WO2008032365A1

WO2008032365A1 - Electronic device and method for manufacturing same

Info

Publication number: WO2008032365A1
Application number: PCT/JP2006/318047
Authority: WO
Inventors: Daisuke Seki
Original assignee: Fujitsu Limited
Priority date: 2006-09-12
Filing date: 2006-09-12
Publication date: 2008-03-20
Also published as: JP4847535B2; JPWO2008032365A1

Abstract

Provided is a method for manufacturing an electronic device composed of a substrate having at least an electrode. A pattern of an electrostatic discharge protecting section is formed in the vicinity of the electrode, and a solder resist layer is formed on the substrate surface excluding at least the pattern. A solder is applied on the pattern, and the solder is heated and clumped by the surface tension of the solder, and an electrostatic discharge conductive section is formed on the pattern. A circuit on the substrate of the electronic device can be protected from ESD, without increasing the number of components and the number of processes, by thus forming the electrostatic discharge conductive section with the solder.

Description

Specification

Electronic device and manufacturing method thereof

Technical field

The present invention relates to a technique for mounting an element on a substrate.

Background art

[0002] Elements mounted on printed circuit boards, especially electronic devices such as ICs, are

Discharge), that is, destruction may be caused by the application of static electricity.

For this reason, if an electronic device that can be housed in the housing is placed more than a certain distance away from the opening of the housing, a countermeasure against static electricity has been taken.

[0003] Further, as a prior art related to the present invention, for example, there are techniques disclosed in Patent Documents 1 and 2 below.

Patent Document 1: Japanese Patent Laid-Open No. 2001-308586

Patent Document 2: JP 2004-342464 A

Disclosure of the invention

Problems to be solved by the invention

[0004] However, with the miniaturization of devices and the variety of electronic devices, electronic devices are often placed on the surface of a casing.

For example, FIG. 15 shows a fingerprint sensor 101 arranged on the surface of a notebook computer or the like. The fingerprint sensor 101 is mounted on a printed circuit board 102 by a BGA (Ball Grid Array) method, and is arranged such that a reading surface 101A is exposed outside the housing 103 for reading a fingerprint.

The surface of an electronic device such as the fingerprint sensor 101 is generally packaged (including a mold) with a material having low conductivity, and is unlikely to receive ESD. Even if this is not the case, some countermeasures have been taken, such as flowing ESD received on the device surface to the ground, and even if ESD is applied to the device surface, the possibility of damage to internal circuits is low.

However, on the back side of the device, there is a terminal (BGA terminal) for connecting the internal circuit to the outside. If the ESD reaches the BGA terminal 104 through the gap between the fingerprint sensor 101 and the housing 103, as shown in FIG. 15, if the ESD reaches the BGA terminal 104, the circuit inside the device and the periphery of the device This circuit (hereinafter also referred to simply as the internal circuit) will be applied with a voltage much higher than the rated voltage, which may cause damage.

In order to prevent damage to the internal circuit, a conductive member 105 may be disposed between the fingerprint sensor 101 and the housing 103 as shown in FIG. 16 and connected to the ground line 106 of the printed board 102. Thereby, since ESD is absorbed by the conductive member 105, the BGA terminal 104 can be protected.

However, the configuration of FIG. 16 increases the number of conductive members 105 and increases the number of steps for connecting the conductive members 105 to the ground line 106 as compared with the configuration of FIG. This increases the manufacturing cost.

Therefore, according to the present invention, when manufacturing an electronic device, by forming the electrostatic discharge conductive portion with solder, the circuit on the substrate of the electronic device is protected from ESD without causing an increase in the number of parts or an increase in processes. Provide technology to do.

Means for solving the problem

In order to solve the above-described problems, the present invention employs the following configuration.

That is, the electronic device of the present invention

In an electronic device that is configured with at least a substrate force,

An electrode formed on the substrate;

A pattern formed in the vicinity of the electrode on the substrate;

And an electrostatic discharge conductive portion made of chevron-shaped solder formed on the pattern.

[0006] The topmost part of the electrostatic discharge conductive part may be displaced from the center of the pattern width so as to be separated from the electrode.

