CN111083879B

CN111083879B - Connection method of electronic element and circuit board, circuit board assembly and electronic equipment

Info

Publication number: CN111083879B
Application number: CN201911411630.7A
Authority: CN
Inventors: 戴聿昌; 庞长林; 刘洋
Original assignee: Intellimicro Medical Co ltd
Current assignee: Intellimicro Medical Co ltd
Priority date: 2019-07-26
Filing date: 2019-07-26
Publication date: 2021-02-02
Anticipated expiration: 2039-07-26
Also published as: CN110324984B; CN110324984A; CN111083879A; WO2021017922A1

Abstract

The invention discloses a method for connecting an electronic element and a circuit board, a circuit board assembly and electronic equipment. The electronic component includes at least one pad, the circuit board includes a through hole corresponding to the pad, and the connecting method includes: placing electronic components on the first surface of the circuit board so that the pads are aligned with the corresponding through holes one by one; forming a first conductive adhesive positioned at the bonding pad and/or the through hole of the first surface; overturning the circuit board so that the second surface of the circuit board faces upwards; and forming second conductive adhesive filled in the through holes, wherein the first conductive adhesive and the second conductive adhesive provide electric connection between the circuit board and the electronic element. The two sides of the connection method are glued, so that the reliability of the electric connection between the electronic element and the circuit board can be greatly improved, and the problem of virtual connection or open circuit between the electronic element and the circuit board is avoided.

Description

Connection method of electronic element and circuit board, circuit board assembly and electronic equipment

The invention is as follows26/07/2019Application No. is201910680922.4The invention is named asElectronic device Method for connecting element and circuit board, circuit board assembly and electronic equipmentDivisional application of the patent application.

Technical Field

The present invention relates to the field of electronic circuit technology, and more particularly, to a method for connecting an electronic component to a circuit board, a circuit board assembly, and an electronic device.

Background

With the popularization of electronic products and the continuous development of electronic circuits, circuit board assemblies have been applied to electronic devices such as implant devices, wearable devices, mobile phones, computers, cameras, displays, and the like.

An electronic component (electronic component) is a basic element in an electronic circuit, and has at least one metal pad, a circuit board is a carrier of the electronic component, and a plurality of electronic components are connected and packaged with each other via the circuit board to form a circuit board assembly. One of the common ways of connecting electronic components to a circuit board is soldering to the circuit board. However, with the miniaturization of electronic devices and electronic components, the volume occupied by the bonding pads also becomes smaller, and when the electronic components are soldered to a circuit board, problems of virtual connection and loose connection of the solder joints occur, even short circuits caused by interconnection of a plurality of bonding pads occur easily, and open circuits occur when the bonding pads are not connected to the metal layer of the circuit board.

Therefore, there is a need for further improvement of the connection method of the electronic component and the circuit board in the prior art to solve the above problems.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a method for connecting an electronic component to a circuit board, a circuit board assembly and an electronic device, so as to increase the reliability of the connection between the electronic component and the circuit board.

According to a first aspect of the present invention, there is provided a method of connecting an electronic component including at least one land to a circuit board including a through hole corresponding to the land, the method comprising: placing the electronic components on the first surface of the circuit board, so that the pads are aligned with the corresponding through holes one by one; forming a first conductive adhesive at the bonding pad and/or at the through hole of the first surface; turning over the circuit board so that a second surface of the circuit board faces upward, wherein the second surface and the first surface are opposite to each other; and forming a second conductive adhesive filled in the through hole, wherein the first conductive adhesive and the second conductive adhesive provide electric connection between the circuit board and the electronic element.

Preferably, the circuit board includes a first insulating layer, a second insulating layer, and a metal layer, the metal layer is located between the first insulating layer and the second insulating layer, and the through hole penetrates through the first insulating layer, the metal layer, and the second insulating layer; the cross section area of the through hole on the second insulating layer is larger than that of the through hole on the first insulating layer, so that part of the surface of the metal layer is exposed; the first surface is an exposed surface of the first insulating layer, and the second surface is an exposed surface of the second insulating layer.

Preferably, the first conductive adhesive closes the through hole on the first surface.

Preferably, the method further comprises the following steps: drying the first conductive adhesive after the first conductive adhesive is formed; and/or drying the second conductive adhesive after the second conductive adhesive is formed.

Preferably, the first conductive adhesive and the second conductive adhesive are metal-based or carbon-based epoxy adhesives.

