`
`Petitioners' Exhibit 1009, pg. 1
`
`Petitioners' Exhibit 1009, pg. 1
`
`

`

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`
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`given to the Society of Plastics Engineers and the conference at which the
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`
`1.
`
`All papers submitted to and accepted by the Society for presentation at
`one of its conferences are copyrighted by and are the property of the
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`
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`COPYRIGHT (O 1999 BY THE SOCIETY OF PLASTICS ENGINEERS,
`PO BOX 403, BROOKFIELD, CONNECTICUT 06804-0403
`
`Petitioners' Exhibit 1009, pg. 2
`
`

`

`ADVANCES IN THERMOPLASTIC ENCAPSULATION OF
`ELECTRICAL/ELECTRONIC COMPONENTS
`
`Thomas D. Boyer and Mark W. Wichmann
`DuPont Engineering Polymers
`
`Abstract
`
`sensors, motor
`solenoids,
`encapsulating
`For
`recently integrated circuit
`(IC)
`components and most
`modules, manufacturers
`are
`increasingly
`choosing
`engineering
`thennoplastics
`and
`injection molding
`technology over traditional thermoset resins and processing
`methods. After
`reviewing the cost and performance
`advantages of thermoplastic encapsulation technology, this
`paper reports on recent advances that are taking the
`technology imo new areas. The advances include improved
`adhesion
`between
`encapsulated
`object
`and
`the
`encapsulating plastic, new coils that can withstand high
`voltage surges and the encapsulation of electronic circuitry
`to produce new kinds of speed sensors and novel devices
`for data storage and information retrieval.
`
`Introduction
`
`Many electrical and electronic devices are encapsulated
`to provide protection against damage by moisture,
`chemicals or solid materials. The traditional approaches
`have used varnishes or therrnoset resins in either liquid or
`solid form. In the 1990's, however, thermoplastics have
`moved into the forefront for encapsulation.
`The main reasons for the shift are that the use of
`
`thermoplastic injection molding technology results in
`lower production costs,
`improved quality and less
`undesirable environmental impact in the workplace than
`thermoset potting and molding technologies.
`
`Processing and Equipment
`
`The typical thermoplastic encapsulation process is an
`insert injection molding operation. The insert, a coil or an
`integrated circuit for example, is placed in a mold equipped
`with either fixed or retractable pins or other features to
`support
`it when molten thermoplastic is injected. The
`electrical device’s lead wires or terminals are clamped off
`from thermoplastic flow during molding.
`
`Insert injection molding is a clean, repeatable process,
`it
`lends
`itself
`to
`automation
`and
`cellular
`and
`manufacturing. The process fits well with total quality
