Electronic package including cavity formed by removal of sacrificial material from within a cap
11545952 · 2023-01-03
Assignee
Inventors
- Atsushi Takano (Kadoma, JP)
- Mitsuhiro Furukawa (Nishinomiya, JP)
- Ichiro Kameyama (Katano, JP)
- Tetsuya Uebayashi (Ibaraki, JP)
Cpc classification
B81C2203/0136
PERFORMING OPERATIONS; TRANSPORTING
B81C1/00333
PERFORMING OPERATIONS; TRANSPORTING
H03H9/1085
ELECTRICITY
B81B1/002
PERFORMING OPERATIONS; TRANSPORTING
H03H9/171
ELECTRICITY
H03H9/54
ELECTRICITY
H03H3/08
ELECTRICITY
International classification
H03H3/007
ELECTRICITY
B81C1/00
PERFORMING OPERATIONS; TRANSPORTING
H03H9/54
ELECTRICITY
B81B1/00
PERFORMING OPERATIONS; TRANSPORTING
Abstract
An electronic component comprises a substrate including a main surface on which a functional unit is formed and a cap layer defining a cavity enclosing and covering the functional unit. The cap layer is provided with holes communicating an inside of the cavity with an outside of the cavity. A resin layer covers the cap layer and the main surface and includes one or more bores and a solder layer having a thickness less than a thickness of the resin layer disposed within the one or more bores.
Claims
1. An electronic component comprising: a substrate including a main surface on which a functional unit is formed; a cap layer defining a cavity enclosing and covering the functional unit, the cap layer being provided with holes communicating an inside of the cavity with an outside of the cavity; and a resin layer covering the cap layer and the main surface, the resin layer including one or more bores and a solder layer having a thickness less than a thickness of the resin layer disposed within the one or more bores.
2. The electronic component of claim 1 wherein the cap layer includes a rectangular periphery, the holes being formed at each one of four corners of the rectangular periphery.
3. The electronic component of claim 2 wherein edges of each hole are defined by both the cap layer and the main surface of the substrate.
4. The electronic component of claim 1 wherein the cap layer includes silicon dioxide containing carbon.
5. The electronic component of claim 4 wherein a linear expansion coefficient of the cap layer is substantially the same as a linear expansion coefficient of the resin layer.
6. The electronic component of claim 1 wherein a gap is defined between a periphery of the solder layer and a peripheral surface defined by a corresponding bore.
7. The electronic component of claim 1 wherein the functional unit is one of a surface acoustic wave element or a film bulk acoustic resonator including a mechanically movable portion.
8. The electronic component of claim 1 wherein the substrate includes a dielectric material.
9. The electronic component of claim 8 wherein the substrate includes a piezoelectric dielectric material.
10. The electronic component of claim 1 wherein the holes are defined in a ceiling of the cap layer.
11. The electronic component of claim 1 wherein the cap layer includes a rectangular periphery and each of the one or more bores is positioned proximate a respective corner of the cap layer.
12. An electronic device comprising an electronic component including a substrate having a main surface on which a functional unit is formed, a cap layer defining a cavity enclosing and covering the functional unit, and a first resin layer covering the cap layer and the main surface, the first resin layer including one or more bores and a solder layer having a thickness less than a thickness of the first resin layer disposed within the one or more bores, the cap layer being provided with holes communicating an inside of the cavity with an outside of the cavity.
13. The electronic device of claim 12 further comprising a printed circuit board including electrode pads, each of the electrode pads disposed within a corresponding bore and bonded to the solder layer in the corresponding bore.
14. The electronic device of claim 13 further comprising a second resin layer sealing the printed circuit board and the electronic component.
15. The electronic device of claim 12 wherein the functional unit is one of a surface acoustic wave element or a film bulk acoustic resonator.
16. The electronic device of claim 12 wherein the substrate includes a piezoelectric material.
17. The electronic device of claim 12 wherein the cap layer includes silicon dioxide and between zero and 20 atomic percent carbon relative to silicon in the silicon dioxide.
