Manufacturing a package using plateable encapsulant
11081417 · 2021-08-03
Assignee
Inventors
- Sook Woon Chan (Melaka, MY)
- Chau Fatt Chiang (Melaka, MY)
- Kok Yau Chua (Melaka, MY)
- Soon Lock Goh (Malacca, MY)
- Swee Kah Lee (Melaka, MY)
- Joachim Mahler (Regensburg, DE)
- Mei Chin NG (Melaka, MY)
- Beng Keh SEE (Melaka, MY)
- Guan Choon Matthew Nelson TEE (Malacca, MY)
Cpc classification
C09D201/00
CHEMISTRY; METALLURGY
C23C18/166
CHEMISTRY; METALLURGY
H01L2224/97
ELECTRICITY
C23C18/1882
CHEMISTRY; METALLURGY
H01L21/568
ELECTRICITY
C23C18/1608
CHEMISTRY; METALLURGY
C23C18/1879
CHEMISTRY; METALLURGY
H01L23/552
ELECTRICITY
H01L2224/97
ELECTRICITY
H01L2223/6677
ELECTRICITY
C23C18/1834
CHEMISTRY; METALLURGY
C23C18/1831
CHEMISTRY; METALLURGY
International classification
H01L23/552
ELECTRICITY
C23C18/16
CHEMISTRY; METALLURGY
C09D5/00
CHEMISTRY; METALLURGY
C09D201/00
CHEMISTRY; METALLURGY
Abstract
A method of manufacturing a package, comprising embedding the semiconductor chip with an encapsulant comprising a transition metal in a concentration in a range between 10 ppm and 10,000 ppm; selectively converting of a part of the transition metal, such that the electrical conductivity of the encapsulant increases; and plating the converted part of the encapsulant with an electrically conductive material.
Claims
1. A method of manufacturing a package, the method comprising: embedding a semiconductor chip with an encapsulant comprising a transition metal in a concentration in a range between 10 ppm and 10,000 ppm, wherein the encapsulant comprises a polymer cluster and a coupling agent between the transition metal and the polymer cluster; selectively converting of a part of the transition metal, such that the electrical conductivity of the encapsulant increases; and plating the converted part of the encapsulant with an electrically conductive material.
2. The Method according to claim 1, further comprising electrically coupling of a redistribution layer with the semiconductor chip.
3. The Method according to claim 1, wherein the encapsulant is a mold compound.
4. The Method according to claim 1, wherein the plating comprises a plating of an outer lateral sidewall of the converted part of the encapsulant with an electrically conductive material.
5. The Method according to claim 1, wherein the sidewall of the encapsulant is exposed before the plating, in particular is exposed by sawing, while the encapsulant of the package is arranged on a temporary carrier.
6. The Method according to claim 1, wherein the selectively converting of a part of the transition metal comprises a laser treatment.
7. The Method according to claim 1, wherein the selectively converting of a part of the transition metal comprises a chemical reduction.
8. The Method according to claim 1, wherein the plating is an electroless plating.
9. The Method according to claim 1, wherein the transition metal is selected from one of the group consisting of palladium, nickel and copper.
10. The Method according to claim 1, wherein the semiconductor chip is a power semiconductor chip.
11. The Method according to claim 1, wherein an external periphery comprises a at least one of a printed circuit board, an antenna structure, a wiring connections for such an antenna structure, an EMI shielding structures and a passive component.
12. The Method according to claim 1, coupling a complexing agent to the transition metal, in particular configured to enhance a chemical stearic effect to maintain an electrically insulating behaviour of the transition metal in a bulk mold compound.
13. The Method according to claim 1, wherein the polymer cluster comprises at least one material of a group consisting of a wax, an adhesion promoter, a mold compound catalyst, and a coupling agent for silica.
14. The Method according to claim 1, wherein the polymer cluster comprises at least one rest, in particular at least one of a hydrophobic group, and a hydrophilic group.
15. The Method according to claim 1, the method further comprising removing a surface portion of the polymer cluster to thereby expose the transition metal; activating the exposed transition metal.