`management (TQM). With off-the-shelf process controls
`and systematic production methods, manufacturers can
`deliver repeatable, high-quality parts.
`
`Parts come out of the tool ready for assembly. They
`generally do not require costly trimming or deflashing as
`thermoset parts do.
`
`1542 / ANTEC '99
`
`injection molding
`clamp
`horizontal
`Although
`equipment can be used for encapsulation, vertical-clamp
`machines allow easier insert placement and greater insert
`stability during mold clamping movement. For high-
`volume production, a vertical machine with a shuttle or
`rotary table is highly efficient. For example, a two-station
`table fitted with two lower mold halves allows molding at
`one station while an operator or a robot unloads finished
`parts and loads inserts at the other station.
`
`Materials
`
`thermoplastic
`to therrnoset powders,
`In contrast
`encapsulation resins are supplied in the form of dust-free
`pellets. And unlike many liquid and solid therrnoset
`materials, the thermoplastic resins release only negligible
`amounts of volatile organic compounds during processing.
`
`Thermoplastic resins are very stable and thus have
`extended shelf life. By contrast,
`thermoset potting and
`molding compounds generally deteriorate with age and
`oftenrequirerefrigeratedortemperature—controlledstorage.
`
`Two families of thermoplastic polymers are now
`widely used for encapsulation: polyarnides, which are
`commonly
`called
`nylons,
`, and
`polyesters. Most
`encapsulation resins contain glass fiber reinforcement for
`added stiffness, strength and dimensional stability. Flame-
`retardant grades are available to meet requirements for
`UL94V-0performance.
`
`Nylon, polyester and other engineering thermoplastics
`offer more impact
`resistance than typical
`thermoset
`encapsulation resins. Their toughness allows the use of
`thin-wall components and provides improved resistance to
`both vibration and impact damage.
`
`The injection molding process gives the designer the
`freedom to incorporate mounting brackets or other features
`in a single multifunctional part. This can result
`in
`assemblies with reduced part count and lower assembly
`costs. An example is the automotive sensor shown in
`Figure 1. It has insert-molded metal compression limiters,
`thus eliminating the need for a separate mounting bracket.
`
`Nylon polymers are highly valued for their toughness,
`chemical and solvent
`resistance and thermal cycling
`performance. Those most commonly used for encapsulation
`are heat-stabilized grades of nylon 66 and nylon 612 that
`are specially tailored for encapsulation molding.
`
`Encapsulation grades of nylon 66 are firmly entrenched
`as workhorse materials. With proper mold design and
`molding process controls, they give excellent results for
`most part configurations.
`
`Petitioners' Exhibit 1009, pg. 3
`
`Petitioners' Exhibit 1009, pg. 3
`
`

