The present invention relates to a method of forming a lens module, comprising a lens assembly and one or more spacer substrates.

Compact optical modules have become a standard component in mobile devices such camera modules in mobile phones. A Camera Module consists of PCB board, an Imaging Sensor Module and a Lens Module. The Lens Module consists of a lens assembly and a housing providing an outer opaque wall to shielding it from unwanted light and environmental influences. The housing may also be shared with the housing of the complete Camera module. The outer contours of a compact optical module are in many cases designed as drop-in component into mobile devices.

US20100052192 and US2009032861 disclose a method for manufacturing an encapsulated single aperture Compact Camera Module obtained by wafer level packaging of the Image Sensor Module and Integrated Lens Stack elements.

The mass volume requirements together with the increasing drive for cost down triggered the development of wafer level based methods for producing and packaging the camera modules and related image sensor and optics.

The aim of packaging is to integrate the several optical, mechanical, environmental and electronic functions of an optical module. The functional elements may comprise a CMOS or CCD image capturing device, the imaging lenses together with optical functions such as IR filters, AR coats and light blocking structures such as baffles, partition walls etc. In most cases, micro lenses and color filters are positioned on the image sensor surface.

A variety of methods have been disclosed to manufacture lens assemblies. The traditional process consists of assembling single lens elements into a lens holder. The lens elements usually being injection molded or glass pressed.

US8013289 discloses a method where single lens elements are mounted on a carrier frame substrate. US7813043 requires dedicated tools for aligning single lens elements in the trough hole of the carrier substrate. It also requires a 'saddle structure' as support to enable dicing. Integrated Lens Stacks relate to lens assemblies based on wafer level manufacturing have been disclosed in WO2004027880.

In this process, lens elements, spacers and other optical functions are manufactured on wafer level. After singulation integrated lens modules are obtained.

Wafer level manufacturing of opto-electronic components in general assumes a wafer to wafer assembly of the optics wafer with the image sensor wafer. The aim is to reduce costs through maximizing the simultaneous processing of components followed by a singulation, usually dicing step.

A new generation of Compact Optical Modules involves multiple or arrayed configurations such as compound eye cameras. The sensor system may be either at least two separate sensors or a single sensor sharing at least two lens apertures. Multiple modules comprise of several functional units within one package. In the case of optical modules, the functional units comprise lens assemblies comprising at least one lens element and additional optical functions such as I R filters, diaphragms, spacers, carriers and active optical elements

In addition to single aperture optical Modules , cross talk between adjacent lens units within one array must be prevented through incorporating light blocking structures or partition walls as disclosed in US20100127157, US7880794 and US20080316323 Another method to provide a light blocking structure is by providing a cavity of the sensor cover substrate and filling the cavity with an opaque material. This involves an additional step in the manufacturing. In addition, the optical modules have to be packaged with an outer opaque wall.

The present inventors found that the process for providing and integrating the partition walls is in practice very difficult to realize, particularly in combination with the total encapsulation and sealing of the optical module with opaque material.

An object of the present invention is to provide a method for manufacturing lens modules allowing the use of a single or limited set of spacer substrates.

Another object of the present invention is to provide a method for manufacturing lens modules in which height tolerances and production platform flexibility are improved towards design and resulting reduced costs. Another object of the present invention is to provide a method for manufacturing camera modules wherein the aforementioned problems of the prior art are minimized.

The present invention relates to a method of forming a module, especially an optical module, comprising a lens assembly, one or more adhesive layers and substrates, the method comprising the provision of a lens assembly, adhering the lens assembly to a substrate by an adhesive, overmoulding the obtained array of lens assemblies and singulating into singulated optical modules, wherein the method comprises:

a) providing a carrier comprising several apertures having dimensions of at least the cross section of the optical path of a lens module.

b) providing a lens assembly comprising at least two lenses in one plane.

c) applying an adhesive on the circumference of said apertures on said carrier for forming a contact interface between said spacer and said lens assembly.

d) aligning the lens assembly on the carrier at said contact interface

e) pressing the lens assembly in the adhesive present at said contact interface

f) curing the adhesive,

g) dicing of a slit between said at least two lenses.

The present method thus relates to a method of forming a module, especially an optical module, comprising a lens assembly, one or more adhesive layers and substrates, the method comprising the provision of a lens assembly, adhering the lens assembly to a substrate by an adhesive, overmoulding the obtained array of lens assemblies and singulation into singulated optical modules. The method simultaneously provides a partition wall and an outer wall on a full or partially singulated lens assembly, whereupon a cover element containing apertures is attached. The apertures may be designed as lens baffles, e.g. now called baffle in the description.

