A method for improving the alignment accuracy between LTCC layers and a method for manufacturing LTCC chip devices

Abstract

The present invention provides a method for improving the alignment accuracy between LTCC layers and a method for manufacturing an LTCC chip device. In this alignment method, patterns with high alignment accuracy requirements for adjacent two layers are printed on the front and back sides of the same green ceramic sheet. The same printing alignment marks are used during the printing on the front and back sides, eliminating the influence of positioning pins and punching accuracy on the alignment accuracy between layers, and improving the alignment accuracy between adjacent layers of the LTCC substrate.

Description

Technical Field

[0001] The present invention relates to a method for improving the interlayer alignment accuracy of LTCC and a method for manufacturing an LTCC chip device, belonging to the field of integrated circuit processing technology. Background Art

[0002] LTCC is a multi-layer ceramic substrate fabricated by using processes such as laser drilling, via filling, and precise conductor paste printing on a green ceramic tape, and then stacking multiple green ceramic sheets together and firing them under a specific sintering curve. As Figure 1 shown, in the LTCC laminating process, several positioning holes are drilled around the green ceramic tape, and the green ceramic tape is stacked layer by layer in a certain order on a laminating table with pins. The alignment accuracy of the interlayer patterns is affected by the positioning pins, drilling accuracy, and deformation of the green ceramic during manual film peeling during lamination.

[0003] For LTCC chip devices with pads distributed on both the front and back sides, if the alignment accuracy between the front and back patterns of the substrate is not high, the product will show a phenomenon where the pad sizes on both sides of one side are the same, while the pad sizes on both sides of the other side are different. The pads on the back side (C00) of the product need to be printed after film peeling on the back side of the green ceramic tape. However, the green ceramic will shrink in size when it is released from the restraint of the polyester film. Usually, printing is carried out after lamination. But the green ceramic block will expand after lamination, and there is an offset in the relative position between the back pads printed after lamination and the front pads printed before lamination. If cutting is based on the front pads, the sizes of the two back pads will be asymmetric, as Figure 2 shown. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for improving the interlayer alignment accuracy of LTCC and a method for manufacturing an LTCC chip device, and this alignment method can improve the interlayer alignment accuracy between adjacent layers of the LTCC substrate. [[ID=!21]]

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for improving the interlayer alignment accuracy of LTCC, including the following steps:

[0007] (1) Making Mark points as printing alignment marks with 4 groups of through holes in the non-graphic areas at the four corners of the green ceramic sheet;

[0008] (2) Mirroring the through holes of the B-layer green ceramic sheet;

[0009] (3) Printing the mirror image of the A layer on the front side of the B-layer green ceramic sheet; wherein, the A layer and the B layer are adjacent green ceramic sheets, and the B layer is located below the A layer;

[0010] (4) Place the green ceramic sheet of layer B with the polyester film facing down on the stacking table, and stack the green ceramic sheet of layer A with the polyester film facing up on the stacking table;

[0011] (5) Cover the metal pressing plate on the stacking table, and vacuum encapsulate the green ceramic sheets of layers A and B and the metal pressing plate;

[0012] (6) Put it into a laminator for isostatic pre-pressing. After pre-pressing, the green ceramic sheets of layers A and B become a green ceramic blank;

[0013] (7) Place the green ceramic blank on the vacuum table and remove the polyester film covering the green ceramic sheet of layer B;

[0014] (8) Use the same set of printing alignment marks as when printing the mirror image pattern on layer A to print the pattern of layer B on the back of the green ceramic sheet of layer B.

[0015] Further, in step (5), wrap the green ceramic sheets of layers A and B and the metal pressing plate with a soft rubber sheet and put them into a packaging bag for vacuum encapsulation.

[0016] Further, in step (6), the isostatic pre-pressing includes preheating and lamination;

[0017] The preheating temperature is 70 °C and the preheating time is 10 min.

[0018] The lamination pressure is 500 - 1000 psi, the temperature is 70 °C, and the time is 10 min.

