HK1160547B - Resistor and method for making same - Google Patents

Description

Resistor and method for manufacturing the same

Technical Field

The invention relates to a metal strip resistor with low resistance value and a manufacturing method thereof.

Background

Metal strip resistors (metal strip resistors) have been constructed in various ways previously. For example, U.S. Pat. No.5,287,083 to Zandman and Person discloses plating nickel onto a resistive material. However, this process has limitations on the size of the resulting metal strip resistor. The nickel plating method is limited to larger dimensions due to the method used to determine the geometry of the plating. In addition, the nickel plating method has limitations for resistance measurement at the time of laser trimming.

Another approach is to solder a copper strip to the resistive material to form a termination (termination). Such a method is disclosed in U.S. patent No.5,604,477 to Rainer. This soldering method is limited to larger size resistors because the soldering size takes up space.

Yet another approach is to coat copper onto the resistive material to form the termination, such as disclosed in U.S. patent No.6,401,329 to Smjekal. This cladding method is limited to larger size resistors due to the tolerances of the cutting process used to remove the copper material to define the width and location of the effective resistor elements.

Other methods are disclosed in U.S. patent No.7,327,214 to Tsukada, U.S. patent No.7,330,099 to Tsukada, and U.S. patent No.7,326,999 to Tsukada. These methods also have limitations.

Thus, the methods all have one or more limitations. Therefore, there is a need for a small-sized metal strip resistor having a low resistance value and a method of manufacturing the same.

Disclosure of Invention

It is therefore a principal object, feature and advantage of the present invention to improve upon the prior art and to provide a small size, low resistance metal strip resistor and method of making the same.

According to one aspect of the invention, a metal strip resistor is provided. Such metal strip resistors include a metal strip that forms a resistive element and provides support for the metal strip resistor without the use of a separate substrate. The first and second opposing terminations are wrapped around (overlapping) metal strips. The first terminal end and the second opposing terminal end each have a plating thereon. There is also an insulating material covering the metal strip between the first terminal and the second opposite terminal.

In accordance with another aspect of the present invention, a metal strip resistor is provided. Such metal strip resistors include a metal strip that forms a resistive element and provides support for the metal strip resistor without the use of a separate substrate. The first and second opposite ends are sputtered directly to the metal strip. Each of the first terminal end and the second opposing terminal end has a plating thereon. There is also an insulating material covering the metal strip between the first terminal and the second opposite terminal.

In accordance with yet another aspect of the present invention, a metal strip resistor is provided. Such metal strip resistors include a metal strip that forms a resistive element and provides support for the metal strip resistor without the use of a separate substrate. The bonding layer is sputtered onto the metal strip. The first terminal and the second opposing terminal are sputtered onto the adhesion layer. The first terminal and the second opposing terminal each have a plating thereon, and there is also an insulating material that surrounds the metal strip between the first terminal and the second opposing terminal.

In accordance with another aspect of the present invention, a method is provided for forming a metal strip resistor in which a metal strip provides support to the metal strip resistor without the use of a separate substrate. The method includes applying an insulating material to the metal strip; applying an image mapping process to form a conductive pattern overlying the resistive material, wherein the conductive pattern includes a first terminal and a second opposite terminal; electroplating the conductive pattern; and adjusting the resistance of the metal strip.

In accordance with another aspect of the present invention, a method is provided for forming a metal strip resistor in which a metal strip provides support to the metal strip resistor without the use of a separate substrate. The method includes mating a mask with the metal strip to cover portions of the metal strip; the adhesion layer is sputtered onto the metal strip, the mask prevents the adhesion layer from being deposited on portions of the metal strip covered by the mask, and those portions of the metal strip covered by the mask form a pattern including a first terminal and a second, opposite terminal. The method further includes applying an insulating material to the metal strip and adjusting the resistance of the metal strip.

Drawings

Fig. 1 is a cross-sectional view of one embodiment of a resistor.

Fig. 2 is a cross-sectional view of a resistive material with an adhesion layer and a mask during the manufacturing process.

Fig. 3 is a cross-sectional view during the manufacturing process after the conductive pattern is applied and plated.

Fig. 4 is a cross-sectional view after stripping of material during the manufacturing process.

Fig. 5 is a top view of a resistive sheet during the manufacturing process.

