JP2012089767A - Dew condensation prevention structure of printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent dew condensation of printed circuit boards without using a drip proof material by attaching a simple member.SOLUTION: A printed circuit board 6 and a case body 7 are assembled with an air shutoff member 101 disposed therebetween. The air shutoff member 101 includes an outer side frame part 13 disposed so as to contact with an outer peripheral edge of an insulation substrate 1 of the printed circuit board 6 and an inner frame part 14 enclosing portions corresponding to outer peripheral edges of respective electronic component 2 to 5 mounted on the insulation substrate 1. The outer side frame part 13 and the inner side frame part 14 of the air shutoff member 101 prevent air containing moisture from flowing into spaces Q1 to Q7 between the printed circuit board 6 and the case body 7.

Description

  The present invention relates to a dew condensation prevention structure for a printed circuit board that prevents dew condensation from occurring on a printed circuit board configured by mounting electronic components on an insulating substrate.

  In a printed circuit board configured with electronic components mounted on an insulating substrate, if a DC voltage is applied with a potential difference between adjacent electrodes, the conductive material copper elutes from the positive conductor and passes through the base material. A phenomenon (migration) in which copper grows toward the side conductor may occur. When migration occurs, insulation failure occurs and the function of the printed circuit board is impaired. The cause of this migration is that copper is ionized by moisture adhering to the printed circuit board, so it is important to prevent condensation on the printed circuit board.

  In order to prevent dew condensation on the printed circuit board, measures are taken such as applying a drip-proof material (silicon or the like) or housing the printed circuit board in a sealed case (see, for example, Patent Document 1). However, in the case of applying a drip-proof material, there are problems that the number of steps is increased and the cost is increased, and the drip-proof material as a drug has a great influence on the environment. Further, when the printed circuit board is accommodated in the sealed case, an extra sealed case is required.

JP 2006-253262 A

  In view of the above-described problems, the present invention has an object to prevent dew condensation on a printed circuit board by attaching a member having a simple configuration without using a drip-proof material.

The present invention for solving the above problems is as follows.
A printed circuit board that is configured by mounting electronic components on an insulating substrate and is fixed to a counterpart member;
In a frame shape of a predetermined height, interposed between the printed circuit board and the mating member, one surface in the height direction contacts the surface of the printed circuit board facing the mating member The other surface is also placed in contact with the mating member, forming a sealed space between the printed circuit board and the mating member, and blocking air from entering and exiting the space. An air blocking member that
Condensation occurs on the printed circuit board by the air blocking member preventing moisture containing air from entering the space formed between the printed circuit board and the mating member. It is characterized by preventing.

  The dew condensation prevention structure for a printed circuit board according to the present invention forms a sealed space portion by an air blocking member interposed between the printed circuit board and a mating member, and air containing moisture in the space portion. Is to prevent inflow. The air blocking member is inexpensive because it has a simple frame-shaped configuration. Further, since the printed circuit board and the mating member can be interposed and assembled together, the assembly is easy.

  One surface of the air blocking member in the height direction is disposed in contact with the outer peripheral edge of the printed circuit board. This reliably prevents the moisture-containing air from flowing between the printed circuit board and the counterpart member. The air blocking member is made of an elastomer, and one surface of the air blocking member in the height direction can be brought into close contact with the outer peripheral edge of the printed circuit board.

The air blocking member includes an outer frame portion disposed in contact with an outer peripheral edge of the printed circuit board;
One or more inner frame portions that are integrally formed on the inner side of the outer frame portion and are arranged in contact with each other so as to surround a portion corresponding to the electronic component in the printed circuit board;
Can be provided.

  When the air blocking member includes the outer frame portion and the inner frame portion, it is possible to more reliably prevent the air containing moisture from flowing in. For example, by surrounding a portion corresponding to a particularly important electronic component with the inner frame portion, it is possible to prevent condensation more reliably.

  Further, one surface in the height direction of the air blocking member is a surface facing the counterpart member of the printed circuit board and is in contact with the printed circuit board so as to surround a portion corresponding to the electronic component. You can also. That is, the air blocking member may be composed only of the inner frame portion.

The air blocking member has an assembly portion that is assembled to the mating member in a state of being integrated with the printed circuit board. For example, the outer peripheral edge of the printed circuit board is provided with a through-hole through which a fixing tool for fixing the printed circuit board to the counterpart member is inserted.
The assembly portion is a through hole provided in a portion corresponding to the through hole in the outer frame portion of the air blocking member.

