A kind of SAW device air-tightness wafer level packaging structure and technique
Technical field
The present invention relates to SAW device, and in particular to a kind of SAW device air-tightness wafer level packaging structure and
Technique, belongs to sound table device packaging technique field.
Background technology
Surface acoustic wave(Surface Acoustic Wave, SAW)Device is a kind of special using surface acoustic wave effect and resonance
There is the device of selection index system made of property to frequency.SAW device, especially SAW filter(Surface
Acoustic Wave Filter, SAWF)With it is small, light-weight, uniformity is good, reliability level is high, can be real to signal
When processing, the advantage such as analog/digital is compatible, electromagnetism interference performance is good, loss is low and frequency selectivity is good, be always to move to lead to
The Primary Component of news and automotive electronics.With the continuous development of the field technologies such as mobile communication, emerging technology is applied to SAWF
Increasingly higher demands are proposed, and the development trend of SAWF is miniaturization in the range of the world today.2001-2015 America and Europes,
The SAWF volume-diminisheds of Japan are to the 1% of original size, so that the volume of mobile phone is substantially reduced, current village of Japan field
The acoustic surface wave duplexer that company releases, size is only 1.8 × 1.4 × 0.6cm3, weight 15mg.
External SAW device experienced wafer-level package(Chip Scale Package, CSP)Afterwards, by 2011
Commercial wafer scale afterwards(Wafer level package, WLP)The SAW device of encapsulation starts volume production, and wafer-level packaging is to utilize crystalline substance
Circle is packaged, and cuts into the device of single after the completion of encapsulation again.
The SAW device size of no pin ceramic shell and Wire Bonding Technology is used as 3.0 × 3.0mm2, it is thick
Degree reaches 1.2mm, package area:Chip area >=2.The CSP SAW devices combined using ceramic substrate and flip chip technology
Appearance and size narrows down to 1.1 × 0.9mm2, the thickness of device is 0.5mm, package area:Chip area≤1.5.The typical case of WLP
Device dimensions shrink is to 0.8 × 0.6mm2, the thickness of device is less than 0.3mm, package area:Chip area ≈ 1, volume are only
The 29% of CSP encapsulation.
Using wafer-level packaging(Wafer level package, WLP)SAW device is current minimum encapsulation shape
Formula, the small-sized encapsulated are mainly non-airtight encapsulation.Widely used SAW filter mainly uses on mobile terminal
Non-airtight encapsulates, and in automotive electronics, radar, military communication system, enemy and we's identification, electronic countermeasure, ranging, positioning, navigation
Then need to use air-tight packaging device with the military equipment field such as remote measuring and controlling.And air-tight packaging is required in realization
The atmosphere in portion is controllable, and internal moisture content is relatively low;The SAW device requirement of high-performance, high reliability has good at the same time
Electromagnetic shielding capability and power bearing ability.But existing surface acoustic wave device structure is not air-tight packaging, internal atmosphere
It is unable to control, can not be electromagnetically shielded.
It is that a kind of wafer-level packaging of non-airtight, the encapsulation will materials identical with function wafer in the prior art shown in Fig. 1
The cover wafer of material is bonded together by polymeric frame, and cavity is formed in sound table workspace.Since polymer cannot prevent water
The diffusion of the atmosphere such as vapour, hermetic seal is can not achieve using polymeric frame as sealing material.In order to form firm bonding, polymerization
Thing sealing frame is wider up to more than 50 μm, is formed external metallization and internal electrode mutually from the side of device using metal line
Even.Since inner lead needs to guide to package outside, it is necessary to increase the size of encapsulation.
The content of the invention
For deficiencies of the prior art, it is an object of the invention to provide a kind of SAW device air-tightness
Wafer level packaging structure and technique, the present invention use the material of homogeneity or are sealed with the material of function wafer similar thermal expansion coefficient
Lid wafer, avoids because wafer or chip sliver caused by the thermal coefficient of expansion difference of different materials.This packaging technology can be real
Existing high Chip Adhesion Strength, the wafer scale that thermal diffusivity is good, encapsulation internal atmosphere is controllable(WLP)The air-tightness envelope of SAW device
Dress, has the characteristics that reliability is high.
To achieve these goals, the technical solution adopted by the present invention is as follows:
A kind of SAW device air-tightness wafer-level packaging technique, using the crystalline substance identical and identical cut type with function wafer material
Circle or with the wafer of function wafer similar thermal expansion coefficient as cover wafer.
