CN113085091A

CN113085091A - Mold, molding method of photocuring adhesive and packaging method of circuit board

Info

Publication number: CN113085091A
Application number: CN202110330202.2A
Authority: CN
Inventors: 文光军
Original assignee: Shanghai Jiaotai New Material Technology Co ltd
Current assignee: Shanghai Jiaotai New Material Technology Co ltd
Priority date: 2021-03-29
Filing date: 2021-03-29
Publication date: 2021-07-09

Abstract

The invention relates to a mold, a molding method of a photocuring adhesive and a packaging method of a circuit board. The mold is used for molding the photocuring adhesive, and at least one part of the mold is provided with a light-transmitting part. In the case of photocuring, the photocurable adhesive can be cured by irradiation with light through the light-transmitting portion via the mold, and thus, the photocurable adhesive can be cured by irradiation with light through the mold even at a portion of the mold cavity away from the gate, particularly at a bevel portion, thereby improving the shape defects of the molded product, particularly at the bevel portion, and improving the efficiency of photocuring.

Description

Mold, molding method of photocuring adhesive and packaging method of circuit board

Technical Field

The invention belongs to the field of molding, and particularly relates to molding of a photocuring adhesive.

Background

The photo-curing adhesive is widely applied to the field of packaging of surface elements of printed circuit boards and the like due to the fact that the photo-curing adhesive can be rapidly formed and bonding of material pieces is achieved.

Patent document 1 discloses an ultraviolet-curing chip packaging process in which an ultraviolet-curing adhesive is applied to a package substrate with a chip to coat the chip, and then the ultraviolet-curing adhesive is irradiated with ultraviolet rays to cure the chip. However, as shown in fig. 1 of patent document 1, the amount of the applied ultraviolet curing adhesive and the shape after curing are difficult to control.

Further, non-patent document 2 reports a technique of combining a photocurable adhesive with molding, in which the photocurable adhesive is injected into a mold and then cured. According to the technology, after the photo-curing adhesive is injected into a mold, the photo-curing adhesive in a mold cavity is irradiated with light through a glue injection port of the mold, so that polymerization and crosslinking reactions are initiated to carry out photo-curing.

However, this technique has a problem that the material in the mold cavity is not cured or is not completely cured, and the shape of the molded product is defective, and particularly, the corner portion of the product is defective. Even if the intensity of light irradiation or the light irradiation time is increased, this drawback cannot be overcome in some cases, and this may lead to a problem of a decrease in production efficiency and an increase in production cost.

Therefore, in the molding process of the photo-curing adhesive, how to improve the shape defects of the molded product, especially the shape defects of the molded product with the folded angle part, improve the production efficiency and reduce the production cost is a problem to be solved urgently.

The prior art is as follows:

patent document

Patent document 1: CN110429170A

Non-patent document

Non-patent document 2: ultraviolet curing moldability study, Changle et al, China plastics, No. 1 in 2014, volume 28, pages 65-69.

Disclosure of Invention

In order to solve at least one of the problems of the prior art, the present inventors have conducted extensive studies and found that by using a mold having at least a part of a light-transmitting portion through which light required for curing a photocurable adhesive can be transmitted, the photocurable adhesive can be cured by irradiation from the portion through the mold during photocuring, and the portion of the mold cavity away from the glue injection port, particularly the bevel portion, can be cured by irradiation through the mold, whereby the shape defect of a molded product, particularly the shape defect of the bevel portion, can be improved, and the photocuring efficiency can be improved. Thus, the present invention has been completed.

Specifically, the present invention provides the following scheme:

one aspect of the present invention relates to a mold for molding a photocurable adhesive, wherein at least a portion of the mold has a light-transmitting portion capable of transmitting light required for curing the photocurable adhesive.

In another aspect, the invention also relates to a molding method of the photo-curing adhesive, which uses the aforementioned mold of the invention to perform molding.

The invention also relates to a packaging method of the circuit board, which adopts the molding method of the photocuring adhesive to package components on the circuit board.

In one aspect, the present invention provides a mold for molding a photo-curable adhesive, wherein at least a portion of the mold has a light-transmitting portion, and the light-transmitting portion is capable of transmitting light required for curing the photo-curable adhesive.