Figure 6 is a top view of the resistive patch during the manufacturing process after the resistance has been adjusted.

Fig. 7 is a top view of the resistive sheet during the manufacturing process with the insulating material covering the exposed resistive material between the terminals.

Fig. 8 is a cross-sectional view of the resistor after a plating process.

Fig. 9 is a plan view showing a resistive sheet of the four-terminal resistor.

Detailed Description

The invention relates to a metal strip resistor and a method of manufacturing a metal strip resistor. This method is suitable for manufacturing a low-ohmic, metal strip surface-mount type resistor of 0402 size or less. The 0402 size is a standard electronic package size for certain passive components having dimensions of 0.04 inch by 0.02 inch (1.0 millimeter by 0.5 millimeter). One example of a smaller size package that may also be used is the 0201 size. In the context of the present invention, a low ohmic value is generally a value suitable for application in power-related applications. Low-ohmic values are typically values less than or equal to 3 ohms, but are often times multiple values in the range of 1 to 1000 milliohms.

The method of manufacturing a metal strip resistor uses a process in which the terminations of the resistor are formed by adding copper to the resistive material by sputtering and plating. This approach employs image mapping masking techniques that allow much smaller and better defined termination features. This approach also allows the use of very thin resistive materials (which is required to achieve the highest values in very small resistors, which do not use a supporting substrate).

Fig. 1 is a cross-sectional view of one embodiment of a metal strip resistor of the present invention. The metal strip resistor 10 is formed from a sheet of resistive material 18 such as, but not limited to EVANOHM (nickel chromium aluminum copper alloy), MANGANIN (copper manganese nickel alloy), or other types of resistive material. The thickness of the resistive material 18 may vary based on the desired resistance. However, the resistive material may be relatively thin, if desired. Note that the resistive material 18 is centered with respect to the resistor 10 and provides support to the resistor 10 and there is no separate substrate.

The resistor 10 shown in fig. 1 also includes an optional adhesion layer 16, which may be formed of CuTiW (copper, titanium, tungsten). An adhesion layer 16, if used, is sputtered on the surface of the resistive material 18 to which the copper plating 14 is bonded. Some resistive materials may require the use of an adhesive layer 16 while others do not. Whether or not the adhesive layer 16 is used depends on the alloy of the resistive material and whether or not it allows the copper plating to be directly bonded by a suitable adhesive. If an adhesive layer 16 is desired and both sides of the resistive material 18 will bear or receive a liner, both sides of the resistive material 18 should be sputter coated with the adhesive layer 16.

Prior to the sputtering process, a metal mask (not shown in fig. 1) may be mated to the sheet of resistive material 18 to prevent deposition of the CuTiW material on those areas of the sheet that will later become the active resistor areas. This mechanical masking step allows gold plating and etch back steps in subsequent processes to be avoided or eliminated, thus reducing cost. When gold plating or other highly conductive plating is used, the gold plating 24 coats the copper plating 14. A plating 28, which may be a nickel plating, is provided. The tin plating 12 is clad with a nickel plating 28 to provide solderability.

Fig. 1 also shows an insulating cover material 20 applied to or applied to the resistive material 18. The insulating cover material 20 is preferably a silicone polyester resistant to high operating temperatures. Other types of insulating materials that are resistant to chemicals and can handle high temperatures can be used.

Fig. 2 illustrates a relatively thin sheet of resistive material, such as EVANOHM, MANGANIN, or other type of resistive material 18. The resistive material 18 serves as a substrate and support structure for the resistor. There is no separate substrate. The thickness of this sheet of resistive material 18 may be selected to achieve a range of higher or lower resistance values. An underside layer of CuTiW (copper, titanium, tungsten) or other suitable material is sputtered onto the surface of the resistive material 18, which serves as an adhesion layer 16 for the copper plating to bond to. A metal mask may be matched to the sheet resistive material 18 prior to the sputtering process to prevent the deposition of the CuTiW material or other material for the adhesion layer 16 on areas of the sheet that will later become the effective resistive areas. This mechanical masking step avoids or eliminates the gold plating and etch back steps in subsequent processes, thereby reducing cost.