The method allows integration without the need to apply an adhesive on the complete top surface of the lens assembly. While the adhesive fixates first the baffle substrate, the following overmoulding process provides the complete optical sealing of the assembly together with providing the partition wall between adjacent lens units in the lens assembly and with providing the outer wall of the complete lens module. A further step involves singulation into individual lens modules.

The method is in particular beneficial for lens modules with close pitch. By applying this method the fill factor in packaging modules can be increased

According to a preferred embodiment of the present method step g) comprises dicing said slit into said adhesive layer present on said carrier.

According to another embodiment of the present method step g) comprises dicing said slit into said adhesive layer and partially through said carrier on which said adhesive is present. This means that the carrier will still function as a platform for the lens assembly, that is the carrier is not separated in individual discrete single carriers.

In addition, in another embodiment step h) comprises applying an adhesive on the lens assemblies mounted on said carrier and provided with a slit between said at least two lenses, followed by a step i) comprising placing a baffle on said adhesive for forming baffle constructed lens assemblies and followed by a step j) curing the adhesive.

Furthermore, according to another embodiment the present method further comprises a step k) of overmoulding the baffle constructed lens assemblies obtained from step j) with a resin to overmoulded baffle constructed lens assemblies.

The present method further comprises a step I) of dicing the overmoulded baffle constructed lens assemblies obtained from step j) to singulated optical modules.

It is preferred that step b) comprises the formation of lens assemblies by replication on a wafer substrate.

It is also preferred that step b) comprises the formation of lenses on both sides of said wafer substrate.

According to another embodiment step b) further comprises the dicing of the outer dimensions to provide lens assemblies comprising at least two lenses in one plane on a wafer substrate. The carrier is preferably made of Alloy 42 and/or Cu.

In the present description the next definitions apply: lens unit = a vertical arrangement of at least one lens element and other optical functional elements such as IR filter, spacers, diaphragms and active optical elements, lens assembly = an assembly comprising at least two adjacent lens units, gap between lens units = a vertical space between two adjacent units, and slit = space between the top peripheral surface of the lens assembly and the bottom surface of the baffle (substrate)

As mentioned before, the process for providing and integrating the partition walls is in practice very difficult to realize, particularly in combination with the total encapsulation and sealing of the optical module with opaque material. According to the present invention the partition wall is preferably realized through filling a gap between two adjacent lens units with opaque material. This gap is realized through (partial) dicing of a lens assembly comprising at least two adjacent lens elements. This process for creating a gap between adjacent lens units is preferred because it safeguards the mutual XYZ positions of adjacent lens assemblies within the optical module. Trough safeguarding this mutual tolerance control, the subsequent overmoulding process can be performed in a controlled way.

In addition, after the cover element is assembled on a gap (in the present case a dicing lane) between two adjacent lens units of a lens assembly , the bottom face of the cover plate cannot be attached to a partition wall as it is not present yet. It is out of reach of any dispenser or any other reliable gluing process. In case of gluing the cover plate, ideally, the glue is over the complete gluing interface. This however requires accurate dispensing methods, which is hard to control in practice. Either insufficient adhesive is present, creating a void between the cover and the lens, or excessive glue will lead to overflow of glue to unwanted places.

In addition, either the optical design and/ or small form factor dictates a very close distance between the outer edges the top lens elements of two adjacent units. Because of this small distance, there is insufficient space left for a reliable sealing between the cover element and the lens module when applying an adhesive.

According to the present method an arrayed optical module is mounted on a carrier, e.g. lead frame- and is partially diced. A baffle substrate is assembled by applying and curing an adhesive on top of the optical assembly. The overmoulding process fills the gaps between two adjacent members and simultaneously seals the cover on top of his gap and provides the outers walls of the device.

The embodiment describes an optical assembly comprising lens elements obtained by a replication of multiple lens elements on at least one side of at least a glass substrate. The lens assembly may further comprise other optical functions such as I R filters, diaphragms, active optical elements and spacers.