According to the mold of the present invention, preferably, the light-transmitting portion is transparent.

According to the mold of the present invention, the entire mold is preferably a light-transmitting portion.

According to the mold of the present invention, preferably, the mold cavity surface of the mold has a coating layer having a surface tension of less than 30 mN/m.

According to the mold of the present invention, preferably, the coating layer is made of 1 or more materials selected from fluorocarbon resin, silicone resin, fluorosilicone resin.

According to the mold of the present invention, preferably, the photo-curing adhesive is an ultraviolet light curing adhesive, the light required for curing the photo-curing adhesive is ultraviolet light,

according to the mold of the invention, preferably, the wavelength of the ultraviolet light is in the range of 200-420 nm.

According to the mold of the present invention, preferably, the light-transmitting portion of the mold is made of 1 or 2 or more selected from quartz, silica glass, polyethylene, and polypropylene.

The die of the invention is preferably used for circuit board packaging.

On the other hand, the invention also provides a molding method of the photocuring adhesive, which is used for molding by using the mold disclosed by the invention.

The molding method of the light-cured adhesive according to the present invention preferably comprises the following steps:

a mold preparation process: preparing the mold of the invention;

a glue injection process: injecting a photocurable adhesive into a mold cavity of the mold obtained in the mold preparation step;

and (3) a photocuring procedure: the photocurable adhesive is cured by irradiation from the light-transmitting portion of the mold through the mold.

The molding method of the light-cured adhesive further comprises the following steps:

a die fixing procedure: and a step of fixing the mold to the wiring board to be packaged.

On the other hand, the invention also provides a packaging method of the circuit board, which adopts the molding method of the photocuring adhesive to package components on the circuit board.

Advantageous effects

Compared with the prior art, by using the mold of the invention in the molding of the photo-curing adhesive, because the mold has the light-transmitting part which can transmit the light required by the curing of the photo-curing adhesive, when the molding of the photo-curing adhesive is carried out, the photo-curing adhesive can be irradiated from the light-transmitting part through the mold so as to carry out the photo-curing. Therefore, the shape defect of the molded product, especially the shape defect of the folded angle part can be improved, the light curing efficiency is further improved, and the production cost is reduced. The die is particularly suitable for packaging the circuit board.

Drawings

Fig. 1 is a schematic structural view of a mold according to an embodiment of the present invention.

Fig. 2 is a schematic structural view of another exemplary mold according to an embodiment of the present invention.

Fig. 3 is a schematic structural view of a mold according to still another example of an embodiment of the present invention.

Fig. 4 is a flowchart of a molding method of a photocurable adhesive according to an embodiment of the present invention.

Fig. 5 is a flowchart of a molding method of a photocurable adhesive according to still another embodiment of the present invention.

Fig. 6 is a flowchart of another example molding method of a photocurable adhesive according to an embodiment of the present invention.

Fig. 7 is a schematic diagram of step S201 of an example of an embodiment of the present invention.

Detailed Description

Various exemplary embodiments, features and aspects of the present invention are described in detail below with reference to the drawings, wherein like reference numerals represent functionally identical or similar elements throughout the separate views, and wherein, although the various aspects of the embodiments are illustrated in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

"exemplary" means "used herein as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

In addition, numerous details are set forth in the following description in order to better illustrate the invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In some instances, materials, techniques, means, methods well known to those skilled in the art have not been described in detail in order to not unnecessarily obscure the present invention.

Fig. 1 shows a schematic view of a mold used in a molding method for a photo-curing adhesive in the prior art.

As shown in fig. 1, an article 2 to be coated with a photo-curing adhesive layer is placed in a mold cavity of a mold 1, a gap 3 for forming the photo-curing adhesive layer is left between the mold cavity and the article 2, and after the photo-curing adhesive is injected from an adhesive injection port 4, the article is irradiated from the adhesive injection port 4 by corresponding irradiation light.

In the case of irradiation from the glue inlet 4 in the prior art, in order to cure and mold the photo-curable adhesive, especially for the bevel portion 5 shown in fig. 1, which is relatively far from the glue inlet, it takes a longer time to cure or the irradiation intensity of light irradiation needs to be increased, which results in low curing efficiency or is uneconomical. In some cases, even if the curing time is prolonged and the irradiation intensity is increased, the corner portion 5 cannot be cured and molded.