  Thereby, it is ready to assemble the printed circuit board and the air blocking member integrally.

It is a perspective view of the state which separated the printed circuit board 6, the air blocking member 101 of 1st Example, and the case body 7. FIG. It is a front view of the state of FIG. It is the front view of the state which displayed the air-blocking member 101 in the cross section in the state which assembled | attached the printed circuit board 6, the air-blocking member 101 of 1st Example, and the case body 7 integrally. (A) is a top view of the printed circuit board 6, (b) is a bottom view similarly. (A) is a plan view of the air blocking member 101, and (b) is a bottom view of the state in which the air blocking member is disposed close to the back surface of the printed circuit board 6. (A) is a top view of the printed circuit board 16, (b) is a top view of the air blocking member 102 of 2nd Example. (A) is a top view of the air blocking member 103 of 3rd Example, (b) is a top view of the air blocking member 104 of 4th Example. (A) is an exploded view of a printed circuit board 22 in which an air blocking member 105 is interposed between an insulating substrate 1 on which electronic components 2 to 5, 2 ′ and 3 ′ are mounted on both sides and a case body 7, b) is a front view of the printed circuit board 22.

  Hereinafter, embodiments of the present invention will be described in detail. 1 is a perspective view of a state where the printed circuit board 6, the air blocking member 101 and the case body 7 of the first embodiment are separated, FIG. 2 is a front view of the state of FIG. 1, and FIG. FIG. 4A is a plan view of the printed circuit board 6, and FIG. 4A is a plan view of the printed circuit board 6. FIG. 4B is a front view of the air blocking member 101 and the case body 7 assembled together. 5A is a bottom view, FIG. 5A is a plan view of the air blocking member 101, and FIG. 5B is a bottom view of the state in which the air blocking member is disposed close to the back surface of the printed circuit board 6.

  As shown in FIGS. 1 and 4, the printed circuit board 6 on which various electronic components 2, 3, 4, and 5 are mounted on the upper surface of the insulating substrate 1 and the counterpart member (for example, the bottom surface of the case body 7). In between, the air blocking member 101 of the first embodiment is interposed. The insulating substrate 1 constituting the printed circuit board 6 has a substantially rectangular shape in plan view, and four insertion holes 9 (through holes) through which the mounting screws 8 are inserted are provided at the corners. A plurality of pins 2 a, 3 a, 4 a, 5 a are projected on the back surface of each electronic component 2-5, and each pin 2 a-5 a is inserted into a pin insertion hole (not shown) provided in the insulating substrate 1 in advance. )) And fixed by soldering.

  A female screw 11 for screwing a mounting screw 8 is provided at a portion of the case body 7 corresponding to each insertion hole 9 of the insulating substrate 1 of the printed circuit board 6. In addition, although the other party member of a present Example is the case body 7, things (for example, frame of a vehicle etc.) other than the case body 7 may be sufficient.

  The air blocking member 101 of the first embodiment will be described. As shown in FIGS. 1 and 2, the air blocking member 101 is made of a resin material (for example, ABS). Cylindrical boss portions 12 are respectively provided in portions corresponding to the respective insertion holes 9 of the insulating substrate 1 of the printed circuit board 6, and adjacent ones of these four boss portions 12 are arranged as thin square bars (outside The frame portion 13) is connected to the frame shape. The upper surface of the outer frame portion 13 is provided so as to be flush with the upper surface of the boss portion 12. Similarly, the lower surface of the outer frame portion 13 is provided so as to be flush with the lower surface of the boss portion 12. The height H of the air blocking member 101 is a little (for example, 1 mm) than the protruding height of a member (for example, a soldering portion not shown) protruding from the back surface (surface facing the case body 7) of the printed circuit board 6. Degree) is provided to be higher. The boss portion 12 is provided with a through hole 12 a corresponding to the insertion hole 9 of the insulating substrate 1 of the printed circuit board 6. The boss portion 12 and the through hole 12a serve as an “assembly portion” through which the mounting screw 8 is inserted when the air blocking member 101 is assembled integrally with the printed circuit board 6.

