JPH04222109A - Connecting structure for electronic parts - Google Patents

Abstract

PURPOSE:To present the connecting structure of electronic parts to be immune to a change with the passage of time or thermal fluctuation and to be suitable for flow soldering. CONSTITUTION:On the upper face of a base 5, a printed wiring circuit board 2 is loaded by a joining member 6 having the center composed of soldering 61 and the surrounding composed of insulated resin 62. On the upper face of the printed wiring circuit board 2, electronic parts 33 are loaded by a joining member 4 having the center composed of soldering 41 and the surrounding composed of insulated resin 42. Crystal oscillator board 2 is installed at the upper part of the printed wiring board 2 by supporters 31 and 32. Since the joining members 4 and 6 are divided into the solder mainly for electric connection and the insulated resin for mechanical connection, a resistance value at a connecting part is not increased even when the cubic volume of the insulated resin is changed by temperature fluctuation or the like.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure for electronic components, and more particularly to a bonding material for bonding various components.

0002

[Prior Art] As is well known, in the past, conductive materials such as solder or silver powder have been used to electrically bond various components of electronic components, or to electrically bond electronic components mounted on a printed wiring board. Bonding was performed using a conductive adhesive mixed with an insulating resin such as epoxy resin.

0003

[Problems to be Solved by the Invention] In most cases, electronic components are subjected to heat cycle tests and aging tests in order to ensure or confirm reliability. What is a heat cycle test? For example, the ambient temperature of an electronic component is changed from -40℃ → 25℃ for 3 minutes → 100℃ for 30 minutes → 25℃
The cycle of 3 minutes at -40°C for 30 minutes is repeated several hundred times. However, in the case of conductive bonding materials that use epoxy resin, repeating these cycles can cause cracks in the bonding material or peeling of the bonding surfaces between parts, making the conductive state unstable. was there. For example, in a crystal oscillator to be described later, such a phenomenon manifests itself as a decrease in output voltage due to an increase in resistance value, which can significantly reduce the reliability of electronic components.

[0004] Recently, with the trend towards automation of the assembly of electronic devices, reflow soldering has become increasingly used to electrically and mechanically bond electronic components to printed wiring boards. What is reflow soldering?
In this method, an appropriate amount of solder is supplied to the joint location in advance, and the solder is melted using an external heat source to perform soldering. Inside the reflow oven, which supplies a heat source, the solder is heated to a temperature that can melt the solder. In such cases, if solder is used to join the inside of the electronic component, the solder will melt and cause damage.
Otherwise, it may become soft, resulting in short-circuit accidents and the like.

The present invention was made to solve the above problems, and its purpose is to provide a connection structure for electronic components that is resistant to changes over time or thermal fluctuations and is suitable for reflow soldering. be.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a bonding material that connects each component constituting an electronic component, in which the bonding state of the bonding material mainly affects the electrical connection. It is characterized by being separated into a low melting point metal region for mechanical bonding and an insulating bonding material region for mechanical bonding. Heat resistance is further improved when the bonding state of the bonding material is such that the region of the low melting point metal is in the center and the region of the insulating bonding material is in the periphery. Taking a crystal oscillator as an example, there is a base on which lead terminals are embedded, a printed wiring board mounted on the top surface of this base via a bonding material, and a printed wiring board mounted on the top surface of this printed wiring board via a bonding material. It consists of an electronic component, a crystal vibrating plate mounted on the top surface of the printed wiring board via a support, and a cap for airtight sealing. It is characterized by being separated into a melting point metal region and an insulating bonding material region for mechanical bonding.

[0007]