[0007] A terminal of an electronic component exposed to the outside of the casing of the electronic device is joined to the electrode, and a distance between the gap between the electronic component and the casing and an electrostatic discharge conductive portion is determined by the gap and the terminal. It may be configured to be closer than the distance between. [0008] Further, the method of manufacturing an electronic device of the present invention includes:

In a method for manufacturing an electronic device comprising at least a substrate having an electrode, a substrate forming step for forming a pattern of an electrostatic discharge protection portion on the substrate in the vicinity of the electrode;

Forming a solder resist layer on the substrate surface excluding at least the pattern; a solder resist forming step;

A solder application step of applying solder on the pattern;

Heating the solder, aggregating the solder by the surface tension of the solder, and forming an electrostatic discharge conductive portion on the pattern.

[0009] In the solder application step, solder may be applied on the substrate wider than the pattern.

[0010] In the heating step, heating of the solder for mounting the element on the electrode may be performed simultaneously with the formation of the electrostatic discharge conductive portion.

The invention's effect

[0011] According to the present invention, when an electronic device is manufactured, a circuit on the substrate of the electronic device that does not cause an increase in the number of parts or an increase in the process by forming an electrostatic discharge conductive portion with solder is provided. Can provide technology to protect against ESD.

Brief Description of Drawings

FIG. 1 is an external view of an electronic device according to the present invention.

[Fig. 2] Schematic diagram of the main part of the present invention

[Figure 3] Plan view of electrode and protective wall pattern

[Figure 4] Flow chart of element mounting method

[Fig.5] Illustration of surface wiring pattern creation

[Figure 6] Illustration of solder resist creation

[Fig.7] Explanation of element mounting system

[Figure 8] Illustration of solder paste printing

[Figure 9] Illustration of solder paste printing

[Fig.10] Explanation of element placement [Figure 11] Explanatory diagram of reflow processing

[Figure 12] Illustration of solder paste printing width

[Figure 13] Explanatory drawing of protective wall formation position

[Figure 14] Illustration of solder paste application position

[Figure 15] Illustration of related technology

[Figure 16] Illustration of related technology

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. The configuration of the following embodiment is an exemplification, and the present invention is not limited to the configuration of the embodiment. FIG. 1 is an external view of an electronic apparatus according to the present invention, and FIG. . The electronic device 10 in this example is a notebook personal computer (notebook PC), and the fingerprint sensor 1 is mounted on the board 2 by the BGA (Ball Grid Array) method, and the reading surface of the fingerprint sensor 1 is used for reading the fingerprint. 1A is exposed outside the housing 3.

The fingerprint sensor 1 is packaged with a non-conductive material, and includes a reading surface 1A on the surface side of the package 1B. In addition, a circuit (internal circuit) 1D for outputting the fingerprint information read on the reading surface 1A as an electric signal of a predetermined format is provided inside the package 1B, and the electric signal is provided on the back side of the nozzle / cage 1B. Terminal 1C for output to outside is provided. The terminal 1C in this example is a BGA in which solder balls are connected to pads arranged in a grid at intervals of about 50 mil on the back of the knocker 1B.

[0015] The substrate 2 is made of an insulating material such as ceramic or glass epoxy resin, and is omitted in the figure, but an internal wiring pattern and a via-hole conductor for forming a predetermined circuit network are formed therein. Has been. A surface wiring pattern 4 including land electrodes from via-hole conductors is formed on the surface of the substrate 2. A part of the surface wiring pattern 4 is an electrode 5 arranged in a grid as shown in FIG. 3 because the terminal 1C of the fingerprint sensor 1 is joined. Another part of the surface wiring pattern 4 is a protective wall pattern 6 formed so as to surround the electrode 5. The protective wall pattern 6 is connected to the ground via a via hole conductor (not shown) and the surface wiring pattern 4. A layer of solder resist 8 is formed around the land electrode such as the electrode 5 and the protective wall pattern 6. In the illustrated example, the land electrode such as the electrode 5 and the protective wall pattern 6 are opened, and a solder resist 8 is formed on the other surface wiring pattern 4. The solder resist 8 is a heat-resistant coating material that covers the surface wiring pattern so that a solder does not adhere to a place where soldering is unnecessary and a short circuit or the like does not occur.

