JP2008235298A - Circuit board and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board having stable quality by assuring shield performance of a circuit component to electromagnetic wave. <P>SOLUTION: The circuit board comprises a wiring board 6 to which a circuit component 10 is fixed, a shield frame 7 fixed to the wiring board 6 and arranged around the circuit component 10, a shield cover 8 which is provided with a plurality of fixing portions 11, fixed to the shield frame 7 by touching these fixing portions 11 to the fixing portions 12 of the shield frame 7, and arranged oppositely to the wiring board 6 with the circuit component 10 therebetween, and an insulator 9 interposed between the shield frame 7 and the shield cover 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a circuit board and an electronic device, and in particular, a circuit board having high shielding performance that prevents electromagnetic waves generated from circuit components from leaking to the outside and prevents electromagnetic waves from surroundings from entering circuit components, and The present invention relates to an electronic device using the circuit board.

  In electronic devices such as mobile phones, personal computers, and PC card type wireless terminals, shielding performance prevents electromagnetic waves from circuit components from leaking to the outside and prevents electromagnetic waves from the surroundings from entering circuit components. Various measures have been taken to increase

  As an example, a shield structure in which a circuit component is surrounded by a shield frame and a shield cover as described in Patent Document 1 below is known.

  A circuit board having a shield structure described in Patent Document 1 and a mobile phone which is an example of an electronic apparatus having the circuit board will be described with reference to FIGS. The mobile phone 100 includes a first case 101, a second case 102, and a circuit board 103. The first case 101 and the second case 102 are made of resin and are bonded using an adhesive. A storage space 104 is formed between the first case 101 and the second case 102, and the circuit board 103 is stored in the storage space 104.

  The circuit board 103 is formed by a wiring board 105, a shield frame 106, and a shield cover 107. Printed wiring (not shown) is formed on the wiring board 105, and a plurality of circuit components 108 connected to the printed wiring are attached to the wiring board. The shield frame 106 is made of metal, is disposed around a circuit component 108 that needs to shield against electromagnetic waves, and is soldered to the wiring board 105. The shield cover 107 is formed of metal, is attached to the shield frame 106, and is disposed at a position facing the wiring board 105 with the circuit component 108 interposed therebetween.

  The shield cover 107 is attached to the shield frame 106 by fitting a plurality of protrusions 109 formed on the shield cover 107 into holes 110 formed on the shield frame 106. By fitting the protrusion 109 into the hole 110, the shield frame 106 and the shield cover 107 are electrically connected. The shield frame 106 and the shield cover 107 are designed so as to come into contact with each other only at the fitting portion formed by the protrusion 109 and the hole portion 110, and other portions are not in contact with each other.

  The shielding performance against electromagnetic waves by the shield frame 106 and the shield cover 107 is affected by the conductive points where the shield frame 106 and the shield cover 107 are in contact, and the shielding performance increases as the number of conductive points and the area of the conductive points increase. Becomes higher.

In addition, the cellular phone 100 is strongly demanded to be thin, and by reducing the width dimension “A” between the shield frame 106 and the shield cover 107 in the height direction from the wiring substrate 105, the thickness is reduced. Yes. The width “A” for preventing the shield frame 106 and the shield cover 107 from contacting each other needs to be 0.1 mm or more.
JP 2003-133777 A

  However, in the circuit board 103 and the mobile phone 100 described above, the following points are not considered.

  Even a portion designed to be non-contact between the shield frame 106 and the shield cover 107 may come into contact due to variations in component dimensions and assembly accuracy. In particular, when the width dimension “A” is reduced in order to reduce the thickness of the mobile phone 100, the shield frame 106 and the shield cover 107 facing each other at a position where the width dimension “A” should be ensured easily come into contact. .

  When a portion designed to be non-contact between the shield frame 106 and the shield cover 107 comes into contact, even if a shield inspection of the circuit board 103 is performed and a good shield result is obtained, the good shield result is not good. This is a result obtained because the part designed to be in contact is in contact, and if that part is non-contacted as designed, good shielding results may not be obtained.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a circuit board and an electronic apparatus that ensure the shielding performance of circuit components against electromagnetic waves and have stable quality.

  A first feature according to an embodiment of the present invention is that, in a circuit board, a wiring board to which circuit components are attached, a shield frame attached to the wiring board and disposed around the circuit parts, and a plurality of attachments A shield cover that is attached to the shield frame by contacting these attachment portions with the attachment portion of the shield frame, and disposed at a position facing the wiring board with the circuit component interposed therebetween, and the shield And an insulator interposed between the frame and the shield cover.

  A second feature according to the embodiment of the present invention is that the electronic device includes the circuit board according to the first feature.

  ADVANTAGE OF THE INVENTION According to this invention, the shielding performance of the circuit component with respect to electromagnetic waves can be ensured, and the circuit board and electronic device with which quality was stabilized can be provided.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a mobile phone 1 that is an electronic apparatus according to an embodiment of the present invention includes a first case 2, a second case 3, and a circuit board 4. The first case 2 and the second case 3 are made of resin and are bonded using an adhesive. A storage space 5 is formed between the first case 2 and the second case 3, and the circuit board 4 is stored in the storage space 5.

  The circuit board 4 includes a wiring board 6, a shield frame 7, a shield cover 8, and an insulator 9.

