JP4271395B2 - Printed wiring board storage case - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is to house the printed circuit board therein relates printed circuit board housing to case provided with a connector insertion hole connector connected to the printed wiring board is inserted, in particular, printed circuit board This relates to the structure of the case that prevents the condensation that occurs in the case.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, electronic components mounted on a printed wiring board are becoming denser as electronic units in automobiles and the like become more functional and smaller. As a result, the problem of migration is a problem.
[0003]
For example, as shown in FIG. 4, this migration is a state in which exposed conductors 51 and 52 connected to the lands 55 a of the printed wiring board 55 with solder 53 are interspersed with water containing electrolytes such as residues. Thus, when a voltage is applied by the battery 54, an electrolysis reaction occurs, and the metal eluted from the anode-side conductor 51 is deposited (59) in a dentlite form on the cathode-side conductor 52. When such a reaction proceeds, the insulation between the conductor 51 and the conductor 52 may be reduced.
[0004]
Therefore, in order to prevent the dew condensation occurring on the surface of the printed wiring board which causes migration, the dew condensation is formed in the case of the electronic unit containing the printed wiring board as described in JP-A-9-102679. What provided the prevention board is known. This anti-condensation plate is provided around the exposed conductors on the surface of the printed wiring board that are particularly prone to migration due to electrolysis when a high voltage is applied. As a result, the outside air that has entered the case hits the condensation prevention plate and causes condensation on the condensation prevention plate by the water vapor contained in the outside air, so that the exposed outside air is blown to the exposed conductor. Therefore, condensation is less likely to occur on the exposed conductor, and migration is prevented.
[0005]
[Problems to be solved by the invention]
However, in the above-described conventional technology in which a dew condensation prevention plate is provided between a conductor that is likely to cause migration and a conductor that is less likely to occur, when a large number of conductors that are likely to cause migration are required, Since it is necessary to collect them so as to be enclosed and arrange them on the surface of the printed wiring board, the printed wiring board and the case may be large. That is, conductors that are likely to cause migration are specifically fine pitch QFP-shaped ICs and chip capacitors that have a short inter-electrode distance due to recent demands for further miniaturization. When 30 to 40 are required, it is difficult in terms of design to surround them all with a condensation prevention plate.
[0006]
Also known is a method of preventing migration by using a highly waterproof flux as shown in FIG. 5 during soldering. The flux generally used may be spherical on the metal as shown in FIG. 5 (a), whereas this highly waterproof flux is a metal as shown in FIG. 5 (b). It forms a protective film having a high adhesion to the lead and stable on the lead 56a and the solder 53. However, in order to perform soldering using such a highly waterproof flux, a complicated work process such as performing in a nitrogen atmosphere is required, which is against the requirement for work efficiency.
[0007]
Therefore, the present invention has been made against the background of the above circumstances, and effectively prevents the dew condensation that occurs when the gas containing water vapor is blown onto the exposed conductor on the surface of the printed wiring board that causes migration. providing a printed circuit board accommodated to case as can be prevented, and its technical problem.
[0008]
[Means for Solving the Problems]
To solve the technical problems described above, the present invention is, as described in claim 1, therein, along with housing a printed circuit board having electronic components mounted, a lead connected to the printed circuit board in the printed wiring board accommodated to case the connector is provided with a connector insertion hole is inserted with, around a is and the connector insertion hole and a position opposed to the connector of the lead connected to the printed wiring board, the printed A dew condensation prevention plate that divides an internal space of the wiring board storage case into a space in which the electronic component is mounted and a space in which the connector is mounted, and prevents dew condensation occurring on an exposed conductor on the surface of the printed wiring board provided, the dew condensation prevention plate is a printed circuit board accommodated to case, wherein a gap 1.5~1mm is formed between the printed circuit board It was.
[0009]
According to the printed circuit board housing to case in the present invention, since there is provided a condensation preventing plate so as to be positioned around the connector, the outside air from the gap between the connector and the connector insertion hole into the case from entering However, since the outside air hits the dew condensation prevention plate and causes dew condensation on the dew condensation prevention plate by the water vapor contained in the outside air, the outside air with low humidity is blown to the exposed conductor located outside the vicinity of the connector. Therefore, condensation hardly occurs on most exposed conductors in the case. In addition, although the connection between the connector and the printed wiring board tends to cause dew condensation, migration is unlikely to occur because the lead pitch of the connector is relatively large. Therefore, occurrence of migration can be effectively prevented.