Fig. 2 shows a schematic structural view of a mold according to an embodiment of the present invention.

As shown in fig. 2, by providing the light-transmitting portion 6 in the mold 1, after the light-curable adhesive is injected into the mold cavity, the light-curable adhesive is irradiated from the light-transmitting portion 6 through the mold 1, thereby curing the light-curable adhesive.

The "light-transmissive portion" of the mold is capable of transmitting or substantially transmitting the illumination light required for curing the light-curable adhesive. The irradiation light is, for example, electron beam, ultraviolet light, gamma ray, or the like, and is appropriately selected depending on the composition of the photocurable adhesive. The "light-transmitting portion" does not need to transmit light in a wavelength range required for curing the photocurable adhesive completely, and only needs light that is transmitted to cure the photocurable adhesive so as to have a desired shape.

The term "substantially transmit" as used herein means that a part of light in a wavelength range required for curing the photocurable adhesive is transmitted. In view of the transmission efficiency, "substantially transmitted" means that light is transmitted by, for example, 20% or more, preferably 50% or more, more preferably 70% or more, further preferably 80% or more, more preferably 95% or more, and most preferably 100%. In view of the wavelength range of the light to be transmitted, the light-transmitting portion of the mold may be configured to allow light in a partial wavelength range to be transmitted, from among light in a wavelength range required for curing the photocurable adhesive. For example, in the case where the photocurable adhesive is an ultraviolet curable adhesive, and in the case where the irradiation light required for curing is, for example, light having a wavelength of 360nm, if the light-transmitting portion of the mold is capable of transmitting light of 360nm, the curing reaction of the resin can be initiated so that the resin is cured to form a desired shape. The light-transmitting portion is not particularly limited as to whether or not light outside the wavelength range of the irradiation light can be transmitted, and may be transmissive or opaque as long as it does not affect photocuring.

The ultraviolet light to be used is not particularly limited as long as it can cure the optical adhesive to be cured. It may be a single wavelength uv light of 254nm, 365nm, 380nm, for example, or a uv light source emitting a continuous band spectrum. Examples of such an ultraviolet light source include a low-pressure mercury lamp, a medium-pressure mercury lamp, and a high-pressure mercury lamp. Instead of ultraviolet light, electron beams or gamma rays may be used, in which case the light-transmitting part is made of a corresponding material that is capable of transmitting electron beams or gamma rays.

As shown in fig. 2, the mold may have a part having a light-transmitting portion and the other part having a non-light-transmitting portion. The light transmission part is arranged at a position corresponding to the position of the photocuring adhesive to be cured. In other words, the photocurable adhesive may be cured by irradiation with light through the light-transmitting portion via a mold. From the viewpoint of improving the photocuring efficiency, reducing the light irradiation intensity and the light irradiation time, it is preferable to set a portion of the mold close to the position of the photocuring adhesive as a light-transmitting portion, and particularly, to set a portion corresponding to the fold portion of the photocuring adhesive as a light-transmitting portion, so that the fold portion can be subjected to photocuring through the portion, and the fold portion can be photocured more efficiently to obtain a desired shape of the photocuring adhesive.

Such a mold having a part having a light-transmitting portion and the other part having a non-light-transmitting portion can be prepared by using different materials for the light-transmitting portion and the non-light-transmitting portion. As the non-light-transmitting portion, a material that does not transmit curing light to be used may be used in some cases. Such as stainless steel, ceramic, etc.

In one example, the mold may also be made entirely of a light permeable material. From the viewpoint of simplifying the design and manufacturing process of the mold and improving the production efficiency, it is preferable that the entire mold is made of a light-permeable material.

On the other hand, if the material of the non-light-transmitting portion is more inexpensive than the material of the light-transmitting portion and the area ratio of the light-transmitting portion required is low, even if the cost of the design and production process is taken into consideration, the case of designing the light-transmitting portion and the non-light-transmitting portion separately is still cheaper than the case of using a mold made of a material capable of transmitting light entirely, and in such a case, it is preferable to provide only the necessary light-transmitting portion in the mold and to make the remaining portion the non-light-transmitting portion from the viewpoint of cost saving.