18. The electronic device of claim 12 wherein the one or more holes are formed in a ceiling of the cap layer.
19. The electronic device of claim 12 wherein edges of each hole are defined by both the cap layer and the main surface of the substrate.
20. The electronic device of claim 12 wherein the solder layer is in electrical communication with the functional unit through a metal layer disposed on the main surface of the substrate.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1)
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(3)
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DETAILED DESCRIPTION
(7) It is to be appreciated that embodiments of the methods and apparatuses discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The methods and apparatuses are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. Any references to front and back, left and right, top and bottom, upper and lower, and vertical and horizontal are intended for convenience of description, not to limit the present systems and methods or their components to any one positional or spatial orientation.
(8) Embodiments directed to an electronic component, an electronic device, and manufacturing methods thereof will now be described with reference to the accompanying drawings. Although a SAW element is illustrated as an example of a MEMS device, aspects and embodiments disclosed herein are not limited to the SAW element but can be applied to a FBAR and other MEMS devices.
(9)
(10) The electronic component 10 includes a substrate 11 formed of dielectric material. A functional unit 13, for example, a SAW element is formed on a main surface 11a of the substrate 11. The functional unit 13 includes a mechanically movable portion having an interdigital transducer (IDT) electrode 12, a SAW propagation path (not shown), and the like. The dielectric material of the substrate 11 may include a piezoelectric single crystal, for example, lithium tantalate or lithium niobate.
(11) The functional unit 13 formed on the main surface 11a of the substrate 11 is enclosed by a cavity 100. The cavity 100 is defined by a cap layer 14 formed of silicon dioxide. A first resin layer 31 covers the main surface 11a of the substrate 11 and the cap layer 14. The cap layer 14 forms a periphery enclosing the cavity 100 on the main surface 11a. The cavity 100 allows the mechanically movable portion to properly operate in the functional unit 13.
(12) The silicon dioxide constituting the cap layer 14 may contain carbon at a certain concentration. The cap layer 14 has a linear expansion coefficient adjusted to be close to that of the first resin layer 31 by containing a suitable amount of carbon. It is to be appreciated that the carbon content of the cap layer 14 may be 20 atomic percent or less relative to silicon because carbon content greater than this amount may degrade the crystallinity of silicon dioxide and decrease the strength of the cap layer 14. Because of the adjustment of the linear expansion coefficient, delamination between the cap layer 14 and the first resin layer 31 can be prevented. Further, inclusion of carbon in the cap layer 14 may improve the adhesion between the cap layer 14 and the first resin layer 31 and therefore increase the heat resistance of the electronic component 10. Still further, the inclusion of carbon may increase the moisture permeability of the cap layer 14 to reduce the amount of moisture remaining within the cavity 100 after fabrication.
(13) The cap layer 14 includes holes 14a, 14b, through which the cavity 100 can communicate with the outside via the cap layer 14. The holes 14a, 14b may include perforations 14a formed only through a ceiling of the cap layer 14. Further, the holes 14a, 14b may include peripheral holes 14b formed along the main surface 11a of the substrate 11. The peripheral holes 14b are disposed on a periphery of the cap layer 14 enclosing the cavity 100 on the main surface 11a. The cavity 100 can communicate with the outside through the peripheral holes 14b when the cap layer 14 is etched as described later. As shown in
(14) As shown in
(15) The peripheral holes 14b can form flow paths along the main surface 11a of the substrate 11. Etching solution may flow through the flow paths from the inside of the cap layer 14 during a wet etching process as described below. As a result, the reflux of the etching solution within the cap layer 14 can be facilitated and the etching process can be accelerated.
(16) Further, the peripheral holes 14b allow the etching solution to easily drain away therethrough during the wet etching process such that the amount of the etching solution remaining within the cavity 100 after the etching process can be reduced. Accordingly, the number of perforations 14a formed through the cap layer 14 to facilitate the flow of the etching solution can be reduced. Thus, the structural strength of the cap layer 14 can be ensured.
