Pressure sensor chip connection

Abstract

A pressure sensor system package or substrate (100) has a groove (110). A first material (adhesive) (400) partially fills the groove (110) and is cured. A second material (500) is added over the first material (400). While the second material (adhesive) (500) is still liquid, a pressure sensor die (200) is placed in the groove so that the bottom (222) of the frame (220) rests on top of the first material (400). The second material (500) is then cured to secure the pressure sensor die (200) in place.

Description

Technical Field

[0001] The present invention is directed to a pressure sensor system that reduces the need for precise placement of a pressure sensor die in a package, reduces leakage in the pressure sensor system, and provides consistent connection of the pressure sensor die to the package. Background Art

[0002] Pressure sensor systems have become ubiquitous over the past few years as they have found their way into many types of products. The demand for pressure sensor systems has surged in automotive, industrial, consumer, and medical products and shows no signs of abating.

[0003] A pressure sensor system may include a pressure sensor chip or die and other components. The pressure sensor die may typically include a diaphragm or membrane. Such a membrane may be formed by forming a Wheatstone bridge in a silicon wafer and then etching away silicon from opposing surfaces until a thin layer of silicon is formed beneath the Wheatstone bridge. The resulting membrane may be surrounded by a thicker, unetched portion of the silicon wafer or a frame, wherein the membrane and frame form a cavity. When the pressure sensor die in a pressure sensor system is subjected to pressure, the membrane may respond by changing shape. This change in shape may cause one or more properties of the electronic components on the membrane to change. The characteristics of these changes may be measured, and from these measurements, the magnitude of the pressure may be determined.

[0004] Difficulties may arise in manufacturing pressure sensor systems. Pressure sensor systems may be formed by attaching a pressure sensor die in a pressure sensor package. These packages may have channels that need to be aligned with the cavity of the pressure die during the attachment process. This alignment may require the use of expensive chip placement equipment.

[0005] Variations in the connection area between the pressure sensor die and the pressure sensor package can cause errors in the pressure readings measured by the pressure sensor system. In the worst case, these variations can cause leakage in the connection area. Any leakage path through the connection area can cause the pressure sensor system to not function. In addition, these variations can cause height differences in the pressure sensor die relative to the package, which can cause packaging issues and thus inconsistent performance.

[0006] Problems to be solved are to provide a pressure sensor system and method of assembling a pressure sensor system that reduces the need for precise placement of the pressure sensor die in a package, reduces leakage in the pressure sensor system, and provides consistent connection of the pressure sensor die to the package. Summary of the invention

[0007] This problem is solved by providing a pressure sensor system and method of assembling a pressure sensor system that reduces the need for precise placement of the pressure sensor die in a package, reduces leakage in the pressure sensor system, and provides consistent connection of the pressure sensor die to the package.

[0008] Illustrative embodiments of the present invention may provide a method of assembling a pressure sensor system that does not rely on the use of a high-precision placement system. These and other embodiments of the present invention may provide a package or other substrate having a groove. A first amount of a first material in a liquefied form may be deposited in the groove. The first material may be cured to form a rubbery or flexible layer. A second amount of a second material may be deposited in the groove above the first material. The second material may be at least slightly liquefied. A pressure sensor die having a membrane and a frame may be positioned so that the frame is located in the groove. Pressure may be applied to the pressure sensor die to hold it in place, but in these and other embodiments of the present invention, gravity is sufficient to accomplish this task. The second material may be cured to hold the pressure sensor die in place in the pressure sensor package. The first material may be located in the groove between the bottom of the frame and the bottom of the groove. The second material may surround the bottom of the frame.

[0009] In these and other embodiments of the invention, the package can be formed from plastic, laser direct structured (LDS) material, acrylic, or other material or material combination. Such packaging can be formed by transfer molding or injection molding, with or without inserts, 3D printing or other techniques. In these and other embodiments of the invention, subassemblies, silicon wafers, printed circuit boards, or other structures can be used in place of the package. These can be formed from ceramics, printed circuit board materials (such as FR4), silicon, or other materials or material combinations.

