JP2009529790A - Manufacturing process of printed wiring board having conductive suppression core - Google Patents

Abstract

A method of manufacturing a printed wiring board that includes a conductive constraining core with a single lamination cycle is disclosed. An example of the method of the present invention is to drill a clearance pattern in a conductive constraining core, to form a B-stage (semi-cured) layer of dielectric material and at least one functional layer on each side of the constraining core. Placing the conductive constraining core in a laminate containing an additional layer of material placed and reflowing the resin in the dielectric B-stage (semi-cured) layer prior to curing and plating through-hole drilling Performing a lamination cycle on the laminate filling the clearance pattern of the conductive constraining core.
[Selection] Figure 1

Description

  The present invention relates generally to the manufacture of printed wiring boards (PWB), and more particularly to filling the clearance pattern of a conductive constraining core layer used in the construction of multilayer printed wiring boards.

  Computers and similar electronic products are pervasive throughout consumer, corporate, military, aerospace, and government activities. The use of electronic devices in critical applications has increased the demand for reliable electronic devices. Many applications require electronic devices that operate for a long period of time with shorter downtime than previously assumed.

  Consumers who place importance on reliability extend to PWB. By using PWB, an electrical connection can be established between devices. In some examples, the device can be mounted on a printed wiring board. The manner in which the device is attached usually depends on the packaging of the device. Printed circuit board applications can include issues such as thermal management, control of expansion mismatch, low stiffness or stiffness, and relatively high weight. Materials used in the past to solve some of these problems include thick metal cores, CIC (Copper-Invar-Copper), and CMC (Copper-Moly-Copper). These metal core materials are electrically conductive and require special processing to be incorporated in the structure of the printed wiring board. These special processes can include clearance pattern drilling, surface pretreatment, clearance pattern filling, and additional lamination steps. The use of these materials and associated additional processes is usually associated with significantly lower manufacturing yields and additional labor costs. Furthermore, perforation of small via holes or plated through holes (PTH) penetrating through a thick metal core may be a problem. Failure to drill small via holes through the material will limit the usefulness of the material in building high density interconnects.

  Various other materials can be used in place of the metal materials described above to solve reliability issues such as thermal management, expansion mismatch control, low stiffness or stiffness, and relatively high weight. It is. U.S. Patent No. 6,869,664 to Vasoya et al., U.S. Patent Application No. 11 / 131,130 to Vasoya, U.S. Patent Application No. 11 / 376,806 to Vasoya, and U.S. Provisional Patent Application No. 60/831 to Vasoya. , 108 discloses a technique that can be used to produce printed wiring boards with a desired coefficient of thermal expansion (CTE) using a layer containing a carbon material such as woven carbon fiber. is doing. U.S. Patent No. 6,869,664 to Vasoya et al., U.S. Patent Application No. 11 / 131,130 to Vasoya, U.S. Patent Application No. 11 / 376,806 to Vasoya, and U.S. Provisional Patent Application No. 60/831 to Vasoya. , 108 is hereby incorporated by reference in its entirety.

  Describes a manufacturing method for drilling and filling printed wiring boards and conductivity constraining core clearance patterns. One aspect of some embodiments of the present invention is the incorporation of a conductive confinement core into the PWB using an existing process for manufacturing a PWB that does not include a conductive confinement core. A further aspect of the invention is the production of a PWB that includes a conductive constraining core using a single lamination cycle. A further aspect of the invention is the generation of a PWB that includes a conductive constraining core that does not require a separate lamination cycle to fill the clearance pattern in the constraining core prior to combining the constraining core with other layers in the PWB. is there.

  One embodiment of the method of the present invention includes drilling a clearance pattern in a conductive constraining core, forming a B-stage (semi-cured) layer of dielectric material and at least one functional layer on each side of the constraining core. Placing the conductive constraining core in a laminate containing additional material layers arranged to reflow the resin in the dielectric B-stage (semi-cured) layer before drilling through the cured and plated through holes Performing a lamination cycle on the laminate that fills the clearance pattern in the conductive constraining core.

  Further embodiments include extracting from the printed circuit board design information regarding the location of the plated through holes that are not intended to be in electrical contact with the conductive constraining core, Determining a clearance pattern using information about the location of the plated through hole that is not intended to be in good contact.

  In another embodiment, the conductive constraining core comprises two major surfaces and can conduct electricity directly from one major surface to another.

  In yet another embodiment, the conductive constraining core has a dielectric constant greater than 6 at 1 MHz.

  In yet another embodiment, the conductive constraining core is constructed using a fibrous material impregnated with resin.

  In a further embodiment, the fibrous material is carbon fiber.

  In a further embodiment, the carbon fibers are metallized.

  In yet another embodiment, the conductive constraining core is constructed from a thick metal layer.

  Another further embodiment also includes screening the resin in the clearance pattern of the conductive constraining core prior to lamination.

  Still another embodiment includes a step of laminating a plurality of conductive suppression cores, a step of drilling a clearance pattern in the laminate of the conductive suppression cores, and a step of generating a lamination positioning hole in the conductive suppression cores. , Including.

  Yet another embodiment includes printing and etching the conductive constraining core to remove debris prior to lamination.

  In a further embodiment, the dielectric B-stage (semi-cured) layer is a prepreg and the stack includes a layer of conductive material.

  In yet another embodiment, the dielectric B-stage (semi-cured) layer comprises a resin content of at least 70% by volume.

  In yet additional embodiments, the region of the conductive constraining core is constructed using a base substrate material, and at least one region of the conductive constraining core is constructed using an insert substrate material. Yes.

  Yet another additional embodiment includes selecting a base substrate material, removing a portion of the base substrate material, selecting an insert substrate material, and within the removed portion of the base substrate material. Cutting an insert substrate material piece that can be accommodated and disposing the base substrate material and the insert substrate material piece as part of the laminate.

  In a further embodiment, the step of drilling the clearance pattern includes determining the location of the clearance channel and the required width from the printed circuit board design, and using the selected drill bit and drill pitch to select the channel. Determining the distance between notches that are likely to be generated when drilling and selecting the drill bit and drill pitch so that the distance between the notches exceeds the required channel width. .

  Yet another embodiment uses a printed wiring board design to identify a plated through hole that creates an electrical connection with the conductive constraining core closest to the clearance channel; and Determining the distance between the plated through-holes identified and selecting the drill bit and drilling pitch such that the resulting channel does not overlap the identified plated through-hole location. Contains.

  Another further embodiment includes determining the height of the notch and selecting the drill bit and drilling pitch such that the height of the notch is less than 3 mils (76.2 microns). Contains.

  Yet another embodiment includes selecting the drill bit and drill pitch so that the height of the notch is less than 1 mil (25.4 microns).

  Referring now to the drawings, a process for manufacturing a printed wiring board including a conductive suppression core is shown. In many embodiments, the printed wiring board is constructed using a single lamination cycle. In some embodiments, a process is performed on the conductive constraining core and other materials used in the construction of the printed wiring board to produce a laminate, which is then laminated into a single lamination cycle. Is formed on the printed wiring board. In other embodiments, printing can be performed without requiring a separate lamination cycle to fill the clearance holes drilled in the conductive constraining core prior to bonding the core to other functional layers of the printed wiring board. A wiring board is generated. The use of a single lamination cycle and / or elimination of the lamination cycle can significantly improve yield and throughput compared to a manufacturing process that uses multiple lamination cycles. In some embodiments, the conductive constraining core includes a carbon material. In other embodiments, the conductive constraining core is a thick metal core. In many embodiments, the conductive constraining core includes local regions with different physical properties, such as CTE.

  One embodiment of a printed wiring board (PWB) according to the present invention is shown in FIG. The PWB 10 includes a number of electronic devices 12 housed in different types of packaging. The printed wiring board includes regions having different CETs. The location of the electronic device on the printed wiring board is determined so that each electronic device is arranged in a region of the printed wiring board having a CTE that matches the CTE of the electronic device. Typically, the target CTE is the in-plane CTE of both the device packaging and the printed wiring board. The compatibility of the packaging device CTE and the printed circuit board region CTE mainly depends on the operating requirements of the particular application intended to use the printed circuit board.

  A cross section of the PWB 10 shown in FIG. 1 is shown in FIG. PWB 10 includes several functional and structural layers constructed from a variety of materials. The functional layer of the PWB is a layer intended to establish circuitry between the electronic devices and / or to contain circuitry that carries signals including a reference voltage such as a power supply or ground voltage. The structural layer of the PWB is a layer that is not intended to establish a connection between electronic devices and / or accommodate circuit traces that carry signals. The structural layer is included because of its physical properties.