(17) The electronic component 10 is provided with a first resin layer 31 to cover the main surface 11a and the cap layer 14. The first resin layer 31 may be formed of thermoset resin material, for example, polyimide or epoxy, in which inorganic fillers, for example, silica and/or alumina may be dispersed.
(18) The first resin layer 31 has a first surface 31a in contact with the main surface 11a of the substrate 11 and a flat second surface 31b in parallel with the main surface 11a. The second surface 31b is a surface opposed to the first surface 31a. The first resin layer 31 is provided with bores 20 opening to the second surface 31b as shown in
(19) It is to be appreciated that the second surface 31b of the first resin layer 31 corresponds to a bottom surface 10a of the electronic component 10. The second surface 31b of the first resin layer 31 is also referred to as a bottom surface 10a of the electronic component 10 hereinafter.
(20) The bore 20 is provided with a metal layer 21 having a certain thickness from the main surface 11a of the substrate 11. The metal layer 21 is connected to the functional unit 13 formed on the main surface 11a via wiring (not shown).
(21) A solder layer 22 is formed in the bore 20 on the metal layer 21. The solder layer 22 has a thickness such that the solder layer 22 does not to extend beyond the second surface 31b of the first resin layer 31. This configuration allows an electrode pad 53 formed on a printed circuit board 51 to be housed into the bore 20 (see
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(23) The printed circuit board 51 may contain halogen at a concentration of, for example, 100 ppm or less to closely match the linear expansion coefficient of the electronic component 10. Closely matching the linear expansion coefficients of the printed circuit board 51 and the electronic component 10 may prevent a break of the connection between the printed circuit board 51 and the electronic component 10 such as a delamination between the solder layer 22 and the electrode pad 53 due to heating and cooling processes.
(24) The printed circuit board 51 includes a flat main surface 51a. The main surface 51a is provided with electrode pads 53, each of which is disposed at a location corresponding to the bore 20 of the electronic component 10. The electronic component 10 is positioned such that a corresponding electrode pad 53 of the printed circuit board 51 can be housed into the bore 20. The solder layer 22 formed on the metal layer 21 of the bore 20 is welded onto the electrode pad 53. It is to be appreciated that the solder layer 22 may have a thickness sufficient to provide an amount of solder sufficient to be used for the welding onto the electrode pad 53.
(25) The welding between the solder layer 22 and the electrode pad 53 is performed by heating the electronic component 10 and the printed circuit board 51 up to a certain temperature, maintaining the temperature for a certain duration of time, and melting the solder layer 22. After the solder layer 22 and the electrode pad 53 are welded, the electronic component 10 and the printed circuit board 51 are cooled. At the time of cooling, the melted solder layer 22 contracts in volume due to the solidification.
(26) The volume contraction may apply a contraction force between the solder layer 22 and the electrode pad 53 in a state that the solder layer 22 is welded and secured onto the electrode pad 53. Accordingly, the bottom surface 10a of the electronic component 10 and the main surface 51a of the printed circuit board 51 are pressure bonded to each other. Consequently, the gap between the bottom surface 10a of the electronic component 10 and the main surface 51a of the printed circuit board 51 can be significantly reduced.
(27) The bottom surface 10a of the electronic component 10 is tightly connected to the main surface 51 of the printed circuit board 51 due to the contraction force applied between the solder layer 22 and the electrode pad 53. Therefore, the first resin layer 31 forming the cavity 100 can be supported substantially entirely by the printed circuit board 51.
(28) The second resin layer 55 sealing the electronic component 10 onto the printed circuit board 51 is formed by transfer molding or compression molding under a temperature of 150° C. or greater and a pressure of several megapascals. The second resin layer 55 may be formed of thermoset resin material, for example, polyimide or epoxy, in which inorganic fillers, for example, silica and/or alumina may be dispersed.
(29) The electronic component 10 has a bottom surface 10a that can be pressure bonded to the main surface 51a of the printed circuit board 51 by a contraction force created when the solder layer 22 is welded onto the electrode pad 53. Therefore, the gap between the bottom surface 10a of the electronic component 10 and the main surface 51a of the printed circuit board 51 can be significantly reduced such that the resin of the second resin layer 55 can be prevented from penetrating into the gap even under the pressure applied by transfer molding or compression molding.
