Hermetic feed-through with hybrid seal structure

A power terminal feed-through includes a housing body, a plurality of conductive pins, and a seal structure that hermetically seals the conductive pins to the housing body and electrically insulates the conductive pins from the housing body. The seal structure includes a first material fused to one of the housing body and the conductive pin, and a second material fused to the other one of the housing body and the conductive pin. The first and second materials may be properly chosen to match thermal expansion of the housing body and the conductive pins, respectively.

FIELD

The present disclosure relates to electric power terminals, and more particularly to hermetic feed-throughs of the electric power terminals with improved seal structures.

BACKGROUND

Hermetically sealed electric power terminals generally include air-tight feed-throughs for use in conjunction with hermetically sealed devices. The feed-through includes a metal housing to be mounted on the hermetically sealed device, and a plurality of conductive pins extending through the metal housing for conducting electric current. A sealing material is generally provided between the metal housing and the conductive pins to electrically insulate the conductive pins from the metal housing. In addition, the sealing material hermetically seals the conductive pins to the metal housing to prohibit air leakage into or from the hermetically sealed device.

A glass or polymer has been used as the sealing material in the feed-through to provide electric insulation and prevent gas permeation. The performance, cost or design flexibility of a glass or polymer, however, may not be preferred for all purposes or environments or operating conditions. For example,

some sealing materials may be used with a limited number of metals. Therefore the selection of metals for the conductive pins and housings is likewise limited.

SUMMARY

In one form, a hermetic feed-through includes a housing body, a conductive pin, and a seal structure that seals the conductive pin to the housing body and that provides electric insulation between the housing body and the conductive pin. The seal structure includes a first material fused (e.g., bonded or sealed) to one of the housing body and the conductive pin, and a second material fused to the other one of the housing body and the conductive pin.

In another form, a hermetic feed-through includes a housing body, a conductive pin, and a seal structure that seals the conductive pin to the housing body and that provides electric insulation between the housing body and the conductive pin. The seal structure includes a first material, a second material, and at least two of a first sealing path, a second sealing path, and a third sealing path. The first sealing path is a glass-to-metal seal. The second sealing path is a polymer-to-metal seal. The third sealing path is a polymer-to-glass seal.

In still another form, a method of manufacturing a feed-through includes: fusing a first material to at least one dummy pin to form a substrate; removing the at least one dummy pin from the substrate to form at least one opening corresponding to the dummy pin; inserting at least one conductive pin to the at least one opening; and fusing a second material to the at least one conductive pin.

DETAILED DESCRIPTION

First Embodiment

Referring toFIG. 1, an electric power terminal feed-through10in accordance with a first embodiment of the present disclosure includes a metallic housing body12and a plurality of conductive pins14. The housing body12includes an inner surface16defining an inner space18(shown inFIG. 4A). The plurality of conductive pins14extend through the inner space18along a central axis Y of the housing body12.

The feed-through10has a first side22and a second side24opposite to the first side22. The feed-through10is mounted to a hermetically sealed device (not shown), for example, a disc drive, wherein the first side22is located inside the hermetically sealed device and the second side24is located outside the hermetically sealed device. A seal structure26is provided in the inner space18to seal the conductive pins14to the inner surface16of the housing body12. The seal structure26electrically insulates the conductive pins14from the housing body12and hermetically blocks air flow from the first side22to the second side24of the feed-through10. The seal structure26precludes leakage into or from the hermetically sealed device (by way of the conductive pins14).

The housing body12may be made of cold-rolled steel. The conductive pins14may include a metal having a low melting point, such as copper, gold, and silver. The conductive pins14may also be copper pins, stainless steel pins coated with gold, or copper-core steel wires.

The seal structure26has a laminated structure including a first material and a second material. The first material and the second material have different fusing temperatures, gas permeation prevention properties, and/or coefficients of thermal expansion. For example, the first material may be selected to function as a gas barrier to prevent gas, particularly helium, from travelling through the seal structure26. The second material may be selected for its low fusing temperature so that the seal structure26may be fused to the conductive pins and/or housing body at a lower fusing temperature than that of the first material, without damaging the housing body and/or conductive pins. Moreover, the first material and the second material may be chosen to have thermal expansion characteristics that match the metals (i.e., conductive pins and housing body) to which they are fused.

For example, the first material may be a sealing glass that can effectively prevent gas permeation. The second material may be a sealing polymer that has a lower fusing temperature than glass and can be fused to metals that have low melting points, such as aluminum, gold, copper, and silver. Alternatively, the first and second materials may have a thermal expansion matching the housing body and the conductive pins, respectively, to avoid damaging the sealing paths at elevated temperatures. Alternatively, both the first material and the second material may be polymers that have different required properties as previously described.