`

`For encapsulating sensors or integrated circuit devices,
`nylon 612 resins are often the best choice. Owing to their
`crystallization characteristics,
`they are inherently well-
`suited to relatively slow,
`low-pressure injection. Such
`process conditions are a key factor in the prevention of
`bunching of very fine magnet wire used in variable-
`reluctance sensors or displacement of delicate electronic
`circuit assemblies. Nylon 612 resins also have better
`chemical resistance and lower moisture absorption than
`nylon 66.
`
`Thermoplastic polyesters provide better heat-aging
`performance than nylon 66 or 612, and they also excel in
`stiffness, strength and low moisture absorption. The main
`thermoplastic polyester candidates for encapsulation are
`polyethylene
`terephthalate
`(PET)
`and
`polybutylene
`terephthalate (PBT). In general, PET encapsulation grades
`offer highertemperature resistance in service.
`
`The choice of a particular thermoplastic type or grade
`depends on several interrelated factors. Two key factors
`discussed here are:
`l) long-term product reliability and
`safety, including compliance with national or international
`standards; and 2) requirements for bonding between the
`encapsulation material and the ground insulation.
`
`Reliability and safety
`
`By applying sound design principles and testing
`prototypes before production, manufacturers have developed
`thennoplastic-encapsulated electrical and electronic devices
`that have proven themselves in the field.
`
`For encapsulated solenoids, transformers, motors, etc.
`requiring use of an approved electrical insulation system
`(EIS), manufacturers can turn to material systems that have
`been tested and approved according to Underwriters
`Laboratories (UL) Standard 1446 and the guidelines of
`International
`Electrotechnical
`Commission
`(IEC)
`Publication 85.
`
`The approval of an EIS involves the testing and
`evaluation of the complete assembled insulation system
`(magnet wire, coil form and encapsulation material) under
`conditions indicative of its performance throughout
`its
`projected service life.
`
`Recognition of an insulation system under either UL
`1446 or
`IEC standards requires testing under cyclic
`conditions of heat aging, cold shock, mechanical stress and
`moisture exposure followed by dielectric stress testing. EIS
`tests are very costly in both money and "time. Final
`
`High-temperature nylon (HTN) resins are available for
`applications requiring resistance to higher temperatures
`than other nylons and/or better chemical or hydrolysis
`resistance than polyesters. Typical HTN resins melt at
`about 300°C while nylon 66 melts at 255°C. One HTN
`grade has a UL electrical relative thermal index (RTI) of
`150°C, which is 10°C higher than nylon 66. HTN resins
`absorb less moisture than standard nylons and thus have
`better dimensional stability, but they retain the toughness
`and thermal cycling resistance characteristic other nylons.
`
`ANTEC ’99 / 1543
`
`recognition of a system can take 18 months, and failure to
`gain the required recognition would mean starting all over
`again
`
`It’s no wonder then that most electrical manufacturers
`choose to use systems that have already been tested and
`approved through the efforts of component material
`suppliers. The availability of EIS’s has lent solid support
`to the growth of thermoplastic encapsulation.
`
`Preapproved UL 1446/IEC 85 EIS’s using nylon 66,
`high-temperature nylon or PET as the encapsulant are
`available for Class B (130°C) service at up to 600 V.
`Class F (155°C) and Class H (180°C) 600 V systems
`using PET encapsulant
`are
`also
`available
`and in
`commercial use for encapsulation applications.
`
`It is very important to note that in all UL 1446/IEC
`85 system recognitions, a minimum thickness is specified
`for both the encapsulant and the coil form.
`
`Encapsulated automotive components such as sensors
`must withstand repeated thermal cycling in the -40 to
`+150°C range. Nylon 66 and 612 and HTN resins
`generally excel in thermal cycling performance.
`
`“Wire-friendly” grades of nylon 66 and 612 have been
`developed to meet a special need in automotive sensors.
`Their formulation contains no metal salts, which can
`contribute to electrolytic corrosion of magnet wire. Since
`corrosion of the very fine wire (AWG 35 to 45) used in
`sensors can quickly lead to failure, “wire-friendly” resins
`greatly improve reliability.
`
`Engineering for adhesion
`
`While a mechanical lock between the encapsulant and
`the insert generally provides adequate structural integrity,
`physical adhesion between them provides added protection
`against three phenomena: moisture penetration, separation
`by mechanical stress such as vibration and the formation of
`gaps that would reduce dielectric performance.
`
`The author’s studies show that three factors are critical
`
`for achieving viable adhesion through melt bonding:
`materials, coil form design and accurate melt temperature
`control in the mold.
`
`Selecting materials
`
`for adhesion
`
`Screening tests to evaluate the relative bond strength
`achieved with various glass-reinforced nylon resins show
`that
`like materials achieve better bonds than dissimilar
`ones and that nylon 612 provides the best bonds of all the
`resins evaluated. Figure 2 shows the results for several
`promising combinations of materials tested in lap shear
`and finger joints (Figures 3 and 4). Even the material with
`the lowest break strength shown in Figure 2 may provide
`adequate adhesion for many applications.
`
`Designing parts for adhesion
`
`Designing the coil form’s flanges with one or more
`reverse-tapered grooves (Figure 5) increases the reliability
`
`Petitioners' Exhibit 1009, pg. 4
`
`