16. The method according to claim 1, wherein the transition metal is presented in the form of organometallic compound.
17. A package, comprising: at least one semiconductor chip; and an encapsulant in which the semiconductor chip is embedded; wherein the encapsulant comprises a transition metal in a concentration in a range between 10 ppm and 10,000 ppm, wherein the encapsulant comprises a polymer cluster and a coupling agent between the transition metal and the polymer cluster, wherein a part of the transition metal comprises a converted part configured for providing an electrical conductivity of the encapsulant, wherein the converted part of the transition metal of the encapsulant is plated with an electrically conductive material.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The accompanying drawings, which are included to provide a further understanding of exemplary embodiments of the invention and constitute a part of the specification, illustrate exemplary embodiments of the invention.
(2) In the drawings:
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DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
(29) The illustration in the drawing is schematically and not to scale.
(30) Before exemplary embodiments will be described in more detail referring to the figures, some general considerations will be summarized based on which exemplary embodiments have been developed.
(31) According to one aspect of the invention, a plateable encapsulant such as a plateable mold compound for semiconductor packages is provided.
(32) Current plating technology on thermoset epoxy mold compound is not catalytically selective. This may cause plating not only on a substrate, but for example also on a jig and a carrier. Moreover, current plating technology on thermoset epoxy mold compound requires chemically roughening using high corrosive chemicals, such as desmear chemistry and glass etch chemistry, which may limit the selection of an appropriate material for carrier and jig.
(33) According to another aspect of the invention, integration of an antenna structure in a semiconductor package is made possible. For this purpose, a plateable encapsulant may be advantageously used for rendering a semiconductor package more compact than possible with conventional approaches.
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(35) The package 100 comprises a first mold compound as a first encapsulant 102 which is configured so that electrically conductive material 106 is plateable thereon. Moreover, the package 100 comprises a second mold compound as a second encapsulant 104 which is configured so that electrically conductive material 106 is not plateable thereon. Two semiconductor chips 108 are fully embedded in the first encapsulant 102. A lateral sidewall of the first encapsulant 102 is plated with electrically conductive material 106. Furthermore, the package 100 comprises a redistribution layer 110 on and in the second encapsulant 104 and being electrically coupled with the semiconductor chips 108. Via exposed surface portions of the redistribution layer 110, an electrically conductive coupling between the semiconductor chips 108 and an electronic periphery such as a printed circuit board (PCB, not shown) may be accomplished.
(36) As can be taken from detail 150 in
(37) In the shown embodiment it is not necessary to roughen the compound surface with corrosive chemical, by using laser roughing, mechanical sawing or proprietary adhesion promoter.
(38) A selectivity area of plating in terms of the z-axis (i.e. the vertical axis according to
(39) The metallic catalyst in form of the transition metal particles 156, which may provide the first encapsulant 102 with a plateable property, may comprise or consists of active metallic particles (such as Pd.sup.0) and none-active metallic particles (such as Pd.sup.2+) within the package 100. Addition of a wax, adhesion promoter and/or catalyst is possible. The none-active metallic particles may comprise or consist of organo-metallic particles such as organo-palladium, organo-copper or organo-nickel. The total metallic amount of the first encapsulant 102 may be in a range from 0.05 weight % to 0.15 weight %. None-active organo-metallic particles may be ionized by a plasma such as Ar and/or H.sub.2 plasma, for instance being operated for a time interval in a range between 5 minutes and 20 minutes, or more.
(40) For patterned plating, selective laser treatment (in terms of activation) using for example a 1064 nm wavelength or a wavelength longer than 1064 nm with a pulse duration in the range of nanoseconds may be followed by an activation. Such an activation may be accomplished by an ionization process using alkaline base solution for example by adding 50 g/l to 70 g/l of NaOH or KOH. After that, the manufacturing method may proceed with the supply of a reducing agent. Subsequently, electroless plating may be carried out. Electroless plating on dicing tape enables package side wall plating without affecting the geometry of plating and the package saw cost. The described method is for instance applicable to an epoxy based mold compound using transfer molding.
