Methods of manufacture of top port surface mount MEMS microphones

A method for manufacturing a plurality of solder reflow surface mount microelectromechanical system (MEMS) microphones, the method comprising:

• providing an unsingulated panel of rectangular base portions, each individual rectangular base portion including:
• a rigid base layer comprised of comprised of multiple sub-layers of printed circuit board material, each sub-layer having a predetermined coefficient of thermal expansion, wherein the base layer has a substantially flat upper surface and a substantially flat lower surface, the upper surface having an inner area and a coupling area, the coupling area located between the inner area and the edges of the base layer, and completely surrounding the inner area;
• a plurality of metal pads located on the upper surface of the base layer and defined by a first solder mask;
• a plurality of flat solder pads located on the lower surface of the base layer and defined by a second solder mask layer, the plurality of solder pads arranged to be within a perimeter of the lower surface of the base layer;
• one or more electrical connections passing through the base layer, wherein the connections electrically couple one or more of the plurality of metal pads on the upper surface of the base layer to one or more of the plurality of solder pads on the lower surface of the base layer;
• and
• at least one passive electrical element disposed within the base layer and electrically coupled between one of the plurality of metal pads and one of the plurality of solder pads;
• mounting a MEMS microphone die to the upper surface of each individual base portion in the unsingulated panel of base portions, and electrically coupling each MEMS microphone die to at least one of the plurality of metal pads on the upper surface of the base layer of its respective base portion;
• and
• providing a plurality of rectangular cover portions, each rectangular cover portion formed from a single piece of solid material and having a predetermined shape, each rectangular cover portion having a top portion and a substantially vertical and continuous sidewall portion that adjoins the top portion at an angle and that completely surrounds and supports the top portion, the sidewall portion having a predetermined height, an exterior surface, an interior surface, and a coupling surface, wherein each rectangular cover further comprises an acoustic port disposed in the top portion of the rectangular cover and passing completely through the rectangular cover, wherein the acoustic port is disposed in a position offset from a centerpoint of the top portion of the rectangular cover;
• coupling one rectangular cover portion to each base portion of the panel of unsingulated base portions having a MEMS microphone die mounted thereon,
• wherein the coupling surface of the sidewall portion of the cover portion being coupled is aligned with and mechanically coupled to the coupling area of the base layer of its respective base portion;
• wherein the predetermined height of the sidewall portion of the cover portion, the interior surface of the sidewall portion of the cover portion, and the interior surface of the top portion of the cover portion, in cooperation with the interior region of the upper surface of the base layer of its respective base portion, define an acoustic chamber for the MEMS microphone die and provide a protective enclosure for its respective MEMS microphone die;
• and
• wherein the overall length of base portions having a MEMS microphone die mounted thereon and their respective cover portions are substantially equal, and the overall width of the base portions having a MEMS microphone die mounted thereon and their respective cover portions are substantially equal;
• and
• singulating the panel of base portions into discrete surface mount MEMS microphones.

A method for manufacturing a plurality of solder reflow surface mount microelectromechanical system (MEMS) microphones, the method comprising:

