CN217881556U - Chip On Board (COB) display module capable of preventing chip from shifting - Google Patents

Abstract

The utility model relates to a prevent COB display module of chip skew, COB display module includes light-passing board, viscidity glued membrane, LED chip, base plate, eutectic layer and packaging material, the viscidity glued membrane set up in the surface of light-passing board, the LED chip passes through viscidity glued membrane adhesion is fixed in on the light-passing board, and pass through the eutectic layer with base plate welded fastening, the packaging material is filled the light-passing board with space between the base plate. Among the COB display module, the welding reliability of LED chip is high, and the rigidity is firm, difficult position deviation that takes place.

Description

Chip On Board (COB) display module capable of preventing chip from shifting

Technical Field

The utility model relates to a COB technical field especially relates to a prevent COB display module of chip skew.

Background

The COB (Chip-on-board) technology is a new LED packaging technology, is different from the traditional SMD surface-mounted package, integrates the light-emitting chips in the PCB instead of being welded on the PCB one by one, and effectively improves the light-emitting color of the LED display screen and reduces the risk and the cost.

In the existing mini COB process, due to the instability of the solder paste printing process, a die floating phenomenon (in the field, the die refers to a crystal grain before the chip is not packaged) occurs after the chip is subjected to reflow soldering, namely, the chip is distorted, and the chip is seriously broken to form a dead spot; COB display screens with serious floating die have poor display effect and more pits under low gray, so that the display effect is influenced; in the COB display screen that has the superficial die phenomenon, the chip is because the welding is firm inadequately, and chip offset can take place gradually during the use, can appear the phenomenon that the chip dropped when serious.

SUMMERY OF THE UTILITY MODEL

Based on this, the utility model provides a prevent COB display module of chip skew to improve the welding reliability of LED chip among the COB display module, effectively fix the position of LED chip.

The utility model adopts the following technical scheme:

the utility model provides a prevent COB display module of chip skew, includes light-passing board, viscidity glued membrane, LED chip, base plate, eutectic layer and packaging material, the viscidity glued membrane set up in the surface of light-passing board, the LED chip passes through viscidity glued membrane adhesion is fixed in on the light-passing board, and pass through eutectic layer with base plate welded fastening, the packaging material is filled the light-passing board with space between the base plate.

In the COB display module, the LED chip is fixedly adhered to the light-transmitting plate, so that one side of the LED chip is fixedly connected with the light-transmitting plate, the other side of the LED chip is fixedly welded with the substrate through the eutectic layer, and both sides of the LED chip are fixed, therefore, the fixing effect of the LED chip is enhanced, and the welding reliability is improved; meanwhile, all gaps between the light-transmitting plates and the substrate which are respectively connected with the two sides of the LED chip are filled and packaged by the packaging material, namely the light-transmitting plates and the substrate are bonded together by the packaging material, the bonding area of the light-transmitting plates and the substrate is large, and the effect of fixing the position of the LED chip is further improved.

Additionally, the utility model discloses utilize the light-passing board to come the adhesion chip, play the effect of location chip, bind chip and light-passing board together and carry out the reflow soldering on the base plate, prevent that the chip that the reflow soldering in-process leads to because of the tin cream is uneven from dragging, avoid the chip to appear floating, askew to turn round offset etc. and effectively solve the superficial die problem in the COB shows the processing procedure.

Furthermore, COB display module still including be located the eutectic layer with diffusion barrier layer between the base plate avoids appearing the welding hole, diffusion barrier layer fixed set up in on the base plate.

Furthermore, the diffusion barrier layer is at least one of a nickel layer, a platinum layer and a palladium layer, and can effectively block metal migration.

Further, the diffusion impervious layer is arranged on the substrate in a mode of electroplating, sputtering coating or thermal evaporation coating.

Further, the eutectic layer is disposed on the substrate by electroplating, sputter coating or thermal evaporation coating.

Further, the thickness of the eutectic layer is 3-5 microns.

Further, the light-transmitting plate is a glass carrier plate.

Further, the adhesive film is light-transmissive.

Further, the thickness of the adhesive glue film is 400-500 micrometers.

Further, the packaging material is a thermosetting adhesive.

For a better understanding and an implementation, the present invention is described in detail below with reference to the accompanying drawings.

Drawings

Fig. 1 is a schematic structural diagram of a COB display module for preventing chip offset according to the present invention;

fig. 2 is a schematic diagram of steps S1-S2 in the manufacturing process of the COB display module according to the present invention;

fig. 3 is a schematic diagram of steps S3-S6 in the manufacturing process of the COB display module according to the present invention.

Detailed Description

As shown in fig. 1, prevent COB display module of chip skew, including light-passing board 1, viscidity glued membrane 2, LED chip 3, base plate 4, eutectic layer 6, encapsulating material 7, more preferably, can also include diffusion barrier layer 5.