According to an embodiment of the present invention, the method comprises the process steps of:

a) providing a carrier comprising several apertures having dimensions of at least the cross section of the optical path of a lens module.

b) providing a lens assembly comprising at least two lenses in one plane.

c) applying an adhesive on the circumference of said apertures on said carrier for forming a contact interface between said spacer and said lens assembly,

d) aligning the lens assembly on the carrier at said contact interface,

e) pressing the lens assembly in the adhesive present at said contact interface

f) curing the adhesive,

g) dicing of a slit between said at least two lenses,

h) comprises applying an adhesive on the lens assemblies mounted on said carrier and provided with a slit between said at least two lenses, i) comprising placing a baffle on said adhesive for forming baffle constructed lens assemblies,

j) curing the adhesive,

k) overmoulding the baffle constructed lens assemblies obtained from step j),

I) dicing the overmoulded baffle constructed lens assemblies obtained from step j) to singulated optical modules.

The present invention further relates to a preferred module comprising a quadrant of four individual lens modules, wherein said four individual lens modules are separated from each other by said overmoulding casing, each lens module comprising a first lens substrate including one or more lenses, a second lens substrate including one or more lenses and a baffle.

According to a preferred embodiment at least one of said individual lens modules has optical properties that differ from one or more of the remaining lens modules. This means that the lenses present in said module can have different optical properties. In an embodiment according to the present invention it is also possible that for example the first substrate does not have any lenses thereon, whereas the second substrate does have lenses, on both sides, or only even on one side. In the embodiment of the quadrant of four individual lens modules it is possible that all four individual lens modules have different optical properties. It is also possible that one or more of the lens substrates of the individual lens modules in the embodiment of the quadrant of four individual lens modules do not have lenses. In such an embodiment the first and second substrate lack the presence of lenses, or only the first substrate contains one or more lenses, or only the second substrate contains one or more lenses.

In another embodiment of the present invention the module comprises two segments of two individual lens modules, wherein said two individual lens modules are separated from each other by said overmoulding casing, each lens module comprising a first lens substrate including one or more lenses, a second lens substrate including one or more lenses and a baffle. It is preferred that said individual lens modules have different optical properties. Different optical properties also include embodiments wherein for example the first lens substrate does not contain any lens, or the second lens substrate does not contain any lens.

In the present module as discussed above one or more diaphragm functions are present, preferably positioned between said first lens substrate and said second lens substrate.

A UV curable adhesive is preferably used for adhering said first lens substrate to said carrier, preferably for adhering said second lens substrate to said baffle.

BRI EF DESCRI PION OF THE DRAWI NGS

Figure 1 illustrates a typical lens substrate as provided by a replication method.

Figure 2 shows a lens assembly according to the method of the present invention

Figure 3 schematically shows a carrier plate according to the method of the invention

Figure 4A shows carrier plate with adhesive according to the method of the invention. Figure 4B shows another embodiment of a carrier plate with adhesive according to the method of the invention.

Figure 5 shows a mounted lens assembly on a pre-taped carrier.

Figure 6 A shows a diced lens assembly diced into the adhesive layer. Figure 6 B shows a diced lens assembly diced into the adhesive layer and a part of the carrier.

Figure 6 C shows another embodiment of a diced lens assembly diced into the adhesive layer and a part of the carrier.

Figure 7 shows a top view of the diced lens assembly on a carrier. Figure 8 shows a top view of an array of diced lens assemblies on a carrier and with adhesive on top surface.

Figure 9 shows a side view of an array of diced lens assemblies on a carrier and with adhesive on top surface.

Figure 10 shows a carrier strip with overmoulded lens assemblies. Figure 1 1 shows a detail of an overmoulded lens assembly.

Figure 12 shows a singulated overmoulded lens assembly.

Figure 13A shows an exploded view of an overmoulded lens assembly.

Figure 13B shows an exploded view of an overmoulded lens assembly in a 2x2 embodiment.

Figure 1 illustrates a typical lens substrate 1 as provided by a replication method. The lens substrate 1 comprises a substrate 2 with both surfaces provided with a spacer layer 3 and replicated lenses 4 present on each buffer layer. Typical examples of substrate 2 are glass, wherein I R pass filter is optional. Critical aspects are the vertex-vertex distance between the lenses on the one side and the lenses on the other side, and the buffer-buffer distance as well. The replication takes place preferably on a wafer level resulting in so called double sided replicated optical wafer. The process disclosed in figure 1 can be seen as a first step in the process of manufacturing optical module. Step one is on wafer level. The lens configuration shown in Figure 1 is not a limitation to the scope of the invention. The shape of the lenses 4 is based on the requirements of the optical properties of the final optical module.

