CN110691459A - Circuit board structure for forming connecting terminal by limiting opening window through solder mask - Google Patents

Abstract

The invention provides a circuit board structure for forming a connecting terminal by limiting windowing through solder mask, which comprises: a substrate, a solder mask layer and a curable conductive medium. The substrate has a plurality of connection terminals. The solder mask is formed on the surface of the substrate and has a plurality of openings respectively corresponding to the connection terminals. The offset between the top surface of the solder mask layer and the top surface of the connecting terminal is larger than 5 mu m. The curable conductive medium is respectively filled in the openings and is used for electrically connecting the connecting terminals, and the offset from the curable conductive medium to the top surface of the solder mask layer is less than 5 mu m.

Description

Circuit board structure using solder mask to define openings to form connecting terminals

technical field

The present invention relates to a circuit board structure that utilizes solder resist to define openings to form connecting terminals.

Background technique

With the trend of miniaturization of electronic products, circuit boards need to be made thinner and lighter, so that the arrangement of conductive lines and connecting terminals on the circuit boards is becoming more and more dense, and the size of light-emitting diodes is also getting smaller and smaller. Correspondingly, during the assembly process, the requirements for the assembly precision of the light-emitting diodes are also getting higher and higher.

Generally speaking, most circuit boards have a solder mask for moisture-proof, insulation and solder mask, and the thickness of the solder mask needs to be at least greater than 10 μm to achieve the effect of insulation and shielding. However, since the connection pads of the light emitting diodes are usually thin, it is difficult for the connection pads of the light emitting diodes to be completely connected with the connection terminals of the substrate, thus resulting in the problem of poor contact.

Therefore, how to reduce the problem of poor contact between the connection pads and the connection terminals of the light-emitting diodes is a technical problem to be solved by the present invention.

SUMMARY OF THE INVENTION

In view of this, the main purpose of the present invention is to provide a circuit board structure that can reduce the occurrence of poor contact.

In order to achieve the above-mentioned purpose, the present invention provides a circuit board structure using a solder mask to define a window to form a connection terminal, comprising: a substrate, a solder mask layer and a curable conductive medium. The substrate has a plurality of connection terminals. The solder resist layer is formed on the surface of the substrate and has a plurality of openings respectively corresponding to the connection terminals, wherein the disconnection from the top surface of the solder resist layer to the top surface of the connection terminals is greater than 5 μm. The curable conductive medium is respectively filled in the openings and used to electrically connect the connection terminals, wherein the difference between the curable conductive medium and the top surface of the solder resist layer is less than 5 μm.

The circuit board structure using the solder mask to define the window to form the connection terminal further includes at least one flip-chip LED, and the flip-chip LED includes a light emitting diode, a P-pole connection pad and an N-pole connection pad. The P-pole connection pad and the N-pole connection pad are respectively in contact with and electrically connected to the curable conductive medium filled in the opening.

The circuit board structure using the solder mask to define the window to form the connection terminal further satisfies the following relationship:

X+Y≧Z;

Wherein, X is the thickness of the P-pole connection pad and the N-pole connection pad, Y is the thickness of the curable conductive medium, and Z is the disconnection from the top surface of the solder mask to the top surface of the connection terminal.

The connecting terminal includes a substrate circuit layer and a surface plating layer.

The material of the surface plating layer is: nickel, gold, silver, palladium or alloys thereof.

The curable conductive medium can be: conductive copper glue, conductive silver glue, conductive graphite glue or solder paste.

By filling the curable conductive medium in the openings of the solder mask, the Surface Mounted Device can be electrically connected to the connecting terminals through a thick curable conductive medium, which can effectively reduce the problem of poor contact. .

The details of other functions and embodiments of the present invention are described below with reference to the accompanying drawings.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments described in this application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

1A to 1G are cross-sectional views of the fabrication process of the circuit board structure provided by the present invention using solder mask to define openings to form connection terminals.

Symbol Description

C Connection terminal X, Y thickness

d, Z break difference 10 substrate

101 First surface 102 Second surface

11-sided copper 111 substrate circuit layer

12 Solder mask 121 Opening

13 Surface coating 14 Curable conductive medium

15 Flip Chip LED 151 Light Emitting Diode

152 P-pole connection pad 153 N-pole connection pad

Detailed ways

First, please refer to FIG. 1A to FIG. 1G . FIGS. 1A to 1G are cross-sectional views of the fabrication process of the circuit board structure provided by the present invention using solder mask defined openings to form connection terminals. First, a substrate 10 is provided, the substrate 10 has a first surface 101 and a second surface 102 , the substrate 10 can be a single-layer board structure or a multi-layer composite board structure, and the substrate 10 can be a flexible printed circuit board (Flexible Printed) Circuit, FPC) substrate or rigid circuit board (Printed Circuit Board, PCB) substrate. In this embodiment, a thin copper foil (not shown in the figure) is laminated on the first surface 101 for copper plating to form a surface copper 11 on the first surface 101 of the substrate 10 (as shown in FIG. 1A ). Next, the surface copper 11 is imaged by a circuit image transfer technique to form a base circuit layer 111 on the surface of the substrate 10 (as shown in FIG. 1B ). There is a gap between the substrate circuit layers 111, and the material of the substrate circuit layer 111 is copper.