  In the case of the air blocking member 101 of the first embodiment, an inner frame portion 14 formed integrally with the outer frame portion 13 is provided on the inner portion of the outer frame portion 13. Here, each square bar constituting the outer frame portion 13 is described as an outer frame portion 13a, an outer frame portion 13b, an outer frame portion 13c, and an outer frame portion 13d in the counterclockwise direction from the front side. An inner frame portion 14a extends in parallel with the outer frame portions 13b and 13d from a portion slightly to the right of the center portion in the length direction of the outer frame portion 13a. The tip of the inner frame portion 14a is connected to the outer frame portion 13c. And the inner frame part 14b extended at right angles so that it may become parallel to the outer frame part 13a toward the outer frame part 13b from the approximate center part of the longitudinal direction of the inner frame part 14a is provided. The tip of the inner frame portion 14b is connected to the outer frame portion 13b. In a portion (space portion) surrounded by the two outer frame portions 13a and 13b and the two inner frame portions 14a and 14b, an inner frame portion 14c parallel to the inner frame portion 14a, an inner frame portion 14b, Parallel inner frame portions 14d are provided so as to intersect each other. Both end portions of the inner frame portion 14c are connected to the outer frame portion 13a and the inner frame portion 14b, and both end portions of the inner frame portion 14d are connected to the outer frame portion 13b and the inner frame portion 14a. In other words, the inner frame portions 14c and 14d arranged in a cross shape define a portion (space portion) surrounded by the two outer frame portions 13a and 13b and the two inner frame portions 14a and 14b. ing. Further, an inner frame portion 14e parallel to the inner frame portion 14a is provided from the middle portion of the inner frame portion 14b toward the outer frame portion 13c. Both end portions of the inner frame portion 14d are connected to the outer frame portion 13c and the inner frame portion 14b.

  As a result, the inside (space portion Q) of the air blocking member 101 of the first embodiment is divided into six space portions Q1 to Q7 by the outer frame portions 13a to 13d and the inner frame portions 14a to 14e. Hereinafter, the space portion defined by the outer frame portions 13a, 13c, 13d and the inner frame portion 14a is referred to as “first space portion Q1,” and the space portion defined by the inner frame portions 14a, 14b, 14c, 14d is referred to as “second. The space portion defined by the space portion Q2 ”, the outer frame portion 13b, and the inner frame portions 14b, 14c, and 14d is defined by the“ third space portion Q3 ”, the outer frame portions 13b and 13c, and the inner frame portions 14b and 14e. The space portion is defined as “fourth space portion Q4”, the space portion defined by the outer frame portion 13c and the inner frame portions 14a, 14b, and 14e is defined as “fifth space portion Q5”, and the outer frame portion 13a and the inner frame portions 14a and 14c. , 14d is referred to as a “sixth space portion Q6”, and a space portion defined by the outer frame portions 13a, 13b and the inner frame portions 14c, 14d is referred to as a “seventh space portion Q7”. Further, the space portions Q1 to Q7 may be collectively referred to as “space portion Q”.

  As shown in FIGS. 2 and 3, an air blocking member 101 is interposed between the printed circuit board 6 and the case body 7, and they are fixed integrally with the mounting screw 8. At this time, the upper surface of each outer frame portion 13 of the air blocking member 101 is disposed in contact with the lower surface of the insulating substrate 1 of the printed circuit board 6, and the lower surface of each outer frame portion 13 is similarly disposed in contact with the upper surface of the case body 7. Is done. Thereby, a space Q sealed by the outer frame 13 of the air blocking member 101 is formed between the printed circuit board 6 and the case body 7.

  Further, portions corresponding to the respective electronic components 2 to 5 constituting the printed circuit board 6 (in FIG. 5B, outer peripheral edges of the respective electronic components 2 to 5 are indicated by broken lines) of the outer frame portion 13. Each is surrounded by an inner frame portion 14 provided inside. Among these, the arrangement | positioning condition of the electronic component 3 is demonstrated. The outer peripheral edge of the electronic component 3 is disposed in the second space Q2 formed by the inner frame portions 14a to 14d. In other words, the inner frame portions 14 a to 14 d of the air blocking member 101 are provided so as to surround the outer peripheral edge of the electronic component 3. At this time, the outer peripheral edge of the electronic component 3 is arranged at a slight distance e from the inner frame portions 14a, 14b, 14c, and 14d constituting the second space portion Q2. This distance e is set in consideration of an error (deviation) when the electronic component 3 is mounted on the insulating substrate 1 of the printed circuit board 6. Thereby, the outer periphery of the electronic component 3 is surrounded by the inner side frame parts 14a-14d.