An image mapping process is then performed. The image mapping process may include laminating a dry photoresist film 22 to both sides of the resistive material 18 to protect the resistive material 18 from copper plating. A photomask may then be used to expose the photoresist material with a pattern corresponding to the areas of copper to be deposited on the resistive material. The photoresist 22 is then developed and the resistive material is exposed only in areas where copper or other conductive material is to be deposited as shown in fig. 2.

Fig. 3 shows a copper pattern 14. The copper pattern may include individual terminal pads, strips, or nearly complete coverage except for what will become the active resistor area. In the case of using tape or almost entirely covering the graphics, the pad size may be defined in the die cutting operation. The geometry and number of terminal pads can vary depending on the PCB mounting requirements and the electrical connections required (e.g., 2-wire or 4-wire circuit patterns or multi-resistor arrays). The copper 14 is plated in an electrolytic process. A thin layer of Au 24 is plated on the copper. The photoresist is then stripped as shown in fig. 4, and then the CuTiW material 16, which is not covered by the copper plating 14, is stripped from the active resistor area in a chemical etching process. In another embodiment, after the photoresist layer is removed, no gold plating layer 14 is added and the CuTiW layer 16 is not stripped to save manufacturing costs, but this while compromising electrical properties. In yet another embodiment, no gold is added and lift-off is not necessary because the CuTiW material is mechanically masked during the sputtering step.

The resulting terminal plate may be processed as a sheet or section of a sheet, or in a strip of one or two rows of resistors. The processing will be described in this connection as a sheet, but these subsequent processes may also be applied or applied to profiles and strips. As shown in fig. 5, the sheet 19 is a continuous solid body (although alignment holes may be present), and then areas of the sheet 19 may be removed to define the desired dimensions of the length and width of the resistor. Preferably this is done with a die cutting tool, but may also be done by a chemical etching process or by laser machining or mechanical removal of unwanted material.

The resistance value of the unregulated resistor is determined by the spacing of the copper pads, which is defined by the length, width and thickness of the photo mask, the sheet of resistive material. As shown in fig. 6, adjustment of the resistance value may be accomplished by removing material 26 with a laser or other tool to increase the resistance while measuring the resistance value. Adjustment of the resistance value may also be accomplished by adding more termination material (termination material) or other conductive material in areas where the resistive material is still exposed to reduce the resistance value. The resistor works equally well without removing or adding material, but with a wider tolerance or tolerance for the resistance value.

As shown in fig. 7 and 8, the resistor material exposed between the terminals is covered by a cover material or coating material 20, which is an insulating material to prevent plating onto the resistive element and to change its resistance value. The cover material 20 is preferably silicone polyester that is resistant to high operating temperatures, but may be other insulating materials that are resistant to chemicals and can handle high temperatures. The covering material 20 is preferably applied or coated by a conveyor blade. A controlled amount of cover material 20 is deposited on the edges of the paddle and then transferred to the resistor through contact between the paddle and the resistor. Other methods of applying the cover material 20 may also be used, such as screen printing, roller contact transfer, ink jet, and other methods. Then, by baking the resistor in an oven, the covering material 20 is solidified. Any indicia disposed on the cover material 20 will be applied or applied by ink transfer or baking or by laser methods at this point during processing. A die cutter may be used to remove each individual resistor from the carrier plate. Other methods of singulating resistors from a carrier may be used, such as laser dicing or photoresist masking and chemical etching.

The individual resistors then enter a plating process where nickel 28 and tin 12 are added to form a portion that can be soldered to the PCB, as shown in fig. 1. Other plating materials may be used for other mounting methods, such as gold for bonding applications. The DC direct resistance of each component is checked and those parts within tolerance are placed into product packaging, typically a tape or roll, for shipment.

Thus, the present invention has disclosed a strip resistor of low resistance material. The resistor may realize a small-sized package including a 0402 size or smaller. The present invention contemplates numerous variations, including variations in the materials used, whether an adhesive layer is used, whether the resistor is 2-or 4-terminal, the specific resistance value of the resistor, and other variations. In addition, a process for forming a low resistance metal strip resistor has also been disclosed. The present invention contemplates numerous variations, options, and alternatives, including the manner in which the cover material is used, whether a mechanical masking step is used, and other variations.

Claims (34)

1. A metal strip resistor, comprising:

a metal strip forming a resistive element and providing support for the metal strip resistor without the use of a separate substrate;

first and second opposite ends of the metal strip formed by image mapping;

a plating layer on each of the first and second terminals; and

an insulating material encasing the metal strip between the first and second terminations.

