JP2006229061A - Printed wiring circuit board accommodation case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress condensation of water vapor present in the interior of a printed wiring circuit board accommodation case. <P>SOLUTION: In a printed wiring circuit board accommodation case 10, a printed wiring circuit board 14 having a plurality of electronic components 22 mounted thereon is accommodated. Recesses and projections conforming to the shapes of the respective electronic components 22 are formed in and on the case, so as to cover the upper surface of the circuit board 14 having the electronic components 22 mounted thereon. Further, a condensation preventing plate 18 may be provided for shielding an ambient air W invading into the interior of the case from a connector insert hole 17 as a gap for insertion of a connector 16 connected to the board 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for preventing condensation that occurs on a printed wiring board on which electronic components are mounted.

  2. Description of the Related Art In recent years, electronic components mounted on a printed wiring board in an electronic unit have been increasingly densified as electronic units have higher functionality and smaller size in automobiles and electrical equipment. Such a printed wiring board is generally housed in a case body and is configured to be electrically connected to an external device via a connector.

  When dew condensation occurs on such a printed wiring board, it causes a problem of migration. Migration means that when there are multiple exposed conductors on the printed circuit board on which electronic components are mounted, and water droplets adhere between the conductors due to condensation, the water droplets contain an electrolyte such as flux contained in the solder. In such a situation, when a voltage is applied between conductors by a vehicle battery, an electrolysis reaction takes place, and metal is eluted from the anode-side conductor and deposited in a branch shape on the cathode-side conductor. . This migration is a phenomenon that is more likely to occur in a printed wiring board that is mounted with high density. When this phenomenon progresses, the insulation between conductors may be reduced.

  As a means for suppressing the dew condensation that occurs on the printed wiring board that causes this migration, Patent Document 1 discloses a substantially rectangular parallelepiped case body that houses the printed wiring board 104 as shown in FIG. In the printed wiring board storage case 100 provided with a connector insertion hole 107 for inserting the connector 106 at a location, a dew condensation prevention plate 108 is provided in the vicinity of the connector 106.

  According to the printed wiring board storage case 100, the outside air W that enters the case through the gap between the connector 106 and the connector insertion hole 107 first hits the condensation prevention plate 108, and the water vapor contained in the outside air W prevents this condensation. Since it is configured to cool and condense on the board 108, the outside air W having a low humidity enters the electronic component housing part 110 in the back thereof, and as a result, on the printed wiring board 104. Condensation is prevented from occurring.

Thus, the dew condensation prevention board 108 is for suppressing the dew condensation of the water vapor | steam contained in the external air W which penetrate | invades into the inside from the exterior of the printed wiring board storage case 100. FIG. As a situation where the outside air W enters the case, for example, there is a case where the case is suddenly moved from a low temperature environment to a high temperature and humidity environment.
JP 2003-188546 A

  However, the dew condensation prevention plate 108 as described above is intended for dew condensation of water vapor contained in the outside air W that enters the printed wiring board storage case 100 from the outside to the inside, and suppresses dew condensation of water vapor already existing in the case. It is not possible.

  For example, when the printed wiring board storage case 100 is moved from a high temperature environment to a low temperature environment, the air already present in the case is cooled, so that water vapor contained in the air is transferred to the printed wiring board 104. However, the condensation prevention plate 108 cannot suppress the condensation under such circumstances.

  In view of such circumstances, an object of the present invention is to suppress dew condensation of water vapor existing inside a printed wiring board storage case.

  As means for solving the above problems, the present invention provides a printed wiring board storage case for storing therein a printed wiring board on which a plurality of electronic components are mounted, wherein the printed wiring board on which the electronic components are mounted is provided. Concavities and convexities are formed on the surface covering the upper surface so as to conform to the shape of each electronic component.