[0010] The first material can be the same as the second material, but the first material and the second material can be different materials. The first and second materials can be room temperature vulcanizing sealants (RTV), silicones, fluorosilicone, gels, epoxy resins, polyurethanes, polymer-based materials, or other materials or combinations thereof. Various additives can be mixed with one or both of the first and second materials before the first and second materials are applied to the groove. For example, colorants such as dyes or pigments can be added. These colorants can provide a desired level of opacity or other optical properties. Hardeners, accelerators, or solvents can be mixed with one or both of the first and second materials. Other materials that adjust the curing rate, curing temperature, or other aspects can also be added to either or both materials. Conductive materials can be added, for example, to provide a shielding or grounding path for the frame of the pressure sensor die.

[0011] Illustrative embodiments of the present invention may provide a pressure sensor system having reduced leakage and consistent attachment of the pressure sensor die to the package. These and other embodiments of the present invention may provide a pressure sensor system having a pressure sensor die including a membrane supported by a frame. The pressure sensor system may also include a package having a top surface and a groove located in the top surface. The bottom of the frame may be located in the groove. A first material may be located in the groove, between the bottom of the frame and the bottom surface of the groove. A second material may be located in the groove and above the first material. The second material may surround the bottom of the frame. As previously described, the first material may be the same as the second material, but the first material and the second material may be different materials. The use of a double layer, particularly a second layer that may surround the bottom of the frame, may reduce leakage through the pressure sensor system. This arrangement may also balance the forces applied to the frame by the first and second materials. Consistent attachment of the pressure sensor die to the package may be achieved by consistently applying a certain amount of the first material and the second material.

[0012] In these and other embodiments of the present invention, different types of pressure sensor systems may be provided. For example, a pressure sensor package may include a channel that forms an opening surrounded by a frame to form a gauge pressure sensor system or a differential pressure sensor system. In an absolute pressure sensor system, the channel may be blocked or missing.

[0013] In these and other embodiments of the present invention, the package can be formed in various ways. For example, the tube can be overmolded to form a substrate, where the tube forms a channel through the substrate. A groove can be formed in the top surface of the substrate so that the top of the tube is exposed in the groove. The pressure sensor die can be placed in the groove as described above so that the exposed portion of the tube is located in the cavity of the pressure sensor die. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0015] Figure 1 shows a cross-section of a pressure sensor system according to an embodiment of the present invention;

[0016] Figure 2 is a top view of a pressure sensor system according to an embodiment of the present invention;

[0017] Figure 3-5 A method of manufacturing a pressure sensor system according to an embodiment of the present invention is shown; and

[0018] Figure 6 A portion of a pressure sensor system according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0019] Figure 1 A cross-section of a pressure sensor system according to an embodiment of the present invention is shown. Figure 1 As such, it is shown for illustrative purposes and does not limit the possible embodiments or claims of the present invention.

[0020] The pressure sensor system may include a pressure sensor package 100. The pressure sensor package (or substrate) 100 may include a trench 110 having a bottom 112. One or more layers of one or more materials may form a layer 300, which may be located in the trench 110. The pressure sensor die 200 may include a membrane 210 and a frame 220. One or more components, such as resistors or transistors (not shown), may be located on or near the membrane 210. For example, a resistor for a Wheatstone bridge may be formed on or near the membrane 210. The bottom 222 of the frame 220 may be surrounded by one or more layers 300. The one or more layers 300 may be located between the bottom 224 of the frame 220 and the bottom 112 of the trench 110.

[0021] In these and other embodiments of the present invention, the pressure sensor package 100 can be formed from plastic, laser direct structuring (LDS) materials, acrylic, or other materials or combinations of materials. The pressure sensor package 100 can be formed by transfer molding or injection molding, with or without inserts, 3D printing, or other techniques. In these and other embodiments of the present invention, subassemblies, silicon wafers, printed circuit boards, or other structures can be used in place of the pressure sensor package 100. These can be formed from ceramics, printed circuit board materials (such as FR4), silicon, or other materials or combinations of materials.