In another example, the light-transmissive portion of the mold is transparent. Through setting up the printing opacity portion in the mould to transparent, can confirm the shaping condition of gluing agent through instrument or visual observation photocuring's process in the photocuring process. Therefore, the intensity and time of light irradiation required for curing can be grasped more accurately, so that the production efficiency is improved, and the production cost is saved.

In yet another example, the mold is made entirely of a light permeable material, and the entirety is transparent. Therefore, the forming condition of the adhesive can be confirmed by observing the photocuring process through an instrument or visually in the photocuring process, so that the intensity and time of light irradiation required by curing can be mastered more accurately, the production efficiency is improved, and the production cost is saved.

The mold is not particularly limited to be prepared, and those skilled in the art can appropriately select a material for the light-transmitting portion and the non-light-transmitting portion as needed.

As the material of the light-transmitting portion, those skilled in the art may select an appropriate light-transmitting material in consideration of the wavelength of curing light required for photocuring of the photocurable adhesive so that the light-transmitting portion can transmit or substantially transmit the curing light. For example, when the light-curable adhesive is an ultraviolet light-curable adhesive, the light-transmitting portion may be allowed to transmit or substantially transmit ultraviolet light of a desired wavelength band. Examples of such a light-permeable material include quartz, silica glass, polyethylene, polypropylene, and the like, and the light-permeable portion may be made of 1 or 2 or more of these. If necessary, other components than these materials may be contained, and there is no particular limitation as long as the curing cannot be completed because light cannot be transmitted.

Fig. 3 shows a schematic view of another exemplary mold.

As shown in fig. 3, the mold 1 has a coating 7 on the cavity surface. As a material used for the coating layer 7, for example, carbon resin, fluorocarbon resin, silicone resin, fluorosilicone resin, or the like can be used. By having the coating layer 7, adhesion with the photo-curing adhesive used in the present invention can be prevented. From this point of view, the coating 7 is preferably a low surface energy material. Surface energy refers to a measure of the breakdown of intermolecular chemical bonds when creating a substance's surface. The light-transmitting portion is preferably made of a material having a surface energy of 100mN/m or less, preferably 50mN/m or less, and more preferably 30mN/m or less. As the low surface energy material of the coating layer 7, 1 or a combination of 2 or more selected from polyamide 6, polyvinyl alcohol, polyoxymethylene, polystyrene, polypropylene, polytetrafluoroethylene, for example, can be used. In order to obtain more excellent film-forming properties, polytetrafluoroethylene is preferred.

The mold may be suitable for use in the encapsulation of devices such as circuit boards, chip scale packages (SiP), device mold compound packaging, and the like. In these applications, the mold is used for molding of a photocurable adhesive.

Molding method of photocuring adhesive

In the method for molding the photocurable adhesive, the specific mode of molding is not particularly limited, and for example, injection molding or blow molding may be used.

FIG. 4 is a flow chart of an exemplary method of molding a photocurable adhesive, including the steps of: a mold preparation step S101, a glue injection step S102, and a photocuring step S103.

The mold preparation step S101 is a step of preparing a mold. In the mold preparation step S101, the position of the mold cavity of the mold is appropriately set as needed.

For example, for a mold for packaging a circuit board, the position and size of a mold cavity of the mold are set according to the position and size of a component on the circuit board, the thickness of a required photocuring adhesive layer is combined, and the performances such as flowability of the photocuring adhesive are considered, so that a space required by the photocuring adhesive is reserved and is suitable for setting.

The mold may be fabricated using techniques such as laser machining. The UV-transparent material was processed using a carbon dioxide laser at 1064nm at 150W. The die is provided with a feed inlet and an exhaust port. When designing a plate die, the pitch of the feed ports is the same as the runner stroke in the die.

In the injection step S102, a photocurable adhesive is injected into the mold cavity of the mold obtained in the mold preparation step.

The photo-curing adhesive used is any photo-curing adhesive suitable for molding. Examples of such a photocurable adhesive include:

acrylic resins such as (meth) acrylate resins, epoxy acrylic resins, urethane acrylic resins, polyether acrylic resins, polyester acrylic resins, and the like.

Such as alicyclic epoxy resin based UV curing glue, acrylate based UV curing glue, UV curing silica gel.