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(43) The premix 300 comprises a transition metal A (which may be present in organometallic form or bound in a compound), a polymer cluster D, and a coupling agent B coupling the transition metal A with the polymer cluster D. The transition metal A may comprise or consist of palladium, nickel and/or copper. The coupling agent B may comprise an N (nitrogen) from an amino group or an azole group, or a C (carbon) from a carbonyl group, or a P (phosphor) from an organophosphine group. The premix 300 moreover comprises a complexing agent which is here embodied in the form of three rests R1, R1′, R1″ coupled to the transition metal A. Alternatively, the complexing agent may comprise only one, only two or at least four rests. The complexing agent may be configured to enhance a chemical stearic effect. The polymer cluster D comprises in the shown embodiment a polymeric core C with two rests R2, R3. Alternatively, the polymer cluster D may comprise no rest, only one rest or at least three rests. For example, one of the rests R2 may be a hydrophobic group, and the other rest R3 may be a hydrophilic group. For example, the polymer cluster D may comprise a wax, an adhesion promoter, a mold compound catalyst and/or a coupling agent for silica.
(44) A mold compound type encapsulant 102, which may be manufactured based on the premix 300 and which may be used for encapsulating semiconductor chip 108 may hence comprise an electrically insulating encapsulant base material in form of part C of the polymer cluster D, and an activatable plating catalyst in form of the transition metal A being convertible from a deactivated state, in which the encapsulant 102 is non-plateable with electrically conductive material 106, into an activated state, in which the encapsulant 102 is plateable with electrically conductive material 106. The plating catalyst in form of the transition metal A comprises a metallic material being electrically insulating or poorly conductive in the deactivated state and being electrically conductive in the activated state. An inactive material in form of at least part of the rests R1, R1′, R1″, R2, R3 may cover the plating catalyst A in the deactivated state and may be removable for exposing the plating catalyst in form of the transition metal A for activation. For example, this removing can be accomplished by a laser treatment and/or a plasma treatment.
(45) The premix 300 of the plateable encapsulant 102 shown in
(46) Hence, a process and an apparatus are provided which first use a thermoset mold material formulation comprising or consisting of a transition metal-polymer matrix to mold semiconductor package 100. The transition metal-polymer matrix may be composed of:
(47) A=Transition metal, preferably Pd, Ni, and/or Cu, wherein the concentration of the transition metal may be in the range from 25 ppm to 2000 ppm
(48) B=Coupling agent between transition metal A and polymer cluster D (from wax component, mold compound catalyst, silica coupling agent), either N from amino group or azole group, C from carbonyl group and P from organophosphine group.
(49) D=Polymer cluster (such as wax, adhesion promoter, mold compound catalyst, and/or coupling agent for silica)
(50) R1, R1′, R1″=Complexing agent preferably comprising or consisting of an aromatic ring to enhance a chemical stearic effect to maintain electrical insulative behavior of transition metal A in bulk mold compound.
(51) R2=may be a hydrophobic group, hydrocarbon, either aliphatic or aromatic
(52) R3=may be a hydrophilic group, carbonyl functional group, epoxy group or hydrophobic group hydrocarbon, either aliphatic or aromatic.
(53) In one embodiment, a transition metal complex may be provided in wax (through carbonyl ester).
(54) In another embodiment, a transition metal complex may be provided in a filler (for instance through amino base silane chemical).
(55) In a further embodiment, a transition metal complex may be provided in a catalyst (for instance through amino base chemical or azole base or phosphine).
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(57) As can be taken from a schematically illustrated structure 400, a basis for the described method of manufacturing a plateable encapsulant 102 is the provision of a transition metal-polymer compound or premix 300 comprising transition metal A (in the shown embodiment palladium in a “2+” charging state) and a polymer cluster D composed of polymer core C and rests R2, R3. Also the above-described coupling agent (in the described embodiment only one rest R1) is provided. This results in the structure 400 which is schematically shown in
(58) In order to obtain a structure 440, a surface portion of both the hydrophilic structure 404 and the hydrophobic structure 406 (i.e. a portion of the rests R2, R3 of the polymer cluster D as well as a portion of the rest R1) is removed to thereby pattern the hydrophilic structure 404 and the hydrophobic structure 406. Consequently, a portion of the transition metal A is exposed for subsequent activation and plating. To obtain structure 440, firstly a portion of the hydrophobic structure 406 is removed by laser processing to thereby obtain intermediate structure 420. Secondly, an exposed portion of the hydrophilic structure 404 is removed by treatment with an alkaline base such as NaOH or KOH to obtain structure 440. Hence, part of the inactive material R1, R2, R3 is removed to thereby expose part of the plating catalyst in form of the still deactivated transition metal A for subsequently converting part of the transition metal A from the deactivated state (palladium in the “2+” charging state) into the activated state (palladium in the “0” charging state).