  The PWB 10 shown in FIG. 2 includes a conductive suppression core 20 that can function as a structural layer, as a functional layer, or as a structural layer in some parts and as a functional layer in other parts. Yes. Throughout the specification, the conductive suppression core layer is referred to as a suppression core. The constraining core 20 includes regions constructed from different materials. The illustrated embodiment includes a region 22 constructed from a base material and at least one region 24 constructed from an insert material. In the example where there are multiple regions 24 constructed from the insert material, each of the insert materials can have different physical properties. By selecting the base and insert material, the physical properties of the constraining core 20 can be customized. In many embodiments, the regions are combined into a single layer by using a resin 26, or equivalent thermoset or thermoplastic material such as an adhesive. The resin can provide structural support to various areas of the material. Also, in many embodiments, the resin electrically insulates the constraining core 20 from the adjacent layer 28 of conductive material. The remaining portion of the PWB includes a layer 30 of conductive material that can form a functional layer of PWB and is separated from each other by a layer 32 of dielectric material. .

  As described further below, by using the techniques described herein, it is possible to combine almost all two types of materials that can be used to construct PWBs. The technique described is whether the base material and the insert material are dielectric materials (ie, effectively hinder the type of electrical signal flow found within the PWB) or non-dielectric materials (ie And whether the resin 26 is dielectric or non-dielectric. Base and insert material options can affect the physical properties of the PWB. In the example where the insert material 24 that forms part of the constraining core 20 is constructed from a material with a different set of physical properties than that of the base material 22, the finished PWB has different physical properties. Can have regions. In many instances, the insert material 24 is selected to provide a region of the PWB having a specific in-plane CTE that matches the in-plane CTE of the device mounted on the PWB.

  In the embodiment shown in FIG. 2, the base material 22 is made of a non-dielectric material such as carbon fiber impregnated with resin such as EP387 and EP450 manufactured by Lewcott Corporation, located in Millbury, MA. The insert material 24 is constructed from a dielectric material such as E glass impregnated with a resin, and the resin 26 that joins the base and the insert material is a dielectric resin.

  The carbon fiber used as the base material in the embodiment shown in FIG. 2 is an example of a non-dielectric material suitable for use in the construction of PWB. Other examples of suitable non-dielectric materials include fibers coated with metal and impregnated with resin, solid carbon plates, Starfire Systems Inc. located in Malta, NY. C-SiC such as C-SiC (Carbon-Silicon Carbide) manufactured by the company, CIC (Copper Inverse Copper), CMC (Copper Molly Copper) by Morgan Advanced, Inc., located in Allentown, PA It includes CVD diamond such as CVD (Chemical Vapor Deposition), diamond, DLC (Diamond Like Carbon), carbon composite and graphite composite, or metal matrix composite. Each of these materials can be clad on at least one side.

  When the non-dielectric material includes carbon fibers, the fibers may be continuous, discontinuous, chopped, or It may be a flake. To use discontinuous fiber, Toho Carbon Fibers Inc. located in Rockwood, Tennessee. It is also possible for the fiber to be spin-broken or stretch broken, such as part number X0219 manufactured by the company. Furthermore, the carbon fibers can include PAN fibers and / or Pitch fibers.

  Suitable fibers for the metal coating include carbon, graphite, aramid, kevlar, quartz, or any combination of these fibers. Metals that can be used to coat the fiber include nickel, copper, palladium, silver, tin, and gold. The coating of fibrous material can be performed by a manufacturer such as Electro Fiber Technologies, located in Stratford, Connecticut.

  Configurations in which fibrous material can be placed include woven mats, unidirectional mats, or non-woven mats. If the material is woven, the material can be plain weave, twill weave, 2 × 2 twill weave, basket weave, leash weave, satin weave, stitched uni weave, or 3D (three dimensional) weave It may be in the form of

  The fibrous material can also be used in a non-woven form such as uni-tape or mat. In many embodiments, in the construction of the region 22 constructed from the first material, a carbon such as a 2 oz mat with grade number 8000040 or a 3 oz mat with 8000047 manufactured by Advanced Fiber NonWovens Company, East Walpole, Massachusetts. A mat is used.

  Carbon plates can be manufactured using compressed carbon powder, carbon flakes, or short chopped carbon fibers.

The constraining core can also be constructed from a composite comprising carbon nanotubes impregnated with a polymer. Carbon nanotubes are available from Raymor Industries Inc. of Canada. Single-walled carbon nanotubes such as C-SWNT (Carbon Single Walled NanoTube) manufactured by the company, National Institute of Advanced Industrial Science and / or Technology, which is located in Tsukuba, Japan. Single-walled carbon nanotubes are an intrinsic form of pure carbon, which are up to 100 times stronger and 1/6 the weight than steel. Since C-SWNT can transmit electricity up to 1000 times faster than copper, it has excellent electrical characteristics. The current density of the carbon nanotubes is 10 ⁹ A / cm ² (1000 times higher than copper). C-SWNT can transfer heat up to 10 times that of copper. The carbon nanotubes can be manufactured using a plasma process, a chemical vapor deposition (CVD) chemical process, a vapor phase CVD process, an arc discharge process, or a laser ablation process. The carbon nanotubes may be less than 1 nm to 100 nm in diameter and <200 nm in length.

  In examples where the non-dielectric material includes a resin (eg, when the substrate is impregnated with a resin), the resin may be epoxy, phenol, BT (Bismaleimide Triazine Epoxy), cyanate ester, and / or BMI. (Polyimide based Bisaleimide), phenol, polyamideimide, polyacrylate, polyphenylene sulfide, tetrafluoroethylene, polysulfone, polyphenylsulfone, polyethersulfone, polyphthalamide, polyacetal, polyketone, polycarbonate, polyphenylene oxide, polyetheretherketone It may be based on or a combination of resins. The basic resins are pyrolytic carbon powders, carbon nanoparticles, carbon nanotubes (diameters in the range <1-100 nm) to modify the physical, mechanical, electrical and thermal properties of the base resin. ), C-SWNT (Carbon Singla Walled Nanotube), carbon powder, carbon particles, diamond powder, boron nitride, alumina, aluminum oxide, aluminum nitride, aluminum hydroxide, magnesium hydroxide, silica powder, and ceramic particles Can also be included. The resin composite can contain 2 to 80% by weight of such a filler. In some embodiments, the filler particle size is limited to 25 μm or less.

  As mentioned above, the insert material 24 shown in FIG. 2 is constructed from a dielectric material. Examples of other dielectric materials that can be used to construct the PWB include aramid, kevlar, or a mixture of these fibrous materials.

  In embodiments where the region 24 constructed from the second material includes a resin, the resin may be an epoxy based resin, a bismaleimide triazine epoxy based resin, a cyanate ester based resin, and / or a polyimide. It may be a based resin. The resin system can also include a filler that changes the properties of the base resin.

  In one embodiment, the resin 26 surrounding regions 24 and 22 is constructed from a thin E glass, such as a 106 style tempered E glass with high resin content, high crack resistance, and high rigidity. In many embodiments, the resin may be based on bismaleimide triazine epoxy, a mixture of epoxy and cyanate ester, based on cyanate ester, based on polyimide, and based on PTFE. The resin 26 can also include one or more adhesives that change the physical properties of the base resin. In many embodiments, the resin has the ability to withstand the forces associated with thermal cycling of various materials in layer 20 that can have different CTEs. Suitable materials include B-stage materials 44N106, 84N106 manufactured by ARLON Electronic Material Division located in Rancho, Cucamonga, CA, USA. Also applicable are B-stage materials of 370HR106, 370106 epoxy and PCL-GIP-785 polyimide 106 manufactured by PolyClad Laminates, located in Franklin, NH, USA. Also applicable are Laser Preg GI30 and 1080 manufactured by ISOLA Laminates, Inc., located in Chandler, Arizona. Other prepreg styles such as 1080, 2113, 2313, 2116, 7628 can also be used.

  Many embodiments of the PWB according to the present invention include a constraining core 20 constructed using at least one or a combination of the aforementioned dielectric and non-dielectric materials. The list provided earlier is not exhaustive. Region 22 constructed from base material and region 24 constructed from insert material can be used substantially alone or in combination with other materials to produce a laminate suitable for use in PWB. Manufactured from all materials. As previously mentioned, material options will typically be affected by the physical properties of the material, including the resulting in-plane CTE in the region of the PWB that incorporates the material.