Referring toFIG. 2, the seal structure26includes a glass layer28and a polymer layer30that are arranged along the central axis Y of the housing body12. The seal structure26defines a plurality of openings. The conductive pins14are inserted into the openings.

Referring toFIG. 3, the seal structure26includes a first sealing path34, a second sealing path36, and a third sealing path38that are continuously connected to form a continuous sealing boundary. It should be noted that the interfaces of the sealing paths, themselves, may be smooth and featureless or include features such as serrations, locking fingers and the like to promote a good seal.

The first, second, and third sealing paths34,36, and38are provided at interfaces between the glass layer28and the inner surface16of the housing body12, between the polymer layer30and the conductive pins14, and between the glass layer28and the polymer layer30, respectively. Angled portions41may be formed at their connecting points, particularly, at the interface between the two sealing materials. Optionally, a fourth sealing path39may be provided at an interface between the housing body12and the polymer layer30. The first sealing path34and the second sealing path36provide a hermetic seal. The third sealing path38may or may not provide a hermetic seal.

The first sealing path34is a glass-to-metal seal that fuses the glass to the housing body12made of cold-rolled steel. The glass layer28may be selected to have a coefficient of thermal expansion that matches that of the housing body12to avoid compromising or interrupting the first sealing path34due to incompatible thermal expansion.

The second sealing path36is a polymer-to-metal seal, which seals the polymer to the gold-coated conductive pins14. The polymer may be epoxy. The materials for the polymer layer30may be properly selected to have a coefficient of thermal expansion matching that of the conductive pins14to avoid compromising or interrupting the second sealing path36due to incompatible thermal expansion when the operating temperature changes.

The third sealing path38is a polymer-to-glass seal. The third sealing path38, which is formed at the interface between the two sealing materials, may be oriented perpendicular to the conductive pins14and the inner surface16of the housing body12. When the feed-through10is operated at elevated temperatures, shear stress may be generated at the third sealing path38due to a difference in thermal expansion between the two sealing materials. The shear stress does not compromise or interrupt the third sealing path38. Therefore, the sealing paths among the first material, the second material, the housing body and the conductive pins remain continuously connected (i.e., closed) at elevated temperatures.

While not shown in the drawings, it is appreciated and understood that the third sealing path38does not have to be perpendicular to the conductive pins14and/or the housing body12to maintain a continuous sealing boundary when temperature changes. The third sealing path38may have an angle relative to the X axis so that the interface between the two sealing materials does not receive significant tensile stress to compromise or interrupt the third sealing path38. The angle of the third sealing path38relative to the X axis may depend on coefficients of thermal expansion of the two sealing materials.

The fourth sealing path39is also a polymer-to-metal seal and can be optionally applied. The fourth sealing path is different from the second sealing path in that the second sealing path is provided between a polymer and a first metal that has a low melting point, whereas the fourth sealing path is provided between the polymer and a second metal that has a higher melting point.

Referring toFIGS. 4A to 4D, to form a feed-through10of the first embodiment, a plurality of dummy pins40are first provided in the inner space18of the housing body12, followed by fusing a glass material to the dummy pins40and the inner surface16of the housing body12to form the glass layer28. The first sealing path34is formed at the interface between the glass layer28and the housing body12.

Next, the dummy pins40are removed to form a plurality of openings42in the glass layer28. A plurality of conductive pins14are inserted into the openings42, followed by fusing a polymer material to the conductive pins14and the glass layer28to form a polymer layer30on an upper surface of the glass layer28. A second sealing path36and the third sealing path38are formed between the polymer layer30and the conductive pins14and between the glass layer28and the polymer layer30, respectively. Optionally, the polymer material may be fused to the inner surface16of the housing body12to form the fourth sealing path39.

Second Embodiment

Referring toFIGS. 5 and 6, a power terminal feed-through in accordance with a second embodiment of the present disclosure has a structure similar to that of first embodiment except for the seal structure and the housing body.

The feed-through50includes a metallic housing body52, a plurality of conductive pins14, and a seal structure54. The housing body52is made of aluminum, which has a low melting point. The housing body52may include an inner surface53and an annular flange55extending from the inner surface53. The flange55includes a horizontal surface57perpendicular to the inner surface53. The seal structure54includes a glass layer56and a polymer layer58formed between the glass layer56and the annular flange55.

Referring toFIG. 7, the seal structure54includes a pair of second sealing paths60, and a third sealing path64between the glass layer56and the polymer layer58. The second sealing paths60are formed between the polymer layer58and the housing body52and between the polymer layer58and the conductive pins14. The second sealing paths60are polymer-to-metal seals. A part of the second sealing paths60is formed between the polymer layer58and the horizontal surface57of the flange55.

