Electronic module having electromagnetic shielding structure and manufacturing method thereof

An electronic module having an electromagnetic shielding structure and its manufacturing method are provided. At first, a first substrate and a second substrate are separately provided. At least one electronic element and at least one connection pad are formed on a surface of the first substrate. The second substrate includes a conductive film and at least one conductive bump is formed on a surface of the conductive film. The first substrate and the second substrate are laminated together wherein the conductive bump is aligned with and connected to the connection pad to obtain the electronic module.

FIELD OF THE INVENTION

The present disclosure relates to an electronic module having an electromagnetic shielding structure and a manufacturing method of the electronic module, and particularly to an electromagnetic shielding structure used in a miniaturized electronic module.

BACKGROUND OF THE INVENTION

For an electronic element, electromagnetic interference (EMI) usually occurs and affects neighboring electronic circuits via electromagnetic induction, electrostatic coupling, or conduction. Disturbance due to electromagnetic interface may degrade performance or cause malfunction of the electronic circuits. Therefore, electromagnetic shielding such as blocking interference of high frequency electromagnetic signals should be considered while designing electronic modules. Furthermore, the progressive miniaturization of electronic modules in recent years will worsen the disturbance, and it is difficult or expensive to build electromagnetic shielding structures within tiny space between electronic circuits.

Electromagnetic shielding solutions include board-level shielding and package-level shielding. The package-level shielding can be applied to smaller electronic module. For example, conformal shielding and compartment shielding are developed to achieve electromagnetic shielding in small space. A simplified, flexible, easily controllable and cost-effective method for forming an electromagnetic shielding structure in a miniaturized electronic module with high yield rate is desired.

SUMMARY OF THE INVENTION

The present disclosure provides an electronic module having an electromagnetic shielding structure. The electronic module includes a first substrate and a second substrate. At least one electronic element and at least one connection pad are formed on a surface of the first substrate. The second substrate includes a conductive film and at least one conductive bump formed on the conductive film. The conductive bump is connected to the connection pad.

In an embodiment, the connection pad is electrically connected to a ground pin of the electronic module through a via connection in the first substrate.

In an embodiment, a ground plane is disposed on the surface of the first substrate or buried in the first substrate. The connection pad is electrically connected to the ground pin through the via connection and/or the ground plane.

In an embodiment, a gap between the first substrate and the second substrate is filled with an insulating adhesive.

In an embodiment, the second substrate includes an insulating film covering the surface of the conductive film and the conductive bump. A top surface of the conductive bump is exposed from the insulating film.

In an embodiment, the second substrate includes an insulating layer disposed on the other surface of the conductive film.

In an embodiment, a plurality of conductive bumps are arranged on periphery of the electronic element, and a distance between any two adjacent conductive bumps is less than 1 mm.

In an embodiment, a portion of the conductive bumps are exposed at a lateral surface of the electronic module, and a protection layer is applied to the lateral surface of the electronic module and the exposed portion of the conductive bumps.

In an embodiment, the conductive bump has a tapering shape and narrows away from the conductive film.

Another aspect of the present disclosure provides a manufacturing method of an electronic module having an electromagnetic shielding structure. A first substrate and a second substrate are separately provided. At least one electronic element and at least one connection pad are formed on a surface of the first substrate. The second substrate includes a conductive film and at least one conductive bump formed on a surface of the conductive film. The first substrate and the second substrate are laminated wherein the conductive bump is aligned with and connected to the connection pad.

In an embodiment, the connection pad is formed on the surface of the first substrate by surface-mount technology before the electronic element is mounted on the first substrate.

In an embodiment, the connection pad is preheated by heating the ground pin electrically connected to the connection pad. The substrates are stacked by aligning the conductive bump with the connection pad. Then, the stacked substrates are laminated wherein the conductive bump is connected to the connection pad.

In an embodiment, the conductive bump is formed on the surface of the conductive film by a printing process.

In an embodiment, the electronic module is cut along the conductive bumps near a boundary of the electronic module to expose a portion of the conductive bumps at a lateral surface of the electronic module. Then, a protection layer is applied to the lateral surface of the electronic module and the exposed portion of the conductive bumps.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Please refer toFIGS. 1A-1C, schematic diagrams illustrating a manufacturing method of an electronic module having an electromagnetic shielding structure according to an embodiment of the preset invention. At first, a first substrate11is provided (FIG. 1A). A plurality of electronic elements111for the electronic module are mounted on a first surface110aof the substrate11. For example, the electronic elements111are mounted on the first surface110aby surface-mount technology (SMT). Leads of the electronic elements111are soldered to respective functional pads132on the first surface110aby using solders131. Before or after the SMT process, a plurality of connection pads112are formed on the first surface110aof the first substrate11wherein the connection pads112are disposed at the positions where the electromagnetic shielding structures will be formed. The connection pads112are electrically connected to a ground plane1121or ground pins119aof the electronic module through via connections1120. The ground plane1121is disposed on the first surface110aof the first substrate11or buried in the first substrate11as an inner ground plane. The ground plane1121is electrically connected to the ground pins119a. The first substrate11may be a rigid printed circuit board, a flexible printed circuit board or any substrate capable of supporting electronic components. A plurality of module pins119a-119fare formed on a second surface110bof the first substrate11which is opposite to the first surface110a. These pins119a-119finclude power pins, data pins, ground pins (e.g.119a) and other essential pins for different functions. The ground pins119aare directly electrically connected to the connection pads112or indirectly electrically connected to the connection pads112through the via connections1120.