  In one embodiment, the layers 28 and 30 of conductive material can be constructed from copper foil manufactured by GOLD Electronics, Inc., located in Eastlake, Ohio. Alternatively, the conductive material can be obtained from Ohmega Technologies, Inc., located in Culver City, California. It can also be constructed from a resistive conductive foil such as a resistor-conductor material manufactured by the company. In other embodiments, the conductive material layer may be formed by depositing copper by a chemical process, such as a process used in depositing copper in plated through holes, to form a RCC (Resin Coated Copper), nickel coating. Can be constructed with a coated copper foil, a nickel-gold coated copper foil, and any other material that can be used to construct a PWB. Further, the layer of conductive material may be a layer similar to the suppression core 20 provided on at least a part of the suppression core 20 that functions as a functional layer.

  In one embodiment, the dielectric layer 32 is constructed using E-glass reinforced with resin. In other embodiments, the dielectric layer is an epoxy based material, a cyanate ester based material, a polyimide based material, a GTek material, a PTFE based material, an aramid based material, a short cut It can be constructed from Kevlar based materials, Kevlar based materials, quartz based materials, and any other material that can be used to construct a dielectric layer in a PWB.

  In addition, although many materials are enumerated in the above, the Example of this invention is not limited to use of the above-mentioned material. It is also possible to construct the PWB according to the present invention by using other materials in combination with the manufacturing method described later.

  The method used to construct the PWB according to the present invention depends on the material used to form the constraining core 20. Changes in the manufacturing process are related to the conductivity of the materials used to construct the PWB. In many instances, a layer of PWB can be constructed by cutting multiple portions of the base material and replacing the cut portions with insert material. A first process that can be used in an embodiment of the present invention in which the insert materials used in the construction of the PWB are all dielectric and the resin used to bond the base and the insert material is also dielectric is illustrated in FIG. 3. A second embodiment that can be used in embodiments of the invention in which at least one of the insert materials used to construct the PWB is non-dielectric and / or the resin used to bond the base and the insert material is non-dielectric. Two processes are illustrated in FIG. In the following, examples of embodiments of each type of process according to the invention will be described.

  A method for constructing a PWB in accordance with one embodiment of the present invention is illustrated in FIG. 3 involving the step of using a dielectric insert material to create a region having physical properties different from those of the rest of the PWB. . By using the method shown in FIG. 3, the PWB embodiment shown in FIG. 2 and all other resins used to bond the insert material to the base and insert material are dielectric. This embodiment can be constructed. The method 40 involves providing a base material and an insert material (42). The material preparation can include removing portions of the base material and cutting the insert material and fitting to the removed portion of the base material. Then, as a preparatory work for lamination, the prepared base and insert materials are placed together with a dielectric layer and a layer of conductive material (44). The dielectric layer and the layer of conductive material may be in the form of prepregs and laminates that are clad or unclad. A lamination cycle is then performed to produce a printed wiring board subassembly (46). Holes are drilled in a portion of the printed wiring board subassembly (48) and the lining of the holes is plated with a conductive and / or thermally conductive material (49). The plated printed wiring board subassembly is printed and etched to form a finished PWB (50). The PWB finish is then performed (52) and the components are mounted on the PWB.

  Materials and printed wiring board subassemblies utilized in the manufacturing process shown in FIG. 3 according to one embodiment of the present invention are shown in FIGS. 4a-4h. As described above, the process of manufacturing the PWB shown in FIG. 3 includes providing a base material 60 and an insert material 62. These materials are those used to build a layer similar to the constraining core 20 shown in FIG. The base material 60 is a material constituting most of the restraining core 20.

  In the illustrated embodiment, the base material 60 is non-dielectric and is clad on both sides with a layer of conductive material such as copper. In other embodiments, the base material 60 may be dielectric and / or one side may or may not be clad. In embodiments where the base material is non-dielectric, it is usually necessary to pre-drill the base material prior to lamination.

  The base material can be prepared by drilling a clearance hole 64 and cutting out portion 66. The drilled clearance holes will eventually be filled with resin, which can electrically insulate the non-dielectric base material from the conductive plating of the vias drilled through the PWB. The clipped portion will ultimately define a region of the completed PWB that has physical properties (such as CTE) that are different from those of other regions of the PWB.

  As described above, the insert material 62 is dielectric. Each of the insert materials is cut to a size that fits within the associated cut portion 66 of the base material. Usually, the insert material is cut to a size slightly smaller than the cut area. In one embodiment, a 30 mil gap 68 may be used. In other embodiments, the gap 68 may be a distance in the range of 10 mils to 125 mils. The gap 68 between the insert material 62 and the base material 60 is typically filled with a bonding material such as an adhesive or resin.

  As part of the manufacturing process, the prepared base and insert materials are placed 44 together with the dielectric layer 70 and the conductive material layer 72 in preparation for the lamination cycle. This process can be understood by referring to FIGS. 4c-4e. First, a laminate 74 whose both surfaces are clad with the conductive material 72 is collected, and the material is arranged by laminating the first prepreg 76 on the clad laminate. Usually, the conductive layer adjacent to the prepreg is etched by a circuit pattern. In the illustrated embodiment, the clad laminate 74 and first prepreg 76 are manufactured using any of the well-known manufacturing methods utilized by those skilled in the art.

  Next, the base material 60 is disposed on the first prepreg 76. As described above, the base material can be prepared by drilling the clearance hole 64 and creating a cut portion 66. The insert material 62 is then placed in the cut portion 66. The insert material 62 is cut so that a gap remains between the insert material 62 and the base material 60 when inserted into the cut portion 66. Arrangement 78 is completed by placing second prepreg layer 80 over the layer formed by base material 60 and insert material 62. A laminate, clad on both sides with a layer 82 of conductive material, is then placed over the second prepreg. The conductive layer 82 adjacent to the second prepreg can be pre-etched with a circuit pattern. The resulting configuration is shown in FIG. 4e. Although the illustrated embodiment includes one prepreg and one laminate above and below the base material 60, other embodiments may include a plurality of patterned claps to form a plurality of functional layers. A coded laminate and / or prepreg may be included on each side of the base material 60. Indeed, each PWB according to the present invention can be constructed using two prepregs, each of which is clad on one side and placed above and below the layer formed by the base and insert material. Further, many embodiments include multiple layers formed by bonding a base material with at least one insert material.

  Next, a lamination cycle is executed (46). The properties of the lamination cycle depend on the properties of the prepreg and dielectric layers used in the configuration 78. Resin, prepreg, and laminate manufacturers specify recommended temperature and pressure conditions during lamination. The lamination cycle is feasible by adhering to the recommendations of the various material manufacturers used in the construction of the PWB.

  The lamination cycle produces the printed wiring board subassembly 84 according to one embodiment of the present invention shown in FIG. 4f. As a result of the lamination cycle, the resin 86 fills the gap 68 between the base material 60 and the insert material 62 and bonds them together. Resin 86 also fills clearance hole 64 and bonds layers 90 and 91 of conductive material to layer 20 ′ formed by base material 60 and insert material 62.

  A through hole is drilled in the printed wiring board subassembly (48). A perforated printed wiring board subassembly is shown in FIG. 4g. The printed wiring board subassembly includes a number of holes 92 that extend through each of the layers of the printed wiring board subassembly.

  After the holes have been drilled, the holes are plated (49) and the layer of conductive material is printed and etched (50). These processes generate circuits on and between the layers of PWB. As described above, the functional layer can include a layer of conductive material and a region of layer 20 '. By using circuits generated between functional layers, electrical signals can be carried. By mounting an electronic device on the PWB, a finished PWB similar to the finished PWB shown in FIG. 2 (ie, the PWB to which the electronic device is to be connected or attached) can be generated.

  As mentioned above, the method used to construct the PWB according to the present invention depends on the material used to form the layer of PWB. A method of the present invention that can be used wherein the PWB layer includes at least one insert material that is non-dielectric with the base material and / or the resin used to bond the base and the insert material is non-dielectric. An example is shown in FIG. Process 100 includes providing a base material and an insert material (102). Next, as a preparatory work for lamination, the prepared base material and insert material are placed together with the resin and conductive material layers (104). A printed wiring board subassembly is then generated (106) by performing a first lamination cycle. A hole is then drilled through the printed wiring board subassembly to create a clearance hole (108). The printed wiring board subassembly is then printed, etched, and oxidized (110). Next, as a preparatory work for the second lamination cycle, the printed wiring board subassembly is placed together with the resin layer and the conductive material layer (112). A second lamination cycle is then performed to produce a second printed wiring board subassembly (114). The second printed wiring board subassembly may include a drilled hole therein (116). These holes can be lined with conductive and / or thermally conductive material (118). After the hole lining is complete, the printed wiring board subassembly can be printed and etched (120) and then a substrate finish can be performed (122).

