TWM623952U - Two-stage photopolymerization equipment for photopolymer layer on a printed circuit board - Google Patents

Abstract

A two-stage photopolymerization equipment includes a transfer platform, a digital micromirror device, a UV light source, a photomask and a mercury lamp. The transfer platform is used to carry a printed circuit board having a photopolymer layer on its top surface. The transfer platform is preset in a first working area. When the transfer platform works, the printed circuit board is moved to a third working area via a second working area. The digital micromirror device and the UV light source are arranged in the second working area. The UV source is used to illuminated the photopolymer layer through the digital micromirror device for a first exposure when the transfer platform passes through the second working area. The power of the UV light source is less than 0.2 kW. The photomask is used to cover and contact the photopolymer layer with its bottom surface when the transfer platform moves to the third working area. The mercury lamp is arranged in the third working area, and is used to illuminate the photopolymer through the mask for a second exposure. The power of the mercury lamp is greater than 5 kW.

Description

Secondary photopolymerization equipment for photopolymerization layers of printed circuit boards

The new model relates to a patterning device for a photopolymerization layer in a printed circuit board, in particular to a device for improving the yield of the photopolymerization process by providing different light sources.

Printed circuit boards generally have multiple layers of insulating materials and multiple layers of circuits, and part of the insulating materials and the photoresist layer used to pattern copper foil into circuits may be made of photopolymer materials (in the form of photopolymer layers) , these photopolymer layers can be patterned by exposure and development.

In the past, the photopolymerization layer was patterned by covering the photomask and then illuminating it. However, since the photopolymerization layer was in an uncured or semi-cured state before the illumination, when the photomask was covered, it may be exposed to the original light. The position is contaminated with particles in the environment, causing the area that should be illuminated to be shielded by the particles and not exposed to light, so that in the subsequent development process, many unnecessary small holes will appear in the photopolymerized layer. In addition, during the process of covering the photopolymer layer with the photomask, the photomask itself may also crush the photopolymer layer. That is to say, a long-standing problem in the prior art is that, for the reasons mentioned above, the use of a photomask will adversely affect the yield of the patterning process.

On the other hand, maskless lithography (Maskless Lithography) technology has gradually become the current trend of improvement, in which the use of digital micromirror device (Digital Micromirror Device; DMD) with UV light source for direct writing digital imaging (Direct Imaging; DI) , so that the photopolymerization layer can be patterned by controlling the range of illumination through the digital micromirror device without using a photomask. Nonetheless, the above-mentioned method of matching the DMD with the UV light source has its obvious drawback that the power of the UV light source cannot be too high since the DMD cannot withstand too high energy (otherwise it may exceed the load on its heat sink), and in order to provide the photopolymerization layer The energy required for polymerization, the UV light source must be supplied with low power and high frequency to the photopolymerizable layer; however, if the photopolymerized layer is thick (such as a solder mask), or even if the photopolymerized layer is colored light polymer layer (low transmittance), then low-power UV light will be difficult to reach the bottom of the photopolymer layer, resulting in insufficient curing at the bottom, so that during subsequent development and window opening, very Severe overcut.

Therefore, how to solve or at least slow down all the above problems is indeed worth considering by those in the art.

In view of this, the main purpose of the present invention is to provide a device that can solve the problem that the above-mentioned mask is easy to cause adverse effects on the yield of patterning processing, and at the same time can be used for processing large-thickness photopolymerization layers.

In order to achieve the above-mentioned purpose, the present invention provides a second-order photopolymerization equipment for the photopolymerization layer of a printed circuit board, which comprises a first working area, a second working area, a third working area, at least one transfer platform, A digital micromirror device, a UV light source, at least one photomask and a mercury lamp. The transfer platform is for carrying a printed circuit board with a photopolymerized layer on the top surface. The transfer platform is preset in the first work area, and when the transfer platform works, the loaded printed circuit board is moved to the second work area through the second work area. Third work area. The digital micromirror device and the UV light source are arranged in the second working area. The UV light source is used to illuminate the photopolymerization layer for the first time through the digital micromirror device during the process of the transfer platform passing through the second working area. The power of the UV light source is less than 0.2 kW. The photomask is used to cover and contact the photopolymer layer with its bottom surface when the transfer platform moves to the third work area. The mercury lamp is set in the third work area. The mercury lamp is used to pass through the photomask after the photomask covers the photopolymer layer. The photopolymerized layer is illuminated for the second time, and the power of the mercury lamp is greater than 5 kW.

