HK1037431B - Method for the packaging of electronic components - Google Patents

Description

Electronic component packaging method

Technical Field

The present invention relates to packaging of electronic components, particularly surface-unoccupied components such as Surface Acoustic Wave (SAW) filters, RF components, sensors, and the like, and more particularly to methods of making such packages.

Background

Surface Wave Components (SWCs) are used in electronic devices, in particular high and medium frequency domain filters, to select frequency bands in mobile phones using the principle of generation and propagation of acoustic waves on piezoelectric substrates. This function requires the preparation of a free space on the surface of the element where the acoustic waves need to propagate. Therefore, in the standard protection method of the surface acoustic wave element, a hermetic ceramic or metal package is used. However, these methods are high in cost and low in throughput, and it is difficult to miniaturize the elements.

In the field of semiconductor elements, an assembly technique called CSP (chip size package or chip scale package technique) can achieve high miniaturization. This technology, which is currently most valuable in terms of miniaturization and cost, is based on a flip-chip mounting technique (well known to those skilled in the art) as shown in fig. 1.

Specifically, one semiconductor element 1 is mounted on one substrate 2 by flip-chip contacts 11 and 12. The conductive pads 21 and 22 connect the entire element 1 to an external circuit through the internal metallization coating and through holes in the substrate. A potting resin will consolidate the mechanical assembly and protect the components.

However, this method cannot be directly applied to surface wave elements: the potting resin fills the gap between the element and the substrate. This interferes with the propagation of surface acoustic waves. Secondly, since a protective film is not formed on the active surface like a semiconductor element, the resin itself is not sufficient to prevent the attack of external factors such as moisture.

In the more specific field of surface acoustic wave filters, the manufacturer siemens matsushita Components GmbH (siemens-sons electronics ltd.) proposes packaging Components in which the cap is formed by a jacket structure which surrounds the chips and is located on the substrate in the region between the chips (WO 99/43084). The sheath may be obtained from a metal foil fixed to the solderable frame of the substrate or a plastic foil bonded to the substrate between the chips. In the case of plastic foils, even if the plastic foils are metallized, the resulting shielding is neither hermetically sealed nor perfectly shielded.

Disclosure of Invention

The invention proposes to collectively wrap the chip with a deformable plastic film that will adhere to the back and sides of the chip and to the substrate. This method has the advantage of improving the mechanical strength of the chip on the substrate. It is also an advantage that after the local removal of the film as described hereinafter, a structure will be presented on which it is easy to continuously deposit a mineral substance to perfectly seal the structure. Finally, if the mineral deposition layer is chosen to be metallized, a continuous electromagnetic shield can be formed and this shield can be in direct contact with the electrical ground of the substrate.

The deformable membrane, which is bonded to the back and sides of the chips and to the substrate between the chips, forms a monolithic assembly with high mechanical strength.

In particular, one object of the present invention is an electronic component packaging method comprising the steps of:

mounting at least one electronic component on an active surface side thereof on a substrate comprising electrical contacts on a first surface and connection pads on a second surface, and comprising a first set of through holes and a set of holes for connecting the electrical contacts to the connection pads;

attaching a deformable membrane to a surface of the one or more electronic components opposite the active surface;

the deformable film is drawn from the second surface of the substrate through a set of holes to encase the one or more electronic components and the components are brought into contact with the deformable film to form a dense assembly.

According to a variant of the invention, the method of the invention may also comprise the step of: the thin film on the substrate in the region between the chips is entirely removed so that the deposited minerals completely cover the element and thus perfect hermetic sealing performance is obtained. In the case of metal deposition, this step also enables the electrical ground contact on the substrate to be re-occupied, thereby providing effective electromagnetic shielding.

Another object of the invention is a method for batch manufacturing of packaged electronic components, comprising the steps of:

mounting electronic components in batches on their active surface side on a substrate comprising electrical contacts on a first surface and connection pads on a second surface, a first set of through holes for connecting the electrical contacts to the connection pads and a second set of holes;

attaching a deformable membrane to all surfaces of each electronic component opposite the active surface;

sucking the deformable film from the second surface of the substrate through a set of holes to encapsulate the electronic component;

depositing a potting resin onto the deformable membrane to provide hermetic sealing protection for the electronic component;

the assembly formed of the resin/deformable film/substrate is cut to separate the packaged electronic components.

