JPH0352292A - Heat radiation structure of multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To promote heat radiation from the inside of a multilayer printed wiring board and eliminate the harmful effects of internal heat accumulation by burying microheat pipes in the internal layers of the multilayer printed wiring board and connecting heat radiation media to the projected sections of the pipes on the printed board. CONSTITUTION:Heat radiation microheat pipes 2 are buried in a multilayer printed wiring board 1, one end of each of the pipes are projected on the printed board 1 for heat radiation, and heat radiation media 4 are connected to the projected sections. Even if heat from a heat-radiating electronic part 51 travels into the printed board 1 through a lead 52, the heat can be released outside effectively by heat absorption and radiation of the microheat pipes 2 buried in the printed board 1. Thereby, the fine heat radiation effect improves the operation reliability of a circuit board including the multilayer printed wiring board 1.

Description

[Detailed Description of the Invention] [Summary] Regarding the heat dissipation structure of a multilayer printed wiring board, there is a need for a multilayer printed wiring board that can effectively discharge heat within the multilayer printed wiring board to the outside and ensure highly reliable circuit operation. For the purpose of providing a heat dissipation structure, one or more micro heat pipes are embedded in the inner layer of a multilayer printed wiring board, and a heat dissipation medium is connected to the part of the micro heat pipe that protrudes from the wiring board. A heat dissipation structure for a multilayer printed wiring board characterized by promoting heat dissipation from inside the slope.

[Industrial application field]

The present invention relates to heat dissipation measures for a so-called multilayer printed wiring board that has wiring patterns made of electrically conductive metals not only on the outer layer but also on the inner layer of the electrically insulating board.

[Conventional technology]

In order to satisfy the rapid demand for high precision, high density, and high reliability in electronic devices, insulators (or dielectrics) and conductors are laminated in layers, and electrical connections are made between each conductive layer. So-called multilayer printed wiring boards that are integrated into one system are often used.

[Problem to be solved by the invention]

However, with the increasing integration of electronic components and the mounting of electronic components on printed wiring boards, the amount of heat generated per unit area of the wiring board has significantly increased. The heat generated from these electronic components is partially radiated from the surface of the electronic component 51, as shown in FIG. This will accumulate inside the plate 53. If heat accumulates inside the wiring board, electronic circuits are likely to malfunction, and the dielectric constant of the printed wiring board base material (epoxy material) is highly temperature dependent as shown in Figure 8, so it cannot be used at high temperatures. This results in a signal propagation delay. Furthermore, in the through-hole plating (copper) portion 54 shown enlarged in FIG. 9, the wiring board base 53
There were problems such as cracks forming at the corner portion A due to the difference in thermal expansion coefficient between the plated portion 54 and the plated portion 54.

In view of the above points, it is an object of the present invention to provide a heat dissipation structure for a multilayer printed wiring board that can promote heat dissipation from inside the multilayer printed wiring board and eliminate the above-mentioned disadvantages caused by internal heat accumulation, which has been a problem in the past. shall be.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, one or more micro heat vibs are embedded in the inner layer of a multilayer printed wiring board, and a heat dissipation medium is connected to a portion of the micro heat vibes that protrudes from the wiring board. A structural feature is that it promotes heat dissipation from inside the wiring.

[For production]

Heat that can accumulate within the multilayer printed wiring board is carried to the outside through micro heat pipes embedded inside and diffused into the outside air through a heat dissipation medium connected to the micro heat pipes that protrude from the wiring board. This allows the inside of the wiring board to be appropriately cooled and protects the multilayer printed wiring board from heat damage.

(Example〕 The present invention will be explained below based on illustrated embodiments.

Figure 1 is a front view of a printed wiring board of an embodiment of the heat dissipation structure for a multilayer printed wiring board according to the present invention, and Figure 2 is a partially enlarged view of the inner layer of the printed wiring board in Figure 1. Figure 3 is a cutaway perspective view of the main parts of the printed wiring board, Figure 4 is a side sectional view of the main parts of the printed wiring board, and Figure 5 shows an example of a heat dissipation medium that affects the main parts of the heat dissipation structure. Main part cutaway perspective view,
FIG. 6 is a cutaway perspective view of a main part of another heat dissipation medium.

Referring to FIGS. 1 to 4, a micro heat pipe 2 for heat dissipation is embedded inside the multilayer printed wiring board 1 of this embodiment. Here, to briefly explain about heat pipes, heat pipes are hollow cylinders with both ends closed and have a wick layer made of wire mesh or fine grooves on the inner surface. ) is included. A heat pipe is a heat transfer element that attempts to cool the surrounding area by transporting a large amount of heat through the flow using the latent heat that accompanies changes in the liquid and gas phases of the working fluid. It has a large amount of heat transfer and can be used in a wide temperature range by changing the working fluid. Note that in this specification, an extremely fine heat pipe with an outer diameter of about 0.8 mm is used, so it is particularly referred to as a micro heat pipe.

This micro heat pipe 2 is connected to the wiring board l in the mounting direction (first direction) when the wiring board 1 is mounted on a rack or the like.
In the figure, a plurality of connectors are arranged approximately parallel to each other at equal intervals (from the left connector side to the right side).

