JPH02226798A - Capacitance adjusting method of capacitor contained in ceramic circuit board - Google Patents

Abstract

PURPOSE:To enable the partial capacitance adjustment of a capacitor by projecting laser rays on a capacitor contained in a ceramic circuit board. CONSTITUTION:A ceramic circuit board containing a capacitor whose capacitance is a little larger than the designed value is operated. Laser rays are projected on the place where the capacitor is contained, from the surface of the ceramic circuit board; by arranging a temperature detector like a thermocouple on the rear, the board temperature is measured; the board is maintained for a specified period, while a temperature previously set at a value approximate to the sintering temperature of the board is kept. When the capacitance value is decreased up to a target value, the laser rays irradiation is interrupted.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method of adjusting the capacitance of a capacitor in a ceramic circuit board incorporating a capacitor.

(B) Conventional technology Conventional ceramic circuit boards have capacitors mounted on the surface of the board, but recently, in order to improve the mounting area of the board, research has been actively conducted to form capacitors inside the board. It is carried out in

Methods for manufacturing circuit boards with built-in capacitors include, for example, sandwiching a dielectric sheet between ceramic green sheets with electrodes printed on them, stacking stones, and firing them together; or printing a dielectric on ceramic green sheets with electrodes printed on them. There are methods such as stacking, laminating, and integrally firing.

(c) Problems to be solved by the invention The capacitance of a ceramic circuit board containing a built-in capacitor is determined by the thickness of the dielectric sheet during the manufacturing process.
Even if the size, position, etc. are strictly controlled, a deviation of up to 10% from the capacity design value occurs, which limits the usage of the circuit board or causes it to be disposed of, resulting in poor product yields. won.

(d) Means for solving the problem When the present inventors repeatedly fired a ceramic substrate with a built-in capacitor, they found that the capacitance of the capacitor decreased as the number of firings increased. The present invention was completed based on the finding that the capacitance of a capacitor can be adjusted by heating the capacitor.

That is, the gist of the present invention resides in a method for adjusting the capacitance of a capacitor built into a ceramic circuit board, which comprises irradiating the capacitor built into the ceramic circuit board with a laser beam.

The procedure for adjusting the capacitance of the capacitor built into the ceramic circuit board by irradiating the ceramic circuit board with a laser beam is as follows.

First, a ceramic circuit board containing a built-in capacitor with a capacitance slightly larger than the designed value is manufactured. The manufacturing method may be the conventional method described above, but the material of the dielectric forming the capacitor must match the firing temperature of the material of the ceramic substrate. For example, it is a combination of a ceramic substrate made of borosilicate glass and alumina and a perovskite dielectric.

Next, a laser beam is irradiated from the surface of the ceramic circuit board to the location where the capacitor is built in, and a temperature detector such as a thermocouple is placed on the back surface to measure the temperature of the board. Maintain the specified temperature for a specified period of time.

The laser light to be used is not particularly limited, as long as the ceramic circuit board in the irradiated area is heated to the required temperature by irradiating the laser light.The larger the beam diameter and output of the laser light, the longer the irradiation time. It has been experimentally confirmed that the longer the capacitor is, the higher the substrate temperature, the lower the capacitor's capacity. Therefore, among ceramic circuit boards with built-in capacitors, the relationship between the board temperature and the predetermined temperature holding time regarding the decrease in capacitor capacity was measured in advance by changing the beam diameter, and the dielectric material of the capacitors is the same. Put that data in a table,
Laser light irradiation conditions are determined in consideration of the degree of difference between the measured value and the target value of the capacitance of the capacitor to be processed.

The capacitor to be processed is irradiated with laser light under the irradiation conditions to reduce its capacity. As a result, if the capacity has not decreased to the target value, irradiation may be repeated again.

(E) Example After printing one mark on each of two green sheets containing 50% by weight of lead borosilicate glass and 50% by weight of alumina, Pb(Mg+7Jbz/z)03 + was used as a dielectric material.
A paste of PbTi01 + PbO powder and vehicle was printed on one green sheet, the other green sheet was laminated thereon, thermocompression bonded, and integrally fired at 850°C for 10 minutes to create a ceramic substrate with 5 built-in capacitors. did.

This substrate was placed on a stainless steel plate having a small hole for temperature measurement, and a thermocouple was fixed to the back surface of the substrate through the hole. Next, a CO□ laser was used to irradiate the substrate at the location where the capacitor was built, and the temperature holding time after the substrate temperature reached a predetermined temperature was varied. Thereafter, the capacitance of the capacitors treated under each condition was measured. The results are shown in Table 1.

Next, the capacitance of the five capacitors built into the negative board was measured. The results are shown in Table 2. All of these had a target capacity value of 40.0 nf/-, but the results were various.

This substrate was placed on a stainless steel plate having a small hole for temperature measurement, and a thermocouple was fixed to the back surface of the substrate through the hole. Next, set the target value for the capacitance of the capacitor to 36.0nF/cd.
A Co2 laser was used to irradiate the position of the substrate where the capacitor was built in under the conditions shown in Table 3. The results are shown in Table 3.

(F) Effects of the Invention According to the present invention, it has become possible to adjust the capacitance of a capacitor built into a ceramic circuit board, which has been impossible until now. In particular, with ceramic circuit boards that have a large number of built-in capacitors, if the capacitance of even one of the capacitors deviates from the set value, the entire board must be disposed of. This allows for precise adjustment, which reduces variations in capacitance and greatly improves product yield.

Claims (1)

[Claims] A method for adjusting the capacitance of a capacitor built into a ceramic circuit board, the method comprising irradiating the capacitor built into the ceramic circuit board with a laser beam.