  Printed wiring (not shown) is formed on the wiring board 6, and a plurality of circuit components 10 connected to the printed wiring are attached to the wiring board 6.

  The shield frame 7 is made of metal, has conductivity, is disposed around the circuit component 10 that needs to shield against electromagnetic waves, and is soldered to the wiring board 6.

  The shield cover 8 is made of metal, has conductivity, is detachably attached to the shield frame 7, and is disposed at a position facing the wiring board 6 with the circuit component 10 interposed therebetween. The shield cover 8 is formed by a frame portion 8 a that surrounds the outer periphery of the shield frame 7 and a cover portion 8 b that covers the circuit component 10 by facing the wiring substrate 6 across the circuit component 10.

  The insulator 9 is interposed between the shield frame 7 and the shield cover 8 and at a position in the height direction from the wiring board 6. The insulator 9 is made of an epoxy resin, silicone, or fluorine resin, and is formed into a film shape or a tape shape, or is formed by applying a liquid. The insulator 9 is affixed or applied to a region of the shield frame 7 that faces the cover portion 8b of the shield cover 8.

  The shield cover 8 is attached to the shield frame 7 with a plurality of protrusions 11 that are attachment portions formed on the frame portion 8 a of the shield cover 8 and a plurality of holes that are attachment portions formed on the shield frame 7. This is done by fitting the part 12. By fitting the protrusion 11 into the hole 12, the shield frame 7 and the shield cover 8 are brought into contact with each other to be conducted. The shield frame 7 and the shield cover 8 are designed such that they are brought into contact with each other only at a fitting portion formed by the protrusion 11 and the hole 12 and are not in contact with each other.

  In such a configuration, the insulator 9 is interposed between the shield frame 7 and the shield cover 8, so that the shield frame 7 and the shield cover 8 are only fitted to the projecting portions 11 and the hole portions 12. In other places, it is possible to ensure a non-contact state as designed. For this reason, the shielding performance against the electromagnetic wave of each circuit board 4 can be maintained constant, the circuit board 4 with stable quality can be manufactured, and the mobile phone 1 manufactured using this circuit board 4 Can stabilize the quality.

  Even if the width “B” between the shield frame 7 and the shield cover 8 is reduced by interposing the insulator 9 between the shield frame 7 and the shield cover 8, for example, 0.05 mm Even if it is made small, contact between the shield frame 7 and the shield cover 8 can be prevented.

  Since the width dimension “B” between the shield frame 7 and the shield cover 8 can be reduced, the height dimension “C” from the wiring board 6 to the shield cover 8 can be reduced. 4 and the thickness of the cellular phone 1 using the circuit board 4 can be reduced.

Here, capacitive coupling with a capacitance value C occurs where two parallel flat plates made of metal face each other with a gap. The capacitance value C of this capacitive coupling is
C = εS / t where ε = ε0 × εr
Can be expressed as

S is the area of the opposing flat plate,
t is the distance between the opposing plates,
ε is the dielectric constant of the insulator between the opposing plates ε0 is the dielectric constant of the vacuum εr is the dielectric constant of the insulator located between the opposing plates.

  Here, assuming that the impedance required for the conduction between the shield frame 7 and the shield cover 8 is 1Ω or less, the capacitance value C necessary for a signal with a frequency of 1 GHz is 160 PF or more.

Considering that this is realized by the shield frame 7 and the shield cover 8 having an opposing area of 100 mm ² , for example, t = 5 μm, which is an unrealistic value. However, if the dielectric constant εr of the insulator 9 interposed between the shield frame 7 and the shield cover 8 is 10, t = 50 μm, which approaches a realistic value.

  Therefore, by interposing the insulator 9 between the shield frame 7 and the shield cover 8, the shield frame 7 and the shield cover 8 can be maintained in a non-contact state, and the shield frame 7 shield cover 8 The width dimension B therebetween can be reduced. As a result, the shield frame 7 and the shield cover 8 are electrically connected to each other in the opposing region, and the shield performance can be improved.

  4 to 6, the shield frame 106 and the shield cover 107 have a large width A, a capacitance value C of capacitive coupling of 8 PF, and an impedance of 20Ω. Electrical connection with the shield cover 107 does not occur.

1 is a longitudinal front view showing a part of a circuit board and a mobile phone according to an embodiment of the present invention. It is a perspective view which shows a shield frame and an insulator. It is a perspective view which shows a shield case. It is a vertical front view which shows a part of circuit board of a prior art example, and a mobile telephone. It is a perspective view which shows a shield frame. It is a perspective view which shows a shield case.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electronic device, 4 ... Circuit board, 6 ... Wiring board, 7 ... Shield frame, 8 ... Shield cover, 9 ... Insulator, 10 ... Circuit component, 11 ... Mounting part, 12 ... Mounting part

Claims (3)

A wiring board on which circuit components can be mounted;
A shield frame attached to the wiring board and disposed around the circuit component;
A shield cover that has a plurality of attachment portions, and is attached to the shield frame by contacting the attachment portions with the attachment portions of the shield frame, and disposed at a position facing the wiring board with the circuit component interposed therebetween; ,
An insulator interposed between the shield frame and the shield cover;
A circuit board comprising:   The circuit board according to claim 1, wherein the insulator is provided between the shield frame and the shield cover at a position in a height direction from the wiring board.   An electronic apparatus comprising the circuit board according to claim 1.

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