[0019] Further, the lamination pressure of the isostatic pre-pressing is 500 psi.

[0020] Further, it further includes:

[0021] Stack the green ceramic sheets in the layer sequence and determine two adjacent green ceramic sheets.

[0022] The present invention also provides a preparation method of an LTCC chip device, including:

[0023] 1) Stack the green ceramic sheets in the layer sequence;

[0024] 2) Use the aforementioned alignment method to print the required image of the upper green ceramic sheet on the front of the lower green ceramic sheet in a mirror image manner and perform isostatic pre-pressing;

[0025] 3) Remove the polyester film on the back of the substrate;

[0026] 4) Print the pads on the back of the substrate;

[0027] 5) Perform lamination according to the conventional process.

[0028] The beneficial effects achieved by the present invention are:

[0029] (1) The present invention provides a method for improving the interlayer alignment accuracy of LTCC. The patterns with high alignment accuracy requirements for adjacent two layers are printed on the front and back sides of the same green ceramic sheet. The same printing alignment marks are used during the printing of the front and back sides, eliminating the influence of positioning pins and punching accuracy on the interlayer alignment accuracy, and improving the interlayer alignment accuracy of adjacent layers of the LTCC substrate. The interlayer pattern alignment accuracy of the LTCC substrate processed by the present invention is improved from the original ±30μm to ±10μm;

[0030] (2) The present invention changes the timing of removing the polyester film during lamination, reducing the change in the size of the green ceramic film strip caused by film removal;

[0031] (3) The preparation method of the LTCC chip device of the present invention can improve the symmetry of the front and back pads of the LTCC chip device. Description of the Drawings

[0032] Figure 1 is a schematic diagram of the LTCC lamination process;

[0033] Figure 2 is a schematic diagram of the front and back pads;

[0034] Figure 3 is a schematic diagram of the pre-pressing process in the present invention;

[0035] Figure 4 is a schematic diagram of the lamination positioning holes and printing alignment marks in the present invention. Specific Embodiments

[0036] The present invention will be further described below. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention.

[0037] The present invention provides a method for improving the interlayer alignment accuracy of LTCC. The patterns with high alignment accuracy requirements for adjacent two layers are printed on the front and back sides of the same green ceramic sheet. The same printing alignment marks are used during the printing of the front and back sides, eliminating the influence of positioning pins and punching accuracy on the interlayer alignment accuracy.

[0038] Refer to Figure 3 , define layers A and B as adjacent two layers. The specific implementation process of a method for improving the interlayer alignment accuracy of LTCC is as follows:

[0039] 1) Use 4 groups of through-holes to make Mark points as printing alignment marks in the non-pattern areas at the four corners of the green ceramic sheet, as Figure 4 .

[0040] 2) Perform through-hole mirroring on layer B;

[0041] 3) Print the mirror image pattern of layer A on the front side of the green ceramic of layer B;

[0042] 4) Place the green ceramic sheet of layer B with the polyester film side down on the stacking table, and then place the green ceramic sheet of layer A with the polyester film side up on the stacking table;

[0043] 5) Cover the metal pressing plate on the stacking table, wrap the green ceramics of layers A and B and the metal pressing plate with a soft rubber sheet, and put them into a packaging bag for vacuum packaging;

[0044] 6) Put it into a laminator for isostatic pre-pressing. After pre-pressing, the green ceramics of layers A and B have become a green ceramic blank. Due to the small applied pressure, the total deformation of the 6-inch green ceramic is ≤5μm;

[0045] After stacking in this step, a small pressure is applied to complete the substrate pre-pressing. After pre-pressing, the size change of the 6-inch green ceramic blank is within 20μm. Then print the back pads and laminate according to the conventional parameters.

[0046] The pre-pressing parameters in this step are set as follows:

[0047] Preheating: 70°C, 10 min;

[0048] Laminating: pressure 500 - 1000 psi, temperature 70°C, time 10 min.