  The materials and printed wiring board subassemblies utilized in the manufacturing process shown in FIG. 5 are shown in FIGS. 6a-6k. As described above, the process of manufacturing the PWB according to the present invention shown in FIG. 5 includes providing a base material 60 'and an insert material 62'. These materials are those used to build a layer similar to the constraining core 20 shown in FIG. Similar to the method shown in FIG. 3, the base material constitutes the majority of the constraining core 20 and is prepared by cutting away a portion of the material. These cut portions 66 'will ultimately contain the insert material 62', which may have physical properties (such as CTE) that are different from the physical properties of other regions of the substrate. A part of the wiring board after completion is defined.

  In the illustrated embodiment, the base material 60 'can be dielectric or non-dielectric and the insert material 62' is non-dielectric. Each of the insert materials is cut to a size that fits within the associated cut portion 66 'of the base material 60'. As described above, the insert material has been cut to a size slightly smaller than the cut-out region 66 'and has tolerances similar to those described in relation to FIGS. 3 and 4a-4h. Is possible.

  At the time of manufacture, the prepared base and insert material are arranged together with the resin-containing layer (104). In many embodiments, the resin-containing layer is in the form of a prepreg. The prepreg may be a substrate and / or a resin film impregnated with a dielectric resin. Typically, the resin used in the prepreg is selected to fill the cut clearance around the insert material during lamination.

  The structure of the layer including the base material, the insert material, and the resin can be understood with reference to FIGS. 6c to 6e. First, a layer of prepreg 70 ′ is laminated onto foil 72 ′ (see FIG. 6 c), then base material 60 ′ is placed over the prepreg and insert material 62 ′ is cut away from the base material. 66 '. The configuration is completed by placing a second prepreg 70 'on the layer formed by the base material 60' and the insert material 62 ', and then placing a second foil 72' on the second prepreg. The final configuration 138 is shown in FIG. In other embodiments, a prepreg clad on one side can be used.

  A first lamination cycle is performed to produce the printed wiring board subassembly 139 shown in FIG. 6f (106). Typically, the lamination cycle is performed in accordance with the manufacturer's recommendations for the various materials used to form configuration 138. During lamination, the resin from the prepreg 70 'will flow and fill the gap 68' between the base material 60 'and the insert material 62'. During lamination, the resin softens, gels, and hardens to join the base material 60 'to the insert material 62'. The resin also bonds the layer formed by the base material 60 'and the insert material 62' to the conductive material layer 72 '.

  Following lamination, clearance holes 140 can be drilled into the printed wiring board subassembly 139 (108). A printed wiring board subassembly with a clearance hole 140 drilled is shown in FIG. 6g. Finally, these clearance holes are filled with a dielectric material such as a dielectric resin, and plated vias are drilled through the clearance holes filled with the resin. The dielectric material filling the clearance hole functions to electrically insulate the base material 60 'and the insert material 62' from the plated via drilled through the clearance hole.

  Following the drilling of the clearance hole, a layer of conductive material is printed, etched, and oxidized to create a clearance pad and debris is removed (110). The printed wiring board subassembly can then be placed (112) along with the prepreg 70 'and the layer of conductive material 72' in preparation for a second lamination cycle. In one embodiment, a laminate 142 is formed using a laminate 142 clad on both sides with a layer of conductive material, a printed wiring board subassembly 139 and a prepreg 144 disposed between the laminates. ing. The laminate 142 has a circuit pattern etched on the layer of conductive material facing the prepreg 144. The laminate can then be completed by adding another prepreg 146 and another laminate 148, both sides of which are clad with a conductive material. A circuit pattern is etched on the layer of conductive material of the laminate 148 facing the prepreg 146. The construction of the clad laminates 142 and 148 and prepregs 144 and 146 can be achieved using conventional manufacturing methods. Note that the laminate shown in FIG. 6h includes one prepreg and one clad laminate above and below the printed wiring board subassembly. One side of the prepreg can be included on the top and bottom of the assembly. Alternatively, embodiments of the present invention can include multiple prepregs and / or laminates. In many embodiments, a PWB can be generated by combining multiple printed wiring board subassemblies as a single stack. Furthermore, this printed wiring board subassembly can also be used as a layer in the construction of a PWB by the method shown in FIG.

  A second lamination cycle is performed (114) to produce the second printed wiring board subassembly shown in FIG. 6i. Again, the characteristics of the lamination cycle performed depend on the recommendations of the manufacturer of the material used to construct the PWB. During lamination, the resin 150 from the prepregs 144 and 146 flows to fill the hole 140. Following lamination, the resin in the prepregs 144 and 146 bonds the layers of the second printed wiring board subassembly together.

  After the second lamination cycle is complete, holes 152 can be drilled in the second printed wiring board subassembly to create mounting holes and plating vias (116). One embodiment 149 of a second printed wiring board subassembly having perforated through holes 152 is shown in FIG. These holes can then be lined to produce plated vias 154, as shown in FIG. 6k. Following the lining of the holes, the outer layer of PWB can be printed and etched (120) prior to finishing the PWB (122) and mounting the component on the PWB.

  An embodiment 160 of a PWB according to the present invention that includes a base material that functions as a functional layer within the PWB is shown in FIG. The illustrated PWB 160 can be constructed according to the process shown in FIG. By using plated through holes 162, an electrical connection is established between the base material and circuits patterned on other conductive layers of the PWB.

  In the above description regarding the production of PWB according to the present invention, a specific material is referred to, but any material that can be used for the production of PWB is used as a base material or an insert material in the production of PWB according to the present invention. It can be used. The combination of materials for forming the PWB according to the present invention depends mainly on the glass transition temperature of the material. In embodiments using C-stage material (ie, material that has already experienced a complete cure cycle) as the insert material, the base material has a glass transition temperature that is less than or equal to the glass transition temperature of the C-stage insert material. It may be a stage material (ie semi-cured material). This is also true when the base material is a C stage material and the insert material is a B stage material. Furthermore, similar considerations in selecting the resin used to bond the base and insert materials should be used when the base and insert materials are C-staged materials. The choice of manufacturing method after the material selection is complete depends on whether the insert material and / or any of the resins used to bond the base material and the insert material are non-dielectric. As described above, if the insert material and the resin used to combine the base material and the insert material are dielectric, either the process shown in FIG. 3 or the process shown in FIG. Can be used to use PWB. If one of the insert materials is electrically conductive and the plating via penetrates the insert material, the process shown in FIG. 5 will typically be used.

  The foregoing method relates to a technique for manufacturing a PWB that includes a constraining core that combines a base and an insert material. Referring now to FIGS. 8-18g, various types of suppression cores that do not require a lamination cycle to be applied to the suppression core prior to combining the suppression core with other materials used in the construction of the PWB. A generalized method for constructing a PWB is disclosed. In some embodiments, the PWB is constructed using a single lamination cycle. In other embodiments, the PWB is constructed using multiple lamination cycles. In many embodiments, a single lamination cycle is used to fill the clearance pattern and / or join the base and insert substrate material and bond the constraining core to the adjacent functional layer. .

  A process for manufacturing a PWB including at least one constraining core according to one embodiment of the present invention is illustrated in FIG. Process 200 includes reviewing and preparing Gerber data for manufacturing PWB (202). This consideration involves determining minimum trace size, minimum gap between traces, minimum via hole size, drilling aspect ratio, signal impedance requirements, dimensional tolerances, surface finish requirements, flatness tolerances, and / or final cutting requirements. It will be. In many embodiments, the PWB design includes an insert material having a CTE that matches the CTE of the component attached to the PWB. Then, after processing the constraining core layer (204), a B-stage (semi-cured) dielectric prepreg is used and laminated (206) with the other inner layers. Then, following lamination, PWB finishing can be performed (208). It should be noted that the above process includes a single lamination cycle, but in other embodiments, in the first lamination cycle, the patterned constraining core is replaced with a B-stage dielectric prepreg and other layers of PWB. It can be combined with the material being used to build and the PWB can be completed in subsequent lamination cycles.