[0022] These and other embodiments of the present invention can be used to form different types of pressure sensor systems. For example, channel 120 can be included to form a gauge pressure system or a differential pressure system. Channel 120 can be blocked or absent to form an absolute pressure sensor.

[0023] Figure 2 is a top view of a pressure sensor system according to an embodiment of the present invention. In this example, the pressure sensor package 100 may include a groove 110. The pressure sensor die 200 may have a frame 220 located in the groove 110. As previously described, one or more layers 300 may be located in the groove 110. The channel 120 may form an opening below the membrane 210 of the pressure sensor die 200. The frame 220 may surround the opening formed by the channel 120 on its side.

[0024] Figure 3-5A method for manufacturing a pressure sensor system according to an embodiment of the present invention is shown. Figure 3 In the embodiment of the present invention, a pressure sensor package 100 and a pressure sensor die 200 may be provided. The pressure sensor package 100 may include a channel 120 and a trench 110 .

[0025] exist Figure 4 In the embodiment of the present invention, a first amount of a first material 400 can be deposited, applied or otherwise placed in the groove 110. The first material 400 can be a room temperature vulcanizing sealant (RTV), silicone, fluorosilicone, gel, epoxy, polyurethane, polymer-based material or other material or combination thereof. Various additives can be mixed with the first material 400 before the first material 400 is applied to the groove. For example, a colorant such as a dye or pigment can be added. These colorants can provide a desired level of opacity or other optical properties. A hardener, accelerator or solvent can be mixed with the first material 400. Other materials that adjust the curing rate, curing temperature or other aspects can also be added to the first material 400. Conductive materials can be added, such as to provide a shielding or grounding path for the frame of the pressure sensor die. The first material 400 can then be cured. In these and other embodiments of the present invention, the first amount of the first material 400 can be accurately provided so that the final height of the pressure sensor die 200 relative to the pressure sensor package 100 can be consistent.

[0026] exist Figure 5In the embodiment of the present invention, a second amount of a second material 500 can be deposited, coated or otherwise placed in the groove 110 of the pressure sensor package 100 over the first material 400. The second material 500 can be a room temperature vulcanizing sealant (RTV), silicone, fluorosilicone, gel, epoxy, polyurethane, polymer-based material, or other material or combination thereof. Various additives can be mixed with the second material 500 before the second material 500 is applied to the groove. For example, a colorant such as a dye or pigment can be added. These colorants can provide a desired level of opacity or other optical properties. A hardener, accelerator or solvent can be mixed with the second material 500. Other materials that adjust the curing rate, curing temperature or other aspects can also be added to the second material 500. Conductive materials can be added, for example, to provide a shielding or grounding path for the frame of the pressure sensor die. Although the second amount of the second material 500 is at least somewhat liquefied, the pressure sensor die 200 can be placed in the groove 110. Specifically, the frame 220 can be placed in the groove 110 so that the channel 120 has an opening below the membrane 210. A force may be applied to the pressure sensor die 200 to hold the pressure sensor die 200 in place. In these and other embodiments of the invention, gravity is sufficient to accomplish this task. The second material 500 may be cured to hold the pressure sensor die 200 in place.

[0027] In this arrangement, bottom 222 of frame 220 of pressure sensor die 200 may be surrounded on vertical sides by second material 500. First material 400 may be located between bottom 224 of frame 220 and bottom 112 of trench 110. This helps reduce leakage paths through the pressure sensor system.

[0028] In this example, the pressure sensor system can remain functional even when the pressure sensor die 200 is misaligned by a distance 590. This is true for misalignment in both the X and Y directions. This error tolerance can allow the pressure sensor system to be manufactured without the need for expensive placement equipment.

