Circuit board with resilient seal as vapor barrier

A circuit board has a socket with at least one plated through-hole. A connector includes a housing that has first and second connector interfaces with, respectively, at least first and second connector contacts. The first connector interface opens into an interior of the housing such that there is a vapor path through the first connector interface and the interior of the housing to the second connector contact at the second connector interface. A resilient seal is located at the first connector interface. The first connector contact extends through the resilient seal and into the plated through-hole. The resilient seal intimately seals around the first connector contact and provides a barrier at the first connector interface into the vapor path.

BACKGROUND

A circuit board can include an array of various electrical devices. Typically, such devices include a connector that permits the circuit board to be electrically connected to auxiliary components. The connector has a circuit board interface with contacts that electrically connect with plated through-holes in the circuit board. The connector also includes a mate interface with contacts to connect to a mating connector of the auxiliary components. A conformal coating can be applied to protect the circuit board and connector from moisture and other substances. Such coatings can be deposited by a vapor deposition process. A cap can be provided on the mating interface of the connector to limit infiltration of the vapor during the deposition process. The cap is then later removed for connection to the auxiliary component.

SUMMARY

A circuit board apparatus according to an example of the present disclosure includes a circuit board that has a socket with at least one plated through-hole. A connector includes a housing that has first and second connector interfaces with, respectively, at least first and second connector contacts. The first connector interface opens into an interior of the housing such that there is a vapor path through the first connector interface and the interior of the housing to the second connector contact at the second connector interface, and a resilient seal at the first connector interface. The first connector contact extends through the resilient seal and into the plated through-hole. The resilient seal intimately seals around the first connector contact and provides a barrier at the first connector interface into the vapor path.

In a further embodiment of any of the foregoing embodiments, the resilient seal has a hardness of 15 Shore-OO to 25 Shore-A.

In a further embodiment of any of the foregoing embodiments, a fully connected position with respect to the first connector contact extending into the plated through-hole, there is a gap thickness between the circuit board and the first connector interface, the resilient seal having an initial thickness that is at least 120% of the gap thickness.

In a further embodiment of any of the foregoing embodiments, the resilient seal has a pilot hole through which the first connector contact extends, the pilot hole initially being smaller in diameter than the first connector contact such that the pilot hole compresses around the first connector contact.

In a further embodiment of any of the foregoing embodiments, the pilot hole is approximately 50% to approximately 75% of the diameter of the first connector contact.

In a further embodiment of any of the foregoing embodiments, the resilient seal comprises a silicone material.

A further embodiment of any of the foregoing embodiments includes a conformal coating on the connector and the circuit board.

A method for fabricating a circuit board apparatus according to an example of the present disclosure includes providing a circuit board that has a socket with at least one plated through-hole, and providing a connector that has a housing with first and second connector interfaces that have, respectively, at least first and second connector contacts. The first connector interface opens into an interior of the housing such that there is a vapor path through the first connector interface and interior of the housing to the second connector contact at the second connector interface The first connector contact is inserted through the resilient seal and into the plated through-hole such that the resilient seal intimately seals around the first connector contact to provide a barrier at the first connector interface into the vapor path.

In a further embodiment of any of the foregoing embodiments, the inserting includes inserting the first connector contact through a pilot hole in the resilient seal, the pilot hole initially being smaller in diameter than the first connector contact such that the pilot hole compresses around the first connector contact upon insertion.

In a further embodiment of any of the foregoing embodiments, the inserting includes using the first connector contact to punch a hole through the resilient seal.

A further embodiment of any of the foregoing embodiments includes using a vapor to deposit a conformal coating on the connector and the circuit board, and using the resilient seal to limit infiltration of the vapor at the first connector interface into the vapor path and thereby limit deposition of the vapor onto the second connector contact at the second connector interface.

A circuit board seal according to an example of the present disclosure includes a resilient seal having a seal geometry configured to fit in a connector interface between a connector and a circuit board and intimately seal around a connector contact to provide a barrier at the connector interface into a vapor path through the connector.