The adhesive film 2 is arranged on the surface of the light-transmitting plate 1, the LED chip 3 is fixedly adhered to the light-transmitting plate 1 through the adhesive film 2 and is fixedly welded to the substrate 4 through the eutectic layer 6, and the packaging material 7 fills a gap between the light-transmitting plate 1 and the substrate 4.

Specifically, one surface of the LED chip 3 having electrodes (not shown) is away from the light-transmitting plate 1, and the other surface is adhered and fixed on the adhesive film 2.

The diffusion barrier layer 5 is located between the eutectic layer 6 and the substrate 4, and is fixedly disposed on the substrate 4.

The diffusion barrier layer 5 is a nickel layer (Ni), a platinum layer (Pt), a palladium layer (Pd), or the like, and is formed on the substrate 4, specifically, on the surface of a bonding pad (not shown) formed on the substrate 4, by electroplating, sputter coating, or thermal evaporation coating.

The eutectic layer 6 is a gold-tin eutectic layer 6 (AuSn eutectic layer) or an eutectic layer of other metals, and is formed on the substrate 4, specifically on the surface of the diffusion barrier layer 5, by electroplating, sputter coating, or thermal evaporation coating. Preferably, the thickness of the eutectic layer 6 is 3-5 microns.

The light-transmitting plate 1 may be a glass carrier plate, or may be other light-transmitting substrate materials.

The adhesive film 2 is transparent, preferably a high temperature and high viscosity resistant adhesive film 2, and comprises a PE film (polyethylene film) and a glue layer on the surface of the PE film. The glue layer is made of a mixture of silica gel, hydroquinone and acrylic acid copolymer. The thickness of the adhesive glue film 2 is 400-500 micrometers.

The substrate 4 may be a PCB substrate 4, a glass substrate, or the like.

The encapsulating material 7 is a thermosetting adhesive, such as epoxy resin, phenolic resin or heterocyclic polymer, and may also be epoxy resin, phenolic resin or heterocyclic polymer doped with carbon black.

Referring to fig. 2 and 3, fig. 2 is a schematic diagram of steps S1-S2, and fig. 3 is a schematic diagram of steps S3-S6. COB display module's preparation technology includes:

s1: a viscous adhesive film 2 is prepared on a light-transmitting plate 1.

The adhesive film 2 is transparent, preferably is a high-temperature-resistant and high-viscosity adhesive film 2, and comprises a PE film and a glue layer on the surface of the PE film, wherein the glue layer is prepared by mixing silica gel, hydroquinone and acrylic acid copolymer.

The preparation of the high-temperature resistant high-viscosity adhesive film 2 comprises the following steps: and (2) under a dust-free condition, paving the PE film on the light-transmitting plate 1, carrying out corona treatment, then coating the mixed glue agent on the corona surface of the PE film, baking and drying at a high temperature of 110-130 ℃, and finally curing at a temperature of 50 ℃ for 36 hours to prepare the high-temperature-resistant and high-viscosity glue film 2 with the thickness of 400-500 micrometers.

S2: and transferring the LED chip 3 on the temporary/transfer substrate S onto the light-transmitting plate 1 in a manner including but not limited to laser stripping, mechanical stripping, chemical etching and the like, wherein one surface of the LED chip 3 with an electrode (not shown) is far away from the light-transmitting plate 1 after the transfer, and the other surface is adhered and fixed on the adhesive film 2.

S3: a diffusion barrier layer 5 is plated on the surface of a welding pad (not shown) on a PCB substrate 4, specifically, a layer of Ni, pt or Pd is prepared by electroplating (electrolysis or chemical), sputtering coating or thermal evaporation coating and the like to be used as the diffusion barrier layer 5, and then, an AuSn layer 6 is added on the diffusion barrier layer 5 by electroplating, sputtering coating or thermal evaporation coating and the like, and the thickness is 3-5 micrometers.

S4: and binding the LED chip 3 together with the light-transmitting plate 1 on the PCB substrate 4, and enabling the LED chip 3 to be in contact positioning with a welding pad on the PCB substrate 4.

Because the LED chip 3 is fixed on the light-transmitting plate 1 through the adhesive glue film 2 without displacement, the LED chip can be conveniently positioned on the welding pad.

S5: and the packaging material 7 is filled between the PCB substrate 4 and the light-transmitting plate 1.

The packaging material 7 is a thermosetting adhesive, the adopted adhesive has good fluidity, the light-transmitting plate 1 and the PCB substrate 4 can be connected, and the adhesive is synchronously cured and molded in the subsequent heating process. The material of the adhesive can be epoxy resin, phenolic resin or heterocyclic polymer, and can also be epoxy resin, phenolic resin or heterocyclic polymer doped with carbon black.