`

`area would almost certainly cause failure in the 8 kV surge
`test.
`
`The bobbin for ABB’s coil has molded-in pockets for
`insulation displacement
`(IDC)
`terminals. Their design
`posed a
`tooling
`challenge
`owing
`to warpage,
`a
`characteristic of
`all
`fiber-reinforced
`therrnoplastics.
`Reasoning that warp can be controlled if not eliminated,
`the molder, Empire Precision Plastics, met the challenge
`by configuring the mold in a way that causes the pockets
`to warp into the desired shape and dimensions.
`
`When the coils are wound, the winding machine ties
`off lead wires to temporary posts molded as part of the
`bobbin’s terminal area. The posts are sheared off during
`automated insertion of insulation displacement terminals
`into the pockets.
`
`In molding the bobbins, Empire uses up-to-date
`machine and mold temperature controllers and carefully
`monitors them to maintain process temperatures within the
`range required to achieve full crystallinity throughout the
`part structure.
`
`Parts that will be encapsulated must always be molded
`with full crystallinity. If not, dimensional changes and
`deformation are likely during overmolding.
`
`of achieving a melt bond during encapsulation and
`provides a meclmnical lock as well. The taper should be
`configured as shown in Figure 5, and edge radii should be
`less than 0.13 mm (0.005 in). This configuration provides
`thin edges that, given the right materials and process
`conditions, will soften and fuse with the encapsulant melt.
`The groove surfaces that do not melt will be filled by the
`encapsulant during molding, providing a mechanical lock
`and a longer, more tortuous path for moisture to travel to
`reach the windings.
`
`To get more sealing area than that provided by a
`single groove, manufacturers have begun designing
`bobbins with multiple grooves in a stepped arrangement.
`The coil form shown in Figure 6, for example, has a
`stepped flange with two grooves.
`
`Melt
`
`temperature control
`
`Accurate control of melt temperature in the area where
`bonding is required is cnicial to the bond. This is achieved
`primarily with a combination of mold design and proper
`adjustment of mold temperature control equipment.
`
`Adhesion at
`
`the metal-plastic interface.
`
`Automotive industry studies indicate that the primary
`cause of failure of encapsulated sensors and circuitry with
`lead-frame assemblies is leakage at the plastic-to-metal
`interface. Possible solutions currently under investigation
`include use of a coating on the insert that will bond with
`the encapsulant and/or adding a material to the encapsulant
`that will adhere to the metal lead frame. Initial scouting
`shows promise that we can achieve effective adhesion in
`this critical interface area.
`
`constituents.
`
`For encapsulating the coil, ABB uses a hot runner
`mold, thus demonstrating the feasrbility of using this type
`of tool for encapsulation work.
`In a hot runner mold,
`heating elements are used to keep sprue and runner material
`in the molten state between shots rather than cooling and
`ejecting them along with finished parts. The advantage is
`the elimination of sprue and runner scrap. The challenge of
`hot runner encapsulation molding, which was met in this
`case, is that the process requires faster injection at higher
`pressure than is typically used in encapsulation molding.
`
`Cracking the high-voltage barrier
`
`The coil shown in Figure 6 is a new encapsulated
`voltage coil for electromechanical watt-hour meters from
`ABB Electric Metering and Control. Using heat-stabilized
`nylon 66 with 33% glass fiber reinforcement for its bobbin
`and encapsulation, the new coil replaces an older design
`overrnolded with therrnoset epoxy.
`
`This coil represents a milestone in the high-voltage
`performance of thennoplastic-encapsulatcd coil devices.
`Before installing the coil in a meter, ABB tests each one
`twice at 8kV with a specific wave form simulating a
`powerful lightning surge.
`
`The design of the coil bobbin, the molding techniques
`used to produce it and encapsulation techniques are all
`critical
`to the coil’s high-voltage resistance, consistent
`quality and economical cost.
`
`The bobbin is molded with a deep groove for the
`terminating lead wire. The wire’s placement in the groove
`is a key factor
`in providing sufficient
`isolation for
`satisfactory performance in ABB’s 8 kV surge test. During
`encapsulation, filling and packing of the encapsulant in the
`lead wire groove are crucial. Microvoids or gaps in that
`
`Encapsulating microelectronics
`
`Until recently, the encapsulation of integrated circuit
`(IC) devices involved potting it in a separate case with a
`liquid therrnoset
`resin. Recently, we have
`assisted
`manufacturers
`in
`adapting
`low-cost
`thermoplastic
`technology to the protection of 105.
`
`Medical records on a chip
`
`The familiar metal dog tag worn by the members of
`the US. armed forces may soon give way to a rugged
`plastic tag containing medical records on a memory chip.
`Called the Medi-Tag®,
`the new record carrier was
`developed by Data-Disk Technology Inc., Sterling, Va.
`
`The Medi-Tag® contains a flash memory chip surface-
`mounted on an integrated circuit (IC) board (Figure 7). It’s
`encapsulated with 33% glass-reinforced nylon 612 resin,
`which is ideally suited for slow, low-pressure mold filling,
`a key means of avoiding damage to the tag’s delicate
`electronic circuitry. The resin is also specially formulated
`for
`excellent
`long-term compatibility with
`circuit
`
`1544 /ANTEC ’99
`
`Petitioners' Exhibit 1009, pg. 5
`
`