Preferably, the alicyclic epoxy resin-based UV adhesive is cured by cation initiation, and has good performance after curing.

The photocurable adhesive may contain additives such as fillers, plasticizers, colorants, lubricants, stabilizers, curing agents, and the like.

The light-curing adhesive can be injected by, for example, natural flowing or vacuum suction. And under the condition of natural inflow, injecting the required amount of the light-cured adhesive from the glue injection port of the mold. The process is suitable for the condition that the workpiece is large and needs more adhesives. Under the condition of vacuum suction, a precise glue injection valve is adopted, the glue output amount is precisely controlled, and the glue is sucked into a mould under the vacuum condition. The process is suitable for the situations of micro electronic devices, large batch and requirement on rapid production.

In the photocuring step S103, the photocuring adhesive is irradiated from the light-transmitting portion of the mold through the mold and cured. The curing light used is appropriately selected depending on the photo-curing adhesive. For example UVA light at a wavelength of 365nm, or UVA light at 405 nm.

The time for photocuring is suitably determined depending on the adhesion of the curing. It is considered that the photocuring is completed when the adhesive is cured and molded into a desired shape by the photocuring. In some examples, the photocuring is finished such that the photocuring adhesive is fully cured. In other examples, semi-curing of the photocurable adhesive may also be considered as the end of photocuring, as long as the photocurable adhesive has been formed into a desired shape. In this case, the photocurable adhesive may be further irradiated with light to be cured after the mold is subsequently removed. In still another exemplary method of molding a photocurable adhesive, the adhesive is simultaneously photocured and thermally cured.

In another example of the method for molding a photocurable adhesive shown in fig. 5, the method may further include the following steps:

mold inspection step S105: and a step of inspecting the mold cavity from which the molded product has been taken out after the photocuring step S103. The mold inspection process may be performed visually or by an instrument. And checking the mold cavity to determine whether the residual adhesive exists on the mold cavity. If the residual adhesive is confirmed, the method further comprises a step of cleaning the residual adhesive on the mold cavity, and after the residual adhesive is removed, the mold is used for molding the photo-curing adhesive in the next cycle. If no residual adhesive is confirmed, the resin composition is directly used for molding the photocuring adhesive in the next cycle.

Fig. 6 shows another example of a molding method of a light-curable adhesive for circuit board packaging. The method further includes a mold fixing step S201.

The mold preparation process, the glue injection process, the photocuring process, the mold inspection process, the mold cleaning process, and the like of the molding method of the photocuring adhesive shown in fig. 6 are similar to those described above, and are not repeated herein.

The mold fixing step 201 will be described with reference to fig. 7.

The circuit board 81 to be packaged has the component 21 mounted thereon, and the mold cavity 31 in the mold 11 has a shape corresponding to the component 21. The "shape corresponding to the component" described herein is a shape in which the mold cavity 31 is set by reserving a space necessary for the photocurable adhesive according to the shape of the component 21 and the amount of the photocurable adhesive to be injected.

In the mold fixing step 201, the prepared mold 11 with the glue injection opening 41 is fixed to the circuit board 81 with the component 22 to be packaged. The glue injection port 41 in fig. 7 is used for injecting a light-curable adhesive into the mold cavity 31, and the injected light-curable adhesive fills a space between the mold cavity 31 and the component 21.

The fixing method of the mold 11 is not particularly limited as long as the mold can be fixed so that the photocurable adhesive can be injected to a desired position. For example, a method of designing a clip and a corresponding slot on a mold and a circuit board to be packaged and fixing the circuit board by the clip;

as previously indicated, the mold 11 may be made entirely of a light permeable material, i.e., the mold 11 as a whole is capable of being permeable to light irradiation. In addition, the mold 11 may be made of a transparent material, so that the curing condition of the light-curing adhesive can be observed through the mold.

In an exemplary embodiment, the mold cavity surface of the mold 11 may further have a surface coating (not shown).

At least one part of the mould used in the molding method of the light-cured adhesive can transmit the light required by curing of the light-cured adhesive. After the photocuring adhesive is injected into the mold, the photocuring adhesive is irradiated from the part of the mold, which can transmit light required by the photocuring adhesive for curing, so that the photocuring adhesive is cured, thereby improving the shape defects of a molded product, particularly the shape defects of a bevel part, further improving the photocuring efficiency and reducing the production cost.