• providing an unsingulated panel comprising a plurality of rectangular base elements, each individual base element including:
• a rigid core layer comprised of multiple sub-layers of FR-4 printed circuit board material, each sub-layer having a predetermined coefficient of thermal expansion, wherein the core layer has a substantially flat top surface and a substantially flat bottom surface, the top surface having a die mount region and an attachment region, the attachment region positioned between the die mount region and the edges of the core layer, and completely surrounding the die mount region;
• a plurality of metal pads located on the top surface of the core layer and defined by a first solder mask;
• a plurality of flat solder pads located on the bottom surface of the core layer and defined by a second solder mask, the plurality of solder pads arranged to be within a perimeter of the bottom surface of the core layer, wherein the solder pads are plated with at least one metal;
• a plurality of electrical connections passing through the core layer that electrically couple one or more of the plurality of metal pads on the top surface of the core layer to one or more of the plurality of solder pads on the bottom surface of the core layer;
• and
• at least one passive electrical element disposed within the core layer and electrically coupled between one of the plurality of metal pads and one of the plurality of solder pads;
• and
• a pressure-equalizing MEMS microphone die having an internal acoustic channel mounted in the die mount region of the core layer, and electrically coupled to one or more of the metal pads on the top surface of the core layer;
• providing a plurality of single-piece rectangular cover elements formed from a solid material and having a predetermined shape, each rectangular cover element having a top region and a continuous wall region, the continuous wall region supporting the top region and adjoining the top region at a substantially perpendicular angle and having a predetermined height, an exterior surface, an interior surface, and an attachment surface, and an acoustic port located in the top region of the cover element and passing completely through the top region, wherein the acoustic port is disposed in a position offset from a centerpoint of the cover element;
• coupling a rectangular cover element to each base element of the panel of unsingulated base elements, one cover element to each individual base element,
• wherein each cover element is coupled to its respective base element such that the attachment surface of the wall region of the cover element is aligned with and physically coupled to the attachment region of the top surface of the core layer of its respective base element, thereby forming a protective enclosure for its respective MEMS microphone die;
• wherein the interior of the protective enclosure is an acoustic chamber having a volume defined by the predetermined height of wall region of the cover element, and the width and length of the top region of the cover element;
• wherein a diaphragm of the MEMS microphone die defines a front volume and a back volume within its respective acoustic chamber, and the acoustic port disposed in the cover element is acoustically coupled to the diaphragm;
• and
• wherein the interface between the attachment surface of the continuous wall region of cover element and the attachment area of the top surface of the core layer of the base element is sealed to prevent the escape of acoustic pressure from the front volume;
• and
• singulating the panel of base elements into discrete surface mount MEMS microphones.

A method for manufacturing a plurality of solder reflow surface mount microelectromechanical system (MEMS) microphones, the method comprising:

• providing a plurality of pressure-equalizing MEMS microphone die, each having an internal acoustic channel;
• providing an unsingulated panel that includes a plurality of first housing elements each having a rectangular shape, the first housing elements further including:
• a rigid core layer comprised of multiple layers of FR-4 printed circuit board material, each layer of FR-4 material having a predetermined coefficient of thermal expansion, wherein the core layer has a substantially flat top surface and a substantially flat bottom surface, wherein the top surface has an die mount region and an attachment region, the attachment region being arranged between the die mount region and the edges of the core layer, and the attachment region completely surrounds the die mount region;
• a plurality of metal pads disposed on the top surface of the core layer and defined by a first solder mask layer, wherein the metal pads are plated with at least one metal;
• a plurality of flat solder pads disposed on the bottom surface of the core layer and defined by a second solder mask layer, the plurality of solder pads arranged to be within a perimeter of the bottom surface of the core layer, wherein the solder pads are plated with at least one metal;
• one or more electrical vias located inside the core layer, wherein the vias electrically couple one or more of the plurality of metal pads on the top surface of the core layer to one or more of the plurality of solder pads on the bottom surface of the core layer;
• and
• at least one passive electrical element disposed within the core layer and electrically coupled between one of the plurality of metal pads and one of the plurality of solder pads, wherein the at least one passive electrical element includes a dielectric or resistive material that is different from the printed circuit board material in the core layer;
• providing a plurality of second housing elements each having a rectangular shape, each second housing element formed from a single piece of solid material, and having a substantially flat top region and a continuous wall region, the continuous wall region supporting the top region and adjoining the top region at a substantially perpendicular angle, the continuous wall region having a predetermined height, an exterior surface, an interior surface, and an attachment surface, and an acoustic port located in the top region of the second housing element and passing completely through the second housing element, wherein the acoustic port is disposed in a position offset from a centerpoint of the second housing element;
• coupling one of the plurality of MEMS microphone die to one or more of the first housing elements in the unsingulated panel of first housing elements, wherein each MEMS microphone die is disposed in the die mount region of the core layer of its respective first housing element, and electrically coupled to one or more of the metal pads on the top surface of the core layer of its respective first housing element;
• assembling a protective housing for each MEMS microphone die mounted on a first housing element in the unsingulated panel of first housing elements by coupling one of the second housing elements to each first housing element in the unsingulated panel of first housing elements having a MEMS microphone die mounted thereon,
• wherein the attachment surface of the wall region of the second housing element is aligned with and physically coupled to the attachment region of the top surface of the core layer of the first housing element, thereby forming a protective enclosure for the MEMS microphone die, and
• wherein the interior of the protective enclosure is an acoustic chamber having a volume defined by the predetermined height of wall region of the second housing element, and the width and length of the top region of the second housing element;
• and
• singulating the panel of first housing elements into discrete surface mount MEMS microphones.