  According to this printed wiring board storage case, the surface covering the upper surface of the printed wiring board on which the electronic component is mounted is formed with irregularities along the shape of each electronic component, so that the case and each electronic component are The space between the case and the printed wiring board can be uniformly reduced, so that the part that houses the electronic components compared to the conventional case that forms a substantially rectangular parallelepiped and surrounds the printed wiring board with a flat surface The volume of can be reduced. As a result, the amount of air present in the printed wiring board storage case and the amount of water vapor contained therein are reduced, so that the water vapor already present in the case is less than that of a conventional rectangular parallelepiped case. The risk of condensation on the plate can be reduced.

  When such a printed wiring board storage case is provided with a connector insertion hole for inserting a connector to be connected to the printed wiring board stored in the case, the gap is formed between the connector and the connector insertion hole. It is preferable to provide an anti-condensation plate in the interior that blocks outside air that enters. In this way, when there is outside air that enters the case through the gap between the connector and the connector insertion hole, water vapor contained in the outside air can be condensed to some extent on the condensation prevention plate. The outside air with reduced humidity will enter the part that houses the electronic components in the back, and as a result, the moisture contained in the outside air entering from the outside of the case to the inside will also be prevented from condensing on the printed wiring board. Can do.

  However, even in this case, since all the water vapor contained in the outside air cannot be condensed on the dew condensation prevention plate, the outside air that contains slightly water vapor (outside air with reduced humidity) is present in the electronic component storage section at the back. However, if the volume of the electronic component storage portion is small as described above, the amount of water vapor that enters the electronic component storage portion with the outside air is reduced, so that compared to the case where only a dew condensation prevention plate is provided. Condensation can be effectively suppressed.

  As described above, according to the printed wiring board storage case of the present invention, it is possible to suppress dew condensation of water vapor existing inside the case.

  A preferred embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a printed wiring board storage case according to an embodiment of the present invention. As shown in the figure, the printed wiring board storage case 10 is configured by fitting an upper case 11 and a lower case 12, and stores a printed wiring board 14 therein. Specifically, a pedestal portion 12 a that protrudes horizontally in the lower case 12 supports and fixes the lower surface of the printed wiring board 14, so that the printed wiring board 14 is stored in the printed wiring board storage case 10. It is the composition to do.

  Further, the printed wiring board storage case 10 is formed with a connector insertion hole 17 which is formed by partially cutting out the vicinity of the joint portion of the upper case 11 and the lower case 12, thereby connecting the connector 16 to the printed wiring board storage case. 10 can be inserted.

  On the other hand, a plurality of electronic components 22 are mounted on the upper surface of the printed wiring board 14. Similarly, a connector 16 is connected to the upper surface of the printed wiring board 14 in a state of being inserted into the connector insertion hole 17, and the printed wiring board 14 is electrically connected to an external device via the connector 16. It has a configuration.

  The upper case 11 is formed with a dew condensation preventing plate 18 extending in the vertical direction in the vicinity of the connector 16 connecting portion, and further on the back, there are irregularities along the shape of each electronic component 22. Is formed. In the present embodiment, the concavo-convex portion of the upper case 11 has a certain plate thickness and is concavo-convex (forms concavo-convex on both the upper and lower surfaces of the concavo-convex portion). The upper surface of the part may be a horizontal surface, and irregularities may be formed only on the lower surface so that the plate thickness varies depending on the location.

  Due to the unevenness formed in the upper case 11, the volume of the electronic component storage unit 20 can be reduced as compared with the conventional printed wiring board storage case 100 (FIG. 3). This is because, in the case of the printed wiring board storage case 10 (FIG. 1) of the present embodiment, the upper case 11 and the electronic components 22 are formed on the upper case 11 so as to conform to the shape of each electronic component 22. 3 (for example, dimension A) and the gap (for example, dimension B) between the upper case 11 and the printed wiring board 14 can be set to be similarly small, whereas the conventional printed wiring board shown in FIG. In the case of a substantially rectangular parallelepiped case such as the storage case 100, the height of the upper case 101 must be increased uniformly in accordance with the highest electronic component 112a, and therefore the gap between the upper case 101 and the electronic component 112a. Is set small (A ′ dimension), the gap (for example, B ′ dimension) between the upper case 101 and the other electronic component 112 and the gap between the upper case 101 and the printed wiring board 104. It is from greater inevitably than the dimension 'wherein A is the size)' C.