The spacer layer 3 may be executed as multiple layers comprising one or more of a buffer layer, adhesive layer, spacer substrates of different materials such as glass; ceramics, silicon, metal, polymers, composites and compound material.

Figure 2 illustrates as a second step in the process of manufacturing optical module a step of dicing in which the double sided replicated optical wafer as shown in Figure 1 is used as starting material. The process steps comprise the placement of double sided replicated optical wafer, comprising replicated lenses 4, spacer layer 3 on both sides of substrate 2, on a dicing tape 5, loading in a dicer, dicing of outer dimensions, cleaning of top side wafer and unload metal wafer frame with optical wafer. The product thus obtained can be characterized as diced optical wafer on tape in metal wafer frame. Step two is on wafer level. Although only one lens substrate 1 is shown, several stacked lens substrates are present on said dicing tape 5.

A third step in the process of manufacturing optical module is a step of mounting the product obtained in the second step on a frame 30, e.g. a lead frame, as illustrated in Figure 3. Carrier plates 30 made from materials such as Alloy 42 and/or Cu carrier plates, pre-taped (not shown in Figure 3), are provided with black adhesive 31 filled with for example 50um spacers as illustrated in Figure 4A. The individual lens units as obtained in step 2 (see Figure 2) are placed in the adhesive 31 present on carrier 30.

In the Figure 4B carrier 30 has been provided with a prefabricated channel or groove 32. After the application of adhesive 31 on the carrier 30 the adhesive 31 will remain on carrier 30 as shown. However, adhesive 31 may also flow into channel 32 and fill channel 32 with adhesive 31 . An advantage of prefabricated channel or groove 32 is that the dicing step, which will be discussed later, can be carried out more precisely, safely and accurately. Subsequently, a step of UV exposure for pre-fixation is carried out. Additional cure can be carried out in an oven. The product 50 thus obtained, as shown in Figure 5, can be characterized as mounted lens units on carrier, pre-taped, cured adhesive. The z-control takes place by spacer thickness. Carrier 30 is located on a tape 51. Step three is on module level.

A fourth step in the process of manufacturing optical module is a step of dicing the product obtained in the third step. More in detail, the product 50 obtained in step 3 is loaded in a dicer in which dicing of a vertical slit in between lenses takes place. After additional cleaning the carrier is unloaded from dicer. The product 60 thus obtained, as shown in Figure 6A and 6B, can be characterized as mounted lens units on carrier, pre-taped (tape 61) having a diced slit, as called a dicing lane or dicing channel 62, in between lenses, into adhesive layer 31 . The dicing is done with cured adhesive layer resulting in no movement of lenses. The dicing lane 62 runs from top into adhesive layer but no into carrier 30 (see Figure 6A). The dicing lane 62 runs from top into adhesive layer 31 and a partly into carrier 30 (see Figure 6B). Consequently, the carrier 30 is still in tact as a carrier. A beneficial aspect of this way of dicing is a mechanical one. There is a kind of mechanical anchoring of the dicing lane 62 in the carrier 30. Furthermore, the risk of leakage of light via the adhesive layer to another compartment is minimized. I n Figure 6C one can see that a prefabricated channel or groove 32 (as shown in Figure 4B) is partly filled with adhesive layer 31 . By said dicing step the adhesive layer 31 present in said prefabricated channel or groove 32 will obtain a somewhat rounded like shape. A benefit of the presence of a prefabricated channel or groove 32 in carrier 30 is that the dicing means, e.g. a mechanical knife or cutter, will not come into contact with carrier 30 thereby preventing excessive abrasion of the dicing means. In addition according to such a construction the presence of small particles in said module resulting from the dicing step is highly prevented.

Step four is on module level. Figure 7 is a top view of the product 60 showing the dicing lane 62 in between lenses located on carrier 30.

