Graphical mass transfer method and system

Abstract

The present invention discloses a graphical mass transfer method, which first forms a solidified flat adhesive layer on the surface of a temporary substrate, processes the adhesive layer into a plurality of array-distributed convex adhesive layer islands before arranging the chips, and arranges each chip on the surface of each convex adhesive layer island during arranging the chips, thereby preventing the circuit substrate from warping and deforming due to the pulling force of the adhesive layer in the groove.

Description

Technical Field

[0001] The present invention belongs to the field of mass transfer. Background Art

[0002] In recent years, Micro LED mass transfer is mainly divided into the following five technologies: laser transfer, stamp, electromagnetic force, electrostatic force, and roll to roll transfer technology. Among them, laser transfer technology requires the use of a primary laser transfer technology to pre-arrange on the adhesive film & temporary high-transmittance substrate, and a secondary laser transfer technology to transfer the chip to the target substrate.

[0003] Designed for secondary laser transfer technology, the existing secondary laser transfer technology is to transfer the micro chip to a temporary high-transmittance substrate (hereinafter referred to as a temporary substrate) by laser. From COC Wafer to the temporary substrate, a layer of adhesive film is required to carry out the transfer. The existing technology is to attach the entire surface film to the temporary substrate to carry the chip on the COC Wafer ( Figure 1 ), but in the welding process, one action is to press the temporary substrate and the circuit substrate together, at this time, the adhesive film on the temporary substrate is completely adhered to the entire surface of the circuit substrate ( Figure 2 ), which results in the inability to separate quickly during separation, and the circuit substrate is prone to bending and damage ( Figure 3 ), the overall yield is unstable. Summary of the invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a graphical mass transfer method and system to effectively improve the yield rate.

[0005] Technical solution: To achieve the above-mentioned purpose, the graphic mass transfer method of the present invention first forms a solidified flat adhesive layer on the surface of a temporary substrate, and processes the adhesive layer into a plurality of array-distributed raised adhesive layer islands before arranging the chips. When arranging the chips, each chip is arranged on the surface of each raised adhesive layer island.

[0006] Further, the following steps are included:

[0007] Step 1, evenly coating the glue with a predetermined thickness on the surface of the temporary substrate by spin coating;

[0008] Step 2, drying the glue coated on the surface of the temporary substrate to form a cured glue layer;

[0009] Step 3, attaching a layer of photoresist on the surface of the adhesive layer to form a photoresist layer;

[0010] Step 4, drying the photoresist layer;

[0011] Step 5, exposing the photoresist layer by an exposure device, the portion of the photoresist layer exposed to light forms a criss-cross exposure pattern, and then dissolving the photoresist layer exposed to light by a developer, after development, the dissolved portion of the photoresist layer forms a criss-cross development pattern, the adhesive layer at the development pattern is in an exposed state, and finally etching the portion of the adhesive layer not covered by the photoresist layer; the etched portion of the adhesive layer forms a plurality of criss-cross segmentation grooves, the criss-cross segmentation grooves divide the adhesive layer into a plurality of array-distributed raised adhesive layer islands, each of which is covered with an unexposed photoresist layer;

[0012] Step 6, removing or dissolving the unexposed photoresist layer covering each convex glue layer island, so that the surface of each convex glue layer island is exposed;

[0013] Step 7, spraying glue uniformly on the upper surface of the array-distributed convex glue layer islands; in the process of uniformly spraying glue on the upper surface of the array-distributed convex glue layer islands, a part of the sprayed glue adheres to the upper surface of the convex glue layer islands, and another part adheres to the bottom of the criss-crossing dividing grooves to form an adhesive layer in the grooves;

[0014] Step eight, semi-drying the glue just sprayed on the surface of each convex glue layer island.

