JPH02303013A - Capacitance value adjustment method of capacitor built in board - Google Patents

Abstract

PURPOSE:To stabilize the specific standard value by a method wherein, as to a capacitor positioned within the range under the effect of static electricity generated by cutting process using a trimming means, a pair of terminal electrodes is shortcircuited. CONSTITUTION:When the second capacitor C from the left side end in the figure is trimmed by a trimming means 13, the static electricity generated during the trimming process is diffused in the right and left side adjacent capacitors in the figure. The right and left side adjacent capacitor are shortcircuited at low impedance between both terminal electrodes by a conductive line 17 through the intermediary of switching contacts 16 so as to be discharged rapidly. Even if the trimming process is shifted to the right side adjacent capacitor after finishing the trimming process of the second capacitor from the left side, the possibility of the fluctuation in the adjusted capacitance value can be avoided after the trimming process regardless of the actual measurement of the capacitance value using a measuring instrument 15 by the effect dependent on DC voltage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a plurality of substrate-embedded capacitors built in the same insulating substrate, such as a ceramic substrate used as a circuit substrate of various electronic circuits. The present invention relates to a method for accurately adjusting the capacitance value of.

[Prior art] Technology has already existed in the past, especially hybrid integrated circuits (HICs).
) etc., a technology was proposed in which a part of the ceramic substrate, which serves as a circuit substrate on which various electronic circuit elements are constructed and supported, is also used as a telephone layer between the terminal electrodes of a capacitor necessary for the circuit, and The board is called a "board with built-in capacitor."

The capacitor-embedded portion of such a capacitor-embedded board is simply as shown in Figure 3, and there are conductor patterns 11 of a predetermined area, one on each of the front and back main surfaces of an insulating substrate lO such as a ceramic substrate. .
A capacitor C is formed in which a pair of terminal electrodes 11.degree. 11 are used, and a substrate portion between them is used as an inter-terminal dielectric layer.

When adopting such a structure, the dielectric layer area between the terminals on the substrate 10 is generally further spread around the surrounding area so that sufficient capacitance can be obtained as the capacitor C even if the electrode area formed by the conductor pattern 11.11 is small. Compared to other areas, the call rate is relatively high. However, since this point has no direct relation to the present invention, further explanation will be omitted.
Even in the drawings, this high dielectric constant region is not specifically shown.

In any case, in this way, the substrate 10 is effectively utilized in its thickness direction, and the pair of terminal electrodes 11, 11 of the capacitor is
If the dielectric layer between the terminals is made to sandwich the substrate IO and the dielectric layer between the terminals is made to have a fairly high dielectric constant, a capacitor with sufficient capacity can be obtained, but the planar occupation required by the terminal electrodes 11 and 11 is The area is relatively small, and only one electrode is required, which improves mounting efficiency.

Therefore, these days, users are using built-in capacitors like this to make full use of this significance.
There is a growing demand for substrates with even more and more densely integrated components.
More advanced technology is required.

For example, if there are multiple built-in capacitors on a single board, all of them must be precisely matched to their design specifications to pass the board as a board with built-in capacitors.In extreme cases, even one of them must meet the standards. If a capacitor fails to meet the required value, that board is discarded. Nevertheless, as the number of capacitors built into one substrate increases, the yield of the substrate tends to decrease. When there are n built-in capacitors, and the probability of defective products occurring in these capacitors is p, the rate of non-defective products as a board is (1-
p)'.

For this reason, for each built-in capacitor, it is of course not possible to leave them as they are, and adjustment of the capacitance value, that is, trimming, is considered to be an essential process. had been adopted.

First, the terminal electrodes 11.11 of each capacitor, which are patterned on the front and back surfaces of the insulating substrate IO, are made slightly thicker, and the capacitance value of each capacitor C is also slightly thicker than the standard value. Make sure it looks sharp.

Next, conductive probes 12, 12 are brought into ohmic contact with each of the capacitor terminal electrodes 11.11 thus formed in the trimming process, and the capacitance value of which built-in capacitor C is determined by operating the changeover switch 14. It is also possible to selectively actually measure the capacitance value using the capacitance value measuring device 15.