(30) For example, if the gap between the bottom surface 10a of the electronic component 10 and the main surface 51a of the printed circuit board 51 is less than the size of a filler dispersed in the resin material of the second resin layer 55, it would be impossible for the resin material to penetrate into such a gap. In addition, if the resin material of the second resin layer 55 has a thixotropic index higher than a certain value in a resin sealing process of the second resin layer 55, it would be impossible for the resin material to penetrate into such a gap. Therefore, the fillers dispersed in the second resin layer 55 may have an average size of 10 μm or greater. Further, in order to increase the thixotropic index, the content of the fillers may be 65 percent by weight or greater.
(31) In some embodiments, the second resin layer 55 is formed by transfer molding or compression molding. Therefore, the transfer molding or compression molding that can realize a packaging process including a robust and stable resin sealing process may protect the electronic device 50 including the substrate 11 and the electronic component 10.
(32)
(33) In some embodiments, novolac resin is used as the photosensitive organic resin 112. This may allow the sacrificial layer 110 to be formed under low temperatures and also allow the etching process to be performed by wet etching under low temperatures. Therefore, the temperature changes applied to the substrate 111 can be suppressed and the substrate 111 can be prevented from cracking.
(34) As shown in
(35) Utilizing a TEOS-CVD process, it is possible to form a silicon dioxide layer under lower temperatures than a conventional plasma-enhanced chemical vapor deposition (PE-CVD) process. PE-CVD conventionally uses polyimide resin for the sacrificial layer 110 because polyimide has a high temperature tolerance. Ashing may be performed for removing such high temperature tolerant polyimide.
(36) In contrast, in some embodiments, a TEOS-CVD process may allow novolac resin, which can be removed by wet etching but has little high temperature tolerance, to be used for the sacrificial layer 110. In the TEOS-CVD process, carbon is added to the source gas such that the silicon dioxide layer 114 forming a cap layer can contain a certain concentration of carbon as described above.
(37) After the silicon dioxide layer 114 is formed, a resist 116 is deposited on the silicon dioxide layer 114 by spin coating as shown in
(38) As a result, the resist 116 is provided with a pattern corresponding to cap layers having holes as shown in
(39)
(40) In some embodiments, the cap layer 14 covering the functional unit 13 is provided with a plurality of types of holes. Although
(41) After the sacrificial layer 110 is removed as shown in
(42) In some embodiments, the cap layer 14 is provided with the perforations 14a passing only through the cap layer 14 as well as the peripheral holes 14b formed along the periphery of the cap layer 14 on the main surface 111a of the substrate 111. The peripheral holes 14b may facilitate the reflux of the etching solution within the cap layer 14 and the etching process can be accelerated during the process of
(43) Further, the peripheral holes 14b may reduce the etching solution remaining within the cavity 100 after the wet etching process. Therefore, the number of the perforations 14a formed through the cap layer 14 can be less than if no peripheral holes 14b were present and, accordingly, the structural strength of the cap layer 14 can be ensured.
(44) For example, when the cap layer 14 is formed to have a rectangular area on the main surface 111a of the substrate 111 as described above, each of the peripheral holes 14b may be positioned at each one of the four corners of the rectangular cap layer 14. The etching solution can drain away through the peripheral holes 14b formed at the four corners such that the residue of the etching solution can be further reduced. In addition, the accelerated draining of the etching solution through the peripheral holes 14b may allow a reduction in the number of perforations 14a and therefore the structural strength of the cap layer 14 can be further ensured.
(45) It is to be appreciated that an ashing process can be added subsequent to the etching process to remove organic materials still remaining within the cavity 100.
