Patent Grant
9934891
Surface mount resistors are widely utilized in electronic devices. One common type of surface mount resistor is the metal strip resistor. A surface mount metal strip resistor may have a value that ranges between 100 micro-Ohms (μΩ) and 10 Ohms (Ω). One exemplary, but non-limiting, use of low ohmic value surface mount metal strips resistors is in current sensing applications. In such applications, the ohmic value of the resistor needs exhibit a relatively precise value.
Conventional techniques for manufacturing surface mount metal strip resistors with relatively precise ohmic values typically suffer from low material utilization, complex manufacturing processes, and the like. Therefore, there is a continuing need for improved manufacturing techniques for surface mount metal strip resistors exhibiting a relatively tight tolerance in their ohmic value.
The present technology may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the present technology directed toward resistors and methods of manufacturing the resistors.
In one embodiment, a method of manufacturing resistors includes coating a resistive material with one or more layers of insulative material. Portions of the insulative material are then removed from the resistive material in a pattern based on a predetermined approximate dimension and predetermined approximate resistance value. A first set of one or more conductive layers are deposited on the portions of the resistive material exposed by the patterned insulative material to form a plurality of conductive pads. A resistance between each set of conductive pads is measured and then a calculated amount of additional insulative material adjacent to the corresponding conductive pads is removed based upon the measured resistance between each set of conductive pads. A second set of one or more conductive layers are then deposited on the first set of one or more conductive layers and the additional exposed portions of the resistive material.
In another embodiment, each resistor includes resistive material, and insulative material disposed on the resistive material between terminations of the resistor. The resistive material has a predetermined resistivity. The insulative material has a substantially uniform thickness and is disposed on a first region of the resistive material. The terminations are disposed at opposing ends of the resistive material. The terminations include a first set of one or more conductive layers disposed on a second region of the resistive material, and a third region of the resistive material at an opposing end from the second region of the resistive material. The terminations also include a second set of one or more conductive layers disposed on the first set of one or more conductive layers, on a fourth region of the resistive material between the insulative material and the first set of one or more conductive layers on the second region of the resistive material, and on a fifth region of the resistive material between the insulative material and the first set of one or more conductive layers on the third region of the resistive material at the opposing end from the second region of the resistive material.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
Embodiments of the present technology are illustrated by way of example and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
Reference will now be made in detail to the embodiments of the present technology, examples of which are illustrated in the accompanying drawings. While the present technology will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present technology, numerous specific details are set forth in order to provide a thorough understanding of the present technology. However, it is understood that the present technology may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present technology.
In this application, the use of the disjunctive is intended to include the conjunctive. The use of definite or indefinite articles is not intended to indicate cardinality. In particular, a reference to “the” object or “a” object is intended to denote also one of a possible plurality of such objects. It is also to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
Referring to
The method begins with coating a resistive material 210 with one or more layers of insulative material 215, at 110, as illustrated in
The resistive material 210 may have a given form factor having a predetermined cross section (e.g., thickness and width). The form factor of the resistive material 210 may have any desired length. In one embodiment, the initial length of the resistive material 210 may be on the order of tens to thousands of resistors to be produced from each length (e.g., a stick). In another embodiment, the initial length of resistive material 210 may be on the order of thousands to hundreds of millions of resistors to be produced from each length (e.g., a spool). The form factor of the resistive material 210 may be produced by any appropriate process such as slitting flat wire or ribbon wire, or by flattening a round wire to a desired cross sectional dimension.
The resistive material 210 is coated on all four lengthwise sides with one or more insulative materials 215, as illustrated in
At 115, portions of the insulative material 215 are removed 220 from the resistive material 210 in a pattern selected based on the approximate dimensions and approximate resistance of resistor to be manufactured, as illustrated in
Optionally, if the resistive material 210 is in a long continuous length (e.g., spool), the resistive material 210 may be shortened into stick lengths before or after selectively removing portions of the insulative material 215, at 120. For example, it may be preferred to coat the resistive material 210 on all sides in one continuous process and then selectively remove portions of the coating of insulative material 215 while the resistive material 210 is in a spool. It may then be preferred to perform the additional processes described herein on sticks of the coated 215 resistive material 210. Shortening the length of the resistive material, for example from a spool to a plurality of sticks, for subsequent processing may provide for improving manufacturability (e.g., cost, quality control, and or the like) of the resistors.
