JPH03232292A - Circuit board - Google Patents

Abstract

PURPOSE:To increase a circuit board in empty space by a method wherein surface-mounted ICs limited in external dimension so as to be housed in a device and electronic components mounted on an inner region where the ICs are mounted on a board are provided. CONSTITUTION:An IC2 and an IC3 mounted on an evaluation board 1 which is limited in size so as to be built in an in-circuit emulator are 64-pin shrink dip packages and mounted on IC sockets 9 so as to be replaceable later. An SRAM6 and an SRAM7 used as memories where programs are stored are flat packages and mounted under the IC2 as located on the inner region of the IC2. Therefore, a PROM 8 serving as a unit external memory, a gate array 4, a connector 5, and others besides the IC2, the IC3, the SRAM6, and the SRAM7 can be mounted on the evaluation board 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a circuit board whose size is limited because it is housed in a device, and in particular to a circuit board on which a dip or shrink dip package IC is mounted. related to circuit boards.

[Conventional technology]

A conventional example will be explained with reference to the drawings.

FIG. 8 is a plan view of a conventional circuit board on which many electronic components are mounted. As shown in the figure, this circuit board is an evaluation board 21 used as a development tool for a microcomputer.

The circuit board that is the evaluation board may be used built-in to a program debugging device (in-circuit emulator) of a microcomputer, or may be used alone as an evaluation board F21.

IC22 and IC23 are microcomputers on which software is to be developed, and are 64-bin link dip package ICs as shown in FIG. Moreover, IC22 and IC23 are mounted on an IC socket so that they can be replaced later. The external memory 26 is a memory for storing microcomputer programs, and when using the evaluation board 21 built into an in-circuit emulator, it is an SRAM.
If you want to use it alone, attach FROM.

Furthermore, since this evaluation board is sometimes used by being built into an in-circuit emulator, the size of the evaluation board is limited to the size that can be built into the in-circuit emulator.

In addition to the IC22, IC23, and external memory 26, this evaluation board also includes a gate array 24. Relatively large components such as the connector 25 are mounted.

In addition to these large components, the evaluation board includes many components used in peripheral circuits, such as resistors, capacitors, and diodes. The parts used in these peripheral circuits are
On the board, IC22, IC23, external memory 26. Gate array 24. It was placed in the empty space after the connector 25 and the like were placed.

FIG. 9 shows an example of another conventional circuit board. Since this circuit board is also used by being incorporated into a device, its external dimensions are limited, and high-density mounting on the board is also required. Also, since this circuit board requires an SRAM with a capacity of 512 bits, the SRAM with a capacity of 256 bits is required.
It is equipped with two M.

SRAM31. The SRAM 32 is a 28-pin flat package as shown in FIG.

Figure 9 shows the two SRAMs referred to here, SRAM31.
．． It is a wiring diagram of SRAM32.

As shown in FIG. 9, all terminals of the SRAM 31 and SRAM 32 except the chip select terminal are wired in common.

Therefore, the wiring of SRAM 31° and SRAM 32 on the substrate is as shown in FIG.

The electrode 33 is connected to the SRAM 31. It is provided to electrically connect the lead wire and the board using solder when surface mounting the SRAM 32.

The terminals of the SRAM 31 and the SRAM 32 other than the chip select terminal must be connected on the substrate, but if wiring is done only in the surface layer as shown at the intersection 34 in FIG. 10, all the wiring will necessarily intersect.

For this reason, since the wiring must once be routed to the back side of the board, a considerable amount of wiring is required also on the back side of the board. Furthermore, since there is a distance between the terminals that must be connected, there is a drawback that a considerable amount of wiring space is required.

[Problem to be solved by the invention]

In the conventional circuit board described above, when placing components on a board with a limited size, ICs 22, IC 23, external memory 26 . Gate array 24. Since there are many large parts such as the connector 25, there is less space for arranging peripheral circuits such as resistors, capacitors, diodes, etc., and the number of peripheral circuit parts that can be arranged is reduced.

Further, when wiring two identical SRAMs, if two flat package SRAMs are used, wiring cannot be done only on the surface layer, and the wiring must also be routed on the back side of the board. Another disadvantage is that the length of the wiring becomes long.