[0015] Step nine, the chip arrangement machine arranges a plurality of chips one by one on the surfaces of a plurality of convex glue layer islands;

[0016] Step 10: Place the side of the temporary substrate with the chip facing downward, and place the circuit substrate horizontally corresponding to the bottom of the temporary substrate. Use the displacement mechanism to align the side of the temporary substrate with the chip and the circuit substrate and then press them together. During the pressing process, the protruding adhesive layer islands will be slightly deformed due to the squeezing force, and the adhesive layer in the groove may contact the circuit substrate. At the same time, the heating device heats up, so that the chips originally attached to the surfaces of the protruding adhesive layer islands are joined to the circuit substrate, completing the welding process of each chip.

[0017] Step eleven, the displacement mechanism controls the temporary substrate to separate from the circuit substrate, and each chip is separated from each protruding adhesive layer island. Thus, the purpose of transferring each chip to the circuit substrate has been completed.

[0018] Furthermore, two steps are added between "Step 6" and "Step 7", and the two added steps are recorded as "Step a" and "Step b".

[0019] Step a: coating a volatile liquid on one side of the temporary substrate surface with protruding adhesive layer islands, and stopping the coating when the volatile liquid just submerges all the protruding adhesive layer islands, at which time the criss-crossing dividing grooves are completely filled with the volatile liquid;

[0020] Step b: let it stand and heat it to make the volatile liquid applied in "step a" evaporate gradually and evenly, and the raised adhesive layer islands that are just submerged gradually "ebb" due to the evaporation of the volatile liquid covering the surface, and the volatile liquid covering the surface of each raised adhesive layer island evaporates completely first, thereby exposing each raised adhesive layer island again; as the volatile liquid continues to evaporate, the volatile liquid in the criss-cross dividing grooves gradually begins to evaporate and become less, thereby causing the liquid level of the volatile liquid in the criss-cross dividing grooves to gradually decrease, and as the evaporation process continues, when the liquid level of the volatile liquid in the dividing grooves drops to the bottom but has not completely evaporated, a volatile liquid isolation layer is formed at the bottom of the criss-cross dividing grooves, and "step seven" is performed before the volatile liquid isolation layer has not completely evaporated.

[0021] Furthermore, the boiling point of the volatile liquid is between 30°C and 70°C.

[0022] Beneficial effects: In the lamination process of the present invention, only the surface of each convex adhesive layer island will contact the circuit substrate at most, and the adhesive layer in the grooves of the criss-cross dividing grooves is theoretically sunken and will not contact the circuit substrate; the contact area between the circuit substrate and the adhesive surface is significantly reduced, the problem of circuit substrate warping can be solved, and the problem of bubbles generated by film lamination in the existing solution does not exist;

[0023] During the pressing process of the temporary substrate and the circuit substrate, even if the adhesive layer in the groove is bonded to the circuit substrate, the volatile liquid isolation layer has separated the temporary substrate surface from the adhesive layer in the groove, so that the temporary substrate and the circuit substrate will not be bonded together, thereby ensuring the smoothness of the separation of the temporary substrate and the circuit substrate in "Step 11". The adhesive layer in the groove will automatically separate from the temporary substrate surface and be taken out together with the circuit substrate, avoiding the circuit substrate from warping and deformation due to the pulling force of the adhesive layer in the groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Attached Figure 1 This is the state after film arrangement in the prior art;

[0025] Attached Figure 2 It is the state when pressing in the prior art;

[0026] Attached Figure 3 This is the state in which the circuit substrate is bent during separation in the prior art;

[0027] Attached Figure 4 It is a schematic diagram of the bending of the new line substrate in the prior art;

[0028] Attached Figure 5 This is a process diagram of "step one" to "step seven" of this solution;

[0029] Attached Figure 6This is the top view in the "step six" state;

[0030] Attached Figure 7 For the attached Figure 5 The process diagram after adding two steps between "step six" and "step seven" is shown on the basis of FIG.

[0031] Attached Figure 8 It is a schematic diagram of the process from “step eight” to “step eleven”. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings.