  PWB Gerber data that includes an embodiment of the present invention typically includes a functional layer and a non-functional layer. Functional layers include signal layer, signal routing layer, trace layer, circuit layer, ground plane layer, power plane layer, split plane layer, reference plane layer, ground heat plane layer, mix plane layer, embedded passive layer, and integrated circuit , Bare die, and / or layers that contribute to electrical communication with other devices connected to the PWB. Non-functional layers usually include fab drawings, drill drawings, drill data, solder mask layers, silk screen layers, solder paste layers, thermal plane layers, mechanical reinforcement layers, structural layers, and devices connected to the PWB. Includes other layers that do not contribute to electrical communication.

  A cross-sectional view of a constraining core according to one embodiment of the present invention is shown in FIG. The suppression core 212 includes a conductive layer 214 sandwiched between the first cladding layer 216 and the second cladding layer 218. It should be noted that although the embodiment shown in FIG. 9 includes a cladding layer on both sides, the embodiment of the constraining core according to the present invention can also include cladding on only one side. The configuration with a constraining core with a cladding layer on one or both sides of the constraining layer shown in FIG. 9 can be referred to as a “cladded composite laminate” or a “cladded laminate”.

  The restraining core 212 can transfer electricity from the first cladding layer 216 to the second cladding layer 218 through the conductive layer 214. In some embodiments, the constraining core has a dielectric constant greater than 6 at 1 MHz. As described below, various materials can be used to construct the constraining core according to embodiments of the present invention. The choice of material used to construct the constraining core can depend on the benefits required at the final product level, such as heat transfer coefficient, coefficient of thermal expansion, stiffness, and combinations thereof.

  In one embodiment, the conductive layer can be constructed using a fibrous material impregnated with resin. In some embodiments, the fibrous material is CN80-3k, CN80-1.5k, CN-60, CN-50, YS-90 manufactured by Nippon Graphite Fiber, Japan, Mitsubishi Chemical, Japan. Inc. Carbon, graphite fibers such as K13B12, K13C1U, K63D2U manufactured by the company, or T300-3k, T300-1k, K800, K1100 manufactured by Cytec Carbon Fibers LLC, located in Greenville, South Carolina. In other embodiments, metal coated fibers are used to build the conductive layer. The fibrous material can be metallized by metallizing individual fibers and forming the metallized fibers into a fabric, and the fibers can also be metallized after being formed into a fabric, Alternatively, a combination of both metallization processes can be used. Metallizable fibers include carbon, graphite, E glass, S glass, aramid, Kevlar, quartz, liquid crystal polymer, or combinations of these fibers. After metallization is complete, a conductive layer can be formed in accordance with the present invention by impregnating the metallized fiber with resin.

  In one embodiment, the fibrous material impregnated with resin may be continuous carbon fiber. In other embodiments, the fibrous material may be discontinuous carbon fibers. An example of a suitable discontinuous fiber is Toho Carbon Fibers Inc., located in Rockwood, Tennessee. A spin broken fiber such as X0219 manufactured by the company.

  The fibrous material used to construct the constraining core according to embodiments of the present invention may be woven or non-woven. The nonwoven material may have the form of a uni-tape or mat. Examples of suitable carbon mats include 2oz and 3oz of grade numbers 8000040 and 8000047 manufactured by Advanced Fiber NonWovens, East Walpole, Massachusetts, respectively. In other embodiments, any combination of fibrous material and resin can be used that results in a layer having a dielectric constant greater than 6.0 at 1 MHz.

  In some embodiments, the conductive layer can be constructed from PAN-based carbon fibers, Pitch-based carbon fibers, or a combination of both PAN and Pitch fibers.

  Conductive layers according to embodiments of the invention can be constructed by impregnating the fiber with various resins. In some embodiments, the resin used may be an epoxy based resin such as EP387 and EP450 manufactured by Lewcott Corporation, located in Millbury, Massachusetts. In some embodiments, the resin may be based on BT (Bismaleimide Triazine epoxy), BMI (Bismaleimide), cyanate ester, polyimide, phenol, or a combination of resins. In many embodiments, the resin used to impregnate the fiber includes filler materials such as pyrolytic carbon powder, carbon powder, carbon particles, diamond powder, boron nitride, aluminum oxide, ceramic particles, and phenol particles. It is out. In many embodiments, the resin is conductive.

  When the conductive layer is constructed from a resin-impregnated fiber, the conductive layer can derive its electrical properties from the fiber. An example of this is a conductive layer constructed from graphite fibers impregnated with reinforced epoxy. In other embodiments, the electrical properties of the conductive layer can be promoted by a resin. An example of this is a conductive layer constructed from a glass fiber impregnated with a reinforced epoxy resin with pyrolytic carbon powder as a filler material.

  The materials that can be used to build the conductive layer are not limited to resin impregnated fibers. In many embodiments, the conductive layer is constructed from a solid carbon plate. In some embodiments, the solid carbon plate is constructed from compressed carbon or graphite powder. In other embodiments, the solid carbon plate is constructed using carbon flakes or short chopped carbon fibers with a thermoplastic or thermosetting binder. In many embodiments, the conductive layer is formed from Starfire Systems Inc. located in Malta, New York. It can be constructed using C-SiC (Carbon-Silicon Carbide) manufactured by the company.

  It is also possible to use a metal core. As described above, the metal core includes a thick metal layer, CIC (Copper-Invar-Copper), and CMC (Copper-Molly-Copper).

  In other embodiments, the materials used to build the conductive layer are not limited to resin-impregnated fibrous materials and carbon composites. Any material or combination of materials that can form a layer with a dielectric constant greater than 6.0 at 1 MHz can be used to construct the conductive layer.

  In many embodiments, the cladding layer is constructed from a conductive material such as a metal. In some embodiments, the cladding layer is constructed using copper.

  A cross-sectional view of a constraining core according to another embodiment of the present invention is shown in FIG. The suppression layer 212 'includes a conductive layer 214'. A constraining core that does not have a cladding layer on either side can be referred to as an “uncladded composite laminate” or “uncladded laminate”.

  The constraining core 212 'can conduct electricity from one major surface to another through the conductive layer 214'. In some embodiments, the constraining core 212 'has a dielectric constant of 6 at 1 MHz. Conductive layer 214 'can be constructed in a manner similar to conductive layer 214 described above in connection with FIG.

  A process for building a PWB incorporating a constraining core material according to one embodiment of the present invention is illustrated in FIG. Process 230 involves preparing a material that is used to produce a constrained core of PWB (232). Preparation of the constraining core material can include drilling or stamping positioning holes, such as lamination positioning holes. The prepared constraining core material is then laminated and perforated with a clearance pattern (234). The perforated constraining core material is then printed and etched to remove debris and the copper is etched back in the area surrounding the PWB (236). If necessary, a prefabricated process can be performed (238). A surface treatment such as brown oxide treatment has been applied to the surface of the constraining core material (240).

  In parallel with the process described above, an internal layer for lamination can be prepared (242) by processing other internal layers of the PWB using conventional processing methods. The inner layer typically includes a layer of prepreg and conductive material. Next, as a preparatory work for lamination, a treated constraining core layer is placed along with the treated inner layer (244). A lamination cycle is then performed to produce a printed wiring board subassembly (246). Through holes can be drilled through the printed wiring board subassembly (248) and PTH can be generated by plating the hole lining with a conductive and / or thermally conductive material (250). The outer layer of the printed wiring board subassembly can then be printed and etched (252). PWB finishing is then performed (254) and components can be attached to the PWB. It should be noted that the above process includes a single lamination cycle, but in other embodiments, in the first lamination cycle, the patterned constraining core is replaced with a B-stage dielectric prepreg and other layers of PWB. It can be combined with the material being used to build and the PWB can be completed in subsequent lamination cycles.

  According to the process outlined above, a PWB can be constructed without the use of additional lamination cycles or special curing cycles to fill the clearance holes in the constraining core. In the lamination cycle (246), the dielectric resin from the prepreg disposed on each surface of the suppression core is reflowed into the clearance holes and slots drilled in the suppression core. In embodiments where the constraining core includes a base material having an insert material having physical properties different from that of the base material, the dielectric resin from the prepreg is within the gap between the base material and the insert material. Reflowing. The dielectric resin that has flowed into the cavity of the restraining core can electrically insulate the restraining core from the conductive plating of PTH drilled through the dielectric resin filled in the cavity of the restraining core.