On the other hand, a second substrate21of the electronic module is provided (FIG. 1B). The second substrate21includes a conductive film12, e.g. copper foil, other metal foil or film made of conductive material. Areas of the first substrate11and the conductive film12are substantially identical. A plurality of micro conductive bumps122are formed on a first surface120of the conductive film12. The positions of the conductive bumps122correspond to the positions of the connection pads112on the first surface110aof the first substrate11. For example, the conductive bumps122are made of silver paste by a printing process. An insulating film123, e.g. prepreg is provided to separate the electronic elements111from the conductive film12. The insulating film123has a plurality of holes1230corresponding to the conductive bumps122so that top surfaces of the conductive bumps122are exposed from the insulating film123. In other words, the insulating film123covers the first surface120of the conductive film12and the conductive bumps122except the top surfaces of the conductive bumps122. The conductive bumps122have a tapering shape and narrow away from the first surface120. Hence, it is easier to align the conductive bumps122with the connection pads112during the PCB stacking process, and the resultant structure has better strength. The prepreg is made of a curable soft material, e.g. resin such as epoxy or polyimide, mixture of resin and glass fiber, ceramic material or glass. In addition, an insulating layer124, e.g. prepreg is disposed on a second surface121of the conductive film12to isolate the conductive film12from external influence. The conductive film12and the insulating film (e.g. prepreg)123and/or the insulating layer124are laminated by hot press lamination. Thus, the second substrate21is formed. In another embodiment, the insulating layer124is disposed on the second surface121of the conductive film12before the micro conductive bumps122are formed on the surface120of the conductive film12.

In another embodiment, no holes are formed on the insulating film123before the lamination step. Then, during the lamination step, tips of the conductive bumps122can protrude from the insulating film123to form the holes1230on the insulating film123.

Please refer toFIG. 1Cillustrating the resultant structure of the electronic module10. The first substrate11formed with the electronic elements111and the second substrate21are stacked face to face wherein the exposed or protruded conductive bumps122of the second substrate21are aligned with the connection pads112on the first substrate11. The stacked structure is laminated to form the electronic module10wherein the conductive bumps122are connected to or joined onto the corresponding connection pads112.

Furthermore, while forming the conductive bumps122by the printing process, additional conductive frames (not shown) may be formed to construct compartments (not shown) for accommodating the electronic elements111. Therefore, the electronic module10takes advantages of both conformal shielding and compartment shielding to achieve electromagnetic shielding.

Since the connection pads112are electrically connected to the ground plane1121or the ground pins119aof the electronic module10through the via connections1120, the connection pads112may be preheated by heating the ground pins119ato slightly melt the connection pads112so as to assist bonding between the connection pads112and the conductive bumps122. For example, a heating element (not shown) is connected to the ground pins119ato provide heat to the ground pins119a. The heat is transferred to the via connections1120, the ground plane1121and the connection pads112on the first substrate11by means of heat conduction.

To enhance the isolating effect and the bonding between the first substrate11and the second substrate21, an underfilling process is performed to inject an insulating adhesive30into gaps between the first substrate11and the second substrate21. An epoxy mixture, for example, can be used in the underfilling process to effectively glue the first substrate11and the second substrate21together.

After the lamination step, solder ball placement is performed to join solder balls130onto the pins119a-119fof the electronic module10. The material of the solder balls130is tin or tin alloy such as silver-tin alloy, copper-tin alloy, tin-lead alloy or tin-zinc alloy. When the electronic module10is soldered to a system printed circuit board (PCB)40by using the solder balls130, the ground pins119aare electrically connected to the grounding pads41a, while the other module pins119b-119fsuch as power pins and data pins are electrically connected to the corresponding functional pads41b-41fof the system printed circuit board40.

Please refer toFIG. 2, a schematic diagram illustrating structure of an electronic module having an electromagnetic shielding structure according to another embodiment of the present invention. The size of the electronic module can be further reduced by cutting the electronic module along the conductive bumps122aand122bnear boundaries of the electronic module. Therefore, the electronic module20has a smaller surface area than the electronic module10in the above embodiment. The conductive bumps122aand122bare exposed at lateral surfaces of the electronic module20. Then, a thin protection layer50is applied to the top surfaces and the lateral surfaces of the electronic module20and the exposed portions of the conductive bumps122aand122b. Under this condition, the insulating layer124may be omitted to further reduce the size of the electronic module20.

Please refer toFIG. 3A, a schematic diagram illustrating layout of the conductive bumps in the electronic module. The conductive bumps122are closely arranged on the periphery of the shielded areas4where the sensitive electronic elements are located. According to the layout of the sensitive electronic elements, the conductive bumps122may be arranged on periphery of the electronic module and/or arranged at inner part of the electronic module. The distance between two adjacent conductive bumps122is less than 1 mm. Thus, electromagnetic signals do not pass in and out the surrounded areas4laterally so that the electronic elements are shielded from the electromagnetic interference. As shown inFIG. 3A, there are two shielded areas4surrounded by the conductive bumps122. It is to be noted that the number of the shielded areas4in an electronic module is not limited and it varies according to the performance and quantity of the electronic elements.FIG. 3Billustrates another example indicating that only a portion4bof the electronic module should be shielded so that the conductive bumps122do not cover all the electronic module. It is to be noted that the electronic element/module may be entirely or partially surrounded by the closely arranged conductive bumps122according to the balance between electromagnetic shielding effect and miniaturization requirement.

According to the present disclosure, the electronic module with electromagnetic shielding function can be manufactured by a simplified method which can be integrated into a package process. The electromagnetic shielding structure can be disposed in much small areas of the electronic module. Therefore, it is advantageous to miniaturization of the electronic module by using the electromagnetic shielding structure of the present disclosure in the electronic module. The electronic module is manufactured in a simplified, flexible, easily controllable and cost-effective manner. Furthermore, high yield rate is achieved due to the easily controllable feature of the manufacturing method.