In this state, for example, as can be seen from the state of the contacts of the changeover switch 14 in FIG. Assuming that the capacitor is connected to the human power of a measuring device 15 through the closing contact of the switch 14, and that the capacitance value of this capacitor is currently being measured by the measuring device 15,
In order to reduce the measured capacitance value to a standard value, one of the pair of terminal electrodes 11, 11 of this capacitor is generally cut by a trimming means 13.

In this way, once the unit trimming procedure of cutting the thick terminal electrode 11 with the trimming means 13 and adjusting it to the standard value in the direction of reducing the electrode area is completed for one capacitor. , select the next capacitor to be trimmed (generally the adjacent capacitor) from among the group of other unprocessed capacitors by switching the selector switch 14, and apply the same unit trimming procedure as above to this capacitor. , After trimming of this capacitor is completed, trimming is performed on all capacitors in the next step B, and so on.

However, even though the trimming procedure is as described above, various devices have been used as the trimming means 13 in the past.

Some of these methods do not cut the capacitor terminal electrode physically or mechanically, but instead use a non-mechanical mechanism such as a laser trimmer that uses a laser beam to melt or evaporate the electrode material. However, there is a problem with this, for example, if the substrate surface becomes black due to oxidation as a result of some pre-process related to capacitor formation, such as patterning of capacitor electrodes, the laser beam should be trimmed. It is absorbed not by the electrodes but by the substrate surface, which may change the quality of the substrate itself, so special measures are required to prevent this.

Due to this problem, mechanical trimming methods have traditionally been preferred. Trimming devices based on the abrasive method, which physically scrape off the conductive material by blowing out highly stable fine particles from a nozzle together with compressed air and hitting the capacitor terminal electrodes, were often used. In fact, with this device, the controllability of the device itself is good, and the trimming precision can be quite high.

[Problems to be Solved by the Invention] However, according to the conventional method shown in FIG. On the other hand, when the present inventor performed trimming, there was no problem with previous capacitor-embedded boards with low integration densities, but with high-integration density capacitors, the spacing between adjacent capacitors has become considerably narrowed. When trimming each capacitor on the board, the capacitance value was actually measured using the measuring device 15 as shown in Figure 3, but after trimming, the capacitance value according to the standard value was not obtained. A situation arose.

Moreover, among the multiple built-in capacitors on the same board, only the first capacitor that was trimmed maintained the desired standard value, but for some reason, such errors occurred in the second and subsequent capacitors that were subsequently trimmed. occured.

The present invention first began by investigating the cause of this problem, and in conclusion, as a result of the study conducted by the present inventor, it was discovered that this was caused by the influence of "static electricity."

In other words, when a triging method is adopted in which fine particles collide with the surface of a terminal electrode at high speed to cut it, such as the abrasive method described above, the fine particles are not only exposed to the terminal electrode, but also to the surface of the surrounding ceramic substrate. collide.

As a result, static electricity is generated in the ceramic substrate, which is a galvanic body, in that area, and this also affects the capacitors that are very close to the capacitor currently being trimmed, resulting in the so-called DC voltage dependent effect (DC bias effect). I had given them an equivalent situation.

As is well known, when a DC voltage is applied to a capacitor, its capacitance value changes to a greater or lesser degree. During this period, the accumulated charge remains and the capacitance value continues to fluctuate as described above. This is what is called the DC voltage dependence effect.

As a result, even with the capacitor-embedded substrate considered here, when the integration density was still low,
Since the spacing between the adjacent capacitors was also relatively wide, the above-mentioned DC voltage dependent effect due to static electricity did not appear noticeably even on the adjacent capacitors and was not noticed.

However, as mentioned above, due to the recent demand for increased integration density, the spacing between adjacent capacitors has become extremely narrow.
The static charge generated when trimming one capacitor spreads to the dielectric layer between the terminal electrodes of the adjacent capacitor.
This accumulation caused the same effect as when a DC voltage was applied to the capacitor, causing the capacitance value to fluctuate.