A fifth step in the process of manufacturing optical module is a step of mounting a baffle on top of the product obtained in the fourth step. More in detail, mounted lens assemblies on carrier, pre-taped, dicing lane 62 in between lenses into adhesive layer, i.e. the product 60 as discussed before, are provided with stencil screen adhesive 81 on each lens unit, as shown in Figure 8, and a baffle 91 is placed on top of each lens unit provided with adhesive 81 (see figure 9). Preferably, the baffles 91 are provided as baffles on wafer tape (not shown). After unloading the carrier thus obtained the assembly 90, located on a tape 92, is placed in an oven to cure adhesive 81 . Adhesive 81 can be placed on the corner areas of the lens areas for securing the baffle 91 thereto. In another embodiment adhesive 81 can be placed over the complete surface of the lens area, except for the lenses itself. Step five is on module level

A sixth step in the process of manufacturing optical module is a step of overmoulding the product 90 obtained in the fifth step. More in detail, the carrier 90 obtained in step five as discussed before is placed in a molder, compound capsules 101 are loaded in a molder and overmoulding takes place by heating under vacuum. After said overmoulding the compound residue capsules if any, are removed and the overmoulded carriers 100 are unloaded (see Figure 10). Step six is on module level. The compound 101 for overmoulding will completely flow through the dicing lane 62.

Figure 1 1 shows a detailed view on an optical module after overmolding showing the slit filled with compound (102) or filled with adhesive (103). The adhesive may contain spacer balls, e.g. 6 micron. Fig 1 1 is only an arbitrary example showing locations with adhesive 103 and with compound 102. The amount of adhesive applied may be minimized trough only application at the corners of the optical modules. The free space will be filled with molding compound during overmoulding. The thickness of horizontal slit 102/103 must be accurately designed towards the diameter of the filling particles in molding compound material.

The rule is that the horizontal slit thickness is between 1/10 to 1/5 of the diameter of the filler particles present in the overmoulding compound. Therefore in case of a overmoulding compound with particles of 50 micron, the slit thickness should be in between 5 and 10 microns. Outside this range either excessive overmoulding compound bleed or voids will occur. In addition potential trapped air bubbles appearing in the overmoulding process can be vented towards the apertures of the baffle substrate. The specific horizontal slit thickness is also necessary to prevent overmoulding compound coming into contact with the lenses, or flowing into the area where the light path is. Such light path may not be hindered by the unwanted presence of any overmoulding compound.

In addition the dicing lane should be at least 1 .5 times and by preference 3 times - the diameter of the filler particles present in the overmoulding compound.

Because of this design rules it is important to start from two adjacent lens unit where the top surfaces on both sides of the dividing gap (dicing lane) are on the same plane in order to comply within these design rules. The process steps a) to g) provide a method to accurately control this mutual close tolerance configuration.

The thickness of slit 102/103 must be accurately designed towards the diameter of the filling particles in molding compound material. . A seventh step in the process of manufacturing optical module is a step of singulating the product 100 obtained in the sixth step. It is preferred to remove tape from overmoulded carrier strip as obtained in the sixth step as discussed before, after which a step of loading takes place in a dicer on a vacuum chuck. The dicing is carried out according to the required outer dimensions of lens units 120, and the individual lens units 120 are picked and placed in JDEC tray.

Figure 13A illustrates an exploded view of the product obtained according to the method of the present invention. From bottom to top one can see carrier 30, adhesive or glue 31 , lens 4,3 including spacer layer, diaphragm 130, overmoulding casing 101 , substrate 2, e.g. a glass layer, lens including buffer layer 4,3 , adhesive or glue 81 , and baffle 91 .

Figure 13b illustrates an exploded view of the product obtained according to the method of the present invention wherein a so called 2x2 construction is manufactured. From bottom to top one can see carrier 230, adhesive or glue 231 , lens 204, 203 including spacer layer, overmoulding casing 201 , lens 203, 204 including spacer layer, substrate 202, e.g. a glass substrate, lens including buffer layer 204, 203 , adhesive or glue 281 , and baffle 291 .

Although Fig 13A illustrates an embodiment comprising a two lens module construction and Fig 13B an embodiment comprising a four lens module construction other lens module constructions such as 3x3, 4x4 can be regarded as preferred embodiments.

It is clear that lenses can be present on one side of substrate 202, or on both sides. And the type of lenses used can differ from each other resulting in different optical properties for each lens module. In another embodiment it is possible that no lenses are present in one or more of the lens modules. For example, in the quadrant or 2x2 type shown in Fig 13b the optical properties of the lens module in the first quadrant may differ from the optical properties of the lens modules in the second, third and fourth quadrant. And the optical properties of lens modules in the second, third and fourth quadrant may also differ from each other. According to another embodiment of the present invention one or more of the lens modules lacks the presence of one or more lenses. In another embodiment of the present invention one or more of the lens modules does not contain any lens at all. In preferred embodiments one or more of IR filters, diaphragms, spacers and carriers are present in the optical module according to the present invention.