[Function] Because the bonding material is separated into a region of low melting point metal such as solder, which mainly makes electrical connections, and an region of insulating resin, which makes mechanical connections, volume changes due to changes in the resin over time are prevented. Even if there is, the electrical connection is maintained, so no conduction failure occurs between the connected components. Furthermore, if a low melting point metal such as solder is located in the center, even if the solder softens due to heat, it will be blocked by the surrounding insulating resin and will not flow out to the surrounding area.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained using a crystal oscillator as an example with reference to the drawings. FIG. 1 is an exploded perspective view showing an embodiment of the present invention, FIG. 2 is a side sectional view of FIG. 1 with the cap covered, and FIG. 3 is a partially enlarged view of FIG. 2. The crystal vibrating blank plate 1 is made of an AT-cut crystal plate, and is cut into a rectangular shape. Excitation electrode 1 is on the front and back surfaces of the
1 (the back surface is not shown) is provided by means such as vapor deposition. The printed wiring board 2 is provided with through holes 21 and 22 near both ends in the longitudinal direction, and supports 31 and 32 for crystal vibration plates are provided facing each other on the upper surface, and supports for electronic devices such as ICs are provided on the top surface. A component 33 is mounted on the printed wiring board 2 via the bonding material 4. This bonding material 4 has a solder 41 in the center and an insulating resin 4 such as epoxy resin around it.
It consists of 2. This joining can be performed by the following manufacturing example. First, an insulating resin 42 is applied to a predetermined position on the printed wiring board 2, and a sheet-shaped solder 41 is placed in the center thereof. The parts to be joined are first electrically connected by first melting the solder while applying a constant pressure, and then the surrounding insulating resin is cured by maintaining a predetermined temperature. The base 5 is provided with three terminals, among which lead terminals 51, 53
penetrates through insulating materials 54 and 55 such as glass to the upper surface of the base, and the remaining ground terminal 52 is connected to the metal part of the base 5. A bonding material 6 consisting of solder 61 and an insulating bonding material 62 is applied to the upper surface of the base, the printed wiring board 2 is mounted thereon, and heat bonding is performed while applying a constant pressure. The crystal vibrating blank plate 1 on which the excitation electrodes are formed is mounted on the supports 31 and 32 of the printed wiring board, and is covered with a metal cap 7 to complete the crystal oscillator. Note that there is no problem even if the bonding using the bonding materials 4 and 6 at the two locations is performed simultaneously. In addition, the solder is not limited to the structure in which the solder is located in the center of the bonding material, but may also be a structure in which the solder is divided into left and right or top and bottom halves with the insulating bonding material, or other structures may be used. This may be determined as appropriate depending on the design of the electrical connection form.

[0009]

Effects of the invention: Since the bonding material is separated into a region of low melting point metal such as solder, which mainly makes electrical connections, and a region of insulating resin, which makes mechanical connections, the volume due to changes in the resin over time is reduced. Even if there is a change, the electrical connection is maintained, so no conduction failure occurs between the connected components. Therefore, even if this connection method is used for an oscillator, for example, there is no drop in output voltage due to an increase in resistance value, and a highly reliable electronic component can be provided.

Furthermore, if the structure has a low melting point metal such as solder in the center, even if this solder softens due to heat,
It is blocked by the surrounding insulating resin and does not flow out into the surrounding area. Therefore, short-circuit accidents with other electronic components are less likely to occur, and it is also useful for internal connection of surface-mounted electronic components that are suitable for reflow soldering.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an embodiment of a crystal oscillator according to the present invention.

FIG. 2 is a cross-sectional view of FIG. 1.

FIG. 3 is a partially enlarged view of FIG. 2.

[Explanation of symbols]

1　Crystal vibration plate 2 Printed wiring board 33 Electronic parts 4,6 Bonding material 41,61 Solder (low melting point metal) 42, 62 Insulating resin 5 Base 7 Cap

Claims (3)

[Claims] Claim 1: In a bonding material that connects parts constituting an electronic component, the bonding state is such that the bonding state is mainly between a low melting point metal region for electrical connection and an insulating bonding material for mechanical bonding. A connection structure for electronic components characterized by being separated into a region and a region. 2. The electronic component according to claim 1, wherein in the bonded state of the bonding material, the region of the low melting point metal is in the center, and the region of the insulating bonding material is in the periphery. connection structure. 3. A base on which lead terminals are implanted, a printed wiring board mounted on the upper surface of this base via a bonding material, and an electronic component mounted on the upper surface of this printed wiring board via a bonding material. It also consists of a crystal vibrating base plate mounted on the top surface of the printed wiring board via a support, and a cap for airtight sealing, and the bonding material is mainly made of a low melting point metal for electrical connection. A crystal oscillator characterized in that it is separated into a region and an insulating bonding material region for performing mechanical bonding.