[0017] The solder resist 8 may be formed by screen printing, or a resist film uniformly formed by curtain coating or spray coating may be used to remove unnecessary portions through a development process or etching. Further, the material of the solder resist 8 is not particularly limited as long as it is a material to which generally used solder does not adhere. For example, carboxyl group-containing polymers such as polymers or copolymers of epoxy resin, styrene, acrylic acid, methacrylic acid, maleic acid, phenol resin, xylene resin, urea resin , Melamine series, alkyd series, vinyl series, acrylic series, salt series, rubber series, polyamide series, fatty acid or aromatic polybasic acids, Anhydrous hydroxyalkyl acrylate (or metatalylate) half ester rosin can be used.

A protective wall (electrostatic discharge conductive portion) 7 made of solder is formed on the protective wall pattern 6. This protective wall 7 is applied on the protective wall pattern 6 together with the electrode 5 when the fingerprint sensor 1 is mounted on the substrate 2, and the agglomerated solder is solidified by the surface tension.

A method for mounting the fingerprint sensor (electronic device) 1 will be described. FIG. 4 is a flowchart of the mounting method.

First, a predetermined wiring pattern is formed on the substrate 2 as shown in FIG. At this time, as a part of the surface wiring pattern 4 formed on the substrate surface, a protective wall pattern 6 is formed so as to surround the electrode 5 to which the fingerprint sensor 1 is connected. This wiring pattern can be formed by a general substrate manufacturing apparatus (Sl).

[0020] Further, a solder resist 8 is screen-printed on the surface of the substrate by a screen printing apparatus so as to cover other than the land electrode such as the electrode 5 and the protective wall wiring pattern 6 as shown in FIG.

S2). In this way, the substrate 2 on which the predetermined surface wiring pattern 4 and the solder resist 8 are formed is prepared, and the fingerprint sensor 1 is mounted on the substrate 2. FIG. 7 shows an example of a production line (element mounting system) for mounting the fingerprint sensor 1.

Solder printer 21 overlays metal mask 9 on the surface of the substrate (FIG. 8, S3), and after applying solder paste 11, on metal electrode 9 and protective wall pattern 6 as shown in FIG. Hanada paste 11 is printed (S4). At this time, the printed pattern of the metal mask 9 is formed so that the solder paste on the protective wall pattern 6 is applied with a width wider than that of the protective wall wiring pattern 6 as shown in FIGS.

[0022] The solder film thickness measurement device 22 measures the solder film thickness (S5). If the film thickness is appropriate, the chip mounting machine 23 causes the fingerprint sensor 1 so that the terminal 1C is in contact with the electrode 5. Place sensor 1 (Fig. 10, S6).

[0023] Further, other elements (not shown) are placed on the electrodes of the substrate 2 by the atypical component mounting machine 24 (S7).

[0024] Then, the substrate is heated to a predetermined temperature by a reflow oven 25 and subjected to a reflow process, the solder paste 11 is melted, and the terminal 1C and the electrode 5 are connected. At this time, the solder paste 11 on the protective wall pattern 6 is also melted, the solder printed on the solder resist is repelled, and aggregates on the protective wall pattern 6 due to surface tension (S8). The agglomerated state is naturally cooled, and the solder is solidified to form the protective wall 7 (FIG. 11, S9).

[0025] By forming the protective wall 7 surrounding the connection portion (terminal 1C and electrode 5) of the fingerprint sensor 1 in this way, the gap 9 between the housing 3 and the package 1B is interposed as shown in FIG. Even if ESD enters, ESD is absorbed by the protective wall 7 connected to the ground, and is prevented from reaching the connection portion of the fingerprint sensor 1. That is, ESD power protection can be provided for internal circuits such as a circuit in the fingerprint sensor and a circuit provided around the fingerprint sensor in the casing.

At this time, as shown in FIG. 12, the width of the solder paste applied onto the protective wall pattern than the width W1 of the protective wall pattern 6, that is, the width W2 of the opening of the metal mask on which the solder paste is printed is set. It is getting bigger.

Accordingly, the solder paste 11 is applied not only on the protective wall pattern 6 but also on the solder resist 8. The solder resist 8 is a material to which solder does not adhere, that is, a molten state. Since the solder paste 11 on the solder resist is melted by the reflow process, the solder paste 11 on the solder resist moves onto the protective wall pattern and aggregates due to the surface tension. That is, the molten solder has a protective wall pattern 6 as a bottom surface, and the vertical cross-section rises in a mountain shape.

[0028] For this reason, when the protective wall 7 is desired to be formed high, the difference between the widths W1 and W2 is increased. To reduce the protective wall 7, the difference between the widths W1 and W2 is set small (however, Wl <W2 ).

That is, the width W 1 of the protective wall pattern 6, the width W2 of the solder paste, the material of the solder resist 8, and the material of the solder paste 11 are set in advance so that the necessary width and height as the protective wall 7 can be obtained. To do.

[0030] By providing the protective wall 7 higher than the substrate surface on which the fingerprint sensor 1 is mounted in this way, ESD is prevented from reaching the wiring pattern 4 to which the fingerprint sensor 1 is connected, and the wiring pattern 4 The internal circuit connected to the can be protected. In addition, since the height can be increased by the surface tension of the solder, when printing on the protective wall pattern and the electrode 5, it is possible to print at one time with one metal mask, and the productivity is good.

Further, as shown in FIG. 13, the distance from the gap 9 between the housing 3 and the package 1B to the protective wall 7, in this example, from the outer peripheral portion of the package 1B (in the illustrated example, the lower end B2 of the outer peripheral surface B1). Shortest distance L1 force The position of the wiring pattern 4 and the height of the protective wall 7 are set so as to be shorter than the distance L2 from the gap 9 to the connection 1C of the fingerprint sensor 1. As a result, the ESD force from the gap 9 is absorbed by the protective wall 7 with high accuracy.

Further, as shown in FIG. 14, in the vertical cross section, the center P1 of the solder paste 11 applied onto the protective wall pattern 6 is outside the center P2 of the protective wall pattern 6, that is, the protective wall pattern. It is formed on the side opposite to the electrode 5 surrounded by 6. The protective wall 7 generated from the solder paste applied in this way has the topmost portion outside the center P2. As a result, the topmost part is separated from the electrode 5 from the center P2 on the substrate surface.

[0033] Thereby, even if the difference between the widths W1 and W2 is increased, the width WA of the solder paste 11 applied to the fingerprint sensor 1 side than the protective wall pattern 6 can be suppressed, and the topmost portion of the protective wall 7 can be reduced. The electrode force of the fingerprint sensor 1 or the fingerprint sensor 1 can also be separated. Therefore, ESD to the connection 1C of the fingerprint sensor 1 can be prevented more reliably. [0034] The difference ΔΡ between the center PI and the center P2 can be arbitrarily set according to the distance L1, etc. In order to form the protective wall 7 closest to the fingerprint sensor 1, as shown in FIG. The protective wall 6 and the solder paste 11 may be aligned with the fingerprint sensor 1 end.

In addition, the setting which concerns on the said protective wall can be used combining as much as possible.

In this embodiment, the protective wall 7 is formed so as to surround the fingerprint sensor 1, but various forms may be considered depending on the shape of the fingerprint sensor 1 and the gap 9. If it is necessary to prevent ESD in a specific direction, the protective wall 7 may be formed only in a specific direction. In addition, a plurality of protective walls 7 that just enclose the fingerprint sensor 1 may be formed in the vicinity of the fingerprint sensor 1.

Claims

The scope of the claims

[1] At least board power In the configured electronic equipment,

An electrode formed on the substrate;

A pattern formed in the vicinity of the electrode on the substrate;

An electronic device comprising: an electrostatic discharge conductive portion made of chevron-shaped solder formed on the pattern.

[2] The electronic device according to [1], wherein an uppermost part of the electrostatic discharge conductive part is shifted from a center of the pattern width so as to be separated from the electrode.

[3] A terminal of an electronic component exposed to the outside of the casing of the electronic device is joined to the electrode, and a distance between the gap between the electronic component and the casing and an electrostatic discharge conductive portion is determined by the gap and the terminal. The electronic device according to claim 1, wherein the electronic device is closer than a distance between the electronic devices.

[4] In a method of manufacturing an electronic device composed of a substrate having at least an electrode,

A substrate forming step for forming an electrostatic discharge protection portion pattern on the substrate in the vicinity of the electrode;

A solder application step of applying solder on the pattern;

A heating method comprising: heating the solder; aggregating the solder by a surface tension of the solder; and forming an electrostatic discharge conductive portion on the pattern.

5. The manufacturing method according to claim 4, wherein in the solder application step, solder is applied on the substrate wider than the pattern.

6. The manufacturing method according to claim 4, wherein, in the heating step, heating of the solder for mounting the element on the electrode is performed simultaneously with the formation of the electrostatic discharge conductive portion.