According to a variant of the invention, the one or more electronic components are surface acoustic wave devices.

Preferably, the operation of sucking the deformable membrane is combined with a heating step and/or a step of applying pressure to the surface of the deformable membrane.

According to a variant of the invention, the packaging method further comprises depositing a mineral substance in order to provide a hermetic seal to the top of the deformable membrane.

Preferably, the encapsulation method may further comprise depositing a conductive material on top of the deformable membrane to provide shielding for the component.

The method of packaging may further comprise attaching a second deformable membrane (which may be the same as the first deformable membrane) to the layer of conductive deposition. The second film is preferably a polymer film to which conductive mineral particles are added. The second film may thus replace the standard encapsulation resin in contact with the outside world.

Drawings

The invention may be more clearly understood and other advantages will appear from the following non-limiting description, based on and with reference to the accompanying drawings, in which:

fig. 1 demonstrates a package element according to the prior art.

Fig. 2a to 2d show the steps of the encapsulation method according to the invention.

Fig. 3a and 3b show a step of the packaging method according to the invention, which comprises adapting the electrical contacts by etching of the deformable membrane.

Figures 4a and 4b show the final protection of the elements previously covered by the deformable film with a thick layer of resin and the cutting of the elements to separate them.

Fig. 5 shows the final protection step by means of a second deformable membrane.

Detailed Description

A method of mass manufacturing packaged electronic components, which is particularly suitable for surface acoustic wave components that must maintain a free space for the propagation of acoustic waves, will be described below.

The manufacturing method comprises a first step shown in fig. 2a, i.e. the components 10 are mounted in batches on one substrate 20. This substrate is provided with connection pads 201 and 202 on one surface, i.e. the outer surface, and connection pads 101 and 102 on the surface opposite to the outer surface. The latter pads 101 and 102 are intended to be connected to the outside of the electrical contacts 103 and 104 of the component 10 by flip-chip mounting, i.e. by means of first conductive vias 301, 302 and intermediate conductive elements 105, 106. These intermediate conductive elements may be gold metal balls or may be solder balls. The electrical contact operation may be accomplished by heat pressing, adhesive bonding or ultrasonic welding.

In a second step, a deformable membrane 40 is attached to all elements, as shown in FIG. 2 b. The film is deformed and coated on the component by sucking the film through a set of holes 50 formed in the substrate 20. The membrane may be, for example, a deformable plastic membrane. The suction operation is preferably combined with a heating operation and/or an operation of applying pressure to the surface of the film to increase the deformation. Generally, the pumping operation may be performed under vacuum in a pressure reaction tank. The deformable membrane is preferably a very thin membrane, which may be about one hundred microns thick. For this purpose, it is preferable to apply an adhesive in advance on the entire surface of the film facing the element or on the entire or partial surface of the substrate. It is also possible to use films with hot-tack properties (for example thermoplastic films) to achieve bonding by the action of temperature and pressure. Specifically, the film may be Pyralux from Du Pont, Ablefilm from Ablestik, or Staystick from Apha Metals. Alternatively, the film may be conductive. In particular, the film may be a polymer with conductive particles added or a film that is metallized on one surface. The film may also be constructed of multiple layers to combine the properties of each layer. For example, a conductive layer with moisture-proof properties or a mineral layer, each of which has a small thickness in the range of several tens of micrometers to several micrometers, may be used.

The mineral layer may be SiO₂Of the SiN type, which are attached by vacuum spray deposition or vacuum plasma deposition. A parylene type organic layer may also be attached to obtain a moisture-proof function.

The use of a particularly conductive layer has the significance that electromagnetic shielding can be provided for the component. If this layer is to be grounded, it may be advantageous to etch the deformable membrane 40 to create a conductive area corresponding to the ground pad of the substrate. This opening can be machined by methods such as laser or mechanical drilling (partial cutting). In particular, FIG. 3a shows a top view of a substrate with holes 50 through which the membrane can be sucked to bring the deformable membrane right against the substrate. In the cross-sectional view along line AA' shown in fig. 3b, the ground ring 107 corresponds to a ground pad. The deformable membrane 40 is etched in a portion of the substrate, as best shown in fig. 3a, and in particular in the portion where the ground ring 107 is located. In this way, electrical contacts can be retrofitted onto pads 107 during subsequent conductive deposition processes.