As shown in FIG. 3, the installation interval P of the micro heat pipes 2 is equal to the installation interval Q of the through holes 3 (for example, 2.
If they are arranged alternately with a pitch of 54 mm, the problem of mutual interference will not occur. Needless to say, it is not necessary to completely fill the entire wiring board with micro heat pipes at equal intervals, and it is not necessary to fill the entire area of the wiring board with micro heat pipes at equal intervals. In order to provide focused cooling only, it is sufficient to embed a micro heat pipe only in the wiring board section.

The other end (the right side in FIG. 1) of the micro heat pipe 2 buried in this way is made to protrude from the wiring board 1 for heat radiation, and the heat radiation medium 4 is connected to the protruding portion. This heat dissipation medium 4 will be described later.

With the above structure, even if the heat from the electronic component 51 that generates heat is conducted into the wiring board 1 through the lead 52, the wiring board 1
The heat can be effectively discharged to the outside by the heat absorption and heat dissipation action of the micro heat pipe 2 buried inside, and therefore, this high heat dissipation effect significantly improves the reliability of the operation of the circuit board from this multilayer printed wiring board. .

Furthermore, in this embodiment, the micro heat pipe 2 is not merely embedded inside the wiring board 1, but is also bonded onto the inner layer earth pattern (hole foil layer) 5 by welding or the like. The micro heat pipes 2 can be embedded by arranging and welding the micro heat pipes 2 on the copper foil at a pitch of 2.54 mm before patterning the inner layer copper foil, and then performing the patterning. This is the same method for manufacturing printed wiring boards.

By welding the micro heat pipe 2 onto the ground pattern 5, the ground area can be substantially stably expanded, and thereby a high shielding effect can be expected.

Here, the story goes back and forth, but to briefly explain the heat dissipation medium connected to the micro heat pipe protrusion, the fifth
Referring to the figure, this heat dissipation medium 14 consists of a pair of vertically symmetrical plates 14a. From 14b, these two plates 14a,
The micro heat pipe 2 protruding from the wiring board 1 is fitted into the semi-cylindrical groove 15 formed by the screw 14b.
This is mechanically clamped using fastening members such as. Plate material 14a. 14b can be made of aluminum or the like having excellent thermal conductivity, and has a large number of heat dissipating fins 17 to improve heat dissipation into the air.

Next, referring to FIG. 6, which shows another type of heat dissipation medium,
The heat dissipation medium 24 is separated from a plate 25 into which the protruding portion of the micro heat pipe 2 is inserted, and a heat dissipation body 26 that supports the plate 25 so as to surround it from above and below and from the sides. The plate 25 can be made of copper, for example, and the plate 25 and the micro heat pipe 2 are connected using a conductive adhesive, soldering, or the like. The heat sink 26 can be made of aluminum, for example, and includes a large number of heat sinks 2 similar to the heat sink 14 in FIG.
It has 7.

Although two examples of the heat dissipation medium have been described above, the idea of the present invention is not limited to these in any way, and therefore, those skilled in the art will be able to come up with various embodiments.

〔Effect of the invention〕

As described above, according to the present invention, the heat inside the wiring board can be extremely effectively discharged to the outside by the micro heat pipe and the heat dissipation medium embedded in the multilayer printed wiring board, and the above-mentioned conventional heat damage can be wiped out.

[Brief explanation of drawings]

Figure 1 is a front view of a printed wiring board of an embodiment of the heat dissipation structure for a multilayer printed wiring board according to the present invention, and Figure 2 is a partially enlarged view of the inner layer of the printed wiring board in Figure 1. Fig. 3 is a cutaway perspective view of the main part of the printed wiring board, Fig. 4 is a side sectional view of the main part of the printed wiring board, and Fig. 5 is the main part showing an example of the heat dissipation medium that affects the main part of the heat dissipation structure. Figure 6 is a broken perspective view of the main part of another heat dissipation medium, Figure 7 is a side sectional view of the main part of a conventional printed wiring board, and Figure 8 is the temperature characteristics of the dielectric constant of the printed wiring board base material. Figure 9 is an enlarged view of the corner portion of the through-hole plating section. DESCRIPTION OF SYMBOLS 1... Multilayer printed wiring board, 2... Micro heat pipe, 4... Heat dissipation medium, 14... Heat dissipation medium, 2
4... Heat dissipation medium. 3 Partially enlarged view of the inner layer part of an embodiment of the heat dissipation structure of a multilayer printed wiring board Fig. 2 4... A broken perspective view of the main part of the heat dissipation medium printed wiring board Fig. 3 Fig. 4 Fig. 52... 4 nodes ↑ ↑ f ↑ Cross-sectional side view of the main part of a conventional printed wiring board 1!7 Figure 7 Temperature characteristic diagram of dielectric constant of the printed wiring board base material Figure 8 Enlarged view of the corner part of the through-hole plating part Figure 9 Figure 53...Wiring Plate 54...Through hole plating part

Claims (1)

[Claims] 1. One or more micro heat pipes (2) are embedded in the inner layer of the multilayer printed wiring board (1), and a heat dissipation medium (4, 14) is embedded in the part of the micro heat pipe (2) that protrudes from the wiring board (1). , 24) are connected to promote heat radiation from inside the wiring board.