In this type of capacitor-embedded board, an appropriate insulating layer is further formed on the terminal electrode of each capacitor, and then various signal circuits are formed on it, and each built-in capacitor functions as a component of such signal circuit. Until assembled, each terminal electrode is often placed in a substantially open state. Therefore, in the above-mentioned trimming process, a low-impedance discharge path does not yet exist, and during trimming, due to the measurement with the measuring device 15, Even if the terminal electrodes 11 and 11 are connected to the input of the measuring device 15 through the respective probes 12 and 12, the human power impedance of the measuring device 15 is still quite high as the measuring device is superior, so There is no way that an impedance discharge path will be created,
After all, the charge once accumulated in the dielectric layer of the built-in capacitor is
This capacitor cannot be discharged by the time it is time for trimming, and most of it remains.

On the other hand, if this is the reason, then the slightly strange fact that only the capacitor that was trimmed first was able to accurately maintain the standard value, as mentioned earlier, can be understood as a matter of course. This is because that capacitor was the only one that had never been exposed to an environment where static electricity was generated before trimming.

The present invention was made based on such knowledge, and
As typified by the above-mentioned abrasive type, the capacitance value may be adjusted by cutting at least one terminal electrode of the built-in capacitor using a trimming method that, in principle, can generate static electricity as a result of trimming. , it is an object of the present invention to provide a trimming method that can protect peripheral capacitors from DC voltage dependent effects.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, for a plurality of substrate-embedded capacitors, each of which uses a part of an insulating substrate as a dielectric layer between a pair of terminal electrodes, each capacitor is While measuring the actual capacitance value of each capacitor, at least one of the pair of terminal electrodes of each capacitor is cut using a trimming method that generates static electricity during the cutting process. When adopting the method of adjusting the capacitance value, the trimming method is applied to capacitors other than capacitors whose terminal electrodes have been actually cut, and which have not yet been subjected to cutting processing.
In addition, for capacitors located within the range affected by static electricity generated due to the cutting process currently being performed, a method is provided in which a pair of terminal electrodes of the capacitors are electrically short-circuited.

However, as mentioned above, this is not limited to capacitors that are located within the range affected by static electricity generated due to the cutting process that is currently being carried out. All capacitors that have no For all capacitors that have not undergone cutting, a pair of terminal electrodes may be short-circuited at once.

In practice, in the equipment system used to implement the method of the present invention, the last case is the most F, 3fJlt
It becomes L. This is because there is no need to consider the capacitors that are currently being trimmed and those that are not.

As is clear from the purpose of the present invention, the "short circuit" mentioned above is, in principle, preferably a conductive path with as low an impedance as possible, but Of course, the amount of resistance expected from electrical cords and printed wiring patterns is tolerable.

[Function] According to the present invention, the trimming means can be used to trim capacitors other than capacitors whose terminal electrodes are currently being cut, which have not yet been subjected to cutting processing, and whose terminal electrodes have not yet been subjected to cutting processing. Concerning capacitors located within the range affected by static electricity generated by static electricity, the pair of terminal electrodes of these capacitors are electrically short-circuited.
Even if a trimming means that generates static electricity is used, there is no risk of causing the aforementioned DC voltage dependent effect on surrounding capacitors.

Even if the electrostatic charge generated by trimming diffuses to an adjacent capacitor, the terminal electrodes of the capacitor are electrically shorted, and a discharge path with a short time constant is intentionally created. Therefore, there is no accumulation in this capacitor and it can be discharged quickly.

Therefore, naturally, when it is your turn to trim this capacitor, if you cut the electrode while actually measuring the capacitance value with a measuring device, you can accurately achieve the desired standard by trimming the first capacitor. The trimmed capacitance value will not fluctuate after that.

As is clear from the above, a capacitor whose pair of terminal electrodes should be electrically short-circuited during trimming is at least The trimming apparatus for realizing the method of the present invention may only be located in the vicinity of the capacitor being trimmed and within the range affected by the static electricity generated by the trimming.
Each time a different capacitor is trimmed, the range affected by the static electricity generated is different, so it may be rather troublesome to change the group of capacitors to be shorted each time. .