[Means to solve the problem]

The circuit board of the present invention is limited to the external dimensions that can be accommodated in the device, and includes an IC in a tip or shrink dip package mounted on one surface and electronic components attached to the inner area where the IC is mounted on the board. have.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a plan view of a circuit board of one embodiment.

The circuit board shown in FIG. 1 is an evaluation board used as a development tool for a microcomputer. Further, the evaluation board 1, which is this circuit board, may be used built-in to a program debugging device (in-circuit emulator), or the evaluation board may be used alone.

Therefore, the size of the evaluation board 1 is limited to a size that can be built into the in-circuit emulator.

The engineering C2 and IC installed on this evaluation board 1
3 is the microcomputer that we will develop here. As shown in FIG. 2, IC2 and IC3 are 64 pin-link deep packages, and are mounted on IC sockets so that they can be replaced later.

When using the evaluation board built into an in-circuit emulator, SRAM6. The SRAM 7 is a flat package as shown in FIG. 3, and is mounted below the IC 2 in the inner area of the socket of the IC 2.

Generally, when an evaluation board is built into an in-circuit emulator, it has an SRAM with a capacity of 256 bits.
When used alone, a FROM with a capacity of 256 bits is attached to the memory socket 8, but in this evaluation board 1, the FROM memory capacity required by the microcomputer to be developed is 512 bits. .

Therefore, when used built-in in an in-circuit emulator, the above-mentioned SRAM6 with a capacity of 256 bits is used.
．． Two pieces of SRAM7 must be used.

In addition, this evaluation board 1 includes IC2, IC3°SRAM.
6. In addition to SRAM7, FR, which is a standalone external memory,
OM8. Gate array 4. Relatively large parts such as the connector 5 must be included in the actual device. Therefore, it is necessary to mount components such as transistors, resistors, capacitors, diodes, etc. used in peripheral circuits in the empty space after arranging these large components.

In this way, the evaluation board 1 of this embodiment has a large number of parts overall, so the S
RAM6. By mounting the SRAM 7 inside the IC socket 9 (IC 217), there is an advantage that other free space on the board is increased.

FIG. 4 is a front view of a portion of the circuit board of the second example.

This circuit board 10 has the same configuration as Example 10,
The 256-bit SRAM is equipped with two SRAMs, but since the mounting methods for the two SRAMs are different, only those parts are shown.

Further, since the circuit board 1O shown in FIG. 4 is used by being incorporated into a device, its external dimensions are limited, and high-density mounting on the board is required.

SRAMII is a 28-bin dip package as shown in Figure 6, and SRAM12 is a 28-bin deep package as shown in Figure 3.
It is an 8-pin flat package. Here SRAM12
is implemented in the inner area of SRAM II.

Figure 5 shows the two SRAMs referred to here, SRAMI.
1. It is a wiring diagram of SRA, Ml 2.

As shown in FIG. 5, all terminals of the SRAM II and SRAM 12 except the chip select terminal 13 are wired in common. For this reason, the SRAM 11. SRAMI 2
The wiring is as shown in Figure 7. Through hole 13 is SR
This is a hole into which an AMII lead wire is inserted, an electrode passes through the inner surface of the hole, and the lead wire and the board are electrically connected here by solder.

The electrodes 14 are provided to electrically connect the wires to the substrate by soldering when the SRAM 12 is surface mounted.

Chip select terminal 15 of SRAM11. SRAM12
Wiring is performed inside the mounting area of the SRAM 1l except for the chip select terminal 16. Therefore, the wiring length becomes extremely short, and a large space can be secured for other wiring. Another advantage is that since the wires do not intersect, the wires can be made only on the surface layer of the board, and the space on the back surface of the board can be used for other wires.

Next, the present invention will be explained with reference to the drawings.

Figure 11 (a), (b) and Figure 12 (a), (b)
) are a partial side view and a partial plan view of a circuit board showing a third embodiment of the present invention. The circuit board shown in this figure is an evaluation board used as a development tool for a microcomputer. Further, the evaluation board 1, which is this circuit board, may be used built into a program debugging device (in-circuit emulator), or may be used alone. The IC2 attached to this evaluation board F1 is the microcomputer to be developed here. IC2 is 64 as shown in Figure 4.
It is a pinsylink deep package and is mounted on the IC socket 9 so that it can be replaced later.