The molding method of the photocuring adhesive is particularly suitable for the packaging process of circuit boards. In general, many components are mounted on a circuit board, and in order to protect the mounted components from damage, the surface of the circuit board on which the components are mounted is usually sealed with a plastic or ceramic material, and the mounted components are fixed and sealed.

Example 1 (without coating)

Example 1 is explained with reference to fig. 7. Firstly, the shape of the mold 11 is designed according to the distribution of the circuit board to be packaged and the components thereon, and the mold 11 with the glue injection port 41 is made of polypropylene as a light-permeable material, wherein the whole light-permeable part of the mold is provided with a light-permeable part. Then, the fabricated mold 11 is fixed to the wiring board 81 with the component 22 to be packaged. Next, an acrylic resin as a light curing adhesive is injected into the mold cavity from the injection port 41, and the injected light curing adhesive fills the space between the mold cavity 31 and the component 21. Further, the photo-curable adhesive was irradiated with 365nm ultraviolet light through a mold 41 at an irradiation intensity of 700mW/cm²And the irradiation time is 5 minutes, so that the light-cured adhesive is cured. After the photocuring irradiation is finished, the mold is taken down from the circuit board, the shape of the photocuring adhesive cured on the circuit board, particularly the shape of a corner is observed visually, and the photocuring adhesive is completely cured, and the corner is a right angle.

Example 2 (coated)

The same procedure as in example 1 was repeated, except that the mold 11 was coated with a coating layer. The coating is polytetrafluoroethylene. After the curing is finished, the mold is taken down from the circuit board, the shape of the cured photocuring adhesive on the circuit board, particularly the shape of a corner is observed visually, and the photocuring adhesive is completely cured, and the corner is a right angle.

Comparative example 1 (prior art)

The same procedure as in example 1 was repeated, except that the mold 11 was made of stainless steel and the photocurable adhesive was subjected to photocuring irradiation from the inlet 41. After the photocuring irradiation is finished, the mold is taken down from the circuit board, the shape of the photocuring adhesive cured on the circuit board, particularly the shape of the corner is observed visually, and the incomplete curing at the corner and the defect at the corner are found.

It should be understood that the above-mentioned examples are for illustrative purposes only and are not intended to limit the embodiments of the present disclosure, and that various other modifications and changes in light thereof will be suggested to persons skilled in the art and are not intended to be exhaustive or to limit the present disclosure to the precise embodiments disclosed herein.

Claims

1. The mold is used for molding and forming of a light-curing adhesive, wherein at least one part of the mold is provided with a light-transmitting part, and the light-transmitting part can transmit light required by curing of the light-curing adhesive.

2. The mold according to claim 1, wherein the light-transmitting portion is transparent.

3. The mold according to claim 1 or 2, wherein the entire mold is a light-transmitting portion.

4. A mould according to any one of claims 1 to 3, having a coating on the mould cavity surface, the coating having a surface tension of less than 30 mN/m.

5. The mold according to claim 4, wherein the coating layer is made of 1 or more materials selected from fluorocarbon resin, silicone resin, fluorosilicone resin.

6. The mold according to claim 1, wherein the light-curable adhesive is an ultraviolet light-curable adhesive, and the light required for curing the light-curable adhesive is ultraviolet light.

7. The mold according to claim 6, wherein the ultraviolet light has a wavelength ranging from 200 to 420 nm.

8. The mold according to any one of claims 1 to 7, wherein the light-transmitting portion of the mold is made of 1 or 2 or more selected from quartz, silica glass, polyethylene, and polypropylene.

9. The mold of claim 1, for use in circuit board packaging.

10. A method for molding a photocurable adhesive by using the mold according to any one of claims 1 to 9.

11. The molding method of the photocurable adhesive according to any one of claims 10, comprising the steps of:

a mold preparation process: preparing a mould according to any one of claims 1 to 9;

12. The method for molding a photocurable adhesive according to claim 11, further comprising the steps of:

13. A method for packaging a circuit board, characterized in that the method for molding the photocurable adhesive according to any one of claims 10 to 12 is used for packaging a component on the circuit board.