by a break. As a result, as shown in FIG. 8D, a strip-shaped substrate 23 provided with a plurality of chip regions is obtained.

  Then, in the next step, the end surface electrode 9 is formed by sputtering Ni / Cr or the like on the divided surface of the strip-shaped substrate 23 or by applying and drying Ag paste or the like, and the end surface electrode 9 forms the back surface. The electrode 3 and the surface electrode 4 are bridged to obtain a base electrode layer continuous in a U shape.

  Thereafter, a secondary break process is performed in which the strip-shaped substrate 23 is divided along the secondary dividing grooves 22 by a break, thereby obtaining a piece (chip alone) having a size equivalent to that of the chip resistor 1.

  Finally, the base electrode layer (surface electrode 4, end face electrode 9, and back electrode 3) of each chip that has been singulated is subjected to nickel plating or solder plating to cover the base electrode layer. By forming the plating layer 10, the chip resistor 1 is completed.

  As described above, in the resistance value adjusting method according to the present embodiment, in the laser trimming process for adjusting the resistance value of the resistor 5, the laser beam passes from the irradiation start position P until it reaches the resistor 5. The resistor arrival time t is measured. At this time, when the laser beam reaches the resistor 5 and the formation of the trimming groove 11 is started, the measured resistance value starts to change (increase) from the point of arrival, so that the resistor arrival time t is equal to the resistor 5. Can be measured with high accuracy based on the change in resistance value. In this embodiment, it is determined that a trimming failure has occurred only when the measured value of the resistor arrival time t is zero (t = 0) or longer than the preset allowable time T (t> T). . Since the relative moving speed of the laser beam along the surface of the collective substrate 20 is constant from the irradiation start time to the trimming groove 11 formation start time, the laser beam irradiation start position P is determined based on the resistor arrival time t. The straight line distance to the resistor 5 can be accurately grasped.

  Thus, by comparing the measured value of the resistor arrival time t with the allowable time T in the laser trimming step, it becomes possible to detect in real time when a trimming failure has occurred. For example, as shown in FIGS. 1 and 2, the resistor arrival time t that elapses from the start of irradiation of the laser beam at the position before the resistor 5 to be trimmed until the edge 5a of the resistor 5 is reached. However, if it is shorter than the allowable time T (t ≦ T) and not zero (t ≠ 0), the trimming groove 11 is formed in the resistor 5 without any problem, and one trimming groove 11 has already been formed. There is no adverse effect on the resistor 5 (lower side in FIG. 1). 2, the horizontal axis (time axis) shows the symbol A when the irradiation start position P is irradiated with the laser beam, and the point when the laser beam reaches the resistor 5 and the trimming groove 11 starts to be formed. The code | symbol B is attached | subjected to.

  However, the irradiation start position P of the laser beam is shifted to the inside of the edge 5a of the resistor 5 to be trimmed, and a trimming defect called “halfway cut” as shown in the upper resistor 5 in FIG. If it occurs, the measured value (t = 0) at which the resistor arrival time t becomes zero as shown in FIG. 4 can be detected promptly. That is, in this case, since the trimming groove 11 starts to be formed in the resistor 5 at the laser beam irradiation start time A, the irradiation start time A becomes the trimming groove formation start time B as it is.

  In addition, the laser beam irradiation start position P is undesirably shifted to the resistor immediately before the trimming groove is formed, and as shown in the lower resistor 5 in FIG. When a defect occurs, as shown in FIG. 6, the resistor arrival time t becomes longer than the allowable time T (t> T), so that the occurrence of such “end cutting” can be detected quickly. However, since the distance d (see FIG. 5) between the resistors 5 adjacent to each other in the same row may vary slightly due to the influence of printing misalignment or blurring, even if such variation is taken into consideration, “end cutting” cannot occur. It is preferable that the longest time for reaching the resistor is determined as the allowable time T. In this way, the resistor arrival time t may be longer than the allowable time T even though “end cutting” has not actually occurred, but on the other hand, “end cutting” has occurred. Reliability can be increased because it can be reliably detected.

  As described above, in the resistance value adjusting method according to this embodiment, the measured value of the resistor arrival time t that elapses until the laser beam reaches the resistor 5 from the irradiation start position P is zero (t = 0) or a trimming failure is determined only when it is longer than a preset allowable time T (t> T). Therefore, when a trimming failure called “halfway cut” or “both end cut” occurs. This can be detected quickly and accurately to stop the trimming operation. When the resistor 5 determined to be defective in trimming is detected, after the trimming operation is interrupted, the collective substrate 20 including the resistor 5 is processed as a defective product, or the resistor 5 is used for identification. If marking is performed, there is no possibility that the defective chip resistor 1 will be commercialized. Therefore, there is no possibility that the defective chip resistor 1 is commercialized, and the highly reliable chip resistor 1 can be mass-produced. Further, since a trimming failure can be detected using a normal trimming facility, the initial cost does not increase and the productivity is not adversely affected.

DESCRIPTION OF SYMBOLS 1 Chip resistor 2 Ceramic substrate 3 Back surface electrode 4 Front surface electrode 5 Resistor 5a (resistance body) edge 6 Protective layer 9 End surface electrode 10 Plating layer 11 Trimming groove 20 Collective substrate 21, 22 Divided groove t Resistor arrival time (elapsed time) time)
P (Laser beam) irradiation start position T Allowable time

Claims (1)

By forming a trimming groove by sequentially irradiating a laser beam while measuring the resistance value on a large number of resistors printed in a predetermined arrangement on a collective substrate for taking a large number of chip resistors In the resistance value adjusting method of the chip resistor for adjusting the resistance value,
The elapsed time t from when the irradiation of the laser beam is started until the trimming groove is formed after the laser beam reaches the resistor is measured based on the change in the measured resistance value. A resistance value adjusting method for a chip resistor, characterized in that it is determined that a trimming failure has occurred only when it is longer than a preset allowable time T (t = 0 or t> T).