(46) As shown in
(47) As shown in
(48) As shown in
(49) As shown in
(50) As shown in
(51) As described above, in some embodiments, the sacrificial layer 110 is formed of novolac-based photosensitive organic resin and is removed by wet etching after the cap layer 14 is formed of carbon-containing silicon dioxide by TEOS-CVD process. Accordingly, no rapid temperature changes would be applied to the substrate 11 in the series of processes that can proceed under low temperatures. Therefore, the substrate 11 can be prevented from cracking. In addition, the working processes can proceed under low temperatures such that slow heating and slow cooling are not necessary and therefore the productivity of the manufacturing process for the electronic components 10 can be improved.
(52) In some embodiments, the peripheral holes 14b are formed along the periphery of the cap layer 14 on the main surface 11a of substrate 11. Accordingly, the etching solution can drain away through the peripheral holes 14b during the wet etching process such that it is possible to reduce the amount of the etching solution remaining within the cavity defined by the cap layer 14. This can reduce the number of the perforations 14a formed through the cap layer 14 conventionally required for draining the etching solution and therefore the structural strength of the cap layer 14 can be ensured.
(53) In some embodiments, the linear expansion coefficient of the cap layer 14 may be adjusted to be close to that of the first resin layer 31 in contact with the cap layer 14 by adding a suitable amount of carbon to the silicon dioxide forming the cap layer 14. This can improve the adhesion between the cap layer 14 and the first surface 31a of the first resin layer 31 in contact with the cap layer 14 and can prevent the delamination therebetween such that the heat resistance of the electronic components 10 can be improved. In addition, the inclusion of carbon can improve the moisture permeability of the cap layer 14 to reduce the amount of moisture remaining within the cavity 100.
(54) Although the electronic component 10 of the present embodiment can be manufactured by an aforementioned series of processes, these processes are directed merely to an example of the manufacturing method of the electronic component 10.
(55) Referring to
(56) The antenna duplexer 210 may include one or more transmission filters 222 connected between the input node 214 and the common node 212, and one or more reception filters 224 connected between the common node 212 and the output node 216. The passband(s) of the transmission filter(s) are different from the passband(s) of the reception filters. Each of the transmission filter(s) 222 and the reception filter(s) 224 may include an embodiment of an electronic component 10 as disclosed herein. An inductor or other matching component 240 may be connected at the common node 212.
(57) In certain examples, the SAW elements used in the transmission filter 222 or the reception filter 224 are disposed on a single piezoelectric substrate. This structure reduces the effect of changes in temperature upon the frequency responses of the respective filter, in particular, reducing degradation in the passing or attenuation characteristics due to changes in the temperature, because each SAW element changes similarly in response to changes in the ambient temperature. In addition, this arrangement may also allow the transmission filter 222 or reception filter 224 to have a small size.
(58)
(59) The front end module 200′ includes a transceiver 230 that is configured to generate signals for transmission or to process received signals. The transceiver 230 can include the transmitter circuit 232, which can be connected to the input node 214 of the duplexer 210, and the receiver circuit 234, which can be connected to the output node 216 of the duplexer 210, as shown in the example of
(60) Signals generated for transmission by the transmitter circuit 232 are received by a power amplifier (PA) module 260, which amplifies the generated signals from the transceiver 230. The power amplifier module 260 can include one or more power amplifiers. The power amplifier module 260 can be used to amplify a wide variety of RF or other frequency-band transmission signals. For example, the power amplifier module 260 can receive an enable signal that can be used to pulse the output of the power amplifier to aid in transmitting a wireless local area network (WLAN) signal or any other suitable pulsed signal. The power amplifier module 260 can be configured to amplify any of a variety of types of signal, including, for example, a Global System for Mobile (GSM) signal, a code division multiple access (CDMA) signal, a W-CDMA signal, a Long Term Evolution (LTE) signal, or an EDGE signal. In certain embodiments, the power amplifier module 260 and associated components including switches and the like can be fabricated on gallium arsenide (GaAs) substrates using, for example, high-electron mobility transistors (pHEMT) or insulated-gate bipolar transistors (BiFET), or on a Silicon substrate using complementary metal-oxide semiconductor (CMOS) field effect transistors.
(61) Still referring to
(62) The wireless device 300 of
(63) Having described above several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention.