TW202007241A - Circuit board structure with conection terminal formed by solder mask defined process - Google Patents

Abstract

A circuit board structure with conection terminal formed by solder resist defined process includes: a substrate, a solder mask layer and a curable conducting media. The substrate includes multiple connection terminals. The solder mask layer is formed on the surface of the substrate and includes multiple openings corresponding to the connection terminals, respectively. The distance between the top surface of the solder mask layer and the top surface of the connection terminals is more than 5 μm. The curable conducting media is filled in the openings and used to electrically connects with the connection terminals respectively. The distance between the curable conducting media and the top surface of the solder mask layer is less than 5 μm.

Description

Circuit board structure using solder-proof limited opening window to form connection terminal

The invention relates to a circuit board structure which forms a connection terminal by using solder-proof restricted opening windows.

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

Generally speaking, most circuit boards have solder masks for moisture, insulation, and solder, 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 generally thin, it is difficult for the connection pads of the light emitting diodes to be completely connected to the connection terminals of the substrate, thereby causing a problem of poor contact.

Therefore, how to reduce the problem of poor contact between the connection pad of the light-emitting diode and the connection terminal is the technical problem to be solved by the present 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 problems.

In order to achieve the above-mentioned object, the present invention provides a circuit board structure using solder-proof limited windows to form connection terminals, including: a substrate, a solder-proof 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 difference between the top surface of the solder resist layer and the top surface of the connection terminal is greater than 5 µm. The curable conductive medium is filled in the openings and used to electrically connect the connection terminals. The difference between the curable conductive medium and the top surface of the solder mask is less than 5 µm.

The circuit board structure that uses solder resist to define windows to form connection terminals further includes at least one flip chip LED. 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 in contact and electrically connected to the curable conductive medium filled in the opening, respectively.

The circuit board structure that uses solder resist to limit the opening of the window to form the connection terminal further satisfies the following relationship: X + Y ≧ Z; where X is the thickness of the P pole connection pad and the N pole connection pad, and Y is the curable conductive medium Thickness, Z is the difference between the top surface of the solder mask layer and the top surface of the connection terminal.

The connection terminal includes a base circuit layer and a surface plating layer.

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

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

By filling the opening of the solder mask with the curable conductive medium, the surface mount device (Surface Mounted Device) can be electrically connected to the connection terminal through the thicker curable conductive medium, which can effectively reduce the poor contact Problem occurred.

First of all, please refer to FIGS. 1A to 1G. FIGS. 1A to 1G are cross-sectional views of the manufacturing process of the circuit board structure provided by the present invention for forming a connection terminal by using a solder-proof limited window. First, a substrate 10 is provided. The substrate 10 has a first surface 101 and a second surface 102. The substrate 10 may be a single-layer board structure or a multi-layer composite board structure, and the substrate 10 may be a flexible printed circuit (Flexible Printed Circuit, FPC) substrate or printed circuit board (PCB) substrate. In this embodiment, the first surface 101 is laminated with a thin copper foil (not shown in the figure) for copper plating, so as 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 line image transfer technology 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 base circuit layer 111, and the material of the base circuit layer 111 is copper.

Please refer to FIG. 1C. Next, a solder resist material is applied to the first surface 101 of the substrate 10 to form the 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 may be: epoxy resin, silicone resin, polyimide resin, phenol resin, fluorine resin, silicon dioxide, or aluminum oxide.

Please continue to refer to FIG. 1D. A window 121 is formed on the solder resist layer 12 to form an opening 121 corresponding to the position of the base circuit layer 111. Subsequently, a surface plating layer 13 (as shown in FIG. 1E) may be formed on the surface of the base circuit layer 111 by chemical plating or electroplating to form a connection for electrically connecting to a semiconductor device, for example, a flip-chip LED The terminal C, that is, the surface plating layer 13 of the present invention is formed by a process of Solder Mask Defined (SMD). The material of the surface plating layer 13 can be: nickel, gold, silver, palladium or alloys thereof. The break Z between the top surface of the connection terminal C and the top surface of the solder mask 12 is greater than 5 µm. In this article, the "breakage" refers to the distance between the two surfaces in the thickness direction of the material.

Please continue to refer to 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 paste, conductive silver paste, The conductive graphite paste or solder paste is filled with a thicker curable conductive medium 14 so that the break d of the curable conductive medium 14 to the top surface of the solder mask layer 12 is less than 5 µm. Preferably, the thickness of the curable conductive medium 14 is close to or greater than 5 µm. Subsequently, the flip chip LED 15 is provided 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 respectively correspond to The opening 121 can extend into the opening 121 and come into contact with the curable conductive medium 14. The thickness of the connection pads of the P and N poles is usually not more than 5 μm. After the curable conductive medium 14 is cured, the flip-chip LED 15 can be fixed above the connection terminal C, and the characteristics 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 breakage 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 gap Z between the top surface of the solder mask layer 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 layer, 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 can effectively reduce the occurrence of poor contact problems.

C‧‧‧Connecting terminal X, Y‧‧‧ Thickness d. Z‧‧‧Breakdown 10‧‧‧ substrate 101‧‧‧First surface 102‧‧‧Second surface 11‧‧‧Copper 111‧‧‧ Base circuit layer 12‧‧‧Soldering layer 121‧‧‧ opening 13‧‧‧Surface coating 14‧‧‧curable conductive medium 15‧‧‧ flip chip LED 151‧‧‧ LED 152‧‧‧P pole connection pad 153‧‧‧N pole connecting pad

FIGS. 1A to 1G are cross-sectional views of the manufacturing process of the circuit board structure provided by the present invention for forming a connection terminal using a solder-resistant limited window.

C‧‧‧Connecting terminal

d‧‧‧Breakdown

10‧‧‧ substrate

101‧‧‧First surface

102‧‧‧Second surface

111‧‧‧ Base circuit layer

12‧‧‧Soldering layer

121‧‧‧ opening

13‧‧‧Surface coating

14‧‧‧curable conductive medium

Claims (6)

A circuit board structure using solder resist to define windows to form connection terminals includes: a substrate having a plurality of connection terminals; a solder resist layer formed on the surface of the substrate and having a plurality of openings respectively corresponding to the connection terminals , Wherein the difference between the top surface of the solder resist layer and the top surfaces of the connection terminals is greater than 5 µm; and a curable conductive medium is filled in the openings and used to electrically connect the connection terminals, wherein the curable The gap between the conductive medium and the top surface of the solder mask is less than 5 µm. As described in claim 1, a circuit board structure using solder resist to define windows to form connection terminals further includes at least one flip chip LED, the flip chip LED includes a light emitting diode, a P pole connection pad, and an N pole The connection pad, the P-pole connection pad and the N-pole connection pad respectively contact and electrically connect the curable conductive medium filled in the openings. As described in claim 2, the circuit board structure using solder resist to define windows to form connection terminals further satisfies the following relationship: X + Y ≧ Z; where X is the P pole connection pad and the N pole connection pad Thickness, Y is the thickness of the curable conductive medium, and Z is the breakage from the top surface of the solder mask layer to the top surfaces of the connection terminals. As described in claim 1, a circuit board structure using solder resist to define a window to form a connection terminal, wherein the connection terminal includes a base circuit layer and a surface plating layer. As described in claim 4, a circuit board structure using solder resist to define a window to form a connection terminal, wherein the material of the surface plating layer is: nickel, gold, silver, palladium or an alloy thereof. As described in claim 1, a circuit board structure using solder resist to define windows to form connection terminals, wherein the curable conductive medium may be: conductive copper paste, conductive silver paste, conductive graphite paste or solder paste.

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