2. The metal strip resistor of claim 1 wherein the metal strip is a metal alloy including at least one of nickel, chromium, aluminum, manganese, and copper.

3. The metal strip resistor of claim 1 further comprising an adhesive layer between each terminal and the metal strip.

4. The metal strip resistor of claim 3 wherein the adhesion layer comprises copper, titanium, and tungsten.

5. The metal strip resistor of claim 1 wherein the metal strip resistor is a 1.0 mm x 0.5 mm chip resistor.

6. The metal strip resistor of claim 1 wherein the insulating material comprises polyimide.

7. The metal strip resistor of claim 1 wherein the insulating material is on a top side of the metal strip and an opposite bottom side of the metal strip.

8. The metal strip resistor of claim 7 wherein the first terminal and the second terminal are on a top side of the metal strip and the metal strip resistor further comprises a pair of terminals on a bottom side of the metal strip.

9. The metal strip resistor of claim 8 further comprising a plating on the pair of terminations on the bottom side of the metal strip.

10. The metal strip resistor of claim 1 wherein the first terminal and the second terminal are sputtered directly to the metal strip.

11. The metal strip resistor of claim 10 wherein the metal strip is a metal alloy including at least one of nickel, chromium, aluminum, manganese, and copper.

12. The metal strip resistor of claim 10 wherein the insulating material comprises silicone polyester.

13. The metal strip resistor of claim 10 wherein the metal strip resistor is a 1.0 mm x 0.5 mm chip resistor.

14. The metal strip resistor of claim 1 further comprising an adhesion layer sputtered onto the metal strip.

15. The metal strip resistor of claim 14 wherein the first terminal and the second terminal are sputtered directly to the metal strip.

16. The metal strip resistor of claim 14 wherein the metal strip is a metal alloy including at least one of nickel, chromium, aluminum, manganese, and copper.

17. The metal strip resistor of claim 14 wherein the insulating material comprises silicone polyester.

18. The metal strip resistor of claim 14 wherein the metal strip resistor is a 1.0 mm x 0.5 mm chip resistor.

19. The metal strip resistor of claim 14 wherein the adhesion layer comprises copper, titanium, and tungsten.

20. A method for forming a metal strip resistor wherein a metal strip provides support for the metal strip resistor without the use of a separate substrate, the method comprising:

applying an insulating material to the metal strip;

applying an image mapping process to form a conductive pattern in the insulating material to define a first terminal and a second opposite terminal;

electroplating the conductive pattern; and

the resistance of the metal strip is adjusted.

21. The method of claim 20, further comprising sputtering an adhesion layer to the metal strip prior to applying the image mapping process.

22. The method of claim 21, wherein the adhesion layer comprises copper, titanium, and tungsten.

23. The method of claim 20, wherein the step of applying an image-mapping film to the metal strip comprises: an insulating material is applied to a first side of the metal strip and an insulating material is applied to a second side of the metal strip, and an image mapping process is applied to the first and second sides to form a four-terminal resistor.

24. The method of claim 20, wherein electroplating the conductive pattern comprises electroplating the conductive pattern with gold.

25. The method of claim 20, wherein adjusting the resistance is accomplished using a die cutting tool.

26. The method of claim 20, further comprising applying an insulating material over the metal strip between the first and second ends, and wherein the insulating material comprises silicone polyester.

27. The method of claim 20, wherein the insulating material is applied using a doctor blade.

28. The method of claim 20, wherein the conductive pattern is made of copper.

29. The method of claim 20, wherein the method further comprises singulating the metal strip resistor.

30. The method of claim 20 wherein the method further comprises packaging the metal strip resistor into a 1.0 mm x 0.5 mm chip resistor package.

31. The method of claim 20, wherein adjusting the resistance is performed using a laser.

32. The method of claim 20, wherein the method further comprises mating a mask to the metal strip to cover portions of the metal strip.

33. The method of claim 32, wherein the method further comprises sputtering an adhesive layer onto the metal strip, the mask preventing deposition of the adhesive layer on portions of the metal strip covered by the mask, the portions of the metal strip covered by the mask forming a pattern comprising the first terminals and the second terminals.

34. The method of claim 33 wherein the adhesion layer comprises copper, titanium and tungsten.