[0010]
Preferably, it is desirable that before Symbol condensation preventing plate provided notch. Due to the cutout, when the humidity of the outside air decreases, the water vapor inside the case also easily evaporates, so that it is possible to prevent the occurrence of condensation due to the accumulation of a small amount of water vapor.
[0011]
More preferably, as described in claim 2 , it is desirable that the connection part between the lead of the connector and the printed wiring board is covered with a waterproof flux contained in the solder. According to this, it is possible to improve the waterproofness at the connection portion between the connector lead and the printed wiring board, and furthermore, the connection between most exposed conductors and the printed wiring board uses a flux with good general workability. By doing so, it becomes possible to prevent the occurrence of migration more effectively.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of a printed circuit board accommodated to case the present invention will be described with reference to the drawings.
[0013]
Figure 1 shows a first embodiment of the present invention, FIG. 1 (a) is a sectional view of the printed circuit board housing to case 10 from the side, FIG. 1 (b) viewed from the top FIG. As shown in FIG. 1, the case 10 includes an upper case 11 and a lower case 12 made of a resin material, and stores a printed wiring board 15. The upper case 11 is fitted into the lower case 12 so that there is no gap. A receiving portion 12a is provided on the inner wall of the lower case 12, and the printed wiring board 15 is fixed to the receiving portion 12a. The case 10 is provided with a connector insertion hole 10 a located between the upper case 11 and the lower case 12.
[0014]
On the printed wiring board 15, 30 or more electronic components such as a fine pitch QFP-shaped IC 16 and a chip capacitor 17 having a small inter-electrode distance are mounted. Conductors such as the leads 16a and 17a of these electronic components (16 and 17) and the lands 15a formed on the printed wiring board 15 are exposed.
[0015]
The connector 13 disposed in the connector insertion hole 10a is connected to the printed wiring board 15 by the lead 13a. Usually, the lead pitch of the connector used for the on-vehicle electronic unit is 1 mm or more, and in this embodiment, the lead pitch is 2.5 mm. A gap of about 0.5 mm is provided between the connector 13 and the connector insertion hole 10a.
[0016]
A dew condensation prevention plate 14 is provided around the connector 13. The condensation prevention plate 14 extends from the ceiling surface inside the upper case 11 toward the upper surface of the printed wiring board 15 and is perpendicular to the printed wiring board 15. A gap of about 1.5 to 1 mm is formed between the lower end of the dew condensation prevention plate 14 and the printed wiring board 15. As shown in FIG. 1B, the dew condensation prevention plate 14 is composed of a plate 14a facing the connector insertion hole 10a and plates 14b and 14c positioned perpendicular to the connector insertion hole 10a. It covers the three sides around. Depending on the size of the case and the required performance, the condensation prevention plate 14 may be constituted only by the plate 14a.
[0017]
As described above, in such a printed wiring board accommodated to case in the present invention, for example, when you move from a low-temperature environment to a high temperature and high humidity environment, through the gap between the connector insertion hole 10a and the connector, the outside air w enters the case 10. The intruded outside air w is blown to the dew condensation prevention plate 14 before being blown to the electronic components (16, 17) on the surface of the printed wiring board 15. That is, the high-temperature outside air w is cooled by hitting the dew condensation prevention plate 14 and causes dew condensation k on the dew condensation prevention plate 14 by the water vapor contained in the outside air w. Therefore, the exposed conductor (electronic component 16) located outside the vicinity of the connector 13 , 17 leads 16a, 17a, etc.) is blown with the outside air w with reduced humidity. Therefore, most of the exposed conductors (such as the leads 16a and 17a of the electronic components 16 and 17) in the case 10 are less likely to cause dew condensation. In addition, although the connection between the connector 13 and the printed wiring board 15 is likely to cause dew condensation, the connector lead pitch is relatively large (1 mm or more), so even if minute dew condensation occurs, migration will not occur. Hard to occur. Therefore, the occurrence of migration can be effectively prevented.