Specific encapsulation step is as follows:
1)Processing forms multi-disc functional chip on same function wafer, and the working face of all functions chip is towards identical, institute
Functional chip is based on same function wafer and is connected to become entirety;In the one circle bonding of periphery plating of each functional chip working face
Layer metal;
2)Then punched in cover wafer wherein in one side using laser boring technique, formed blind hole, the quantity of blind hole and
Position with functional chip circuit depending on being connected and needing;
3)Then metal seed layer is coated with cover wafer, in favor of follow-up electroplating activity;
4)That face of blind hole is formed in cover wafer and carries out electroplating activity to fill metal in blind hole, then removes the envelope outside blind hole
The metal layer at other positions of lid wafer;
5)A circle bonding layer metals are made respectively with every functional chip bonding layer metals correspondence position in cover wafer, at the same time
Bonding layer metals are manufactured at each blind hole;
6)By step 1)Obtained all functions chip is placed in cover wafer as an entirety and makes the key on functional chip
Corresponding with the cover wafer bonding layer metals of layer metal face one by one up and down is closed, then by the bonded layer on every functional chip
Corresponding bonding layer metals are bonded together on metal and cover wafer;At the same time by the bonding layer metals at cover wafer blind hole with
Corresponding electrode bonding, which is realized, on function wafer is electrically connected;Bonding process is completed in vacuum or inert gas, to avoid sky
Vapor corrosion chip surface in gas;
7)The grinding and polishing cover wafer blind hole back side, to expose the metal in blind hole, while realizes cover wafer thinning;
8)External electrode and the external circuit structure needed are made at the cover wafer blind hole back side;
9)Function wafer is thinned in grinding.
In step 8)The external electrode surface of making makes external solder ball.
Cover wafer is identical with the bonding layer metals on function wafer, for gold or golden tin.
SAW device air-tightness wafer level packaging structure, including functional chip and cover wafer, in functional chip work
The periphery for making face is coated with a circle bonding layer metals, and one is coated with respectively with every piece of chip bonding layer metal correspondence position in cover wafer
Bonding layer metals are enclosed, functional chip is tied with the bonding layer metals in cover wafer by the way that gold-gold bonding or eutectic bonding are corresponding
It is combined;In cover wafer external circuit wire structures and external electrode are equipped with backwards to that face of functional chip working face;In dispatch from foreign news agency
Extremely upper making has external solder ball;Cover wafer be equipped with via hole with by functional chip working face circuit pass sequentially through via hole,
Outer electrode and external solder ball are electrically connected;Bonding layer metals width in cover wafer and functional chip is 20-30 microns.
Conducting metal is filled with via hole, conducting metal has manufactured electrical connection bonding gold towards that face of functional chip
Belong to, the electrode bonding connection corresponding with functional chip of electrical connection bond wire.
Compared with prior art, the present invention has the advantages that:
1st, in one circle bonding layer metals of functional chip working face periphery plating, in cover wafer with every piece of functional chip bonding layer metals
Correspondence position also plates a circle bonding layer metals, and functional chip and capping are then made by way of gold-gold bonding or eutectic bonding
Wafer is combined together, and can form the air-tight structure to play a protective role to chip operation face, relatively before polymeric frame
Bonding encapsulation, air-tightness greatly improve, and Chip Adhesion Strength is high.
2nd, processing efficiency further improves.For the present invention by the way of gold-gold bonding or eutectic bonding, functional chip need not
Cut into single chip, you can the function wafer that full wafer includes multi-plate chip is directly bonded with cover wafer, will not
The bonding effect of every chip is reduced, greatly improves processing efficiency.
3rd, gold-gold bonding or eutectic bonding are carried out in the environment of vacuum or nitrogen charging, it can be achieved that to encapsulate internal atmosphere controllable.
4th, since wafer is thinned, the thickness of detector only 0.25mm after encapsulation, thermal resistance reduces, and thermal diffusivity is good.
Brief description of the drawings
Fig. 1-existing SAW device encapsulating structure schematic diagram.
Fig. 2-SAW device of the present invention encapsulating structure schematic diagram.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention will be described in detail.
This packaging technology is applied to high reliability SAW device encapsulation technology field, specifically using wafer level packaging skill
The functional chip of SAW device is bonded together by art with cover wafer, forms hermetic seal.
The surface acoustic wave device structure that this packaging technology is directed to is as shown in Fig. 2, as can be seen that the surface acoustic wave from figure
Device includes functional chip 1 and cover wafer 2, and a circle bonding layer metals 3 are coated with the periphery of 1 working face of functional chip, capping
Also it is coated with a circle bonding layer metals 3, functional chip 1 and capping on wafer 2 respectively with every piece of chip bonding layer metal correspondence position
Wafer 2 is combined together by gold-gold bonding mode or eutectic bonding.Set in cover wafer 2 backwards to that face of chip operation face
There are external circuit wire structures and the outer electrode for being electrically connected with pcb board.For convenience of electrical connection, further in external electrical
Also being made on extremely has external solder ball 5.Cover wafer 2 is led equipped with via hole 4 with functional chip working face circuit is passed sequentially through
Through hole 4, outer electrode and external solder ball 5 are electrically connected.The device so formed can be directly electrically connected by external solder ball and pcb board
Connect.The present invention is combined together the wafer of functional chip and cover wafer by way of gold-gold bonding or eutectic bonding,
Can form the air-tight structure to play a protective role to chip operation face, relatively before polymeric frame bonding encapsulation, air-tightness
Greatly improve.