[0033] Embodiment 1:

[0034] As attached Figures 5 to 8 The graphical mass transfer method specifically comprises the following steps:

[0035] Step 1, evenly coating the glue with a predetermined thickness on the surface of the temporary substrate by spin coating;

[0036] Step 2, drying the glue coated on the surface of the temporary substrate to form a cured glue layer 1;

[0037] Step 3, attaching a layer of photoresist on the surface of the adhesive layer 1 to form a photoresist layer;

[0038] Step 4, drying the photoresist layer;

[0039] Step 5: Figure 5 and 6 As shown, the photoresist layer is exposed by an exposure device, and the photoresist layer is exposed to light (strong ultraviolet light) to form a criss-cross exposure pattern. The principle is that the photoresist is photosensitive after exposure, that is, the part exposed to light will become easily soluble, so that the photoresist layer exposed to light can be dissolved by the developer, while the photoresist layer that is not exposed is a dense high molecular polymer with excellent chemical resistance and heat resistance, and can maintain stable performance, thereby protecting the covered glue layer from being damaged in the subsequent etching process. After development, the photoresist layer is dissolved. The degraded part forms a criss-cross development pattern, and the glue layer 1 at the development pattern is in an exposed state. Finally, the part of the glue layer 1 not covered by the photoresist layer (the exposed part of the glue layer) is etched. This scheme adopts wet etching, and the etchant can be a glue remover, etc.; the etched part of the glue layer 1 forms a plurality of criss-cross segmentation grooves 4, and the part not etched is covered and protected by the photoresist layer. The criss-cross segmentation grooves 4 divide the glue layer 1 into a plurality of array-distributed convex glue layer islands 3, and each convex glue layer island 3 is covered with an unexposed photoresist layer;

[0040] Step 6, removing or dissolving the unexposed photoresist layer covering each convex glue layer island 3, so that the surface of each convex glue layer island 3 is exposed;

[0041] Step 7, spray glue evenly on the upper surface of the array-distributed convex glue layer islands 3; in the process of spraying glue evenly on the upper surface of the array-distributed convex glue layer islands 3, a part of the sprayed glue adheres to the upper surface of the convex glue layer islands 3, and another part adheres to the bottom of the criss-crossing dividing grooves 4, forming an adhesive layer 6 in the grooves;

[0042] Step eight, then half-dry the glue just sprayed on the surface of each convex glue layer island 3, so as to ensure that the surface of each convex glue layer island 3 has a certain adhesion ability, so that each convex glue layer island 3 can stably adhere to a chip;

[0043] Step nine, the chip arrangement machine arranges a plurality of chips one by one on the surfaces of a plurality of convex glue layer islands 3;

[0044] Step 10: Place the side of the temporary substrate with the chip facing downward, and place the circuit substrate horizontally corresponding to the bottom of the temporary substrate. Use the displacement mechanism to align the side of the temporary substrate with the chip and the circuit substrate, and then press them together. During the pressing process, the protruding adhesive layer islands 3 will be slightly deformed due to the squeezing force, and the adhesive layer 6 in the groove may contact the circuit substrate. At the same time, the heating device heats, so that the chips originally attached to the surfaces of the protruding adhesive layer islands 3 are joined to the circuit substrate, completing the welding process of each chip.

[0045] Step 11: The displacement mechanism controls the temporary substrate to separate from the circuit substrate, and each chip is separated from each protruding glue layer island 3. At this point, the purpose of transferring each chip to the circuit substrate has been completed. Due to the structural characteristics of each protruding glue layer island 3 compared with the existing solution, during the pressing process, only the surface of each protruding glue layer island 3 will contact the circuit substrate at most, and the adhesive layer 6 in the grooves of the criss-cross dividing grooves 4 is theoretically sunken and will not contact the circuit substrate; the contact area between the circuit substrate and the adhesive surface is significantly reduced, which can solve the problem of warping of the circuit substrate, and there is no bubble problem caused by film pasting in the existing solution;

[0046] The above steps can achieve the expected purpose in most cases, and the yield rate is significantly higher than the existing solution, and the circuit substrate warping problem is reduced, but the following problems still exist in practice:

