JPWO2008032365A1 - Electronic device and manufacturing method thereof - Google Patents

Abstract

In a method of manufacturing an electronic device including at least a substrate having an electrode, a pattern of an electrostatic discharge protection portion is formed on the substrate in the vicinity of the electrode, and the solder resist layer is formed on the substrate surface excluding at least the pattern Then, solder is applied onto the pattern, the solder is heated, the solder is aggregated by the surface tension of the solder, and an electrostatic discharge conductive portion is formed on the pattern. In this way, by forming the electrostatic discharge conductive portion with solder, the circuit on the substrate of the electronic device can be protected from ESD without increasing the number of components or increasing the number of processes.

Description

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

An element mounted on a printed circuit board, particularly an electronic device such as an IC, may be destroyed by ESD (Electoric Static Discharge), that is, application of static electricity.
For this reason, countermeasures against static electricity have been taken, such as disposing the electronic device housed in the housing at a certain distance from the opening of the housing.

Moreover, as a prior art relevant to this invention, there exists a technique disclosed by the following patent documents 1, 2, for example.
JP 2001-308586 A JP 2004-342464 A

However, with the miniaturization of devices and the diversification of electronic devices, electronic devices are often placed on the surface of a housing.
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.
In general, the surface of an electronic device such as the fingerprint sensor 101 is often packaged (including a mold) with a material having low conductivity, and is unlikely to be subjected to ESD. Even if this is not the case, some countermeasures such as flowing ESD received on the device surface to the ground have been taken, and even if ESD is applied to the device surface, the possibility of damage to the internal circuit is low.
However, a terminal (BGA terminal) 104 for connecting an internal circuit to the outside is present on the back side of the device, and a gap between the fingerprint sensor 101 and the housing 103 is interposed as shown in FIG. If the ESD reaches the BGA terminal 104, a voltage much higher than the rating is applied to the circuit inside the device and the circuit around the device (hereinafter also simply referred to as an internal circuit), which may cause damage. is there.
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 and connected to the ground line 106 of the printed circuit board 102 as shown in FIG. Thereby, since ESD is absorbed by the conductive member 105, the BGA terminal 104 can be protected.
However, with the configuration shown in FIG. 16, the number of conductive members 105 is increased and the number of steps for connecting the conductive members 105 to the ground line 106 is increased compared to the configuration shown in FIG. This will increase the cost.
Therefore, according to the present invention, when an electronic device is manufactured, 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 the number of processes. Provide technology to do.

In order to solve the above problems, the present invention employs the following configuration.
That is, the electronic device of the present invention
At least in electronic equipment composed of substrates
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.

  The topmost part of the electrostatic discharge conductive part may be shifted from the center of the pattern width so as to be away from the electrode.

A terminal of an electronic component exposed outside the casing of the electronic device is joined to the electrode,
The distance between the gap between the electronic component and the housing and the electrostatic discharge conductive part may be configured to be closer than the distance between the gap and the terminal.

In addition, the method for manufacturing the electronic device of the present invention includes:
In a method of manufacturing an electronic device composed of a substrate having at least an electrode,
A substrate forming step of forming an electrostatic discharge protection portion pattern on the substrate in the vicinity of the electrode;
A solder resist forming step of forming the solder resist layer on the substrate surface excluding at least the pattern;
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.

  In the solder application step, solder may be applied to the substrate wider than the pattern.

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

  According to the present invention, when an electronic device is manufactured, by forming the electrostatic discharge conductive portion with solder, the circuit on the substrate of the electronic device is protected from ESD without increasing the number of components or increasing the number of processes. Technology can be provided.

External view of electronic apparatus according to the present invention Main part schematic diagram of the present invention Plan view of electrode and protective wall pattern Flow chart of device mounting method Illustration of surface wiring pattern creation Illustration of creating solder resist Illustration of element mounting system Illustration of solder paste printing Illustration of solder paste printing Illustration of device placement Explanatory diagram of reflow processing Illustration of solder paste printing width Illustration of protective wall formation position Illustration of solder paste application position Illustration of related technology Illustration of related technology

The best mode for carrying out the present invention will be described below 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. 2 is an explanatory view of a main part of the present invention.
The electronic device 10 of this example is a notebook personal computer (notebook PC), and the fingerprint sensor 1 is mounted on the substrate 2 by the BGA (Ball Grid Array) method, and the reading surface 1A of the fingerprint sensor 1 is used for reading the fingerprint. 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 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 output to the outside on the back side of the package 1B. A terminal 1C is provided. The terminal 1C of this example is a BGA in which solder balls are connected to pads arranged in a grid pattern at intervals of about 50 mil on the back surface of the package 1B.

  The substrate 2 is made of an insulating material such as ceramic or glass epoxy resin, and although not shown in the drawing, an internal wiring pattern and a via-hole conductor for forming a predetermined circuit network are formed therein. 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 the solder does not adhere to a portion where soldering is unnecessary and a short circuit or the like does not occur.

  The solder resist 8 may be formed by screen printing, or may be a resist film uniformly formed by curtain coating or spray coating to remove unnecessary portions through a development process or etching. 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 epoxy resins, polymers such as styrene, acrylic acid, methacrylic acid, maleic acid or copolymers, phenol resins, xylene resins, urea resins, melamine resins , Alkyd resins, vinyl resins, acrylic resins, chlorinated rubber resins, polyamide resins, fatty acid or aromatic polybasic acids and anhydride hydroxyalkyl acrylate (or methacrylate) halves Ester resins can be used.