Polylith functional chip is bonded with same cover wafer, all functions chip is formed at same function wafer
On, which is bonded and is connected at the same time as an entirety by all functions chip with cover wafer.The present invention by
In by the way of gold-gold bonding or eutectic bonding, therefore functional chip need not cut into single chip, you can include full wafer
The function wafer of multi-disc functional chip is directly bonded with cover wafer, will not reduce the bonding effect of every chip, greatly
It is big to improve processing efficiency.
Based on above-mentioned new construction, the present invention proposes a kind of new SAW device air-tightness wafer-level packaging technique,
Encapsulation step is as follows,
1)Processing forms multi-disc functional chip on same function wafer, and the working face of all functions chip is towards identical, institute
Functional chip is based on same function wafer and is connected to become entirety;In the one circle bonding of periphery plating of each functional chip working face
Layer metal;3-5 microns of bonding layer metals thickness, 20-30 microns of width.
2)Then punched in cover wafer wherein in one side using laser boring technique, form blind hole, the number of blind hole
Amount and position with functional chip circuit depending on being connected and needing;
3)Then metal seed layer is coated with cover wafer, in favor of follow-up electroplating activity;
4)That face of blind hole is formed in cover wafer and carries out electroplating activity to fill metal in blind hole, then removes the envelope outside blind hole
The metal layer at other positions of lid wafer;
5)Make a circle bonding layer metals respectively with every functional chip bonding layer metals correspondence position in cover wafer, and
Bonding layer metals are made at blind hole at the same time, for being connected with function wafer bonding;3-5 microns of bonding layer metals thickness, width 20-
30 microns.Cover wafer is identical with the bonding layer metals on function wafer, for gold(Au)Or golden tin(AuSn)Deng.
6)By step 1)Obtained all functions chip is placed in cover wafer as an entirety and makes on functional chip
Bonding layer metals bonding layer metals corresponding with cover wafer face one by one up and down, then by the key on every functional chip
Corresponding bonding layer metals in layer metal and cover wafer are closed to be bonded together;At the same time by the bonded layer gold at cover wafer blind hole
Belong to electrode bonding corresponding with function wafer and realize electrical connection;Bonding process is completed in vacuum or inert gas, to keep away
Exempt from the vapor corrosion chip surface in air;
7)The grinding and polishing cover wafer blind hole back side, to expose the metal in blind hole;The present invention, which pre-sets blind hole and polishes again, to wear
Thoroughly, cover wafer thinning is also realized while realizing and being electrically connected, and blind hole processing is got up easily;
8)External electrode and the external circuit structure needed are made at the cover wafer blind hole back side.As needed, can also be in dispatch from foreign news agency
Pole surface makes soldered ball.
9)Function wafer is thinned in grinding.
This packaging technology using the wafer identical and identical cut type with function wafer material or with function wafer thermal expansion system
Material similar in number is avoided after bonding caused by thermal expansion coefficient difference, the warpage of cover wafer and chip as cover wafer
And sliver, and performance change.
After the completion of this packaging technology sound table function wafer manufacturing, using material identical with this function wafer and the piezoelectricity of cut type
Wafer is as cover wafer, the making metal sealing frame in cover wafer and function wafer, and is directed at bonding, realizes sealing.Together
When make via in cover wafer, carry out via metal to realize the connection of internal and external electrode.The present invention is made using metal frame
For sealing frame, closed cavity is realized using golden gold bonding, so as to fulfill air-tight packaging truly and realizes crystalline substance
Circle level encapsulation.Since metal sealing is efficient, metal width of frame can be reduced to 20~30 μm, and the size of device is small, and can be real
The internal controllable hermetic seal of now encapsulation, meets the highly reliable requirement of device.
Cause that cover wafer and function wafer material are inconsistent, and cover wafer of the present invention can also if as reality
Using glass material, the glass material has the function of the thermal coefficient of expansion identical or close with wafer.The present invention uses glass
Glass does encapsulation wafer, instead of the other materials of thermal coefficient of expansion fixation, such as silicon materials, and the thermal coefficient of expansion due to glass is adding
It is easy to by the change of component and adjustable, therefore can be readily available and function wafer material thermal coefficient of expansion when work
Consistent or close glass material, and price is also inexpensive, so that when reducing or eliminate in post production process or using
The thermal mismatching phenomenon of appearance, improves the reliability of device.
The present invention can substantially reduce the package dimension of device, and compared with other wafer-level packaging forms, this structure can
To form hermetic seal well, and it is of low cost, the reliability of device can be greatly improved, and wafer bond techniques have been used,
It can be produced in enormous quantities.
The above embodiment of the present invention is only example to illustrate the invention, and is not the implementation to the present invention
The restriction of mode.For those of ordinary skill in the field, other can also be made not on the basis of the above description
With the change and variation of form.Here all embodiments can not be exhaustive.It is every to belong to technical scheme
Row of the changes and variations that derived from still in protection scope of the present invention.