[0047] During the execution of "step seven", due to the aggregation effect of the sprayed glue by the criss-cross dividing grooves 4, when the ambient temperature during spraying is high, the glue viscosity is low, or there is local overspray, the thickness of the in-groove adhesive layer 6 formed in the criss-cross dividing grooves 4 will be correspondingly thickened. When the thickness of the in-groove adhesive layer 6 at any place is too thick, during the subsequent pressing of the temporary substrate and the circuit substrate in "step ten", the in-groove adhesive layer 6 is likely to contact the circuit substrate, and then the temporary substrate and the circuit substrate are adhered to each other through the in-groove adhesive layer 6, resulting in the temporary substrate and the circuit substrate being pulled against each other under the adhesion of the in-groove adhesive layer 6 when the temporary substrate and the circuit substrate are separated in the subsequent "step eleven", and then the circuit substrate is warped and deformed due to the pulling force of the in-groove adhesive layer 6;

[0048] In order to eliminate the above possible problems, this solution designs the following optimization scheme:

[0049] Embodiment 2:

[0050] like Figure 7 As shown, two steps are added between "Step 6" and "Step 7", and the two added steps are recorded as "Step a" and "Step b".

[0051] Step a: coating a volatile liquid on one side of the temporary substrate surface with the protruding adhesive layer islands 3, and stopping the coating when the volatile liquid just submerges all the protruding adhesive layer islands 3, at which time the criss-crossing dividing grooves 4 are completely filled with the volatile liquid;

[0052] Step b: standing still and supplemented with heating or ventilation, so that the volatile liquid applied in "step a" gradually evaporates evenly, and the convex glue layer islands 3 that are just submerged gradually "ebb" due to the volatile liquid covering the surface evaporating, and the volatile liquid covering the surface of each convex glue layer island 3 evaporates completely first, so that each convex glue layer island 3 is exposed again; as the volatile liquid continues to evaporate, the volatile liquid in the criss-cross dividing grooves 4 gradually begins to evaporate and decrease, thereby causing the liquid level of the volatile liquid in the criss-cross dividing grooves 4 to gradually decrease, and as the evaporation process continues, when the liquid level of the volatile liquid in the dividing grooves 4 drops to the bottom, but has not completely evaporated, a volatile liquid isolation layer 5 is formed at the bottom of the criss-cross dividing grooves 4, and "step seven" is performed before the volatile liquid isolation layer 5 has not completely evaporated;

[0053] After "step a" and "step b", "step seven" has the following characteristics:

[0054] "Step 7": Before the volatile liquid isolation layer 5 is completely evaporated, in the process of uniformly spraying glue on the upper surface of the array-distributed convex glue layer islands 3, a part of the sprayed glue adheres to the upper surface of the convex glue layer islands 3, and the other part adheres to the bottom of the criss-crossing dividing grooves 4. Since there is a layer of volatile liquid isolation layer 5 that has not completely evaporated at the bottom of the criss-crossing dividing grooves 4, the adhesive layer 6 in the groove adheres to the upper surface of the volatile liquid isolation layer 5. The adhesive layer 6 in the groove inhibits the further evaporation of the volatile liquid isolation layer 5. At the same time, the volatile liquid isolation layer 5 temporarily adheres to the surface of the substrate. Separated from the adhesive layer 6 in the groove; thus, in the subsequent "step 10", during the pressing process of the temporary substrate and the circuit substrate, even if the adhesive layer 6 in the groove is bonded to the circuit substrate, the volatile liquid isolation layer 5 has separated the temporary substrate surface from the adhesive layer 6 in the groove, so that the temporary substrate and the circuit substrate will not be bonded together, thereby ensuring the smoothness of the separation of the temporary substrate and the circuit substrate in "step 11", the adhesive layer 6 in the groove will automatically separate from the temporary substrate surface and be taken out together with the circuit substrate, avoiding the circuit substrate from warping and deformation due to the pulling force of the adhesive layer 6 in the groove;