Preferably, after the second conductive paste is formed, the method further includes: and forming a protective film integrally wrapped on the surfaces of the circuit board and the electronic element.

Preferably, the electronic component is any one of a capacitor, an inductor, a resistor, an oscillator, a filter, a sensor, and an integrated circuit chip.

According to a second aspect of the present invention, there is provided a circuit board assembly comprising: a circuit board having at least one through hole; the electronic component is positioned on the first surface of the circuit board and provided with a bonding pad corresponding to the through hole; and an adhesive providing an electrical connection between the circuit board and the electronic component; the adhesive comprises a first conductive adhesive and a second conductive adhesive which are formed in at least two different steps, wherein the first conductive adhesive is positioned on the first surface, and the second conductive adhesive is filled in the through hole.

According to a third aspect of the present invention, there is provided an electronic apparatus comprising: a circuit board assembly manufactured by the connection method as described above.

Preferably, the electronic device is any one of a cochlear implant, a retinal stimulating visual prosthesis, a cortical stimulator, a spinal stimulator, and a deep brain stimulator (brain pacemaker).

According to the technical scheme provided by the invention, the electronic element is connected to the first surface of the circuit board through the first conductive adhesive, the second conductive adhesive is filled in the through hole of the circuit board, and the glue is dispensed from the two surfaces, so that the electric connection reliability between the electronic element and the circuit board can be greatly improved, and the problem of virtual connection or open circuit between the electronic element and the circuit board is avoided. The scheme has simple process, improves the process yield, ensures that the electronic element normally works under the condition of limited size, and is particularly suitable for miniature electronic equipment.

Furthermore, the through hole of the circuit board has different sectional areas at the first surface and the second surface, and partial surface of the metal layer is exposed, so that the contact resistance between the circuit board and the electronic element can be reduced, the second conductive adhesive with a step structure can be formed, and the bonding strength between the circuit board and the electronic element is increased.

Further, according to the technical scheme provided by the invention, the through hole on the first surface is sealed by the first conductive adhesive, so that when the second conductive adhesive is formed, the conductive adhesive does not leak to the bottom surface or the side wall of the electronic element, and the short circuit problem caused by interconnection of a plurality of pads or interconnection of the pads and the side wall of the electronic element is avoided.

Furthermore, according to the technical scheme provided by the invention, after the electronic element is connected with the circuit board, the protective film integrally wrapped on the surfaces of the electronic element and the circuit board is formed, so that the mechanical damage, the water vapor corrosion and the chemical corrosion can be prevented, and the reliability and the stability of the electronic element are improved.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

fig. 1a to 1d show cross-sectional views of various stages of a method of connecting an electronic component to a circuit board according to an embodiment of the present invention.

FIG. 2 illustrates a partial perspective view of a circuit board assembly according to an embodiment of the present invention;

FIG. 3 illustrates a partially exploded view of a circuit board assembly according to an embodiment of the present invention;

FIG. 4 illustrates a top view of a circuit board according to an embodiment of the present invention;

fig. 5a to 5h show sectional views of stages of a method of manufacturing a circuit board according to an embodiment of the present invention.

List of reference numerals

100 circuit board

101 substrate

102 first photoresist layer

103 second photoresist layer

104 first opening

105 mask

106 second opening

110 introduction part

111 first insulating layer

112 metal layer

113 second insulating layer

114 through hole

120 connecting part

130 stimulation end

131 stimulating electrode

200 electronic component

201 pad

300 adhesive

301 first conductive paste

302 second conductive paste

310 glue dispensing device

Detailed Description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples.

As shown in fig. 1a, an electronic component 200 is attached to a first surface of the circuit board 100. The electronic component 200 includes at least one pad 201, and the circuit board 100 includes a through-hole 114 corresponding to the pad 201. In this step, the first surface of the circuit board 100 is directed upward, and the electronic components 200 are placed on the first surface of the circuit board 100 such that the pads 201 are aligned with the corresponding through holes 114 one by one, and the first conductive paste 301 is formed at the pads 201 and/or the through holes 114 on the first surface to connect the electronic components 200 to the first surface of the circuit board 100 via the first conductive paste 301. Preferably, after the first conductive paste 201 is formed, the first conductive paste 301 is dried.