[0029] In these and other embodiments of the invention, the package may be formed in a variety of ways. An example is shown in the following figure.

[0030] Figure 6A portion of a pressure sensor system according to an embodiment of the present invention is shown. In this example, a tube 600 having a central channel 610 can be provided. A substrate 620 can be formed around the tube 600. The substrate 620 can include a groove or recess 622 on the top side and an opening 624 on the bottom side. The top of the tube 600 can be exposed in the groove or recess 622. The central channel 610 in the tube 600 can provide a path for gas or other fluids from the opening 624 to the back side cavity 230 in the pressure sensor die 200. The bottom of the tube 600 can include a flange at a location 630 to further secure the tube 600 in place in the substrate 620.

[0031] The pressure sensor die 200 may include a frame 220, which may be located in a trench or groove 622 of a substrate 620. The pressure sensor die 200 may also include a membrane 210. The membrane 210 and the frame 220 may define a backside cavity 230 in the pressure sensor die 200.

[0032] As previously described, one or more materials, such as the first material 400 and the second material 500 (eg Figure 4 and Figure 5 ), may be used as an adhesive layer 300 to secure the pressure sensor die 200 in place in a groove or recess 622 of a substrate 620 .

[0033] In this configuration, the pressure sensor die 200 can measure a pressure differential between the top side of the membrane 210 of the pressure sensor die 200 and the opening 624 in the substrate 620 .

[0034] In this example, the overmolded substrate 620 can be formed of plastic, LDS, or other material or combination of materials. The tube 600 can be formed of metal, plastic, ceramic, or other material or combination of materials. The overmolded substrate 620 can be formed by transfer molding or injection molding, with or without inserts, 3D printing, or other techniques. In these and other embodiments of the present invention, subassemblies, silicon wafers, printed circuit boards, or other structures can be used instead of the overmolded substrate 620. These can be formed of ceramic, printed circuit board materials (such as FR4), silicon, or other materials or combinations of materials. For example, the tube 600 can be inserted through an opening in a printed circuit board and fixed in place by welding, applying an adhesive, or other methods.

[0035] The above description of the embodiments of the present invention has been presented for the purpose of illustration and description. This is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the above teachings. These embodiments are selected and described in order to best explain the principles of the invention and its practical application, so that other technical personnel in the field can best utilize the invention in various embodiments, and make various modifications to suit the intended specific use. Therefore, it will be understood that the present invention is intended to cover all modifications and equivalents within the scope of the appended claims.

Claims

1. A pressure sensor system, comprising: a tube (600) having a central passage (610); a base plate (620) formed around the tube (600), having a groove (622) open to the top side, so that the top of the tube (600) is exposed in the groove (622), and the central channel (610) of the tube (600) forms at least a part of the channel through the base plate (620); A pressure sensor die (200) having a membrane (210) supported by a frame (220), wherein the membrane (210) and the frame (220) define a backside cavity (230) in the pressure sensor die (200), and wherein a portion of the frame (220) is located in the groove (622) so that the top of the tube (600) is located in the backside cavity (230) of the pressure sensor die (200) a first material (400) located in the groove (622), wherein the first material (400) is located between the bottom (224) of the frame (220) and the bottom surface (112) of the groove (622); and A second material (500) is located in the groove (622) and on the first material (400), wherein the second material (500) surrounds the bottom (222) of the frame (220) so that the second material is disposed between the bottom (222) and the inner wall of the groove (622) and between the bottom (222) and the tube (600).

2. The pressure sensor system according to claim 1, wherein the substrate (620) is formed by injection molding.

3. The pressure sensor system according to claim 1 or 2, wherein the first material (400) and the second material (500) are one or more adhesives.

4. The pressure sensor system of claim 1, wherein the first material (400) and the second material (500) comprise the same material.

5. The pressure sensor system according to claim 1 or 4, wherein the second material (500) is silicone.

Images