JPH0747873Y2 - Printed wiring board with semiconductor memory mounted - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention discloses that at least one terminal of a printed wiring board mounted with a semiconductor memory capable of reading out data from the terminal is higher than a high voltage in a binary state. The present invention relates to a printed wiring board including a memory that operates differently when a voltage exceeds a certain level.

(Prior Art) A conventional printed wiring board on which a semiconductor memory is mounted will be described with reference to the drawings. FIG. 3 is a plan view of a conventional printed wiring board, and FIG. 2 is a bottom view of the same.

On the surface (21) of the printed wiring board, as shown in FIG. 3, a terminal row (23) for electrical connection between the memory and an external device is formed. In this embodiment, a large number of terminals are provided. In order to arrange them efficiently, they are formed in two rows along the short side of the card, and the first row and the second row are arranged (staggered) so as to be located between each other. On the other hand, as shown in FIG. 2, a semiconductor memory (24) is mounted on the back surface (22) of the printed wiring board and is connected to the printed wiring pattern by wire bonding or the like.
The printed wiring pattern and the external connection terminals are connected by an through hole, and the front and back surfaces of the printed wiring board are made of epoxy resin for the purpose of insulation and protection except for the external connection terminals (23) and the memory mount. Is applied to the entire surface.

(Problems to be Solved by the Invention) In the printed wiring board as described above, many printed wiring patterns are provided in a small area. Therefore, the coupling capacitance between the wiring patterns tends to be high. In the presence of such coupling capacitance, when one voltage rises, the other voltage is also affected and the voltage rises in a dragged manner. A terminal that has the function of performing another operation when the semiconductor memory is at a high voltage in the binary state when one terminal becomes higher than a certain voltage that is higher than the high voltage in the binary state (hereinafter referred to as a ternary value terminal). In general, there may be a coupling capacitance between the binary terminal and the binary terminal. At that time, when the ternary terminal has a medium voltage and the binary terminal changes from a low voltage to a high voltage, the voltage of the ternary terminal is slightly higher than the medium voltage due to the increase in the voltage of the binary terminal. Pull up. This development is sometimes remarkable, and in such a case, the semiconductor memory judges that the constant high voltage, which is higher than the medium voltage which is the high voltage in the binary state, is reached, and the third value operation is performed. Reading will occur.

(Means for Solving the Problem) In order to solve the above problems, it is possible to compensate the coupling capacitance between the ternary terminal and the terminal that defines the high voltage or the low voltage of the binary state. The printing resistance is applied within the range and having high resistance.

(Operation) In the printed wiring board according to the present invention, the voltage of the ternary terminal is the medium voltage which is the high voltage in the binary state, and the binary terminal having the coupling capacitance with this terminal becomes the high voltage At this time, the ternary terminal tries to reach a high voltage due to the coupling capacitance. Therefore, since this terminal is connected to the terminal that defines the high voltage or low voltage of the binary state by the printing resistance that is high resistance within the range that can compensate the coupling capacitance, current flows through the resistance, The coupling capacitance compensates for the voltage that should be raised above the medium voltage, and the voltage drops to near the medium voltage within the access time, and before the time to perform another operation, the medium voltage band Voltage drops to.

(Example) A printed wiring board mounted with a semiconductor memory according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view of the printed wiring board of the present invention.