Preferably, the circuit board 100 includes a first insulating layer 111, a metal layer 112, and a second insulating layer 113, the metal layer 112 is located between the first insulating layer 111 and the second insulating layer 113, and the via hole 114 penetrates the first insulating layer 111, the metal layer 112, and the second insulating layer 123. The cross-sectional area of the via hole 114 at the second insulating layer 113 is larger than that at the first insulating layer 111 to expose a portion of the surface of the metal layer 112, and the exposed surface of the metal layer 112 is used for electrical connection. The exposed surface of the first insulating layer 111 is a first surface of the circuit board 100, and the exposed surface of the second insulating layer 113 is a second surface of the circuit board 100. The Circuit board 100 is preferably a Flexible Printed Circuit (FPC). In alternative embodiments, circuit board 100 is any circuit board having through-holes.

Further, the circuit board 100 is flipped over so that the second surface of the circuit board 100 faces upward, as shown in fig. 1 b. In this embodiment, preferably, the first conductive adhesive 301 seals the through hole 114 on the first surface of the circuit board 100, after the circuit board 100 is turned over, the first conductive adhesive 301 and the sidewall of the through hole of the circuit board 100 form a semi-closed structure with an open top, and when the second conductive adhesive is formed, the conductive adhesive does not leak to the bottom surface or the sidewall of the electronic component 200, thereby avoiding a short circuit problem caused by the conductive adhesive interconnecting a plurality of pads 201 or the pads 201 and the sidewall of the electronic component 200.

Further, the via 114 is filled with a second conductive paste 302, as shown in fig. 1c and 1 d. In this step, for example, the second conductive paste 302 is dispensed into the through hole 114 by using the dispensing device 310, and the second conductive paste 302 is dried. In a preferred embodiment, the exposed surface of the metal layer 112 is connected to the pad 201 via the second conductive paste 302 and the first conductive paste 301, which not only reduces the contact resistance between the circuit board 100 and the electronic component 200, but also increases the bonding strength between the circuit board and the electronic component due to the step structure of the second conductive paste 302.

In this embodiment, the first conductive paste 301 and the second conductive paste 302 are any one of silver-based conductive paste, gold-based conductive paste, platinum-based conductive paste, aluminum-based conductive paste, copper-based conductive paste, and carbon-based conductive paste, and preferably, the first conductive paste 301 and the second conductive paste 302 are metal epoxy adhesive.

In the circuit board assembly shown in fig. 1d, the electronic component 200 is connected to the first surface of the circuit board 100 through the first conductive adhesive 301, the through hole 114 of the circuit board 100 is filled with the second conductive adhesive 302, the first conductive adhesive 301 can ensure the reliability of the mechanical connection between the electronic component 200 and the circuit board 100, the second conductive adhesive 302 can ensure the reliability of the electrical connection between the electronic component 200 and the circuit board 100, the two-sided adhesive dispensing greatly improves the connection reliability between the electronic component 200 and the circuit board 100, and the problem of virtual connection or open circuit between the electronic component 200 and the circuit board 100 is avoided. The scheme has simple process, improves the process yield, ensures that the electronic element 200 can normally work under the condition of limited size, and is particularly suitable for miniature electronic equipment.

Preferably, after the circuit board assembly shown in fig. 1d is formed, a protective film (not shown) integrally wrapped on the circuit board assembly is formed, wherein the protective film is one or more of a parylene film, a polyimide film, a polypropylene film, a poly terephthalic acid film and a silicon gel film, and is formed by a chemical vapor deposition process, a spin coating method or an injection molding method. The protective film can prevent mechanical damage, water vapor erosion and chemical corrosion, and the reliability and the stability of the electronic element are improved.

In this embodiment, the circuit board assembly as described above is energized, or electrically connected, to other electronic circuits to form an electronic device. Electronic devices include, for example, implants, wearable devices, cell phones, computers, cameras, displays, and the like, and are particularly suitable for miniature electronic devices because the solution allows for the formation of small-sized flexible circuit board assemblies.

Fig. 2 and 3 show a partial perspective view and a partial exploded view, respectively, of a circuit board assembly according to an embodiment of the present invention. The circuit board assembly includes a circuit board 100, an electronic component 200, and an adhesive 300.

The circuit board 100 includes at least one through hole 114, the electronic component 200 includes pads 201 corresponding to the through holes 114, and the through holes 114 correspond to the pads 201 one to one. The electronic component 200 is connected to the first surface of the circuit board 100 via an adhesive 300, the adhesive 300 includes a first conductive paste 301 and a second conductive paste 302 formed in at least two different steps, the first conductive paste 301 is dispensed from the first surface of the circuit board 100, and the second conductive paste 302 is dispensed from the second surface of the circuit board 100. The electronic component 200 is any one of components such as a capacitor, an inductor, a resistor, an oscillator, a filter, a sensor, and an integrated circuit chip.