Therefore, if all uncut capacitors are shorted together, all of the uncut capacitors will be adjacent to the capacitor currently undergoing trimming, and the static electricity generated by trimming will within the range affected by.

Since a group of capacitors is necessarily included, the object of the present invention can of course be achieved, and at the same time, the burden on the device system is lightened.

This also applies regardless of whether or not the machine has undergone machining
If all capacitors that are not currently being trimmed are configured so that their terminal electrodes are short-circuited, then as explained earlier, for the capacitor that is currently being trimmed, the probe that is selectively selected by the changeover switch will be connected. When trimming is performed while actually measuring the capacitance value with a measuring device, the simplest device configuration can be adopted in relation to the contact configuration of the changeover switch.

[Embodiment] FIG. 1 shows an example of the configuration of a trimming device to which the present invention is applied. The same reference numerals as in FIG. 3 described above indicate constituent elements that may be the same or similar to those of the conventional example.

A plurality of capacitors C having a pair of terminal electrodes 11 and 11 sandwiching a part of this substrate in the thickness direction are built into the insulating substrate lO, and at least one of the pair of terminal electrodes 11 and 11 is connected to the insulating substrate lO. The electrode 11 is formed to have a slightly larger area than expected when giving a standard value to the capacitor, and is scheduled to be cut by the trimming means 13.

In this embodiment, as in the conventional example described above, the trimming means 13 blows fine particles having appropriate hardness and chemical and physical stability, such as alumina fine particles with a diameter of several tens of microns, from a nozzle together with compressed air. A trimming device that follows the abrasive method is used, which physically scrapes off the conductive material by hitting the capacitor terminal electrode with the conductive material.

However, this is not limiting; on the contrary, the present invention can be effectively applied even when using other known trimming means such as a sand trimmer or a rotary grindstone. This is because anything that follows mechanical cutting principles is likely to induce static electricity during trimming.

Also, in this embodiment, similarly to the conventional example described above,
A capacitor-embedded board containing a plurality of capacitors C, each of which has at least one terminal electrode 11 made slightly thicker, is placed at a predetermined position on a trimming device in order to adjust the capacitance value of each capacitor C. , each dedicated probe 12.1 is attached to each terminal electrode 11.11 of each capacitor.
2 are in ohmic contact.

Each probe 12 , 12 is also connected to each corresponding contact of a changeover switch 14 , and by operating the changeover switch 14 , only one set of probes is connected to the capacitance measuring device 15 at a time.
The probes 12 of all other sets can be connected to
．． The period between 12 and 12 is substantially open.

In the illustrated case, contacts with contact terminals indicated by filled black circles indicate contacts that are closed to be connected to the measuring device 15, and contacts indicated by outlined contact terminals are in an open state. Therefore, in the case shown in the first diagram, only the second capacitor C from the left is currently being measured, out of a total of four capacitors C built-in and integrated on the board. The capacitor 15 is in a state where the capacitance value is measured, and this capacitor is currently the capacitor to be trimmed by the trimming means 13.

However, as is clear from a comparison with the conventional device shown in FIG. 3, in this embodiment, characteristically, the pair of terminal electrodes 11. Electricity is transmitted through the low-impedance conductive line 17 provided in the The probes 12 and 12 are short-circuited.
The conductive line 17 for the capacitor to be trimmed, which is connected to the measuring instrument, has its corresponding contact 16 open, so that there is no short circuit between the terminal electrodes 11 and 11, and as described above. Measuring device 15
can remain connected to.

In other words, the switch contacts 16 newly provided for each capacitor are linked so that the closed and open states are exactly the opposite of the existing contact for connection to the measuring device. Such a configuration is a type of multi-stage configuration or multi-circuit configuration that can be assembled most easily using known switch configuration techniques of this type. When automating the measurement system, selector switch 1
4 is also an electronic switch that switches in synchronization with the trimming process, so each of these contact groups is an analog switch.

The same can be said when configuring.