[0018]
Further, a well-known flux (such as described in Japanese Patent Application Laid-Open No. 2001-150184 and Japanese Patent Application Laid-Open No. 9-24488) is provided at the connection portion between the lead 13a of the connector 13 and the printed wiring board 15. Is used for soldering, the waterproofness of the conductor on the surface of the printed wiring board 15 around the connector 13 can be enhanced. Also, the connection between most exposed conductors (leads 16a, 17a, etc. of the electronic components 16, 17) and the printed wiring board 15 uses a flux with good workability, and the work efficiency is sufficiently satisfied. Therefore, the occurrence of migration can be prevented more effectively.
[0019]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 corresponds to FIG. 1B and is a partial cross-sectional view of the printed wiring board storage case 20 as viewed from above. The difference from the first embodiment is that the condensation prevention plate 24 is provided with a notch 24a1 as shown in FIG. The notch 24a1 has a slit shape formed perpendicular to the printed wiring board 15 at the center of the plate 24a of the dew condensation prevention plate 24 facing the connector insertion hole 20a.
[0020]
Due to the cutout 24a1, when the case 20 moves to a low humidity environment, the water vapor and the condensation k inside the case 20 easily evaporate, so that it is possible to prevent the occurrence of condensation due to the accumulation of a small amount of water vapor.
[0021]
Next, a modification of the above-described second embodiment will be described with reference to FIG. 3, but this is not a specific example of the invention described in the claims . Figure 3, which corresponds to FIG. 2 is a partial cross-sectional view of the printed circuit board housing to case 30 from the upper surface. As shown in FIG. 3, the case 30 includes a bag-shaped case portion 31 and a cover portion 32, and a dew condensation prevention plate 34 is provided on the cover portion 32. The dew condensation prevention plate 34 is configured by plates 34b and 34c positioned perpendicular to the connector insertion hole 30a, and the connector 13 is not covered at a position facing the connector insertion hole 10a. As in this, even simple condensation prevention plate 34 described above, depending on the performances use environment and requirements, it is possible to obtain the same effect as the above embodiment.
[0022]
【The invention's effect】
As described above, according to the present invention, a printed wiring board that can effectively prevent dew condensation caused by spraying a gas containing water vapor onto an exposed conductor on the surface of the printed wiring board that causes migration. it is possible to provide an accommodation to case.
[Brief description of the drawings]
[1] shows a first embodiment of such a printed circuit board housing case in the present invention, FIG. 1 (a) is a sectional view of the printed circuit board housing to case 10 from the side, Figure 1 (B) is the fragmentary sectional view seen from the upper surface.
FIG. 2 is a partial cross-sectional view showing a second embodiment of a printed wiring board storage case according to the present invention.
FIG. 3 is a partial sectional view showing a modification of the sunroof device according to the second embodiment of the present invention shown in FIG. 2;
FIG. 4 is an explanatory diagram showing a problem caused by migration.
FIG. 5 is a cross-sectional view showing a state after soldering due to a difference in flux to be used.
[Explanation of symbols]
10, 20, 30 Case 10a, 20a, 30a Connector insertion hole 13 Connector 13a Lead 14, 24, 34 Anti-condensation plate 24a1 Notch 15 Printed wiring board 15a Land 16, 17 Electronic component 16a, 17a Lead (exposed conductor)
k condensation w open air

Claims (2)

Therein, as well as accommodating a printed circuit board having electronic components mounted in the printed circuit board housing to case provided with a connector insertion hole connector having a lead connected to the printed circuit board is inserted,
The internal space of the printed wiring board storage case, the space in which the electronic component is mounted, and the connector are located around the lead of the connector connected to the printed wiring board and facing the connector insertion hole. And a dew condensation preventing plate for preventing dew condensation occurring on the exposed conductor on the surface of the printed wiring board , and the dew condensation preventing plate is 1.5 to 1 mm between the printed wiring board and the printed wiring board . printed circuit board housing to case, wherein a gap is formed. Connection portions between the lead and the printed circuit board of the connector, printed circuit board housing to case according to claim 1, characterized in that covered by waterproof flux contained in the solder.

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