`

`a variety of
`chip’s memory can include
`The
`information, including the individual’s complete medical
`history, X-rays, allergies to medications, dental records,
`etc. Medical personnel in the field or at base hospitals
`around the world will be able to read and update the record
`in the Medi-Tag® by inserting it into a slot in a standard
`PCMCIA reader attached to a personal computer.
`
`to issue a
`The US. military’s ultimate plan is
`personal infomiation carrier to all members of the active
`Armed Forces and Reserves. Another very large potential
`use involves their use by retired military personnel and
`their dependents, who look to military facilities for medical
`care.
`
`in miniature
`speed sensors
`Wheel
`A new electronic type of automotive wheel-speed sensor
`(Figure 8) promises lower costs and smaller size than
`conventional
`coil-type
`(variable
`reluctance)
`sensors.
`Developed by the Lucas-Varity Group in the UK, the new
`sensor measures just 25 mm long by 6 mm in diameter (1
`in by 1/4 in.).
`The electronic sensor is mounted on a fixed member
`
`near a rotating part fitted with magnets. It uses either the
`Hall or the magneto resistive effect to generate digital
`
`signals for controlling anti-lock braking,
`shifting or other automotive systems.
`
`transmission
`
`Conclusions
`
`engineering
`using
`technology
`Injection molding
`thermoplastics such as nylons and PET polyesters has
`emerged as the most cost-effective method of encapsulating
`coil devices such as solenoids, sensors and transformers.
`Recent advances include the encapsulation of coils that can
`withstand high-voltage testing and the encapsulation of
`electronic circuitry. The latter may herald the development
`of an array of portable new products for data storage,
`information retrieval and control.
`
`Keywords: Electrical, Electronic, Encapsulation, Sensors
`
`Overmold Adhesion Strength
`
`D Lap shearlowts
`
`§ Fingerlomts
`
`
`
`Figure I: Wheel-speed sensor with molded-in
`compression limiters.
`
`N 01o0
`
`
`
`Breakload.
`
`
`
`The sensor’s electronic components consist of an IC, a
`capacitor and possibly a diode welded to a lead frame
`(Figure 9). A major challenge in encapsulating this
`assembly is to avoid damaging or displacing the unit’s
`delimte electronic circuitry. Displacement is a critical issue
`because precise positioning of the chip within the shell is
`necessary for accurate speed sensing. The challenge is met
`with the use of a glass-reinforced nylon 612 resin. It allows
`the slow,
`low-pressure mold fill at moderate melt
`temperature which is necessary to avoid displacing or
`damaging the delicate electronic assembly.
`
`ANTEC ’99/ 1545
`
`
`
`
`
`
`
`Mod nylon/ Mod nylon/
`Mod. nylon
`Nylon 6l2
`
`Nylon 612/
`Nylon 6l2/
`Ny on 612 Mod. nylon
`Insen/Encapsulant
`
`Nylon 66/
`Nylon 66
`
`NOIE All resrns contain 33% glass fiber reinforcement
`
`Figure 2: Overmold adhesion strength between various
`nylon resins.
`
`Petitioners' Exhibit 1009, pg. 6
`
`

`

`Figure 3: Lap shearjoim.
`
`Figure 6: Vot'rage coiffor wan-hour meters.
`Encapsulant
`
`
`
`Figure 4: Finger joint.
`
`between coilform and encapsm'am.
`
`Figure 5: Taperedflange design to improve adhesion
`
`1546 iANTEC ’99
`
`Figure 9: J’mema! components ofeieflronic- wheeI—speed
`sensor.
`
`Petitioners' Exhibit 1009, pg. 7
`
`Petitioners' Exhibit 1009, pg. 7
`
`