After all, with such a configuration, if the second capacitor from the left is being trimmed by the trimming means 13 in the state shown in FIG. For example, even if static electricity is generated in the drawing and spreads to the capacitors on the right and left, the capacitors on the right and left are connected to the conductive line through the closed switch contact 16. 17, the two terminal electrodes are short-circuited with low impedance, so the electrostatic charges that have been diffused are discharged through the intentionally formed discharge path 16.
, 17, the capacitors can be quickly discharged without producing the undesirable effect of causing fluctuations in capacitance values as when DC bias is applied to these capacitors.

Therefore, it is natural that after trimming of the second capacitor from the left shown in the diagram is completed, even if the capacitors to the left or to the right are immediately trimmed, as in the past, due to the DC voltage dependent effect, the measurement Even though the capacitance value is actually measured by the measuring device 15, there is no fear that the adjusted capacitance value will change after trimming, and the capacitance value adjusted according to the indicated value of the measuring device 15 will be accurate from now on. can be maintained as is.

As a result, the switch contact configuration shown in Figure 1 can be used even for capacitors that are far enough away from the capacitor to be unaffected by static electricity generated during trimming of the capacitor, and for capacitors that have already been cut. Even for capacitors that have finished, the switch has a contact configuration that short-circuits both terminal electrodes at once.

Obviously, according to the most basic gist of the present invention, it is not necessary to short-circuit both terminal electrodes of the capacitor, which are not affected by static electricity, as in this embodiment. This is especially true for capacitors that have already been trimmed.

However, as mentioned above, it is also clear that such a configuration is the simplest when attempting to construct an apparatus system to which the method of the present invention is actually applied.

However, especially when the measurement system is automated in synchronization with the trimming device, the selector switch 14 is also made electronic, and its on/off switching is performed under the commands of a microcomputer. etc., the capacitors that are currently being trimmed or will be trimmed next, and the capacitors that are nearby and are within the range affected by the static electricity generated by the trimming operation. , can be easily identified, so of course the corresponding switch contacts are turned on and off, and both terminal electrodes of the capacitor to be trimmed are connected to the measurement system while maintaining the most basic configuration of the present invention. It is also possible to perform a local and selective switching operation relatively easily so that only the terminal electrodes of the capacitor located in the vicinity of the conductive line 17 are short-circuited by the conductive line 17 and within the range affected by static electricity.

Of course, in the alternative, it is also relatively easy to position the switch contacts so as to short the terminal electrodes of all other capacitors except the capacitor being trimmed and the capacitor that has been machined.

Furthermore, in view of the above, the present invention is particularly effective for capacitor-embedded substrates in which built-in capacitors are densely integrated; Even for high-density capacitor built-in boards,
Naturally, there may be cases where applying the present invention is effective.

In addition, in conventional capacitor-embedded boards, the first
．． As shown in Figure 3, each built-in capacitor C fully utilizes the thickness direction of the board, and each pair of terminal electrodes is provided on the front and back surfaces of the board. As shown in FIG. 2, the applicant has recently developed a pair of terminal electrodes 11 on only one side of the substrate IO as a configuration suitable for obtaining a capacitor with a particularly small capacitance.
11, therefore, these pair of terminal electrodes 11
, 11 is also disclosed in a configuration in which the capacitor C formed between the capacitors C is parallel to the main surface of the substrate, as shown by the virtual line in the figure.

Naturally, it is obvious that the present invention can be effectively applied to trimming such a type of capacitor built into a substrate. Even in this "horizontal" structured capacitor, the part of the board under the pair of terminal electrodes may be formed with a relatively high call rate compared to other surrounding areas, but this is also the case. The illustrations are omitted since they are directly related to the present invention.

Furthermore, the present applicant has proposed that, in each capacitor C section shown in Figure 1.3, for example, the terminal electrode 11 on at least one side of the substrate is composed of a pair of terminal electrodes arranged in parallel, and the required capacitance is maintained between these terminal electrodes. We also present an improved structure to obtain this.

That is, in this structure, one partial capacitor is first formed by one of a pair of terminal electrodes formed in parallel on the substrate-main surface side and an electrode formed on the back surface side of the substrate; By forming another partial capacitor with the other electrode formed on the substrate and the electrode formed on the back side of the substrate,
The electrode on the back side of the substrate is simply used as an intermediate connection electrode, and the series combined capacitance value of the two partial capacitors is obtained between a pair of terminal electrodes formed in parallel on the substrate and main surface side. .