  Similarly, the other electronic components 2, 4, and 5 are also arranged on the inner side by a slight distance e from the outer frame portions 13a to 13d and the inner frame portions 14a to 14e.

  As described above, when the air blocking member 101 is attached between the printed circuit board 6 and the case body 7, the outer frame portion 13 seals between the printed circuit board 6 and the case body 7. The space portion Q is formed. The outer frame portion 13 prevents moisture containing air from flowing into the space portion Q. This prevents condensation on the printed circuit board 6. Moreover, a portion (space portion Q2) corresponding to the outer peripheral edge of the electronic component 3 is surrounded by the inner frame portion 14 of the air blocking member 101. In other words, since the space portion Q2 is doubly surrounded by the outer frame portion 13 and the inner frame portion 14, air containing moisture is more reliably prevented from flowing into the space portion Q2. It is more reliably prevented that condensation occurs in the electronic component 3. This also applies to the other electronic components 2, 4, and 5.

  Further, the air blocking member 101 prevents dust and dirt from entering the space Q between the printed circuit board 6 and the case body 7.

  The air blocking member 101 is provided in each boss portion 12 provided at a corner portion of the outer frame portion 13 in a through hole 12 a corresponding to the insertion hole 9 of the insulating substrate 1 of the printed circuit board 6. Therefore, when the printed circuit board 6 is assembled to the case body 7, the printed circuit board 6 and the air blocking member 101 are overlapped so that the insertion hole 9 of the insulating substrate 1 and the through hole 12a of the boss portion 12 are matched. . Then, the mounting screw 8 is inserted into the insertion hole 9 and the through hole 12a from above the printed circuit board 6 so that the printed circuit board 6 and the air blocking member 101 are integrated, and the mounting screw 8 is screwed into the case body 7. Fix together. For this reason, since it is almost the same as the conventional assembly method, assembly is not troublesome.

  And even if it is a case where a drip-proof material is applied in order to ensure the prevention of dew condensation, it is partitioned without adopting a method (conventional method) of applying to the entire insulating substrate 1 of the printed circuit board 6. Therefore, the amount of drip-proof material used can be reduced and the number of man-hours required for application can be reduced.

  The air blocking member 101 of the first embodiment is made of a resin material such as ABS. For this reason, when the air blocking member 101 is disposed below the insulating substrate 1 of the printed circuit board 6, the pins 2 a to 5 a of the electronic components 2 to 5 are soldered to protrude from the insulating substrate 1 of the printed circuit board 6. There is a case where a slight gap is generated in the interference portion. In order to avoid this, the air blocking member 101 can be made of an elastomer and can be brought into close contact with the insulating substrate 1 of the printed circuit board 6.

  Next, the air blocking member 102 of the second embodiment will be described. As shown in FIG. 6A, there is a printed circuit board 16 in which a part of the insulating substrate 1 is cut away and a notch 15 is provided. Electronic components 2, 3, 4, 18 and 19 are mounted on an insulating substrate 17 of the printed circuit board 6. The air blocking member 102 for the printed circuit board 16 is provided with a notch 21 corresponding to the notch 15 of the printed circuit board 16 as shown in FIG. As a result, the outer side frame portion on the near side (corresponding to the outer frame portion 13a in the air blocking member 101 of the first embodiment) is divided into the outer frame portion 13a1 and the outer frame portion 13a2. And like air blocking member 101 of the 1st example, space parts Q2, Q3, and Q4 and space parts Q6 and Q7 which surround electronic parts 2-4 are formed by inner frame parts 14a-14e. In the air blocking member 102 of the second embodiment, the inner frame portion 14f that is parallel to the outer frame portion 13c from the inner frame portion 14a and goes toward the outer frame portion 13d is orthogonal to the middle of the inner frame portion 14f. An inner frame portion 14g that is extended and connected to the outer frame portion 13a1 is provided, and space portions Q8 and Q9 that surround the electronic components 17 and 18 are formed by the inner frame portions 14f and 14g.

  When the air blocking member 102 of the second embodiment is interposed between the printed circuit board 16 and the case body 7 and fixed by the mounting screw 8, the air blocking member 102 of the second embodiment is similar to the air blocking member 101 of the first embodiment. A portion corresponding to the electronic components 2, 3, 4, 17 and 18 on the lower surface of the insulating substrate 17 of the printed circuit board 16 is surrounded by the outer frame portion 13 and the inner frame portion 14 by the blocking member 102. As a result, air containing moisture is prevented from flowing into the spaces Q2 to Q4, Q8, and Q9 corresponding to the electronic components 2, 3, 4, 17, and 18, and condensation is prevented from occurring.

