JP2827608B2 - Laser trimming method for thick film resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick film hybrid IC.
The present invention relates to a laser trimming method for a thick-film resistor for correcting a thick-film resistor used for a device or the like to a predetermined resistance value, and more particularly to a laser trimming method for obtaining high power handling characteristics and high pulse characteristics.

[0002]

2. Description of the Related Art Conventionally, in manufacturing a thick film hybrid IC, in order to set the resistance accuracy of a thick film resistor which is a constituent element of the thick film hybrid IC to a predetermined value, after printing and firing, a laser beam is used. Trimming has been performed.

In a conventional trimming process, a desired resistance value is obtained by cutting a fired thick film resistor into a predetermined shape with a laser beam while measuring the resistance value in real time. Further, as the trimming shape, various shapes have been proposed depending on desired resistance value accuracy, power resistance characteristics, pulse resistance characteristics, production cost, and the like.

A conventional trimming method will be described with reference to FIGS. 2A and 2B are plan views of a thick film resistor trimmed by a conventional trimming method. FIG. 2A shows a thick film resistor trimmed by an L-cut, and FIG. 2B shows a thick film resistor trimmed by a hook cut. FIG. 3C shows a thick film resistor that has been processed, and FIG. 3C shows a thick film resistor that has been trimmed by scan cutting. FIG.
FIG. 4 is an enlarged plan view showing a thick film resistor trimmed by an L-cut, and FIG. 4 is an enlarged plan view showing a thick film resistor trimmed by a scan cut.

In these figures, reference numeral 1 denotes a substrate (not shown)
The thick film resistor 2 formed thereon is an electrode of the thick film resistor 1.

Reference numeral 3 denotes a trimming trace at the time of the L-cut, 4 denotes a trimming trace at the time of the hook cut, and 5 denotes a trimming trace at the time of the scan cut.

The L-cut shown in FIG. 2A has an advantage that the trimming accuracy is as good as about ± 0.5% and the cutting speed is high. However, since the trimming end point 7 remains inside the thick film resistor 1, there is a problem that a micro crack 8 is generated from the trimming end point 7 as shown in an enlarged manner in FIG. When the micro crack 8 occurs, the power resistance characteristic and the pulse resistance characteristic are deteriorated.

In the hook cut shown in FIG. 2B, since the trimming end point does not remain in the thick film resistor 1, the power resistance characteristics and the pulse resistance characteristics are good, but after reaching the desired resistance value. Since the thick-film resistor 1 must be unconditionally cut from the site, the resistance value accuracy is reduced to about ± 3%.

The scan cut shown in FIG. 2 (c) is a method of trimming by overlapping cuts by a laser beam in parallel with the direction of current flow in the thick film resistor 1, and the pitch of the cuts compared to the cut width. Is set to a small value and trimming is performed. In this method, as shown in FIG. 4, microcracks 8 are generated from the trimming end point 9, but the above-described L
The amount is smaller than the cut, and the influence on the remaining thick film resistor 1 is also reduced.

For this reason, according to the scan cut, both the power resistance characteristic and the pulse resistance characteristic are good, and the resistance value accuracy by trimming is about ± 0.5%.

[0011]

However, when trimming is performed by the above-described scan cutting, the laser light must be reciprocated a number of times in this method, so that there has been a problem that the processing time becomes long.
The processing time for this scan cut is several tens of times longer than the processing time for the L cut.

[0012]

According to a laser trimming method for a thick film resistor according to the present invention, a first cut is made in a direction orthogonal to the direction of a current flowing through the thick film resistor, and then the thick film resistor is cut. The second cut is made in an arc shape with the end point of the first cut as an apex from the side of, and the resistance value is measured. Based on this resistance value, the radial direction of the second cut from the first cut end point is determined. Calculate the dimension up to the area where the corrected resistance value is obtained outside, and then set the area separated from the end point of the first cut by the calculated dimension as the apex, and circle through the start point and end point of the second cut. The third cut is performed in an arc shape.

[0013]

The micro crack generated at the trimming end point of the first cut is deleted by the second cut and the third cut. Further, the first to third cuts are performed in such a manner that a straight line or a curve is drawn in one behavior, and thus each of the first and third cuts is performed quickly by a simple operation.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIG. FIG. 1 is a plan view of a thick film resistor trimmed by a laser trimming method for a thick film resistor according to the present invention. In this figure, the same or equivalent members as those described in FIGS. 2 to 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. In FIG. 1, reference numeral 11 denotes a trimming trace by the first cut of the present invention, and 12 denotes a second trace.
Traces of trimming by cutting, and 13 indicate traces of trimming by the third cut. These are all formed by irradiating the thick film resistor 1 with a laser beam.

Next, a laser trimming method according to the present invention will be described. First, a rough first cut is performed in a direction orthogonal to the direction of the current flowing through the thick film resistor 1.
At this time, the desired set value of the thick film resistor 1 is set to R _N
(Ω), the initial value before trimming is R _i1 (Ω),
The trimming target value R ₁ (Ω) for the first cut is obtained by the following equation.