Referring to FIG. 1C , next, a solder resist material is coated on the first surface 101 of the substrate 10 to form a solder resist layer 12 covering the substrate 10 and the base circuit layer 111 . The solder resist layer 12 is an insulating layer, and its material can be epoxy resin, silicone resin, polyimide resin, phenolic resin, fluororesin, silicon dioxide or aluminum oxide.

Please continue to refer to FIG. 1D , a window is opened on the solder resist layer 12 to form an opening 121 corresponding to the position of the substrate circuit layer 111 . Subsequently, a surface plating layer 13 (as shown in FIG. 1E ) can be formed on the surface of the substrate circuit layer 111 by chemical plating or electroplating, so as to form a connection for electrical connection to semiconductor components, such as flip-chip LEDs The terminal C, that is, the surface plating layer 13 of the present invention is formed by the process of Solder Mask Defined (SMD). Wherein, the material of the surface plating layer 13 may be: nickel, gold, silver, palladium or alloys thereof. The difference Z from the top surface of the connection terminal C to the top surface of the solder resist layer 12 is greater than 5 μm. Herein, the "break" refers to the distance between the two surfaces in the thickness direction of the material.

Please continue to see Figure 1F. In FIG. 1F, the curable conductive medium 14 is filled in the opening 121, so that the curable conductive medium 14 is electrically connected to the connection terminal C, and the curable conductive medium 14 can be: conductive copper glue, conductive silver glue, conductive The graphite glue or solder paste is filled with a thick curable conductive medium 14 so that the distance d from the curable conductive medium 14 to the top surface of the solder resist layer 12 is less than 5 μm. Preferably, the thickness of the curable conductive medium 14 is close to or greater than μm. Subsequently, the flip-chip LED 15 is disposed above the connection terminal C (as shown in FIG. 1G ). In FIG. 1G , the flip-chip LED 15 includes: a light emitting diode 151 and a P-pole connection pad 152 and an N-pole connection pad 153 disposed on the bottom surface thereof, and the P-pole connection pad 152 and the N-pole connection pad 153 correspond to the opening 121 respectively. It can extend into the opening 121 and be in contact with the curable conductive medium 14, and the thickness of the P and N electrode connection pads is usually not more than 5 μm. After the curable conductive medium 14 is cured, the flip-chip LED 15 can be fixed on the top of the connection terminal C, and the properties of the conductive material of the curable conductive medium 14 are used to electrically connect the P-pole connection pad 152 and the N-pole connection pad 153 and connection terminal C. In this embodiment, the thickness of the P-pole connection pad 152 and the N-pole connection pad 153 is X; the thickness of the curable conductive medium 14 is Y; the disconnection between the top surface of the solder mask 12 and the connection terminal C is Z. , and the thickness X of the P-pole connection pad 152 and the N-pole connection pad 153 plus the thickness Y of the curable conductive medium 14 is greater than or equal to the difference Z between the top surface of the solder mask 12 and the top surface of the connection terminal C (ie: X+Y≧Z).

In the present invention, the curable conductive medium 14 is filled in the opening of the solder mask, so that the P-pole connection pad 152 and the N-pole connection pad 154 can be electrically connected to the connection terminal C through the thicker curable conductive medium 14, and It can effectively reduce the occurrence of poor contact problems.

The above-mentioned embodiments and/or implementations are only used to illustrate the preferred embodiments and/or implementations for realizing the technology of the present invention, and are not intended to limit the implementation of the technology of the present invention in any form. Personnel, without departing from the scope of the technical means disclosed in the content of the present invention, may make some changes or modifications to other equivalent embodiments, but they should still be regarded as substantially the same technology or embodiment of the present invention.

Claims (6)

1. A circuit board structure for forming connection terminals by limiting windowing using solder mask, comprising:

a substrate having a plurality of connection terminals;

a solder mask layer formed on the surface of the substrate and having a plurality of openings corresponding to the connection terminals, wherein the difference between the top surface of the solder mask layer and the top surfaces of the connection terminals is greater than 5 μm; and

and a curable conductive medium respectively filled in the openings and used for electrically connecting the connecting terminals, wherein the offset between the curable conductive medium and the top surface of the solder mask layer is less than 5 μm.

2. The circuit board structure of claim 1, further comprising at least one flip-chip LED, wherein the flip-chip LED comprises a light emitting diode, a P-pad and an N-pad, and the P-pad and the N-pad are respectively in contact with and electrically connected to the curable conductive medium filled in the openings.

3. A circuit board structure for forming connection terminals by solder mask defining openings as recited in claim 2, further satisfying the following relationship:

X+Y≧Z；

wherein X is the thickness of the P-pole connecting pad and the N-pole connecting pad, Y is the thickness of the solidifiable conductive medium, and Z is the difference between the top surface of the solder mask layer and the top surfaces of the connecting terminals.

4. The circuit board structure of claim 1, wherein the connection terminal comprises a substrate circuit layer and a surface plating layer.

5. A circuit board structure utilizing solder mask to define openings for forming connection terminals according to claim 4, wherein the surface plating layer is made of: nickel, gold, silver, palladium, or alloys thereof.

6. A circuit board structure for forming connection terminals by solder mask defining openings as claimed in claim 1 wherein the curable conductive medium is: conductive copper paste, conductive silver paste, conductive ink paste or solder paste.

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