  The materials used in the construction of the constraining core according to the process shown in FIG. 11 are shown in FIGS. 12a-12d. A constraining core similar to that shown in FIG. 9 is shown in FIG. 12a. This constraining core is prepared so that it can be used for the production of PWB by drilling a clearance hole. The drilled clearance holes will eventually be filled with resin, which can electrically insulate the constraining core material from PTH.

  A treated constraining core layer used as a ground layer in a PWB according to one embodiment of the present invention is shown in FIG. 12b. The restraining core 212a includes a first pattern clearance hole 262. A treated constraining core layer used as a power layer in a PWB according to one embodiment of the present invention is shown in FIG. 12c. The restraining core 212b includes a second pattern of clearance holes 264. A treated constraining core layer used as a non-functional layer in a PWB according to one embodiment of the present invention is shown in FIG. 12d. The suppression core 212c includes a third pattern of clearance holes 266.

  As described above in relation to the manufacturing process shown in FIG. 11, the prepared constraining core, together with a layer of prepreg, a layer of dielectric core material, and a layer of conductive material, is prepared for the lamination cycle. The material is arranged. A stack of constraining core, prepreg, dielectric core layer, and layer of conductive material according to one embodiment of the present invention is shown in FIG. 13a. First, a laminate 270 is formed by collecting a conductive material (in this case, a copper foil) and laminating a first prepreg 274 on the copper foil. In the illustrated embodiment, the copper foil 272 and the first prepreg 274 are manufactured using any of the well-known manufacturing methods utilized by those skilled in the art.

  Next, the suppression core layer 212 b is disposed on the first prepreg 274. As described above, the constraining core layer can be prepared by drilling a pattern 264 of clearance holes. The suppression core layer 212b functions as a power supply layer in the stacked body. Next, the second prepreg 276 is disposed on the suppression core layer 212. Next, a laminate 278 clad with a conductive material 280 on both sides is placed on the second prepreg 276. Usually, the conductive layers on both sides of the laminate 278 are etched with a circuit pattern. A third prepreg 282 is then placed on the laminate 278. Next, another suppressing core layer 212 a is disposed on the third prepreg 282. As described above, the constraining core layer can be prepared by drilling a set of clearance holes 262. The suppression core layer 212a functions as a ground layer in the stacked body. The 4th prepreg 284 is arrange | positioned on the suppression core layer 212a. The layered body 270 is completed by disposing a second conductive material layer 286 (in this case, a copper foil) on the fourth prepreg layer 284.

  It should be noted that the laminate shown in FIG. 13a includes one prepreg and one laminate above and below each of the constraining core layers, but other embodiments form multiple functional layers. Thus, a plurality of patterned cladding laminates and / or prepregs can be included on each side of the constraining core layer. In fact, it is possible to construct a PWB according to the present invention using two prepregs, each of which is clad on one side and arranged above and below the constraining core. Further, many embodiments include a plurality of constraining cores and layers of conductive material separated by a dielectric layer.

  In one embodiment, the prepreg layers used on both sides of the constraining core layers 212a and 212b have a very high resin content, such as 106 type prepregs. The resin content of normal 106 prepreg exceeds 70% by volume. In other embodiments, the prepreg layers used on both sides of the constraining core layers 212a and 212b have sufficient resin to fill the perforated clearance pattern and are flat after lamination. Provide an external surface. In another embodiment, clearance holes and slots can be filled by using multiple layers of prepreg on each side of the constraining core layer.

  In some embodiments, laminates according to one embodiment of the present invention can be formed by using prepregs such as 44N106 and 84N106 manufactured by Arlon Materials, Inc., located in Rancho Cucamonga, CA. In other examples, the laminates were manufactured by Hitachi Chemical Co., Japan. , Ltd., Ltd. 1080F epoxy manufactured by the company, Hitachi Chemical Co. in Japan. , Ltd., Ltd. Polyimide prepreg manufactured by the company, PCL-FRP-370 106 (78% PC) prepreg manufactured by Plylad Laminates, located in Franklin, New Hamshire, manufactured by Isola Laminates, located in Chandler, Arizona GI30, 1080 prepregs, Epoxy 106 prepreg manufactured by Taconic, located in Petersburg, New York, and Epoxy 106 prepreg manufactured by Nanya Technology Corporation, Taiwan. In one embodiment, two layers of 106 prepreg are used on each side of each constraining core. In other embodiments, if the thickness of the constraining core is greater than 0.012 ″, more than two layers of 106 prepregs can be used on each side of the constraining core.

  In other embodiments, it is also possible to fill the clearance pattern by using RCC (Resin Coated Copper) foil on each side of the constraining core.

  In some embodiments, the thickness of the constraining core may be up to 0.012 ″. In many embodiments, the thickness of the constraining core is limited to 0.010 ″, In some embodiments, the thickness is limited to 0.080 ".

  As described above in connection with the manufacturing process shown in FIG. 11, a lamination cycle is performed on the laminate 270. The characteristics of the lamination cycle depend on the characteristics of the prepreg and dielectric layer used in the laminate 270. Resin and prepreg manufacturers specify recommended temperature and pressure conditions during lamination. By following the recommendations of the manufacturers of the various materials used in the construction of the PWB, a lamination cycle can be performed.

  The lamination cycle produces a printed wiring board subassembly 270 'according to one embodiment of the invention shown in FIG. 13b. As a result of the lamination cycle, the dielectric resin reflows from the dielectric prepregs 274 and 276 and fills the pattern 264 'of clearance holes in the constraining core 212b. Similarly, the dielectric resin reflows from the dielectric prepregs 282 and 284 and fills the clearance holes 262 'in the constraining core 212a. These various prepreg layers also bond the layers in the laminate 270 'together.

  A printed wiring board subassembly with perforated PTH is shown in FIG. The printed wiring board subassembly 270 "includes a PHT 290 that extends through each of the layers of the printed wiring board subassembly. The suppression cores 212a and 212b are functional layers. At some places where the PTH intersects the constraining core, a resin filled clearance hole 262 '' electrically insulates the constrained core and the plated through lining of the through hole. At some places where the PTH intersects the constraining core, the plated through lining of the through hole is in direct contact with the material of the constraining core. At these locations 292, an electrical connection exists between the PTH and the constraining core. A similar printed wiring board subassembly is shown in FIG. The printed wiring board subassembly 270 "" includes two constraining cores 34 that function only as non-functional or structural layers. Each of the PTHs in the printed wiring board subassembly 270 "" is electrically isolated from the constraining core by a clearance hole 262 "" filled with resin.

  Solves thermal and coefficient of thermal expansion (CTE) control problems by using materials such as thick copper core, thick metal core, CIC (Copper-Invar-Copper), CMC (Copper-Molybdenum-Copper) in PWB is doing. Thick metals are usually difficult to process and require special processes to produce. By using special etching chemicals, a clearance pattern can be produced. Alternatively, it is possible to pattern the clearance holes by using a drilling process similar to that described above. However, it is usually impossible to stack a thick metal layer when drilling the clearance hole. The ability to stack the constraining cores when drilling clearance holes can improve the throughput of manufacturing because multiple cores can be drilled simultaneously. A further problem that can occur when using a thick metal core is that drilling through the PWB of the metal core is more likely because smaller drill bits tend to deflect and / or break when drilling into thick metal layers. There is a limit to the size of possible PTH.

  A method for constructing a PWB with a metal core is shown in FIG. Process 300 describes a process for manufacturing a PWB that includes a metal core such as CIC, CMC, and / or thick copper. A metal core is provided (304). Furthermore, an inner layer of PWB is prepared (302). Typically, the preparation includes patterning a circuit on the inner metal layer. Clearance holes can be patterned on the metal core using any of the aforementioned drilling methods (306). A clearance hole pattern can also be created in the metal core by using a metal etch chemistry (308). In many instances, it is desirable to perform a smooth bonding with other layers in the PWB by applying a special surface treatment to the metal layer (310). Unlike the process described above, the clearance hole pattern is not filled with resin during lamination. Instead, the clearance hole pattern is filled with resin before lamination. In some embodiments, a screening method is used to fill (312) the clearance holes with a resin containing a suitable filler material. The resin used to fill the clearance hole may be in the form of a liquid, a paste, or a powder. The resin is then cured or semi-cured by baking and pressing the metal layer at a temperature recommended by the resin manufacturer. Next, the laminated metal core layer is disposed together with the inner layer to form a laminate, and a lamination process is performed. Various processes are then performed to complete the PWB (318). It should be noted that the above process includes a single lamination cycle, but in other embodiments, in the first lamination cycle, the patterned metal constraining core is replaced with a B-stage dielectric prepreg and other layers of PWB. Can be combined with the materials used to build the PWB, and the PWB can be completed in subsequent lamination cycles.