S6: and heating the COB module filled with the adhesive (the heating temperature is 200-260 ℃, and heating is carried out by reflow soldering or baking and the like) to realize eutectic soldering and complete bonding, and the thermosetting adhesive is synchronously cured to firmly connect the PCB substrate 4 and the light-transmitting plate 1 and prevent the LED chip 3 from floating.

The light-transmitting plate 1 can apply certain pressure to the LED chip 3 during bonding, so that the LED chip 3 is fixed, and the phenomenon of die floating is avoided.

The eutectic welding process is that under certain temperature and certain pressure, the chip is rubbed lightly on the gold-plated base to wipe off the unstable oxide layer on the interface, so that the contact surface is melted, and two solid phases form a liquid phase. After cooling, when the temperature is below the "gold-core eutectic point", the crystalline grain forms formed by the liquid phases are combined with each other into a mechanical mixture, i.e.: the gold-core eutectic crystal ensures that the chip is firmly welded on the base and forms good low-resistance ohmic contact.

The LED chip 3 and the AuSn layer 6 on the surface of the welding pad form eutectic welding connection, and then the AuSn layer 6 forms a gold-tin eutectic layer 6.

The diffusion barrier layer 5 is used for preventing metal elements in a welding pad from being immersed into the formed gold-tin eutectic layer 6 under overlong welding time, so that the melting point of the metal elements is increased to cause welding holes, the die bonding strength and the heat conductivity are reduced, and meanwhile, the holes can cause poor ohmic contact and current concentration effect to form destructive thermoelectric breakdown, so that hidden danger is brought to the reliability of an LED device.

For convenience of description and understanding, the number of LED chips is not specified in the specification of the present invention, and is not limited, and as is well known in the art, the number of LED chips in the COB display module is more than one, and usually more. Those skilled in the art can understand that the number of the LED chips in the present invention is greater than 1, and the numbers of the eutectic layer and the diffusion barrier layer correspond to the number of the LED chips, which is not described herein.

In the COB display module of the utility model, the LED chip is fixedly adhered on the light-transmitting plate, so that one side of the LED chip is fixedly connected with the light-transmitting plate, the other side of the LED chip is welded and fixed with the substrate through the eutectic layer, and both sides of the LED chip are fixed, therefore, the fixing effect of the LED chip is enhanced, and the welding reliability is improved; meanwhile, all gaps between the light-transmitting plates and the substrate which are respectively connected with the two sides of the LED chip are filled and packaged by the packaging material, namely the light-transmitting plates and the substrate are bonded together by the packaging material, the bonding area of the light-transmitting plates and the substrate is large, and the effect of fixing the position of the LED chip is further improved.

Additionally, the utility model discloses utilize the light-passing board to come the adhesion chip, play the effect of location chip, bind chip and light-passing board together and carry out the reflow soldering on the base plate, prevent that the chip that the reflow soldering in-process leads to because of the tin cream is uneven from dragging, avoid the chip to appear floating, askew to turn round offset etc. and effectively solve the superficial die problem in the COB shows the processing procedure.

The above-mentioned embodiments only represent several embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention.

Claims (10)

1. The utility model provides a prevent COB display module of chip skew, its characterized in that, includes light-passing board, viscidity glued membrane, LED chip, base plate, eutectic layer and packaging material, the viscidity glued membrane set up in the surface of light-passing board, the LED chip passes through viscidity glued membrane adhesion is fixed in on the light-passing board, and pass through eutectic layer with base plate welded fastening, the packaging material is filled the light-passing board with space between the base plate.

2. The COB display module of claim 1, further including a diffusion barrier layer between the eutectic layer and the substrate, the diffusion barrier layer being fixedly disposed on the substrate.

3. The COB display module of claim 2, wherein the diffusion barrier is at least one of a nickel layer, a platinum layer, a palladium layer.

4. The COB display module of claim 3, wherein the diffusion barrier layer is disposed on the substrate by electroplating, sputter coating, or thermal evaporation coating.

5. The COB display module of claim 1, wherein the eutectic layer is disposed on the substrate by electroplating, sputter coating, or thermal evaporation coating.

6. A COB display module according to claim 1, wherein the eutectic layer has a thickness of 3-5 microns.

7. A COB display module according to any one of claims 1 to 6, wherein the light-transmitting plate is a glass carrier plate.

8. A COB display module according to any one of claims 1 to 6, wherein the adhesive film is light-transmissive.

9. A COB display module according to any one of claims 1 to 6, wherein the adhesive film has a thickness of 400 to 500 μm.

10. A COB display module according to any one of claims 1 to 6, wherein the encapsulant is a thermosetting adhesive.

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