R ₁ = (R _N −R _i1 ) × (α / 100) + R _i1 (Ω) The constant α is set in advance (α: 0 to 0)
100%). The start point of the first cut is designated by reference numeral 1 in FIG.
4 and the end point is indicated by 15.

Next, a first cut end point 15, an arc cut start point 16 and an arc cut end point which are separated from the first cut start point 14 by a half of a preset arc cut / cut width L. Then, a trimming process is performed in an arc shape so as to pass through the step 17, and a second cut which is a second coarse adjustment is performed. The arc cut start point 16 (second cut start point) and the arc cut end point 17 (second cut end point) are positioned on the sides of the thick film resistor 1.

Next, after the second cut is performed, the resistance value is measured again. If the resistance value at this time is R _i2 (Ω) and the cut length of the first cut is D ₁ , the cut depth D ₂ of the third cut to be obtained is obtained by the following equation.

D ₂ = D ₁ + {(R _N −R _i2 ) / R _N } × β (mm)

Here, the constant β is set in advance.

Thereafter, the third cut vertex 18 based on the calculated third cut / cut depth D ₂ , the circular cut start point 16 (second cut start point), and the circular cut end point 17 (second cut start point) Then, trimming is performed in an arc shape so as to pass through (cut end point), and a third cut, which is a fine adjustment, is performed.

In performing the above-described first to third cuts, the predetermined constants α, β and L are determined by the distribution of the external dimensions, aspect ratio (aspect ratio), and initial value of the thick film resistor 1. Therefore, a test is performed on the thick film resistor 1 before actually performing the trimming process.

Therefore, according to the laser trimming method according to the present invention, the micro crack generated at the first cut end point 15 is deleted by the second cut and the third cut. Further, since the first to third cuts are performed so as to draw a straight line or a curve in one behavior, they can be quickly performed by simple operations.

[0024]

As described above, the laser trimming method for a thick-film resistor according to the present invention performs the first cut in a direction perpendicular to the direction of the current flowing through the thick-film resistor.
From the side of the thick film resistor, a second cut is made in an arc shape with the end point of the first cut as a vertex, and a resistance value is measured. Based on this resistance value, a second cut is made from the end point of the first cut. Calculate the dimension up to the portion where the corrected resistance value is obtained on the radially outer side of the cut, and then set the portion separated from the end of the first cut by the calculated size as the vertex, and Since the third cut is performed in an arc shape through the end point, the micro crack generated at the trimming end point of the first cut is deleted by the second cut and the third cut. Further, the first to third cuts are performed in such a manner that a straight line or a curve is drawn in one behavior, and thus each of the first and third cuts is performed quickly by a simple operation.

For this reason, the resistance value accuracy (about ± 0.5%) of the conventional scan cut can be obtained. In addition, since the cut end point does not remain in the thick film resistor and there is no portion bent at a right angle such as an L-cut or a hook-cut, extremely excellent high power handling characteristics and high pulse characteristics can be obtained. The cut amount is 2-3 for L cut and hook cut.
Since the trimming speed is about twice, the trim speed does not become so slow, and the trimming can be performed in a processing time of about two to three times the L-cut.

Therefore, according to the present invention, it is possible to manufacture a thick film resistor having high accuracy, high withstand power characteristics, and high withstand pulse characteristics at a practical production cost.

[Brief description of the drawings]

FIG. 1 is a plan view of a thick film resistor trimmed by a laser trimming method for a thick film resistor according to the present invention.

FIG. 2 is a plan view of a thick-film resistor trimmed by a conventional trimming method. FIG. 2A shows a thick-film resistor trimmed by L-cut, and FIG.
Shows a thick film resistor trimmed by hook cut, and FIG. 3C shows a thick film resistor trimmed by scan cut.

FIG. 3 is an enlarged plan view showing a thick film resistor trimmed by L-cut.

FIG. 4 is an enlarged plan view showing a thick film resistor trimmed by scan cutting.

[Explanation of symbols]

 1 Thick film resistor 2 Electrode 14 First cut start point 15 First cut end point 16 Second cut start point 17 Second cut end point 18 Third cut vertex

Claims (1)

(57) [Claims] 1. A laser trimming method for a thick film resistor for trimming a thick film resistor with a laser beam and correcting the resistance value to a specified value. The method for trimming a thick film resistor in a direction orthogonal to a direction of a current flowing through the thick film resistor. One cut is made, and then a second cut is made in an arc shape from the side of the thick film resistor with the end point of the first cut as a vertex, and the resistance value is measured. Based on this resistance value, Calculate a dimension from the first cut end point to a portion radially outside the second cut and at which a corrected resistance value is obtained, and then set a portion separated from the first cut end point by the calculated size as a vertex, And performing a third cut in an arc shape through a start point and an end point of the second cut.