Furthermore, a resistor 7 which is a component of the peripheral circuit of the evaluation board 1
It is located in the inner region of the IC socket 9 in which the IC 2 is mounted, and is attached to the lower side of the IC 2. Here, by mounting the resistor 7 inside the IC socket 9 of the IC 2, there is an advantage that the free space on the board increases. Also, the resistor 7 will be mounted below the IC2 on the board, but even if the resistor 7 needs to be replaced, since the IC2 is mounted on the IC socket 9, it is not necessary to remove the IC2. Therefore, the resistor 7 can be replaced.

On the other hand, when using the evaluation board built into an in-circuit emulator, use it by inserting a connector on another board within the in-circuit emulator. Therefore, the size of the evaluation board is limited to the size that can be built into the in-circuit emulator. For this reason, the external memory is the one that is external to the microcomputer, RAM is used when the evaluation board is built into an in-circuit emulator, and F is used when used alone.
Install and use ROM.

Here, such a circuit board is an SRAM shown in FIG.
42 is mounted on the evaluation board on the same mounting surface as IC8, which is FROM 41, and socket 13. Here, the IC 8 is mounted in the IC socket 13 because it needs to be used by replacing it. Furthermore, when using an IC, which is an external memory, with the evaluation board 1 built into the in-circuit emulator, use IC8,
When using it alone, use IC12. For this reason, the wiring such as the address bus and the I10 bus within the evaluation board 1 is made to be common regardless of whether IC8 or IC12 is used.

For example, a switch may be provided to switch between IC8 and IC12, and the input signal to each terminal may be switched. Also, by wiring the IC8 and IC12 within the area of the IC socket 13,
The amount of wiring on the board can be reduced.

〔Effect of the invention〕

As explained above, the circuit board of the present invention is capable of mounting other electronic components within the area of the circuit board in which the IC of the dip or shrink dip package is mounted, thereby removing the area occupied by the IC on the circuit board. The number of components mounted on the board can be increased, and the amount of free space on the board increases, resulting in less wiring.

Also, when wiring two identical SRAMs, a flat package SRAM is connected to a deep package SRAM.
When mounted inside the board, not only the wiring length is shortened, but also the wiring space on the board can be used effectively because the wiring can be done only on the surface layer.

[Brief explanation of drawings]

Fig. 1 is a plan view of a circuit board of one embodiment, Fig. 2 is an external view of a microcomputer (64 vinyl link dip package), Fig. 3 is an external view of an SRAM (flat package), and Fig. 4 is an external view of a second implementation. A partial front view of the circuit board of the example, Fig. 5 is an SRAM wiring diagram, Fig. 6 is an external view of the SRAM (dip package), Fig. 7 is a wiring diagram on the board of the second embodiment, and Fig. 8 is an SRAM wiring diagram. A plan view of the circuit board of the conventional example, FIG. 9 is an SRAM wiring diagram of the conventional example, FIG. 10 is a wiring diagram on the board of the conventional example, FIGS. 11(a), (b), and 12(a).
(b) is a partial side view and two partial molecular plane views showing the third embodiment, respectively. ■...Evaluation board, 2...IC (microcomputer), 3...IC (microcomputer), 4...gate array, 5...・
...Connector, 6...SRAM, 7...
...SRAM, 8...PROM. 9...Socket for IC2, 10...
Circuit board of actual journey example 2, 11... SRAM (deep package), 12... SRAM (flat package), 13... SRAM II through hole, 14... ...SRAM12 electrode, 15
・・・・・・SRAM12 chip select terminal, 16
...SRAMII chip select terminal, 21
...Conventional evaluation board, 22...
IC (Microphone Computer), 23...IC
(-v microcomputer), 24... Group Kate array, 25... Connector, 26... External memory, 31... SRAM of conventional example 2, 32...
... Conventional example 2f7) SRAM', 33 = SRAM
electrode, 34...intersection of wiring.

Claims (1)

[Claims] A circuit board that is housed in a device and whose external dimensions are limited, characterized by having an IC mounted on one surface and electronic components attached to an inner area where the IC is mounted on the board. .