In a further embodiment of any of the foregoing embodiments, the resilient seal has a hardness of 15 Shore-OO to 25 Shore-A.

In a further embodiment of any of the foregoing embodiments, the resilient seal has at least one pre-formed pilot hole.

In a further embodiment of any of the foregoing embodiments, the pre-formed pilot hole is approximately 50% to approximately 75% of a diameter of the connector pin.

DETAILED DESCRIPTION

FIG. 1illustrates an example circuit board apparatus20. Circuit boards can include electrical connectors for electrically connecting the board to one or more auxiliary components. The circuit board and connectors may be sealed with a conformal coating to protect against infiltration of moisture or other substances that can compromise electrical connections. In this regard, the circuit board apparatus20includes a vapor barrier to limit infiltration moisture or other substances into the interior of such connectors and/or to limit infiltration of vapor during application of the conformal coating.

In this example, the circuit board apparatus20includes a circuit board22that has a socket24with at least one plated through-hole26. The socket24may include a single plated through-hole26or an array of plated though-holes26, depending on the requirements for electrical connection to the circuit board22. The socket24with plated though-holes26permit connection with a connector28. The socket24refers to one or more plated through-holes26that are grouped for a common connection and may or may not include other structural features on the circuit board22.

The connector28is a dual-interface connector and includes first and second connector interfaces30/32with, respectively, corresponding connector contacts, generally represented at34. The contacts34are illustrated as pins, but can alternatively be sockets. In this example, the contacts34at the first connector interface30are received into the corresponding plated through-holes26of the socket24, while the contacts34at the second connector interface32will later be connected to a corresponding mating connector for electrical connection with an auxiliary component. The connector contact or contacts34at the first connector interface30thus correspond in number and location to the number and location of the plated through-hole or holes26of the socket24. Additionally, the contacts34and holes26may be provided in a pattern to ensure fail-safe assembly of the connector28to the socket24such that the connector28cannot be installed in an improper orientation.

The connector28includes a housing36that defines the first and second connector interfaces30/32. As an example, the housing36may be, but is not limited to, a molded plastic housing. In this example, the first connector interface30includes a mouth30athat opens into an interior36aof the housing36. The mouth30amay open directly into the interior36aor, alternatively, may include a mouth floor30bthrough which the contacts34extend. The opening into the interior36a, either by direct opening or by gaps between the contacts34and the mouth floor30b, provides a vapor path, represented generally at38, through the first connector interface30and the interior36aof the housing28to the contacts34at the second connector interface32. Unless sealed, moisture or other substances may infiltrate through the first connector interface30to the interior36and accumulate onto the contacts34at the second connector interface32. The accumulation can impair electrical contact between the contacts34at the second connector interface32and a mating connector.

In this regard, the circuit board apparatus20includes a resilient seal40located at the first connector interface30. The contacts34of the first connector interface30extend through the resilient seal40and into the plated through-holes26. The resilient seal40intimately seals around the contacts34and mouth30ato provide a barrier at the first connector interface30to thereby limit infiltration of vapor into the vapor path38. For example, the resilient seal40intimately seals by providing a constant resilience force against the contacts34and/or mouth30a.

A conformal coating42can optionally be deposited over the connector28and circuit board22to protect the connector from moisture and substance infiltration once the circuit board apparatus20is in use. As an example, the coating can be, but is not limited to, a poly(p-xylylene) polymer coating. The coating42can be applied by vapor deposition. Unless sealed, the vapor during the vapor deposition may infiltrate through the first connector interface30into the connector28and deposit on the contacts34at the second connector interface32, which is itself sealed with a cap, C, until connection with the mating connector. However, the intimate sealing of the resilient seal40around the contacts34and in the mouth30aat the first connector interface30serves as a vapor barrier to limit infiltration into the vapor path38. Even if such a coating42is not used, the resilient seal40can be utilized to limit infiltration of other vapors or substances into the interior36aof the connector28, for example other liquid conformal coatings.