The third sealing path64is formed at an interface between the glass layer56and the polymer layer58and may be oriented perpendicular to the conductive pins14and the inner surface53of the housing body52. The third sealing path64is a polymer-to-glass seal. The pair of second sealing paths60are connected by the third sealing path64. Angled portions66are formed at their connecting points.

Referring toFIGS. 8A to 8D, to form the feed-through50of the second embodiment, a glass material (i.e., a glass pellet) is fused to a plurality of dummy pins40to form a glass layer56or a glass substrate. The dummy pins40are removed from the glass layer56to form a plurality of openings42. A plurality of conductive pins14are inserted into the plurality of openings42. The sub-assembly of the glass layer56and the conductive pins14is placed in the housing body52. A polymer pellet (such as epoxy) is disposed in the space between the glass layer56and the upper horizontal surface57of the flange55to fuse the conductive pins14and the housing body52. The second sealing paths60and the third sealing path64are formed when the polymer material is cured.

Third Embodiment

Referring toFIG. 9, a feed-through70in accordance with a third embodiment of the present disclosure includes a structure similar to that in the second embodiment except for a seal structure72. The seal structure72includes a first glass layer74, a second glass layer76, and a polymer layer78between the first and second glass layers74and76. The seal structure72has improved gas permeation prevention properties due to the presence of two glass layers74and76and can be fused to the conductive pins14and the housing body52having low melting points. The glass layers74and76may be properly chosen to have a thermal expansion matching that of the housing body52. The polymer layer78may be properly chosen to have a thermal expansion matching that of the conductive pins14.

Referring toFIG. 10, the seal structure72includes a pair of second sealing paths80and a pair of third sealing paths82. The pair of second sealing paths80are formed at interfaces between the polymer layer78and the aluminum housing body52and between the polymer layer78and the conductive pins14. The third sealing paths82are formed at interfaces between the polymer layer78and the first glass layer74and between the polymer layer78and the second glass layer76. The second sealing paths80are polymer-to-metal seals. The third sealing paths82are polymer-to-glass seals.

Optionally, the seal structure72may include a plurality of fourth sealing paths88that are polymer-glass-metal seals, formed between the glass layers74,76and the housing body52. The second sealing paths80, the third sealing paths82, and the fourth sealing paths88are continuously connected to form a continuous sealing boundary that has angled portions89.

To manufacture the feed-through70or71of the present embodiment, the first glass material and the second glass material are fused to dummy pins to form a first glass layer74and a second glass layer76, respectively. After the first glass layer74and the second glass layer76are cured, the dummy pins are removed to form a plurality of openings that correspond to the conductive pins. The first glass layer74is placed in the inner space of the housing body52against the flange55. A molten polymer material is then applied on the entire upper surface of the first glass layer74.

Next, the second glass layer76is placed on the molten polymer material. The conductive pins14are then inserted into the openings. Next, the second glass layer76is pressed against the first glass layer74. After the polymer layer78is cured, the seal structure that has a laminated structure is formed, as shown inFIG. 10.

Alternatively, gaps may be formed between the conductive pins14and the first glass layer74and the second glass layer76, and between the housing body52and the first glass layer74and the second glass layer76. Polymer pellets may be provided in the gaps to form additional sealing paths88, as shown inFIG. 11.

Fourth Embodiment

Referring toFIGS. 12 and 13, a feed-through100in accordance with a fourth embodiment of the present disclosure has a housing body12made of cold-rolled steel, similar to that of the first embodiment. A seal structure104seals a plurality of conductive pins14to the housing body12. The seal structure104includes a glass layer106and a plurality of polymer layers108. The polymer layers108each have a tubular body112and a flange portion114extending perpendicularly and outwardly from the tubular body112.

Referring toFIG. 14, the glass layer106is fused to the inner surface16of the housing body12to form a first sealing path110, i.e., glass-to-metal seal. The tubular bodies112of the polymer layers108are fused to the conductive pins14and the glass layer106to form second sealing paths107(i.e., polymer-to-metal seals) and third sealing paths109(i.e., polymer-to-glass seals). The flange portions114of the polymer layers108are fused to an upper surface116of the glass layer106to form polymer-to-glass seals.

To manufacture the feed-through100of the present embodiment, a glass material is fused to the housing body12and a plurality of dummy pins to form the glass layer106. After the glass material is cured, the dummy pins are removed to create a plurality of openings in the glass layer106. A plurality of conductive pins14are inserted into the openings. Polymer pellets are applied around the conductive pins14to form the tubular portions112between the glass layer106and the conductive pins14. A portion of the polymer pellets may be formed on the upper surface116of the glass layer106to form the flange portions114.