[0049] 7) Place the green ceramic blank on the vacuum table and remove the polyester film covering layer B.

[0050] 8) Print the pattern of layer B on the back of layer B. At this time, the alignment marks used are the same set as those used when printing the mirror image pattern of layer A, and the polyester film of layer A can still play a role in stabilizing the size of the green ceramic during drying after pattern printing.

[0051] In the present invention, the green ceramic sheets are stacked in the layer sequence, two adjacent green ceramic sheets are determined, and the required image of the upper green ceramic sheet is printed on the front of the lower green ceramic sheet in a mirror image manner.

[0052] In the present invention, for the isostatic pre-pressing in step 6), the preferred laminating pressure is 500 psi.

[0053] The present invention also provides a method for preparing LTCC chip devices, including:

[0054] 1) Stack the green ceramic sheets in the layer sequence;

[0055] 2) Perform pre-pressing on adjacent green ceramic sheets according to the above alignment method;

[0056] 3) Remove the polyester film on the back of the substrate;

[0057] 4) Print the back pads of the substrate;

[0058] 5) Laminating according to the conventional process:

[0059] The parameters are set as:

[0060] ① Preheating: 70°C, 10 min;

[0061] ② Laminating: Pressure 3000 psi, temperature 70°C, time 10 min.

[0062] The LTCC chip device prepared based on this process improves the symmetry of the front and back pads of the LTCC chip device after cutting.

[0063] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for improving the alignment accuracy between LTCC layers, characterized in that, It includes the following steps: (1) Make Mark points as printing alignment marks with 4 groups of through holes in the non-graphic areas at the four corners of the green ceramic chip; (2) Mirror the through holes of the B-layer green ceramic chip; (3) Print the mirror image pattern of the A layer on the front side of the B-layer green ceramic chip; wherein, the A layer and the B layer are adjacent two layers of green ceramic chips, and the B layer is located below the A layer; (4) Place the B-layer green ceramic chip with the polyester film facing down on the stacking table, and place the A-layer green ceramic chip with the polyester film facing up on the stacking table; (5) Cover the metal pressing plate on the stacking table, and wrap the A and B layer green ceramic chips and the metal pressing plate for vacuum encapsulation; (6) Put it into a laminator for isostatic pre-pressing. After pre-pressing, the A and B layer green ceramic chips become a green ceramic blank; (7) Place the green ceramic blank on the vacuum table and remove the polyester film covering the B-layer green ceramic chip; (8) Use the same set of printing alignment marks as when printing the mirror image pattern of the A layer to print the B layer pattern on the back side of the B-layer green ceramic chip.

2. A method for improving the alignment accuracy between LTCC layers according to claim 1, characterized in that, In the step (5), wrap the A and B layer green ceramic chips and the metal pressing plate with a soft rubber sheet and put them into an encapsulation bag for vacuum encapsulation.

3. A method for improving the alignment accuracy between LTCC layers according to claim 1, characterized in that In the step (6), the isostatic pre-pressing includes preheating and lamination; The preheating temperature is 70°C and the preheating time is 10 min; The lamination pressure is 500-1000 psi, the temperature is 70°C, and the time is 10 min.

4. A method for improving the alignment accuracy between LTCC layers according to claim 3, characterized in that The lamination pressure of the isostatic pre-pressing is 500 psi.

5. A method for improving the alignment accuracy between LTCC layers according to claim 1, characterized in that It also includes: Stack the green ceramic chips in the interlayer order to determine two adjacent green ceramic chips.

6. A preparation method of an LTCC chip device, characterized in that, It includes: 1) Stack the green ceramic chips in the interlayer order; 2) Use the alignment method described in any one of claims 1 to 5 to print the required image of the upper green ceramic chip on the front side of the lower green ceramic chip in a mirror image manner and perform isostatic pre-pressing; 3) Remove the polyester film on the back side of the substrate; 4) Print the pads on the back side of the substrate; 5) Perform lamination according to the conventional process.

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