(59) The exposed surface of the transition metal A (palladium in the “2+” charging state) of the structure 440 can then be activated in terms of platability by a chemical reduction (thereby converting the palladium from the “2+” charging state into the electrically neutralized “0” charging state). By this activation, the palladium becomes properly electrically conductive and thereby becomes able to serve as a base for plating electrically conductive material 106 thereon, see structure 460. Consequently, the converting of part of the transition metal A for activation comprises electrically neutralizing previously electrically charged material of the transition metal A.
(60) Thus, in order to obtain structure 460, the electrically conductive material 106 (for instance nickel) is formed by electroless plating on the exposed and activated surface of the transition metal A.
(61) Summarizing, the activation and ionization process according to
(62) By laser processing (preferably using a wavelength in a range from 1060 nm to 2700 nm) of structure 400, a portion of the hydrophilic structure 404 or hydrophilic component at the transition metal-polymer matrix is exposed, thereby obtaining structure 420. This is followed by an ionization using an alkaline base (for example NaOH or KOH) with a concentration of 30 g/l to 70 g/l to activate the transition metal-polymer matrix in the mold compound to enable the plating process.
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(64) As an alternative to the method described referring to
(65) As a further alternative to this, it is possible to use an Ar+H.sub.2 plasma which can eliminate the necessity for a reduction process in plating.
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(67) In order to remove part of the hydrophilic structure 404 and of the hydrophobic structure 406, an inverse part of the inactive material in form of the rests R1, R2, R3 may be converted into non-plateable material by carbonization. Consequently, structure 600 with a carbonized structure as non-plateable material 602 is obtained. In order to obtain structure 620 according to
(68) Alternatively to the methods described referring to
(69) By using a high power laser, it is possible to carbonize the non-plating area on the package body, see transition from structure 400 to structure 600 according to
(70) The plateable mold compound manufactured according to
(71) For example, the packages 100 shown in
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(78) A process flow may be as follows:
(79) 1. An argon plasma or laser treatment may be used to remove a hydrophobic component of an organometallic which is attach to a wax, an adhesion promoter, a catalyst and coupling agent, etc.
(80) 2. Ionization of the organometallic can be carried out, for example by an Argon plasma or by NaOH.
(81) 3. Activation of the epoxy's compound organometallic may be carried out by reduction of ion novel metal by a reduction agent. An active surface may act as catalyst surface.
(82) A corresponding chemical reaction can be:
Pd.sup.2++Red.fwdarw.Pd+O
(83) 4. The active surface will become electrically conductive for electroless plating via catalyst by palladium, and it will go through a redox process in metal aqueous solution.
(84) A chemical reaction regarding an oxidation of the reducing agent may be as follows:
Red−Ox+ne
(85) Reduction of nickel ion (catalysed by a catalyst) may be as follows:
mNi.sup.2++2me.sup.−.fwdarw.mNi.sup.0,2m=n
(86) Overall or sum reaction:
mNi.sup.2++Red.fwdarw.mNi.sup.0+Ox
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(88) In a block 1302, post mold curing is performed. In a subsequent block 1304, laser roughening on the top side and laser marking is carried out. In a subsequent block 1306, the package is sawn with a chemical resistance ultraviolet tape/selective ultraviolet treatment. Copper roughening is carried out in a subsequent block 1308. Subsequently, a plasma is applied (such as an argon and/or hydrogen plasma), see block 1310. In a subsequent block 1312, ultrasonic cleaning in water is carried out. In the following block 1314, a palladium activator for the copper surface is provided. In an optional subsequent block 1316, a reducing agent is added. Next, nickel is deposited in an electroless procedure, see block 1318. Finally, post processing can be carried out (see block 1320).
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(96) According to
(97) The substrate 2004 is a molded interconnect substrate with redistribution layer 110, solder structure 2002 connected to die pads 2010 via the redistribution layer 110, and the mold compound being of the none plateable type. There is a section of the second encapsulant 104 constituting a mold compound protrusion extending from and beyond the substrate 2004 as isolation bars for preventing metal plating at side walls in the four corners of the package 100. The semiconductor chip 108 is configured as a functional chip with attached die pad 2010 and is molded within the plateable first encapsulant 102 as plateable mold compound. Package 100 may be thinned down to expose the isolation bar(s). To obtain package 100, solder mask printing and curing may be carried out, as well as package singularization to expose the package sidewalls, followed by electroless plating.