The inventors found that the photopolymerized layer has the characteristic of curing from the top when the low-power UV light source is used for the first illumination. At the same time, the digital micromirror device does not need to contact the photopolymerized layer, so there will be no particle contamination and crushing. Problems with cured/semi-cured photopolymerizable layers. Then, when the mercury lamp is illuminated for the second time, its high power is sufficient to completely cure even the bottom of the photopolymerized layer with a large thickness, and because before the second illumination, the top of the photopolymerized layer is subjected to the first The light treatment has been cured, so even if the particles stick to the place where the second light should be, it will not form pinholes in the subsequent development process (the top of the hardened photopolymer layer can form a protection), and will not The top of the cured photopolymerized layer is crushed, thereby solving the long-standing problem of patterning through the photomask in the past. Therefore, this new model can become a good photopolymer patterning processing equipment, especially for the processing of generally thick solder mask, and also in the trend of maskless lithography, it provides another high Value for money choice.

Please refer to Figures 1 and 2, which are the first embodiment of the novel second-order photopolymerization apparatus, which can be used for photopolymerization of the photopolymerization layer of a printed circuit board for patterning. The printed circuit board can be a single-layer board structure or a multi-layer composite board structure, which can be a carrier board of a flexible printed circuit (FPC) or a carrier board of a rigid circuit board (Printed Circuit Board, PCB). The material can be but not limited to polyethylene terephthalate (PET) or other polyester film, polyimide film, polyimide film, polypropylene film, polystyrene film. The photopolymerization layer refers to a layer formed by photopolymer (photopolymer), these photopolymers will be polymerized after being irradiated with light, and then be cured. A photoresist layer or a printed circuit board dielectric layer required for patterning, such as an opaque solder mask ink. The second-order photopolymerization apparatus of this embodiment includes a first working area S1, a second working area S2, a third working area S3, a transfer platform 10, a digital micromirror device 20, a UV light source 30, a light source Cover 40 and a mercury lamp 50.

The transfer platform 10 is used for carrying the printed circuit board 2 with the photopolymer layer 1 on the top surface. The transfer platform 10 is preset in the first work area S1, and when the transfer platform 10 is located in the first work area S1, manual labor can be used. Or automated equipment moves the printed circuit board 2 onto the transfer platform 10 . When the transfer platform 10 is working, a screw mechanism or other displacement mechanism can be used to move the loaded printed circuit board 1 to the third work area S3 via the second work area S2. In a possible embodiment, after photopolymerization of the photopolymerization layer 1 is completed, the transfer platform 10 will return to the first working area S1, and the printed circuit board 2 will be removed from the transfer platform 10 by manual or automated equipment.

The digital micromirror device 20 is set in the second working area S2, and the digital micromirror device 20 has many micromirrors, and uses control signals to control the flipping of each micromirror to become a fast digital optical switch, which can control whether light can pass through the digital micromirror. The mirror device 20 has the function of performing patterned photopolymerization processing on the photopolymerization layer 1 .

The UV light source 30 is also located in the second working area S2, which has a plurality of UV lamps that can excite the photopolymer to polymerize. When the power of the UV light source is high, it may cause damage to the digital micromirror device 20. Therefore, the UV light source less than 0.2 kW, or even less than 0.1 kW. The UV light source 30 may illuminate the photopolymerization layer 1 for the first time through the digital micromirror device 20 during the process of the transfer platform 10 passing through the second working area S2 .

The photomask 40 is used to cover and contact the photopolymer layer 1 with its bottom surface when the transfer platform 10 moves to the third working area S3 . The reticle 40 can be placed in a reticle frame and displaced by automated equipment. In a possible implementation, different photomasks 40 may be selected to be used according to the expansion and contraction values of different printed circuit boards or for other considerations, and the replacement of the photomasks may be accomplished by manual or automated equipment.

The mercury lamp 50 is arranged in the third working area S3 , and is used to illuminate the photopolymer layer 1 for the second time through the mask 40 after the mask 40 covers the photopolymer layer 1 . In the present invention, the power of the mercury lamp 50 is greater than 5 kW, which ensures that the bottom of the photopolymerization layer 1 can be fully illuminated.