At 125, one or more conductive layers may be deposited on the exposed portions of the resistive material to form a plurality of conductive pads 240, as illustrated in
At 130, sets of conductive pads 240 are probed to measure the resistance value there between. In one embodiment, the resistive material 210 between each pair of adjacent conductive pads 240 is probed to determine a preliminary resistance value of each corresponding resistor to be manufactured. In other embodiments, the resistive material 210 between every second, third, fourth or more conductive pads 240 may be probed. In one implementation, the resistance value between each set of conductive pads 240 may be measured by an appropriate test apparatus via a set of probes 250, as illustrated in
At 135, a calculated amount of additional insulative material is removed 260 adjacent to one or more sets of conductive pads 240 based upon the corresponding measured resistance value. Additional resistive material 210 is exposed between the conductive pads 240 and the remaining insulating material 215, as illustrated in
Alternatively, a calculated amount of a section of resistive material 210 and a section of the coating of insulative material 215 thereon may be removed 265 between one or more sets of conductive pads 240 based upon the measured resistance value, at 140, as illustrated in
In other embodiments, the processes of reducing the resistance value by removing 260 an additional portion of the insulative material 215 adjacent to the sets of conductive pads 240 and increasing the resistance value by removing a section 265 of the resistive material 210 between corresponding sets of conductive pads 240 may be combined to achieve the predetermined resistance value, as illustrated in
The processes of reducing the resistance value and increasing the resistance value may be combined in any order or number of steps. For example, both processes could be used along the same length of resistive material 210, but not both on the same resistor, where the resistor values are centered at the nominal value and some need to be increased in value while other resistors need to be reduced in value, as illustrated in
If the optional process of removing 265 a section of the resistive material 210 and corresponding section of the insulative material 215 between corresponding set of preliminary terminations 240 is utilized, the exposed surface of the resistive material 210 may be re-insulated with an insulative material 275, at 145, as illustrated in
Also illustrated in
At 155, a second set of one or more additional conductive layers may be deposited to form terminations 285 at opposing ends of each piece. The second set of one or more additional conductive layers 285 are deposited over the first and second portions of the conductive pads 270. If applicable, the second set of one or more conductive layers may also be deposited on the exposed 260 resistive material 210 between the each of first and second portions of the conductive pads 270 and the remaining insulating material 215, as illustrated in
Referring now to
The resistor has a predetermined form factor, such as an industry standard or customer specific surface mount resistor package size. Common sizes for surface mount resistors may range between 0.50 by 0.25 millimeters (mm) and 6.40 by 3.20 mm. The geometry may also be reversed and may range between 0.25 by 0.50 mm and 3.20 by 6.50 mm. The resistor may have a value that ranges between 100 micro-Ohms (μΩ) and 10 Ohms (Ω).
Referring now to
Each resistor formed according to the above described method includes terminations on opposing ends. The terminations are advantageously deposited in the transverse direction on a continuous strip of resistive material. The body of the resistor is insulated and the terminations are solderable, wire bondable, or the like. Embodiments of the present technology advantageously results in a very high utilization of materials, particularly when the resistive material is not removed to increase the resistance. The coating method for applying the insulative material may advantageously be done in a continuous method covering all four side of the resistive material.
Embodiments of the present technology use laser etching, abrasive machining or the like to expose resistive material to make an area to form conductive pads. This allows for very precise control of insulative coverage as coating definition becomes a subtractive process instead of the normal additive process.
Embodiments of the present technology also use laser etching, abrasive machining or the like to define the final resistance value of the resistor by changing the coating length of the material between the terminations. This again allows for very precise control of insulative coverage as coating definition becomes a subtractive process instead of the normal additive process. Alternatively or in addition, laser etching, abrasive machining or the like can be used to define the final resistance value of the resistor by removing a cross-section portion of the resistive material between the terminations. Accordingly, the resistance value of the resistor can be changed very easily using laser etching, abrasive machining or the like. In addition, the techniques for making a final adjustment of the resistance value advantageously do not change the outside dimension of the resistors, which may be unacceptable by some customers that want a consistent part size. The constant overall part dimension may also improve automated test/package equipment handling.
The foregoing descriptions of specific embodiments of the present technology have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present technology and its practical application, to thereby enable others skilled in the art to best utilize the present technology and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
The present application is a Divisional Application of, and claims priority to, commonly-assigned U.S. patent application Ser. No. 14/203,234, now U.S. Pat. No. 9,396,849, filed Mar. 10, 2014, entitled “Resistor And Method Of Manufacture,” to Wyatt et al., which is hereby incorporated herein by reference in its entirety.
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| Number | Date | Country | |
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