JPS634922B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for trimming thick film resistors in a thick film hybrid integrated circuit in which the thick film resistors form a double closed circuit.

Thick film resistors of thick film hybrid integrated circuits are formed by printing, but the accuracy is generally poor, and therefore it is common to trim them to a predetermined resistance value. When trimming a thick film resistor, normally, a measuring probe is brought into contact with the electrode patterns at both ends of the thick film resistor, a voltage is applied, and a minute current is passed through the thick film resistor, and the resistance is automatically calculated based on the ratio of voltage and current. Trim while measuring the resistance value by converting it to a value. If the thick film resistor forms a closed circuit, connect another probe. This will be explained with reference to FIG. FIG. 1 shows a part of a circuit diagram of a thick film hybrid integrated circuit, in which thick film resistors R ₁ to _{R 3} constitute a closed circuit.
_L1 to _L3 are the currents flowing through the thick film resistors _R1 to _R3 ,
T ₁ to T ₃ indicate terminals based on electrode patterns. When trimming the thick film resistor R ₁ in such a circuit,
Terminals T ₂ and T ₃ are used as measurement terminals, and a guard pin is brought into contact with terminal T ₁ . The guard pin allows the terminal
T ₁ and terminal T ₃ or terminal T ₁ and terminal T ₂ have the same potential, current I ₂ or I ₃ becomes zero, and resistance R ₂ and
Resistance R ₁ can be measured without the influence of R ₃ .
Many trimming devices or resistance measuring instruments with guard pin functions are commonly used.
Resistance measurement and trimming of the circuit shown in the figure can be easily performed.

However, if the thick film resistor forms a double closed circuit, the above method cannot be used for measurement. Second
The figure is a part of a circuit diagram of a thick film hybrid integrated circuit, in which thick film resistors R ₁ to _{R 5} constitute a double closed circuit.
When trimming resistor R ₁ in such a circuit,
Even if terminals T ₂ and T ₃ are used as measurement terminals and terminal T ₁ is used as a guard terminal, current will still flow through resistors R ₄ and R ₅ .
Precise trimming of resistor _R1 is not possible. Terminal T ₄
If R is used as a guard terminal, current will flow through resistors R ₂ and R ₃ , and accurate trimming of resistor R ₁ will not be possible. If the terminals T ₁ and T ₄ are used as guard terminals at the same time, accurate trimming of the resistor R ₁ is possible, but there is generally no trimming device that has two guard pins.

Therefore, in the case of a thick film hybrid integrated circuit including such a double closed circuit, for example, as shown in Figure 3, the terminal
Divide T ₄ into terminals T ₄ ′ and T ₄ ″ to eliminate double closed circuits, and after trimming the thick film resistor, use components such as chip capacitors to connect terminal T ₄ during assembly. ′ and T ₄ ″. FIG. 4 is a part of a pattern diagram of a thick film hybrid integrated circuit, and shows a method of connecting the above-mentioned divided patterns. In FIG. 4, 1 is a ceramic substrate, 2 is an electrode pattern, 3 is a chip capacitor, and 4 is solder. When trimming thick film resistors, terminals T ₄ ′ and T ₄ ″ are not connected,
After trimming, the chip capacitor 3 is mounted, and when the electrode of the chip capacitor 3 and the electrode 2 on the ceramic substrate 1 are connected by the solder 4, the terminals T ₄ ' and T ₄ '' are connected by the solder 4.

However, compared to normal component mounting patterns such as terminal T ₄ ′ and T ₄ ″, the overlapping area between _the electrode pattern and the chip component is small, and the solderability is poor. In particular, the mounting position of the component may be misaligned. If the terminal
There is a drawback that soldering failure occurs in that the solder does not stick to either T ₄ ′ or T ₄ ″.

The purpose of the present invention is to prevent the solderability during assembly from deteriorating even in a thick film hybrid integrated circuit in which thick film resistors form a double closed circuit, and to trim each thick film resistor with high precision. An object of the present invention is to provide a method for trimming a thick film resistor.

The present invention enables trimming without cutting the closed circuit by dividing a part of the thick film resistors in a double closed circuit, connecting them in series, and trimming each divided thick film resistor separately. It is meant to be.

An embodiment of the present invention will be explained with reference to FIGS. 5 and 6. FIG. 5 is a circuit diagram of a thick film hybrid integrated circuit, and FIG. 6 is a pattern diagram thereof, which is equivalent to FIG. 2.
That is, the resistor R ₁ in Fig. 2 is divided into two resistors R ₁ ′ and R ₁ ″ in Fig. 5, connected in series, and R ₁ ′+
R ₁ ″=R _1. With this configuration, when trimming the resistor R ₁ ′, the terminal
By using T ₂ and T ₅ as measurement terminals and using terminal T ₃ as a guard terminal, trimming can be performed without being affected by other resistances. Similarly, when trimming the resistor R ₁ ″, use terminals T ₅ and T ₃ as measurement terminals, and terminal T ₂
By using this as a guard terminal, trimming is possible. In the same way, all other resistors are
It can be trimmed without being affected by other resistances.

According to this embodiment, all thick film resistors can be trimmed without deteriorating solderability because the method of dividing the terminal and connecting the divided patterns using chip components during assembly is not used. Can be done.

According to the present invention described above, even in a thick film hybrid integrated circuit including a double closed circuit of thick film resistors, the thick film resistor can be trimmed with the same precision as a circuit without a double closed circuit, and the Since there is no need to divide the terminals in the circuit, the solderability of the mounted components will not be impaired during assembly. Therefore, there is an effect of reducing soldering defects during assembly.

[Brief explanation of the drawing]

Figures 1 to 3 are circuit diagrams showing a part of a thick film hybrid integrated circuit, Figure 4 is a pattern diagram of a thick film hybrid integrated circuit, and Figure 5 is a part of a thick film hybrid integrated circuit of the present invention. FIG. FIG. 6 is a pattern diagram of a thick film hybrid integrated circuit corresponding to the circuit diagram of FIG. 5. 1... Ceramic substrate, 2... Electrode pattern, 3...
Chip capacitor, 4...solder, 5...resistor pattern.

Claims (1)

[Claims] 1. In a thick film hybrid integrated circuit in which thick film resistors formed by printing constitute a double closed circuit,
A method for trimming a thick film resistor, comprising dividing one or more thick film resistors in the closed circuit into two or more series thick film resistors, and trimming each resistor separately.