The following describes the novel second-order photopolymerization process:

First, provide a printed circuit board 2 with a photopolymerized layer 1 on the top surface. The photopolymerized layer 1 can be formed by directly coating the printed circuit board 2 with a photopolymer paste, or the photopolymer can also be fabricated first In the form of a dry film, and then laminated on the top surface of the printed circuit board 2 to form the photopolymerized layer 1; after the photopolymerized layer 1 is formed, the printed circuit board 2 can be moved to the first working area S1 by manual or automated equipment The transfer platform 10 is as shown in Figure 3;

Next, as shown in FIG. 4, the transfer platform 10 is moved from the first working area S1 to the second working area S2, and then the UV light source 30 is used to illuminate the photopolymerization layer 1 for the first time through the digital micromirror device 20. The UV light source The energy provided by 30 in the first illumination is less than the illumination energy required for complete curing of the photopolymerization layer 1, and preferably, the energy provided by the UV light source 30 in the first illumination is less than that required for complete curing of the photopolymerization layer 1. 1/2 of the energy of the light to reduce the process time of the first light; after the first light, at least the top of the photopolymerization layer can be cured;

After that, the first illumination is stopped, and the transfer platform 10 continues to move to the third work area S3;

Next, as shown in FIG. 5, a photomask 40 is covered on the photopolymer layer 1, and the bottom surface of the photomask 40 is in contact with the photopolymer layer 1; is crushed by the photomask 40, and no particles of the photopolymerization layer 1 stick to the photomask 40;

Finally, the mercury lamp 50 is used to illuminate the photopolymer layer 1 for the second time through the photomask 40, and the energy provided by the mercury lamp 50 during the second illumination is not less than the illumination energy required for the complete curing of the photopolymer layer 4 minus the first illumination energy. The energy supplied by the secondary illumination, and since the power of the mercury lamp 50 exceeds 5 kW, even the photopolymer at the bottom of the photopolymerization layer 1 can be completely cured (even the photopolymerization layer 1 with a maximum thickness of not less than 20 ㎛). bottom), so as to avoid the problem of serious internal rotation when the photopolymerized layer 1 is subsequently developed and opened. In a possible implementation manner, after the second illumination is completed, the printed circuit board 2 may also be removed in the third working area S3.

In addition, please refer to FIG. 6 , which shows a second embodiment of the second-order photopolymerization apparatus. The difference from the first embodiment is that it has two transfer platforms 10 . When one of the transfer platforms 10 is in the second When the second to third work areas are moved, another transfer platform can continue to move in and out of another printed circuit board, and the two can alternately transport the printed circuit boards in the first to third work areas.

1: Photopolymerization layer 2: Printed circuit board 10: Transfer platform 20: Digital Micromirror Device 30: UV light source 40: Photomask 50: Mercury lamp S1: The first work area S2: Second work area S3: The third workspace

Fig. 1 is a schematic diagram of the second-order photopolymerization equipment according to the first embodiment of the present invention.

FIG. 2 is a schematic side view of the second-order photopolymerization apparatus according to the first embodiment of the present invention, and some elements are omitted and not shown.

FIGS. 3 to 5 are schematic diagrams of the work flow of the second-order photopolymerization apparatus according to the first embodiment of the present invention.

FIG. 6 is a schematic side view of a second-stage photopolymerization apparatus according to the second embodiment of the present invention, wherein some components are omitted and not shown.

10: Transfer platform

20: Digital Micromirror Device

30: UV light source

40: Photomask

50: Mercury lamp

S1: The first work area

S2: Second work area

S3: The third workspace

Claims (2)

A second-order photopolymerization device for a photopolymerized layer of a printed circuit board, comprising: a first work area; a second work area; a third work area; At least one transfer platform for carrying a printed circuit board with a photopolymerization layer on the top surface, the transfer platform is preset in the first working area, and the transfer platform will carry the printed circuit board during operation. moving the circuit board to the third working area through the second working area; a digital micromirror device, located in the second working area; A UV light source is arranged in the second working area, and the UV light source is used to illuminate the photopolymerization layer for the first time through the digital micromirror device during the process of the transfer platform passing through the second working area. The power of the light source is less than 0.2 kW; at least one photomask for covering and contacting the photopolymer layer with its bottom surface when the transfer platform moves to the third working area; and A mercury lamp is set in the third working area, the mercury lamp is used to illuminate the photopolymer layer for the second time through the mask after the mask covers the photopolymer layer, and the power of the mercury lamp is greater than 5 kW . The second-order photopolymerization apparatus for a photopolymerized layer of a printed circuit board as claimed in claim 1, wherein the power of the UV light source is less than 0.1 kW.

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