Fig. 4 shows a top view of a circuit board according to an embodiment of the invention. The circuit board 100 includes a lead-in portion 110, a connection portion 120, and a stimulation end 130, the circuit board 100 is a flexible cable suitable for an implant device such as a cochlear implant, a retinal stimulating visual prosthesis, a cortical stimulator, a spinal cord stimulator, and a deep brain stimulator (brain pacemaker), and the flexible cable can prevent tissue damage when in contact with tissue and can ensure biocompatibility and reliability.

The lead-in portion 110 has at least one through hole 114 thereon, and the through hole 114 is used for filling a conductive material to connect an electronic component on the lead-in portion 110. The surface or the inside of the connection part 120 includes a metal layer (not shown) corresponding to the stimulation terminal 130. The stimulation end 130 has a plurality of stimulation electrodes 131 thereon and is connected to the introduction part 110 via the connection part 120, and the stimulation electrodes 131 are connected to the electronic components via the through holes 114 to form a complete circuit.

In this embodiment, the structure of the circuit board is described by taking the circuit board of the implant device as an example, but the circuit board of the present invention is not limited to the flexible cable, and the electronic device is not limited to the implant device, and the circuit board 100 may be a circuit board of any shape formed by an insulating layer and a metal layer to provide electrical connection between electronic components or to provide electrical connection between the electronic components and other electronic circuits, so as to form other electronic devices.

Fig. 5a to 5h show sectional views of stages of a method of manufacturing a circuit board according to an embodiment of the present invention. The cross-sectional view is taken along line AA in fig. 2.

The method starts with a substrate 101 and a first photoresist layer 102 on the substrate 101 as shown in fig. 5 a. The substrate 101 is used to provide mechanical support and the first photoresist layer 102 is used to protect the substrate 101 during the dicing process and as a sacrificial layer during the step of releasing the circuit board. In an alternative embodiment, the first photoresist layer 102 may be omitted to reduce cost and simplify process flow.

In this step, the substrate 101 is preferably a wafer (wafer) to facilitate the formation of a small area circuit board. And after the wafer is cleaned, spin-coating negative photoresist on the surface of the wafer, and hard-baking the negative photoresist.

Further, a first insulating layer 111 is formed on the first photoresist layer 102, as shown in fig. 5 b. The material of the first insulating layer 111 is PMMA (poly (methyl methacrylate)), teflon, silicone, polyimide, poly (ethylene terephthalate), Parylene (especially Parylene-C). In this step, it is preferable that the first insulating layer 111 is a parylene film, and the parylene film is formed using a Chemical Vapor Deposition (CVD) process.

Further, a second photoresist layer 103 having a pattern is formed on the surface of the first insulating layer 111, as shown in fig. 5 c. In this step, for example, a second photoresist layer 103 is formed on the surface of the first insulating layer 111, and the second photoresist layer 103 is exposed and developed to form the second photoresist layer 103 having a pattern.

Further, a patterned metal layer 112 is formed, as shown in fig. 5 d. In this step, a metal layer 112 filled in the pattern of the second photoresist layer 103 is formed, and the second photoresist layer 103 is removed to form a patterned metal layer 112, the metal layer 112 having a first opening 104, the first opening 104 being to be used for forming a portion of the via hole.

In an alternative embodiment, the step of forming the second photolithography layer 103 may be omitted, and the metal layer 112 may be patterned after the metal layer 112 is formed on the surface of the first insulating layer 111.

Further, a second insulating layer 113 is formed covering the metal layer 112, as shown in fig. 5 e. In this step, the material of the second insulating layer 113 is the same as that of the first insulating layer, preferably, the second insulating layer 113 is a parylene film, and a chemical vapor deposition process is used to form the parylene film covering the exposed surfaces of the metal layer 112 and the first insulating layer 111, preferably, the parylene film is also subjected to a planarization process.

Further, a mask 105 is formed on the second insulating layer 113, as shown in fig. 5 f. The surface of the mask 105 has a second opening 106, and the cross-sectional area of the second opening 106 is larger than the cross-sectional area of the first opening 104. Preferably, the plurality of first openings 104 and the plurality of second openings 106 may be designed according to the position and shape of the pads of the electronic component to form a circuit board that accommodates various electronic components.