The method according to the invention also comprises a final protection step, which is carried out by casting over the entire substrate a potting resin 70, which may be of the epoxy type with the addition of mineral particles and which is located on top of the conductive deposit 60 and of the deformable membrane 40. The previously attached deformable membrane may act as a barrier to prevent the above mentioned potting resin from penetrating between the substrate and the element as shown in fig. 4 a.

In a standard procedure, the components can then be electrically tested on the substrate, individually marked, and separated by mechanical cutting, as shown in fig. 4 b.

In this way, a high degree of integration can be achieved with the batch packaging method according to the invention, since the thickness of the deformable membrane is small. Furthermore, the film and the covering resin improve the mechanical strength of the assembly, making the present invention perfectly suitable for large-sized surface acoustic wave elements (which is not the case in standard hermetic packages with flip-chip assemblies).

According to another variant of the invention, a second deformable film layer may be used instead of a thick layer of resin, so as to obtain hermetic sealing protection of one or more components. To this end, FIG. 5 shows a configuration in which the second deformable membrane 80 is attached on top of the conductive layer 60, and the conductive layer 60 itself is attached to the surface of the first deformable membrane 40.

Claims (15)

1. An electronic component packaging method, comprising the following steps:

mounting at least one electronic component on an active surface side thereof on a substrate comprising electrical contacts on a first surface and connection pads on a second surface, and comprising a first set of through holes and a set of holes for connecting the electrical contacts to the connection pads;

attaching a deformable membrane to a surface of the one or more electronic components opposite the active surface;

the deformable film is drawn from the second surface of the substrate through a set of holes to encase the one or more electronic components and the components are brought into contact with the deformable film to form a dense assembly.

2. The method of claim 1, wherein the one or more electronic components are surface acoustic wave devices.

3. Method of encapsulation according to claim 1 or 2, characterized in that the mounting is achieved by beads of soldering material.

4. A method of packaging according to claim 1 or 2, comprising a heating step in combination with the pumping step.

5. Method for encapsulating according to claim 1 or 2, characterized in that the suction step is carried out by applying pressure on the surface of the film.

6. Method for encapsulating according to claim 1 or 2, characterized in that the deformable membrane is provided with an adhesive on a surface thereof which is to be brought into contact with a surface of the electronic component or components opposite the active surface.

7. Method for encapsulating according to claim 1 or 2, characterized in that the deformable film is a thermoplastic film.

8. Method for encapsulating according to claim 1 or 2, characterized in that the deformable film is an electrically conductive film.

9. Method of encapsulation according to claim 1 or 2, characterized in that the thickness of the deformable film is of the order of a few tens of microns.

10. The method of packaging of claim 1 or 2, further comprising depositing a mineral on the deformable membrane.

11. A method of packaging according to claim 1 or 2, comprising depositing a conductive material to shield the element.

12. The encapsulation method according to claim 1 or 2, comprising the following steps: the deformable membrane is partially cut at least on some of the grounding rings in order to adapt the electrical contacts.

13. A method of packaging according to claim 1 or 2, comprising depositing a layer of potting resin onto the deformable membrane to provide hermetic sealing protection for the one or more electronic components.

14. A method of packaging according to claim 1 or 2, comprising attaching a second deformable membrane to the deformable membrane to provide hermetic sealing protection for the one or more electronic components.

15. A method of batch manufacturing packaged electronic components, comprising the steps of:

mounting electronic components in batches on their active surface side onto a substrate comprising electrical contacts on a first surface and connection pads on a second surface, and further comprising a first set of through holes and a second set of holes for connecting the electrical contacts to the connection pads;

attaching a deformable membrane to all surfaces of each electronic component opposite the active surface;

sucking the deformable film from the second surface of the substrate through a set of holes to encapsulate the electronic component;

depositing a potting resin onto the deformable membrane to provide hermetic sealing protection for the electronic component;

the assembly formed of the resin/deformable film/substrate is cut to separate the packaged electronic components.