  The limitations on filling these separate holes and the limitations on the use of relatively small plated through holes associated with the use of thick metal constraining cores are overcome by replacing the metal core with other types of constraining core materials. Is possible.

  A method for constructing a PWB comprising a conductive constraining core utilizing different materials with different physical properties across different regions within the constraining core according to one embodiment of the present invention is shown in FIG. The method 340 involves providing a constraining core material (342). As part of the suppression core material preparation step, the portion of the suppression core material is removed. Then, as a preparatory work for lamination, the prepared constraining core material is placed along with the dielectric layer and the layer of conductive material (344). The dielectric layer and the layer of conductive material may be in the form of clad or uncladded prepregs and laminates. A lamination cycle is then performed to generate a printed wiring board subassembly (346). Holes can be drilled in a portion of the printed wiring board subassembly (348), and the lining of these holes can be plated with a conductive and / or thermally conductive material (349). The plated PWB subassembly is printed and etched to form a finished PWB (350). The component can then be mounted on the PWB after performing a PWB finish (352). Although the above process includes a single lamination cycle, in other embodiments, in the first lamination cycle, the patterned base and insert material are transferred to the B-stage dielectric prepreg and other PWBs. It can be combined with the materials used to build the layer, and the PWB can be completed in subsequent lamination cycles.

  Materials and printed wiring board subassemblies utilized in the manufacturing process shown in FIG. 17, according to one embodiment of the present invention, are shown in FIGS. 18a-18h. As described above, the process for manufacturing the PWB shown in FIG. 17 includes providing a constraining core material 360. This material is similar to the layer 212 shown in FIG.

  In the illustrated embodiment, the constraining core material 360 is non-dielectric and is clad with layers of conductive material such as copper on both sides. In other embodiments, the constraining core material 360 may be clad on one side or uncladded. In embodiments where the constraining core material is non-dielectric, it is usually necessary to pre-perforate the constraining core material prior to lamination.

  The constraining core material can be prepared by drilling clearance holes 364 and clearance channels 366. The clearance channel can be manufactured by drilling several holes in close proximity to each other or by using a router. The perforated clearance holes and channels will eventually be filled with resin, which can electrically insulate the non-dielectric constraining core material from PTH perforated through the PWB.

  As part of the manufacturing process, the prepared constraining core material is placed together with the dielectric layer 370 and the layer of conductive material 372 as a preparatory work for the lamination cycle (344). This process can be understood with reference to FIGS. First, a laminate 374 whose both surfaces are clad with a conductive material 372 is taken, and a material is arranged by laminating a first prepreg 376 on the clad laminate. Usually, the conductive layer adjacent to the prepreg is etched by a circuit pattern. In the illustrated embodiment, the clad laminate 374 and the first prepreg 376 are manufactured using any of the well-known manufacturing methods utilized by those skilled in the art.

  A constraining core material 360 is then disposed on the first prepreg 376. As described above, the constraining core material can be prepared by drilling clearance holes 364 and clearance channels 366. Arrangement 378 is completed by placing second prepreg layer 380 on the layer formed by constraining core material 360. Next, a laminate 382 having both surfaces clad with a conductive material is disposed on the second prepreg. The conductive layer 372 adjacent to the second prepreg can be pre-etched with a circuit pattern. The resulting configuration is shown in FIG. 18e. Although the illustrated embodiment includes one prepreg and one laminate above and below the constraining core material 360, other embodiments may include a constraining core material 360 to form a plurality of functional layers. A plurality of patterned cladding laminates and / or prepregs can be included on each side. In fact, the PWB according to the present invention can be constructed using two prepregs that are arranged above and below the layer formed by the constraining core and are each clad on one side. Furthermore, many embodiments include multiple layers formed by combining a constraining core material with at least one dielectric material.

  Next, a lamination cycle is executed (346). The properties of the lamination cycle depend on the properties of the prepreg and the dielectric layer used in the structure 378. Resin, prepreg, and laminate manufacturers specify recommended temperature and pressure conditions during lamination. The lamination cycle can be performed by adhering to the recommendations of the various material manufacturers used in the construction of the PWB.

  The lamination cycle produces a printed wiring board subassembly 384 according to one embodiment of the invention shown in FIG. 18f. As a result of the lamination cycle, resin 386 fills the clearance channel gap and connects the layers together. Resin 386 also fills clearance hole 364 and bonds layers 390 and 391 of conductive material to layer 320 ′ formed by constraining core 360.

  A through hole is drilled in the printed wiring board subassembly (48). A perforated printed wiring board subassembly according to one embodiment of the present invention is shown in FIG. 18g. The printed wiring board subassembly includes a number of holes 392 that extend through each of the layers of the printed wiring board subassembly.

  After the hole has been drilled, the hole is plated (349) and the layer of conductive material is printed and etched (350). These processes generate circuits on and between the layers of PWB. As described above, the functional layer can include a layer of conductive material and a region of layer 320 '. By using circuits generated between functional layers, electrical signals can be carried. As a result, a finished PWB (that is, a PWB to which an electronic device is connected or attached) can be formed.

  By using the process described above, it is also possible to produce PWBs including buried vias, blind vias, and / or micro vias. By using similar process steps, an integrated circuit substrate (IC substrate or package substrate) with at least one constraining core can be manufactured.

  Many of the processes outlined above involve forming slots in the constraining core. Referring now to FIGS. 19-21, a technique for generating a slot using a drill with effective use of the drill is shown.

  A top view of a constraining core drilled with a pattern of clearance holes and slots (or clearance channels) according to one embodiment of the present invention is shown in FIG. The constraining core 400 includes a clearance hole 404 and a clearance channel 402. Clearance channels are manufactured as a result of clearance holes being too close to each other or overlapping clearance holes. The clearance channel on the suppression core layer is a portion that penetrates the suppression core in a state where a plurality of PTHs are close to each other, or a portion where the cross-section exposure of the suppression core is not desirable after finishing the printed wiring substrate (that is, the printed wiring board) Or a section wall of a cut-out area in the PWB area where finishing is completed. In general, clearance channels can be formed in the constraining core by mechanical drilling, laser drilling, CNC routing, punching, laser cutting, water jet cutting processes, or a combination of these processes. Clearance channels located in the area of the PWB with multiple plated through holes in close proximity can be formed by mechanical drilling, laser drilling, or laser cutting, because these processes are used in CNC routing. This is because it is stricter and more accurate than the water jet cutting process. Mechanical drilling and laser drilling processes are preferred where high accuracy is required.

  The clearance channel differs from the plated through channel in that it is perforated to electrically isolate one material from the constraining core. The clearance channel is typically much wider than PTH. A plated through channel is typically a channel that creates an electrical connection between the PWB and the electrical component leads. A plated through channel according to one embodiment of the present invention is shown in FIG. 20a. Channel 410 includes a very smooth wall profile 412. In embodiments where channels are used to house component leads, such walls can facilitate lead insertion. The smooth wall profile 412 has a plurality of fine pitches such as 1 to 3 mil (25.4 microns to 76.2 microns) pitch (preferably 1 mil (25.4 microns) pitch). It can be formed by drilling holes. For a 1 mil (25.4 micron) pitch, 1000 holes form a 1.0 inch (2.54 centimeter) long plated through channel.

  As described above, the clearance channel is typically wider than the plated through channel and is generated using a relatively large diameter tool. A clearance channel is shown in FIG. 20b. The clearance channel 420 has a smooth surface 422 similar to that of a plated through channel. The plurality of holes 426 drilled to create the clearance channel 420 has a very fine pitch. As can be observed in FIG. 20b, the walls of the clearance channel are not completely smooth. There are wavy irregularities associated with the repetitive drilling process. The notch height 424 (ie, the extent to which the wall material extends into the channel, see FIG. 21b) is very small, less than 0.5 mil. A large number of holes are required to achieve such a smooth clearance channel wall profile.

  When creating a clearance channel in the constraining core, a smooth wall is not always required. As observed in FIGS. 20c and 20d, clearance channels can be formed by using a relatively coarse pitch (see clearance channels 430 and 440 in FIGS. 20c and 20d). The clearance channel shown includes wall profiles 432 and 442 that are not as smooth as the wall profile 422. A relatively coarse pitch will increase niche heights 434 and 444. In many embodiments, a relatively coarse pitch can be used to drill channels having a width equal to the distance between notches. As a result, it is possible to produce a channel with a rough finish that does not have a notch that goes inside the required channel width. By reducing the number of holes required to form the channel, the throughput in drilling clearance hoses and channel patterns into the constraining core can be greatly improved.