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(99) In the embodiment of
(100) The plateable first encapsulant 102 may comprise a dielectric material with a high dielectric constant. In the embodiment of
(101) According to
(102) The semiconductor chip 108 is attached to die pad 2010 and encapsulated (here molded) with plateable mold compound in form of the first encapsulant 102. The package 100 may be thinned down to expose the isolation bar(s). It is furthermore possible to carry out solder mask printing and curing, package singulation to expose the package sidewall, followed by electroless plating.
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(104) In the embodiment of
(105) Hence, the embodiment of
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(107) As can be taken from block 2302, substrate 2004 can be manufactured with non-plateable mold compound protrusion (i.e. with the isolation bar(s)). As can be taken from a subsequent block 2304, semiconductor chip 108 can then be attached to the substrate 2004. As can be taken from a subsequent block 2306, the obtained structure may be molded with the plateable first encapsulant 102. As can be taken from a subsequent block 2308, laser marking can then be carried out. As can be taken from a subsequent block 2310, the obtained structure may be processed by backgrinding. As can be taken from a subsequent block 2312, a solder mask 2006 may then be printed and cured. As can be taken from a subsequent block 2314, the packages may then be sawn with mold compound facing up and with a chemical resistance tape. As can be taken from a subsequent block 2316, an adhesion promoter may be applied by spraying and may be cured. As can be taken from a subsequent block 2318, metal on the surface may be roughened. As can be taken from a subsequent block 2320, a plasma treatment may be carried out, for example by argon and/or hydrogen. As can be taken from a subsequent block 2322, a metal such as copper may be applied in an electroless plating procedure. As can be taken from a subsequent block 2324, a surface finish may be applied, for example ENIG (electroless nickel immersion gold). The resulting structure may be tested, see block 2326.
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(109) As compared to the flowchart 2300, block 2306 is substituted by separate blocks 2402 and 2404 according to flowchart 2400. According to block 2402, an isolation mold attach procedure is carried out, followed by overmolding by a plateable mold compound (see block 2404).
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(111) According to
(112) According to
(113) According to
(114) According to
(115) According to
(116) According to
(117) According to
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(122) In the following exemplary Aspects are described:
(123) Aspect 1. A package, comprising: a first encapsulant configured so that electrically conductive material is plateable thereon; a second encapsulant configured so that electrically conductive material is not plateable thereon.
(124) Aspect 2. The package according to aspect 1, comprising at least one semiconductor chip at least partially encapsulated in the first encapsulant.
(125) Aspect 3. The package according to aspect 1, comprising at least one antenna structure at least partially on and/or in at least one of the first encapsulant and the second encapsulant, in particular at least partially located at a surface of the package.
(126) Aspect 4. The package according to aspect 1, wherein at least one of the first encapsulant and the second encapsulant is a mold compound, in particular a mold compound with activated or deactivated organometallic cluster component, more particularly organometallic polymer cluster component, in a mold matrix.
(127) Aspect 5. The package according to aspect 1, wherein at least part of a surface of the first encapsulant is plated with electrically conductive material.
(128) Aspect 6. The package according to aspect 5, comprising at least one of the following features: at least part of a lateral sidewall of the first encapsulant is plated with electrically conductive material; at least part of a planar wall of the first encapsulant is plated with a planar layer of electrically conductive material.
(129) Aspect 7. The package according to aspect 5, wherein the plated electrically conductive material is configured for at least one of the group consisting of: for electrically connecting at least one semiconductor chip with at least one antenna structure; for providing an electromagnetic interference shielding of the package; for electrically connecting at least one semiconductor chip with at least one solder structure.
(130) Aspect 8. The package according to aspect 1, wherein at least part of the second encapsulant is configured as at least one vertically extending isolation bar vertically protruding into the first encapsulant, in particular at least one vertically extending isolation bar forming at least one corner section of the package.