  A protective wall (electrostatic discharge conductive portion) 7 made of solder is formed on the protective wall pattern 6. When the fingerprint sensor 1 is mounted on the substrate 2, the protective wall 7 is applied onto the protective wall pattern 6 together with the electrodes 5, and the agglomerated solder is solidified by 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, the 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 (S1).

  Further, the solder resist 8 is screen-printed on the surface of the substrate by a screen printing apparatus, and the parts other than the land electrodes such as the electrodes 5 and the protective wall wiring pattern 6 are coated as shown in FIG. 6 (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 is an example of a production line (element mounting system) for mounting the fingerprint sensor 1.
The solder printer 21 superimposes the metal mask 9 on the substrate surface (FIG. 8, S3), and after applying the solder paste 11, the metal mask 9 is removed and the electrode 5 and the protective wall pattern 6 as shown in FIG. The solder 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.

  The solder film thickness measuring device 22 measures the solder film thickness (S5), and if the film thickness is appropriate, the chip mounting machine 23 controls the fingerprint sensor 1 so that the terminal 1C of the fingerprint sensor 1 is in contact with the electrode 5. Place (FIG. 10, S6).

  Other elements (not shown) are also placed on the electrodes of the substrate 2 by the atypical component mounting machine 24 (S7).

  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 agglomerates on the protective wall pattern 6 due to surface tension (S8). In this aggregated state, it is naturally cooled, and the solder is solidified to form the protective wall 7 (FIG. 11, S9).

  By forming the protective wall 7 surrounding the connection portion (terminal 1C and electrode 5) of the fingerprint sensor 1 in this way, ESD enters through the gap 9 between the housing 3 and the package 1B as shown in FIG. However, the 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, an internal circuit such as a circuit in the fingerprint sensor and a circuit provided around the fingerprint sensor in the casing can be protected from ESD.

  At this time, as shown in FIG. 12, the width of the solder paste applied on the protective wall pattern, that is, the width W2 of the opening of the metal mask for printing the solder paste is made larger than the width W1 of the protective wall pattern 6. Yes.

  Therefore, the solder paste 11 is applied not only on the protective wall pattern 6 but also on the solder resist 8. However, since the solder resist 8 is a material to which solder does not adhere, that is, a material that repels molten solder, the solder paste 11 on the solder resist moves onto the protective wall pattern when melted by the reflow process, and is caused by surface tension. Aggregate. That is, the molten solder has the protective wall pattern 6 as the bottom surface, and the vertical cross section rises in a mountain shape.

  Therefore, when the protective wall 7 is desired to be formed high, the difference between the widths W1 and W2 is increased, and in order to reduce the protective wall 7, the difference between the widths W1 and W2 is set small (W1 <W2).

  That is, the width W1 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 width and height necessary for the protective wall 7 can be obtained.

  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 is connected. The internal circuit can be protected. Further, since the height can be increased by the surface tension of the solder, when printing on the protective wall pattern and the electrode 5, printing can be performed 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, the shortest distance L1 from the outer peripheral portion of the package 1B (the lower end B2 of the outer peripheral surface B1 in the illustrated example). However, 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 portion 1C of the fingerprint sensor 1. Thereby, ESD from the gap 9 is absorbed into the protective wall 7 with high accuracy.

  Further, as shown in FIG. 14, in the vertical cross section, the electrode P surrounds the center P1 of the solder paste 11 applied on the protective wall pattern 6 outside the central P2 of the protective wall pattern 6, that is, the protective wall pattern 6 surrounds. 5 on the opposite side. The protective wall 7 generated from the solder paste applied in this way has its 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.

  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 with respect to the protective wall pattern 6 is suppressed, and the topmost portion of the protective wall 7 is placed on the top of the fingerprint sensor 1. Alternatively, it can be formed away from the electrode of the fingerprint sensor 1. Therefore, ESD to the connection part 1C of the fingerprint sensor 1 can be prevented more reliably.

The difference ΔP between the center P1 and the center P2 can be arbitrarily set according to the distance L1 and the like. In order to form the protective wall 7 closest to the fingerprint sensor 1, the protective wall 6 and the protective wall 6 and the center P2 are formed as shown in FIG. What is necessary is just to make the edge part by the side of the fingerprint sensor 1 of the solder paste 11 correspond.
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 from a specific direction, the protective wall 7 may be formed only in the specific direction. In addition to the shape surrounding the fingerprint sensor 1, a plurality of protective walls 7 may be formed in the vicinity of the fingerprint sensor 1.

Claims (6)

At least in electronic equipment composed of substrates
An electrode formed on the substrate;
A pattern formed in the vicinity of the electrode on the substrate;
An electronic apparatus comprising: an electrostatic discharge conductive portion made of a chevron-shaped solder formed on the pattern.   The electronic device according to claim 1, wherein an uppermost portion of the electrostatic discharge conductive portion is shifted from a center of the pattern width so as to be separated from the electrode. A terminal of an electronic component exposed outside the casing of the electronic device is joined to the electrode,
The electronic apparatus according to claim 1, wherein a distance between the gap between the electronic component and the housing and the electrostatic discharge conductive portion is shorter than a distance between the gap and the terminal. In a method of manufacturing an electronic device composed of a substrate having at least an electrode,
A substrate forming step of forming an electrostatic discharge protection portion pattern on the substrate in the vicinity of the electrode;
A solder resist forming step of forming the solder resist layer on the substrate surface excluding at least the pattern;
A solder application step of applying solder on the pattern;
A heating step of heating the solder, aggregating the solder by a surface tension of the solder, and forming an electrostatic discharge conductive portion on the pattern.   The manufacturing method according to claim 4, wherein, in the solder application step, solder is applied to the substrate wider than the pattern.   5. 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.

Images