In this case, compared to the conventional structure in which a specific capacitance value is obtained with only a single opposing terminal electrode 11.11, the area of each terminal electrode becomes larger, so even if trimmed with the same cutting width, Although the trimming resolution can be relatively improved compared to when the electrodes are configured, even when such a structure is adopted, it is difficult to trim the pair of terminal electrodes formed in parallel (generally only one side). The invention can be applied in exactly the same way.

Of course, the lower the impedance of the short-circuiting conductive line 17 mentioned above, the higher the charge discharging function, which is desirable. Naturally, the resistance can be tolerated, and in fact, 11 is sufficient. In some cases, even if the short circuit is not a milli-ohm, but a few ohms,
This is much better than the conventional example without such a short-circuit line, and the same effect can be obtained.

Rather, as in the past, when a certain capacitor was being trimmed, the terminal electrodes of other capacitors were essentially open or very close to it. Even if a small amount of resistance remains, the effect of actively shorting the terminal electrodes according to the idea of the present invention is much greater.

[Effects] According to the present invention, a trimming means that generally adopts a mechanical cutting principle is used, and therefore, even if the trimming operation tends to generate static electricity in principle, and also, even if the trimming operation tends to be accompanied by the generation of static electricity, the spacing between adjacent capacitors can be considerably narrowed. The principle of this type of trimming method remains the same, since even with high integration density capacitor-embedded boards, there is no DC voltage dependent effect on other capacitors when trimming individual capacitors. After cutting the terminal electrodes while actually measuring the capacitance value of the capacitor to be trimmed and adjusting it to the desired standard value, that state can be stably maintained.

Therefore, it not only improves the accuracy of each capacitor, but also improves the yield and reliability of the entire board with built-in capacitors.Also, continuous trimming at high speed is possible without any inconvenience due to the existence of a forced discharge path for static electricity.
It is possible to streamline the trimming process and, by extension, greatly streamline the construction of integrated circuits using this rice substrate.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram when the method of the present invention is applied to adjust the capacitance value of a capacitor built into a substrate. FIG. 2 is an explanatory diagram of another structural example of a substrate-embedded capacitor that can be trimmed according to the present invention. FIG. 3 is an explanatory diagram of a conventional basic method for adjusting the capacitance value of a capacitor built into a substrate. It is. , In the figure, lO is an insulating substrate, 11 is a terminal electrode of a capacitor built in the substrate, 12 is a measurement probe, 13 is a trimming means, 14 is a changeover switch or its contact group, 15 is a capacitance value measuring device, and 16 is a terminal electrode between the terminal electrodes. A switching contact for selective short-circuiting, 17 a conductive line for short-circuiting, and C a capacitor built into the substrate.

Claims (3)

[Claims] (1) While sequentially measuring the actual capacitance of multiple capacitors each using a part of the insulating substrate as a dielectric layer between a pair of terminal electrodes, static electricity is generated during the cutting process. By means of trimming,
A capacitance value adjustment method for a capacitor built in a substrate, wherein the capacitance value of each capacitor is adjusted by cutting at least one terminal electrode of the pair of terminal electrodes of each of the capacitors, wherein the trimming means A capacitor other than a capacitor whose terminal electrode is currently being cut, which has not yet been subjected to the cutting process, and which is affected by the static electricity generated due to the cutting process that is currently being performed. A method for adjusting a capacitance value of a capacitor built into a substrate, characterized in that a pair of terminal electrodes of the capacitor located inside the capacitor are electrically short-circuited. (2) A capacitor other than a capacitor whose terminal electrode is actually cut by the above-mentioned trimming means,
The method according to claim 1, characterized in that all capacitors that have not yet undergone the cutting process are electrically short-circuited between their pair of terminal electrodes. (3) The trimming means electrically shorts the pair of terminal electrodes of all capacitors other than those whose terminal electrodes are actually cut. ).