[0055] The boiling point of the volatile liquid is between 30°C and 70°C. In this solution, the volatile liquid can specifically be selected as methyl tert-butyl ether with high stability. Since there are many volatile liquids that meet the requirements, they will not be described in detail in this case.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A graphical mass transfer method, characterized in that: First, a solidified flat adhesive layer (1) is formed on the surface of a temporary substrate, and before chip arrangement, the adhesive layer (1) is processed into a plurality of array-distributed convex adhesive layer islands (3), and when arranging chips, each chip is arranged on the surface of each convex adhesive layer island (3); The steps include: Step 1, evenly coating the glue with a predetermined thickness on the surface of the temporary substrate by spin coating; Step 2, drying the glue coated on the surface of the temporary substrate to form a cured glue layer (1); Step 3, attaching a layer of photoresist on the surface of the adhesive layer (1) to form a photoresist layer; Step 4, drying the photoresist layer; Step 5, exposing the photoresist layer by an exposure device, the portion of the photoresist layer exposed to light forms a crisscross exposure pattern, then dissolving the photoresist layer in the portion exposed to light by a developer, after development, the portion of the photoresist layer that is dissolved forms a crisscross development pattern, the adhesive layer (1) at the development pattern is in an exposed state, and finally etching the portion of the adhesive layer (1) not covered by the photoresist layer; The etched portion of the adhesive layer forms a plurality of crisscross dividing grooves (4), the crisscross dividing grooves (4) dividing the adhesive layer (1) into a plurality of array-distributed raised adhesive layer islands (3), each of the raised adhesive layer islands (3) being covered with an unexposed photoresist layer; Step six, removing or dissolving the unexposed photoresist layer covering each convex glue layer island (3) to expose the surface of each convex glue layer island (3); Step 7, spraying glue uniformly on the upper surface of the array-distributed convex glue layer islands (3); in the process of uniformly spraying glue on the upper surface of the array-distributed convex glue layer islands (3), a portion of the sprayed glue adheres to the upper surface of the convex glue layer islands (3), and another portion adheres to the bottom of the criss-crossed dividing grooves (4), forming an adhesive layer (6) in the grooves; Step eight, semi-drying the glue just sprayed on the surface of each convex glue layer island (3); Step nine, a chip arrangement machine arranges a plurality of chips one by one on the surface of a plurality of convex glue layer islands (3); Step 10, the side of the temporary substrate with the chip on it is horizontally facing downwards, and the circuit substrate is horizontally aligned with the bottom of the temporary substrate, and the side of the temporary substrate with the chip is aligned with the circuit substrate by a displacement mechanism and then pressed together, and at the same time, a heating device is heated, so that the chip originally attached to the surface of each convex glue layer island (3) is joined with the circuit substrate, and the welding process of each chip is completed; Step 11: The displacement mechanism controls the temporary substrate to separate from the circuit substrate, and each chip is separated from each protruding glue layer island (3); Add two steps between "Step 6" and "Step 7", and record the two added steps as "Step a" and "Step b" Step a: coating a volatile liquid on one side of the temporary substrate surface having the protruding adhesive layer islands (3), and stopping the coating when the volatile liquid just submerges all the protruding adhesive layer islands (3), at which time the criss-crossing dividing grooves (4) are completely filled with the volatile liquid; Step b: standing still and heating, so that the volatile liquid applied in "step a" gradually evaporates evenly, and the volatile liquid covering the upper surface of each protruding adhesive layer island (3) evaporates completely first, so that each protruding adhesive layer island (3) is exposed again; as the volatile liquid continues to evaporate, the volatile liquid in the criss-cross dividing grooves (4) gradually evaporates and becomes less, thereby causing the liquid level of the volatile liquid in the criss-cross dividing grooves (4) to gradually decrease. When the liquid level of the volatile liquid in the dividing grooves (4) drops to the bottom but has not completely evaporated, a volatile liquid isolation layer (5) is formed at the bottom of the criss-cross dividing grooves (4), and "step seven" is performed before the volatile liquid isolation layer (5) has not completely evaporated.

2. The graphical mass transfer method according to claim 1, wherein: The boiling point of the volatile liquid is between 30°C and 70°C.

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