(131) Aspect 9. A method of manufacturing a package, the method comprising: configuring a first encapsulant so that electrically conductive material is plateable thereon; configuring a second encapsulant so that electrically conductive material is not plateable thereon; plating, in particular electroless plating, electrically conductive material selectively on a surface of the first encapsulant without plating electrically conductive material on a surface of the second encapsulant.
(132) Aspect 10. The method according to aspect 9, wherein a surface, in particular a sidewall, of the first encapsulant is exposed before the plating, in particular is exposed by sawing while the first encapsulant and the second encapsulant of the package are arranged on a temporary carrier.
(133) Aspect 11. A premix of a plateable encapsulant, the premix comprising: a transition metal; a polymer cluster; and a coupling agent between the transition metal and the polymer cluster.
(134) Aspect 12. The premix according to aspect 11, wherein the polymer cluster comprises at least one material of a group consisting of a wax, an adhesion promoter, a mold compound catalyst, and a coupling agent for silica.
(135) Aspect 13. The premix according to aspect 11, wherein the polymer cluster comprises at least one rest, in particular at least one of a hydrophobic group, and a hydrophilic group.
(136) Aspect 14. The premix according to aspect 11, further comprising a complexing agent coupled to the transition metal, in particular configured to enhance a chemical stearic effect to maintain an electrically insulating behaviour of the transition metal in a bulk mold compound.
(137) Aspect 15. The premix according to aspect 11, wherein the transition metal is provided in a concentration in a range between 10 ppm and 10,000 ppm, in particular 25 ppm and 2,000 ppm.
(138) Aspect 16. A method of manufacturing a plateable encapsulant, the method comprising: providing a transition metal-polymer compound comprising a transition metal and a polymer cluster; removing a surface portion of the polymer cluster, in particular a surface portion of the polymeric structure and of a complexing agent, to thereby expose the transition metal; activating the exposed transition metal.
(139) Aspect 17. The method according to aspect 16, wherein the method comprises using, as the transition metal-polymer compound, a premix according to aspect 10.
(140) Aspect 18. An encapsulant for encapsulating a semiconductor chip, wherein the encapsulant comprises: an electrically insulating encapsulant base material; an activatable plating catalyst being convertible from a deactivated state, in which the encapsulant is non-plateable with electrically conductive material, into an activated state, in which the encapsulant is plateable with electrically conductive material.
(141) Aspect 19. The encapsulant according to aspect 18, wherein the plating catalyst comprises a metallic material being electrically insulating in the deactivated state and being electrically conductive in the activated state.
(142) Aspect 20. The encapsulant according to aspect 18, comprising an inactive material covering the plating catalyst in the deactivated state and being removable, in particular by at least one of the group consisting of a laser treatment and a plasma treatment, for exposing the plating catalyst for activation.
(143) Aspect 21. The encapsulant according to aspect 18, wherein the activatable plating catalyst is convertible into the activated state so that a planar wall of the encapsulant is plateable with a planar layer of electrically conductive material.
(144) Aspect 22. A method of manufacturing an encapsulant, wherein the method comprises: providing a compound comprising an electrically insulating encapsulant base material and an activatable plating catalyst in a deactivated state, in which the compound is non-plateable with electrically conductive material; converting at least part of the plating catalyst from the deactivated state into an activated state, in which the compound is plateable with electrically conductive material.
(145) Aspect 23. The method according to aspect 22, wherein the compound further comprises an inactive material covering the plating catalyst in the deactivated state; wherein the method further comprises removing at least part of the inactive material to thereby expose at least part of the plating catalyst for subsequently converting at least part of the plating catalyst from the deactivated state into the activated state.
(146) Aspect 24. The method according to aspect 23, wherein the removing comprises patterning the inactive material.
(147) Aspect 25. The method according to aspect 23, wherein the removing comprises: converting part of the inactive material into non-plateable material; removing a remaining non-converted part of the inactive material to thereby expose part of the plating catalyst for subsequently converting part of the plating catalyst from the deactivated state into the activated state.
(148) Aspect 26. The method according to aspect 22, wherein the converting of at least part of the plating catalyst comprises electrically neutralizing previously electrically charged metallic material of the plating catalyst.
(149) It should be noted that the term “comprising” does not exclude other elements or features and the “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs shall not be construed as limiting the scope of the claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.