  The air blocking members 101 and 102 of the first and second embodiments described above include an outer frame portion 13 and an inner frame portion 14, and the outer frame portion 13 is an insulating substrate 1, 7 of the printed circuit boards 6, 16. It is the form which contacts and arranges at a peripheral part. However, as shown in FIG. 7A, the air blocking member 103 having a part of the outer frame part 13 and a part of the inner frame part 14 may be used. The air blocking member 103 includes a part of the outer frame portions 13b and 13c and the inner frame portions 14a, 14b, 14c, 14d, and 14e in order to prevent condensation on the electronic components 2, 3, and 4. It consists of. In FIG. 7A, outer frame portions 13a, 13b (part), 13c (part), and 13d are indicated by two-dot chain lines.

  Further, as shown in FIG. 7B, the air blocking member 104 including only the inner frame portions 14 a to 14 d may be used in order to prevent condensation from occurring only on the electronic component 2.

  In each of the above-described embodiments, the printed circuit board 6 in which the electronic components 2 to 5 are mounted only on one side of the insulating substrates 1 and 17 has been described. However, as shown in FIGS. 8A and 8B, the present invention is also applied to a printed circuit board 22 in which electronic components 2 to 5, 2 ′, and 3 ′ are mounted on both surfaces of the insulating substrate 1. At this time, the inner frame portion of the air blocking member 105 is provided so as to surround the electronic components 2 ′ and 3 ′ mounted on the bottom surface side of the insulating substrate 1.

  The present invention can be used as a structure for preventing condensation on a printed circuit board used in a vehicle.

101-105 Air blocking member 1, 17 Insulating substrate 2-5, 2 ', 3', 18, 19 Electronic component 6, 16, 22 Printed circuit board 7 Case body (mating member)
12 Boss part (assembly part)
13, 13a-13d, 13a1, 13a2 Outer frame 14, 14a-14g Inner frame H Height Q1-Q9 Space

Claims (8)

A printed circuit board that is configured by mounting electronic components on an insulating substrate and is fixed to a counterpart member;
In a frame shape of a predetermined height, interposed between the printed circuit board and the mating member, one surface in the height direction contacts the surface of the printed circuit board facing the mating member The other surface is also placed in contact with the mating member, forming a sealed space between the printed circuit board and the mating member, and blocking air from entering and exiting the space. An air blocking member that
Condensation occurs on the printed circuit board by the air blocking member preventing moisture containing air from entering the space formed between the printed circuit board and the mating member. A structure for preventing dew condensation on a printed circuit board.   2. The dew condensation prevention structure for a printed circuit board according to claim 1, wherein one surface in the height direction of the air blocking member is disposed in contact with an outer peripheral edge of the printed circuit board. The air blocking member includes an outer frame portion disposed in contact with an outer peripheral edge of the printed circuit board;
One or more inner frame portions that are integrally formed on the inner side of the outer frame portion and are arranged in contact with each other so as to surround a portion corresponding to the electronic component in the printed circuit board;
The dew condensation prevention structure for a printed circuit board according to claim 2, comprising:   One surface in the height direction of the air blocking member is a surface facing the mating member of the printed circuit board, and is disposed in contact with the printed circuit board so as to surround a portion corresponding to the electronic component. The dew condensation prevention structure for a printed circuit board according to claim 1.   The height of the air blocking member is provided to be higher than a protruding height of a member protruding from a surface of the printed circuit board facing the counterpart member. 5. A dew condensation prevention structure for a printed circuit board according to any one of 4 above.   6. The printed circuit board according to claim 1, wherein the air blocking member has an assembly part that is assembled to the mating member in a state of being integrated with the printed circuit board. 7. Anti-condensation structure. The outer peripheral edge of the printed circuit board is provided with a through-hole through which a fixture for fixing the printed circuit board to the counterpart member is inserted,
The dew condensation prevention structure for a printed circuit board according to claim 6, wherein the assembly portion is a through hole provided in a portion corresponding to the through hole in the outer frame portion of the air blocking member.   The dew condensation prevention structure for a printed circuit board according to claim 1, wherein the air blocking member is made of a resin material.

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