  As shown in FIG. 1, when the outside air W enters through the gap between the connector 16 and the connector insertion hole 17 due to a change in the external environment, the outside air W first hits the condensation prevention plate 18 as shown in FIG. 1. It is provided in such a position. Accordingly, since the outside air W is cooled on the dew condensation prevention plate 18, the water vapor contained in the outside air W is condensed on the dew condensation prevention plate 18 to some extent.

  As described above, according to the printed wiring board storage case 10 of the present embodiment, first, since the volume of the electronic component storage unit 20 is small, the amount of air present in the case and the amount of water vapor contained in the air itself are reduced. Since the amount of the water vapor can be reduced, it is possible to reduce the risk that water vapor already present inside the case is condensed on the printed wiring board 14 as compared with a case of a substantially rectangular parallelepiped as in the prior art.

  Further, in a situation where the outside air W enters from the gap of the connector insertion hole 17, the water vapor contained in the outside air W is condensed on the condensation prevention plate 18. The outside air W with reduced humidity enters the storage unit 20, and as a result, it is possible to prevent the water vapor contained in the outside air W that enters from the outside of the case from condensing on the printed wiring board 14.

  However, even in this case, it is impossible to condense all the water vapor on the dew condensation preventing plate 18, so that the outside air W that enters the electronic component storage unit 20 contains a slight amount of water vapor. If the volume of the electronic component storage unit 20 is reduced by providing irregularities on the case 11, the amount of water vapor that enters the electronic component storage unit 20 with the outside air W is reduced, so the dew condensation prevention plate 18 is simply provided. Compared with the case of only this, dew condensation can be suppressed more effectively.

  In the present embodiment, the connector 16 is inserted in the horizontal direction. However, the connector 16 may have to be inserted in the vertical direction due to a layout problem of the electronic unit. An embodiment in such a case is shown in FIG. In this case, the dew condensation prevention plate 18 ′ may be constituted by a member that surrounds the connector 16 ′ so as to form a connector insertion hole 17 ′ and extends along the vertical direction thereof. In this way, the gap between the connector 16 ′ and the dew condensation prevention plate 18 ′ becomes longer in the vertical direction, and the outside air W is cooled while passing through the gap, so that the water vapor contained in the outside air W is removed from the dew condensation prevention plate. It is possible to cause condensation on 18 '.

  In the present embodiment, the electronic component 22 is not mounted on the lower surface of the printed wiring board 14. However, when the electronic component 22 is mounted on the lower surface, the lower case 12 is also connected to the upper case 11. Similarly, unevenness along the shape of the electronic component 22 may be formed.

It is sectional drawing which shows the printed wiring board storage case concerning this embodiment. It is sectional drawing which shows the printed wiring board storage case concerning a modification. It is sectional drawing which shows the conventional printed wiring board storage case.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printed wiring board storage case 14 Printed wiring board 16 Connector 17 Connector insertion hole 18 Condensation prevention board 22 Electronic component W Outside air

Claims (2)

A printed wiring board storage case for storing therein a printed wiring board on which a plurality of electronic components are mounted,
A printed wiring board storage case, wherein unevenness along the shape of each electronic component is formed on a surface covering an upper surface of the printed wiring board on which the electronic component is mounted. In the printed wiring board storage case according to claim 1,
While having a connector insertion hole for inserting a connector connected to a printed wiring board housed inside,
A printed wiring board storage case having a dew condensation prevention plate formed therein so as to block outside air entering the inside through a gap between the connector and the connector insertion hole.

Images