  In some embodiments, the length of the notch is limited by the risk of the notch breaking during lamination and the risk of a short circuit between the PTH and the constraining core. Preferably, the height of the notch in the constraining core clearance channel is less than 3 mils (76.2 microns). More preferably, the height of the notch in the clearance channel is 1 mil (25.4 microns) or less.

  A table relating notch size to clearance hole pitch and drill diameter is shown in FIG. 21a. For example, if the hole size is 28 mils, the notch size is still well below 1.0 mils even if the hole pitch is increased to 10 mils. This example demonstrates a 1/10 reduction in the number of holes needed to achieve wall smoothness comparable to that of a plated through channel.

  The above embodiments are disclosed as representative examples, and further modifications, substitutions, and changes can be made to the above-described system without departing from the scope of the present invention. Want to be understood. For example, multiple layers similar to the constraining core of reference number 20 in FIG. 2 or reference number 139 in FIG. 7 can be included in a single PWB. It is also possible to use a combination of base material and insert material as a functional layer or a non-functional layer. In embodiments where the functional layer is formed using a base material and an insert material, the functional layer can be used as a ground layer, a power supply layer, or a split plane layer. Furthermore, any type of dielectric and conductive material can be used as the base material or insert material. Furthermore, the cut and insert may be of any shape, and multiple inserts may be placed within a single cut area of the base material. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.

1 is an isometric view of a printed wiring board according to one embodiment of the present invention on which several electronic devices having different types of packaging are mounted; FIG. It is a schematic sectional drawing of the printed wiring board shown by FIG. 4 is a flowchart illustrating a process for manufacturing a printed wiring board from a base material and a dielectric insert according to one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 3. FIG. 4 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 3. FIG. 4 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 3. FIG. 4 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 3. FIG. 4 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 3. FIG. 4 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 3. FIG. 4 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 3. FIG. 4 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 3. 4 is a flowchart illustrating a process for manufacturing a printed wiring board from a base material and at least one non-dielectric (ie, conductive) insert material in accordance with one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 5. It is a schematic sectional drawing of the printed wiring board containing the plating through hole by one Example of this invention. 4 is a flowchart illustrating a process for manufacturing a printed wiring board according to an embodiment of the present invention. It is a schematic sectional drawing of the electroconductive suppression core by one Example of this invention. It is a schematic sectional drawing of the electroconductive suppression core by one Example of this invention. 4 is a flowchart illustrating a process for manufacturing a printed wiring board according to an embodiment of the present invention. FIG. 12 is a schematic cross-sectional view of a conductive constraining core as various processes are performed in the manufacturing process shown in FIG. 11. FIG. 12 is a schematic cross-sectional view of a conductive constraining core as various processes are performed in the manufacturing process shown in FIG. 11. FIG. 12 is a schematic cross-sectional view of a conductive constraining core as various processes are performed in the manufacturing process shown in FIG. 11. FIG. 12 is a schematic cross-sectional view of a conductive constraining core as various processes are performed in the manufacturing process shown in FIG. 11. FIG. 12 is a schematic cross-sectional view of a printed wiring board assembly constructed as part of the manufacturing process shown in FIG. FIG. 12 is a schematic cross-sectional view of a printed wiring board assembly constructed as part of the manufacturing process shown in FIG. 1 is a schematic cross-sectional view of a PWB including two conductive constraining cores that function as electrical layers according to one embodiment of the present invention. 1 is a schematic cross-sectional view showing a PWB including two conductive constraining cores that function as physical layers rather than as electrical layers, according to one embodiment of the present invention. 4 is a flowchart illustrating a process for manufacturing a printed wiring board with a metal core according to an embodiment of the present invention. 6 is a flowchart illustrating a process for manufacturing a printed wiring board having a conductive suppression core according to another embodiment of the present invention. FIG. 18 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 17. FIG. 18 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 17. FIG. 18 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 17. FIG. 18 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 17. FIG. 18 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 17. FIG. 18 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 17. FIG. 18 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 17. FIG. 18 is a schematic cross-sectional view of one printed wiring board subassembly constructed as part of the manufacturing process shown in FIG. 17. FIG. 3 is a schematic plan view of a constraining core having a pattern of clearance holes and slots according to an embodiment of the present invention. FIG. 4 is a schematic view of slots drilled using holes spaced at different distances according to one embodiment of the present invention. FIG. 4 is a schematic view of slots drilled using holes spaced at different distances according to one embodiment of the present invention. FIG. 4 is a schematic view of slots drilled using holes spaced at different distances according to one embodiment of the present invention. FIG. 4 is a schematic view of slots drilled using holes spaced at different distances according to one embodiment of the present invention. It is a table | surface which shows the size of the notch produced | generated when two holes are drilled in the state spaced apart by the defined distance by the drill bit provided with the defined diameter. FIG. 3 is a schematic view of a pair of holes drilled in a constraining core according to one embodiment of the present invention.

Claims (19)

In a method of constructing a printed wiring board comprising a conductive suppression core and at least one functional layer,
Drilling a clearance pattern in the conductive constraining core;
The conductivity suppression in a laminate comprising a B-stage (semi-cured) layer of dielectric material on each face of the suppression core and an additional material layer arranged to form the at least one functional layer Placing the core, and
Performing a lamination cycle on the laminate prior to curing to reflow the resin in the B-stage (semi-cured) layer of the dielectric to fill the clearance pattern of the conductive suppression core;
Drilling a plated through hole; and
Having a method. Extracting information about the location of the plated through hole that is not intended to be in electrical contact with the conductive constraining core from the design of the printed wiring board;
Determining the clearance pattern using the information regarding the location of the plated through hole that is not intended to be in electrical contact with the conductive constraining core; and
The method of claim 1, further comprising:   The method of claim 1, wherein the conductive constraining core comprises two major surfaces and is capable of transferring electricity directly from one major surface to another.   The method of claim 3, wherein the conductivity constraining core comprises a dielectric constant greater than 6 at 1 MHz.   The method of claim 3, wherein the conductive constraining core is constructed using a fibrous material impregnated with a resin.   The method of claim 5, wherein the fibrous material is carbon fiber.   The method of claim 6, wherein the carbon fiber is metallized.   The method of claim 3, wherein the conductive constraining core is constructed from a thick metal layer.   9. The method of claim 8, further comprising screening a resin within the clearance pattern of the conductivity constraining core prior to lamination. Laminating a plurality of conductive suppression cores;
Drilling the clearance pattern in the laminate of conductive suppression cores;
Generating a lamination positioning hole in the conductive suppression core;
The method of claim 1, further comprising:   The method of claim 10, further comprising printing and etching the conductive constraining core to remove debris prior to lamination. The B-stage (semi-cured) layer of the dielectric is a prepreg,
The method of claim 1, wherein the laminate includes a layer of conductive material.   The method of claim 1, wherein the B-staged (semi-cured) layer of dielectric comprises a resin content of at least 70% by volume.   The region of the conductive constraining core is constructed using a base substrate material, and at least one region of the conductive constraining core is constructed using an insert substrate material. Method. Selecting a base substrate material; and
Removing a portion of the base substrate material;
Selecting an insert substrate material; and
Cutting the insert substrate material piece that can be accommodated in the removed portion of the base substrate material;
Arranging the base substrate material and the insert substrate material piece as part of the laminate;
15. The method of claim 14, further comprising: The step of drilling the clearance pattern is
Determining the location of the clearance channel and the required width from the printed circuit board design;
Determining a distance between notches that is likely to be generated when drilling the channel using a selected drill bit and drill pitch;
Selecting the drill bit and drilling pitch such that the distance between the notches exceeds the required width of the channel;
The method of claim 1, further comprising: Identifying a plated through hole that creates an electrical connection with the conductive constraining core closest to the clearance channel by using the printed wiring board design;
Determining a distance between the clearance channel and the identified plating through hole;
Selecting the drill bit and drilling pitch such that the resulting channel does not overlap the location of the identified plating through hole;
The method of claim 16, further comprising: Determining the height of the notch;
Selecting a drill bit and drilling pitch such that the notch height is less than 3 mils (76.2 microns);
The method of claim 16, further comprising:   19. The method of claim 18, further comprising selecting a drill bit and drilling pitch such that the height of the notch is less than 1 mil (25.4 microns).

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