Further, a via hole 114 penetrating the first insulating layer 111, the metal layer 112, and the second insulating layer 113 is formed as shown in fig. 5 g. In this step, the via hole 114 is formed by an anisotropic dry etching process, and after the via hole 114 in the second insulating layer 113 is formed, since the first opening of the metal layer 112 is smaller than the second opening of the mask 105, the metal layer 112 serves as a mask for shielding the first insulating layer 111, and the etching is continued, so that the via hole 114 having different sectional areas in the second insulating layer 113 and the first insulating layer 111 is formed, and a part of the surface of the metal layer 112 is exposed.

Further, the mask 105, the first photoresist layer 102 and the substrate 101 are removed to release the circuit board 100, as shown in fig. 5 h. In this step, the mask 105 is removed, for example, by soaking with a remover, the first photoresist layer 102 is dissolved, and the substrate 101 is removed, followed by a water rinsing and baking step.

In this embodiment, a manufacturing method of a circuit board is described as an example of a manufacturing method of a flexible cable, but the circuit board of the present invention is not limited to the flexible cable, and the structure of the circuit board is not limited thereto, and the circuit board 100 may be a circuit board of any structure formed by an insulating layer and a metal layer.

While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of connecting an electronic component to a circuit board, the electronic component including at least one land, the circuit board including a via corresponding to the land, the circuit board being a flexible cable, the method comprising:

placing the electronic components on the first surface of the circuit board, so that the pads are aligned with the corresponding through holes one by one;

forming a first conductive adhesive at the bonding pad and/or at the through hole of the first surface;

turning over the circuit board so that a second surface of the circuit board faces upward, wherein the second surface and the first surface are opposite to each other; and

and forming second conductive adhesive filled in the through holes, wherein the first conductive adhesive and the second conductive adhesive provide electric connection between the circuit board and the electronic element, the first conductive adhesive and the second conductive adhesive are the same type of conductive adhesive, and the through holes are only connected with the bonding pads of the electronic element on one side of the first surface.

2. The connecting method according to claim 1, wherein the circuit board includes a first insulating layer, a second insulating layer, and a metal layer, the metal layer being located between the first insulating layer and the second insulating layer, the via hole penetrating the first insulating layer, the metal layer, and the second insulating layer;

the cross section area of the through hole on the second insulating layer is larger than that of the through hole on the first insulating layer, so that part of the surface of the metal layer is exposed;

the first surface is an exposed surface of the first insulating layer, and the second surface is an exposed surface of the second insulating layer.

3. The connecting method according to claim 1, wherein the first conductive paste closes the through hole on the first surface.

4. The connecting method according to claim 1, further comprising:

drying the first conductive adhesive after the first conductive adhesive is formed; and/or

And drying the second conductive adhesive after the second conductive adhesive is formed.

5. The connecting method according to claim 1, wherein the first conductive adhesive and the second conductive adhesive are metal-based or carbon-based epoxy adhesives.

6. The connecting method according to any one of claims 1 to 5, further comprising, after forming the second conductive paste: and forming a protective film integrally wrapped on the surfaces of the circuit board and the electronic element.

7. The connecting method according to any one of claims 1 to 5, wherein the electronic component is any one of a capacitor, an inductor, a resistor, an oscillator, a filter, a sensor, and an integrated circuit chip.

8. A circuit board assembly, comprising:

the circuit board is provided with at least one through hole and is a flexible cable;

the electronic component is positioned on the first surface of the circuit board and provided with a bonding pad corresponding to the through hole; and

an adhesive providing an electrical connection between the circuit board and the electronic component;

the adhesive comprises a first conductive adhesive and a second conductive adhesive which are formed in at least two different steps, the first conductive adhesive is located on the first surface, the second conductive adhesive is filled in the through holes, the first conductive adhesive and the second conductive adhesive are the same type of conductive adhesive, and the through holes are only connected with the bonding pads of the electronic elements on one side of the first surface.

9. An electronic device, comprising: a circuit board assembly manufactured by the connection method according to any one of claims 1 to 7, or a circuit board assembly according to claim 8.

10. The electronic device of claim 9, wherein the electronic device is any one of a cochlear implant, a retinal stimulating visual prosthesis, a cortical stimulator, a spinal stimulator, and a cerebral pacemaker.