As shown in FIG. 1, on the front surface (21) of the printed wiring board, a terminal row (23) for electrical connection between the memory and an external device is formed as in the conventional example, while the back surface is formed. The semiconductor memory (24) is mounted on (22) and is connected to the printed wiring pattern by wire bonding or the like. Furthermore, the front and back surfaces of the printed wiring board include the external connection terminal row (23) and the memory mount section. Except,
An epoxy resin is applied to the entire surface for the purpose of insulation and protection. In addition, when a certain high voltage above the high voltage of the binary state is applied to a specific terminal among the external connection terminals described here, a three-valued semiconductor memory that performs another operation called a silicon signature Where there is a terminal, a coupling capacitance may occur between this ternary terminal and a specific binary terminal. For example, in this example, the terminal called A9 terminal (11) is called A8 terminal (12). The coupling capacitance with the terminal is 30pF or more. Of course, in other terminals, such a phenomenon also appears in terminals called A11, CE, A0, and A5. Then, even if it becomes access time,
A voltage of 2.6V remains in the actually measured value. In the case of this example, the medium voltage, which is a high voltage in the binary state, is 5V, and the high voltage, which is the silicon signature voltage, is 7.5V.
When trying to make the A8 terminal (12) high voltage A9 terminal (11)
If is already a medium voltage, the A9 terminal (11), which is a ternary terminal, performs a silicon signature operation even if the voltage is the same. In order to prevent this, a terminal that operates as a silicon signature is connected to a high voltage or low voltage in a binary state through a resistor. In this example, the GND terminal (1
There is a printing resistor (14) between it and 3). The width of the non-conductor part between terminals is 1.04 ± 0.2 mm, but in consideration of printing variations, misalignment, development of conductive ink, etc., print pattern from each terminal with a width of about 0.4 mm. Is extended and joined at the central part. The printed pattern of the joint from each terminal to the GND terminal (13) should be 1mm to 0.4mm depending on the circuit length so that the voltage between terminals is equal. It has been changed. Note that the conductive ink used here has a different composition depending on the resistance value sought, but in this example, we used about 30% by weight of phenol, about 70% by weight of carbon, and thinner as another material. . Screen printing was performed on the printed wiring board using such a conductive ink to provide a printing resistor.

When the printed path is applied in this way, the resistance between the A9 terminal and the GND terminal is about 25 KΩ, and the voltage drops to about 6 V within the fast operation time of 155 ns or less that does not reach the signature voltage within the access time. If the resistance value is lowered too much, the output current value becomes large. However, since the output guaranteed current of the drive CPU is often in units of sub-milliamperes, it cannot be lowered too much.

Therefore, it seems appropriate that the resistance value of the printing resistor is between 10KΩ and 100KΩ. The printed wiring board printed in this way is heated to 150 ° C. to volatilize the solvent, and then another resin such as phenol resin may be used on the printing resistor, but in this example the epoxy resin hides the entire printing resistor. To print. This is because the printed resistance material is not completely waterproof and the film strength is not sufficient, so that it is intended to reinforce the material. Of course, this can be omitted if a conductive ink having high water resistance and strong resistance is used.

The following test was performed on the printed wiring board that had been treated in this way, but no abnormality was observed.

i) Torsion test Twist 100 times at ± 15 °.

ii) Folding test Fold it up to a height of 10 mm with respect to the longitudinal direction of the card.
Bend 0 times repeatedly.

iii) Scratch test A scratch test is performed with a writing pressure tester at 200g (writing pressure for children) and 300g (writing pressure for adults).

iv) Hold at high temperature Hold for 48 hours in an atmosphere of 70 ° C and 90%.

v) Thermal cycle test A heat shock of 24 cycles is given under the conditions of -10 ° C (30 minutes) and + 50 ° C (30 minutes).

(Effects of the Invention) According to the present invention, when one terminal of the semiconductor memory becomes higher than the high voltage of the binary state by a certain voltage or more, the semiconductor memory operates differently from the high voltage of the binary state. Assuming that the terminal is in the high voltage state of the binary state, the malfunction does not occur even if the terminal having the coupling capacitance enough to malfunction with the terminal becomes the high voltage.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, and FIG.
A bottom view showing a conventional example and FIG. 3 are plan views of the same. (11) …… A9 terminal, (12) …… A8 terminal (13) …… GND terminal, (14) …… Printing resistor

Claims (1)

[Scope of utility model registration request] 1. A semiconductor memory and a terminal led out from the semiconductor memory are provided, and when at least one of the terminals has a certain voltage higher than a high voltage in a binary state, the semiconductor memory has the second voltage. A printed wiring board that is a terminal that has a function of performing another operation at a high voltage of a value state, and a terminal that has a function of performing another operation has a coupling capacitance with another terminal In the above item, a printing resistor within a range capable of compensating for the coupling capacitance is provided between the terminal having the function of performing the other operation and the terminal defining the high voltage or the low voltage in the binary state. A printed wiring board mounted with a semiconductor memory.