Fifth Embodiment

Referring toFIGS. 15 and 16, a feed-through120in accordance with a fifth embodiment of the present disclosure is similar to the feed-through in the fourth embodiment except for the housing body and the seal structure. The housing body52of the present embodiment is similar to that of the second embodiment, which is made of aluminum. The seal structure124of the present embodiment is similar to the seal structure104of the fourth embodiment except that the glass layer126of the present embodiment is not fused to the housing body52.

The glass layer156is fused to the inner surface of the housing body12to form a first sealing path166, i.e., a glass-to-metal seal. The first polymer layer158and the second polymer layer160are fused to the conductive pins14to form a pair of second sealing paths168, which are polymer-to-metal seals. Additionally, the first polymer layer158and the second polymer layer160are fused to the lower surface162and the upper surface164of the glass layer156, respectively, to form a pair of third sealing paths170, which are polymer-to-glass seals. The first sealing path166, the pair of the second sealing paths168, and the pair of the third sealing paths170are connected to form a continuous sealing boundary.

The seal structure124includes a pair of second sealing paths, which are polymer-to-metal seals and a pair of third sealing paths, which are glass-to-polymer seals.

Sixth Embodiment

Referring toFIGS. 17 and 18, a feed-through140in accordance with a sixth embodiment of the present disclosure is similar to the fifth embodiment, except for the seal structure and the conductive pins. The seal structure144has a glass layer146and a polymer layer having a second tubular body148and a flange portion149extending perpendicularly and inwardly from the second tubular body148. The conductive pins141are palladium plated. Because the conductive pins141have a high melting point, the glass layer146can be directly fused to the conductive pins141, thereby eliminating the first tubular bodies of the fourth embodiment.

The seal structure144has a first sealing path143, a second sealing path145, and a third sealing path147. The first sealing path143is a glass-to-metal seal at an interface between the conductive pin141and the glass layer146. The second sealing path145is a polymer-to-metal seal at an interface between the housing body52and the polymer material. The third sealing path147is a polymer-to-glass layer at an interface between the glass layer146and the polymer material.

Seventh Embodiment

Referring toFIG. 19, a feed-through150in accordance with a seventh embodiment of the present disclosure includes a housing body12, a conductive pin14, and a seal structure154. The housing body12and the conductive pins14are similar to those in the first embodiment. The housing body12is made of cold-rolled steel. The conductive pins14are gold-coated. The seal structure154includes a glass layer156, a first polymer layer158, and a second polymer layer160. The glass layer156fills in the entire inner space of the housing body12. The first polymer layer158and the second polymer layer160are formed on a lower surface162and an upper surface164of the housing body12, respectively.

The glass layer156is fused to the inner surface of the housing body152to form a first sealing path166, i.e., a glass-to-metal seal. The first polymer layer158and the second polymer layer160are fused to the conductive pins14to form a pair of second sealing paths168, which are polymer-to-metal seals. Additionally, the first polymer layer158and the second polymer layer160are fused to the lower surface162and the upper surface164of the glass layer156, respectively, to form a pair of third sealing paths170, which are polymer-to-glass seals. The first sealing path166, the pair of the second sealing paths168, and the pair of the third sealing paths170are connected to form a continuous sealing boundary.

The hybrid seal structure that includes a first material and a second material according to any of the embodiments described in the present disclosure allows for a wide selection of materials for the seal structure, the housing body, and the conductive pins. The first material may be used to prevent gas permeation, whereas the second material may be used for fusing the seal structure to the conductive pins and/or housing body if the conductive pins and housing body have low melting points. Therefore, the hybrid seal structure can effectively prevent gas permeation without damaging the housing body and the conductive pins.

The polymers used in any of the embodiments described above may be a thermoset polymer or a thermoplastic polymer. A suitable thermoset polymer includes Rohm and Haas's Corvel™ ECB-1363A Red 2036. Testing of this material confirms that satisfactory hermetic seal(s) (with a gas permeation rate as low as 10−8cm3He/sec at 1 atmosphere) in the hybrid seal structure are achieved. In addition, it is contemplated that suitable thermoplastic polymers for the disclosed construction may include Nanocor's Imperm™ 103 (a Nylon/Nanocomposite), Nylon 6,6, Ticona's Liquid Crystalline Polymer (glass-filled or no-glass-filled), Chevron Phillips's Polyphenylene Sulfide, Chevron Phillips's Polyphenylene Sulfide-Glass, Chevron Phillips's Polyphenylene Sulfide-glass and mineral, Dow's Saranex™ 11 co-polymer, EVAL™ Ethylene Vinyle Alcohol co-polymer, INEOS Barex's Polyacrylonitrile, and DuPont's Polybutylene terephthalate.

Further, the first and second materials may be properly selected to match the thermal expansion of the housing body and the conductive pins, respectively. Therefore, the hybrid seal structure can maintain integrity of the sealing paths at high temperatures.