The resilient seal40is a pre-fabricated seal that is assembled into position between the first connector interface30and the circuit board22during assembly of the circuit board apparatus20. For example,FIG. 2illustrates an isolated view of an example of the resilient seal40. In this example, the resilient seal40has a rectangular geometry that is configured to fit in the first connector interface30. That is, the first connector interface30is likewise rectangular such that the resilient seal40fits within the mouth30a. Thus, the geometry of the resilient seal40, whether rectangular or other shape, is configured to correspond to the geometry of the first connector interface30.

The mouth30ahas a gap thickness44(FIG. 1) between the circuit board22, which is flush with the sides of the mouth30a, and the floor30bof the mouth30a. The resilient seal40has an initial thickness, t, defined with respect to the gap thickness44of the first connector interface30. For instance, the initial thickness of the resilient seal40is greater than the gap thickness44by at least 120% such that once the connector28is in a fully connected position with respect to the contacts34being received into the plated through-holes26, the resilient seal40is compressed to thereby maintain a resilient force in the mouth30a. As can be appreciated, if the resilient seal40is too thick, the contacts34may not properly reach the plated though-holes26, and if the resilient seal40is thin, there will be no resilient force to maintain intimate sealing in the mouth30a.

In order to provide the proper level of resilience, and thus also resilient force, the resilient seal40is fabricated of a relatively soft, elastomeric material. As an example, the resilient seal40is fabricated of, but is not limited to, silicone or fluorosilicone. Silicone and fluorosilicone have relatively high temperature resistance and are resistant to degradation from moisture, oils and other substances. Silicone is a polymer that generally has a polymeric backbone of Si—O repeat units and organic side chains. Fluorosilicone is a sub-set of silicone and also has a polymeric backbone of Si—O repeat units, but includes fluorinated side chains. As a further example, the silicone or fluorosilicone material has a hardness of 15 Shore-OO to 25 Shore-A. Such a range is relatively soft and permits the resilient seal40to compress around the contacts34to provide a resilient force and good vapor barrier. However, if the resilient seal40is too soft, it will not resile and provide the intimate resilient force. If the resilient seal40is too hard, it will not sufficiently compress to provide the intimate resilient force.

The resilient seal40can have pre-formed pilot holes, as shown inFIG. 2at40aor, alternatively, can have no pilot holes as shown in the alternate example resilient seal40′ inFIG. 3. The number and location of the pilot holes40a, if used, corresponds to the number and location of the contacts34at the first connector interface30. For example, each of the pilot holes40is smaller in diameter than the corresponding contact34such that each pilot hole compresses around the contacts34to provide the resilient force for intimate sealing. In a further example, the pilot hole40acan have a diameter of approximately 50% to approximately 75% of the diameter of the contact34.

Alternatively, if the pilot holes40aare not used, the resilient seal40′ is soft enough to permit the contacts34to punch through the resilient seal40′ and into the plated through-holes26, without significantly damaging or compromising the resilient seal40′. In such an example, the contacts34thus self-form holes in the resilient seal40′.

FIG. 4illustrates another example circuit board apparatus120that is similar to the circuit board apparatus20with the exception that the second connector interface132is on top of the connector128in a straight configuration rather than the right angle configuration of the circuit board apparatus20.

A method for fabricating the circuit board apparatus20/120can include providing the circuit board22as described herein, providing the connector28as described herein, and inserting the contact or contacts34through the resilient seal40/40′ and into the plated through-hole or holes26such that the resilient seal40/40′ intimately seals around the contact or contacts34to provide a barrier at the first connector interface30into the vapor path38. If the resilient seal40with the pilot holes40ais used in the method, the contacts34are inserted through the pilot holes40a. If the resilient seal40′ is used in the method, the contacts34are used to punch through the resilient seal40′ and into the plated through-holes26. In either variation, the resilient seal40/40′ can either be applied i) onto the contacts34followed by applying the connector28with the resilient seal40/40′ to the socket24to fit the contacts34into the plated though-holes26or ii) onto the socket24followed by inserting the contacts34through the resilient seal40/40′ and into the plated through-holes26. As can be appreciated, further variations of the method incorporate the features described with respect to the circuit board apparatus20/120herein.