Method, foil, die component, and surface layer for encapsulating an electronic component mounted on a carrier using an expanded space that absorbs local foil layer displacement

Abstract

The present invention relates to a method for encapsulating an electronic component mounted on a carrier, the method comprising the following processing steps: covering a mold part with a foil layer; placing a carrier equipped with an electronic component between two mold parts; moving the mold parts relative to each other; introducing an encapsulation material into the mold cavity; separating the mold parts and removing the carrier with the molded electronic component. The present invention also relates to a foil and a mold part for encapsulating an electronic component according to the method of the present invention. The present invention also relates to a surface layer for detachably connecting to the surface of a metal mold substrate.

Description

[0001] The present invention relates to a method for encapsulating an electronic component mounted on a carrier. The present invention also relates to a foil and a mold part for encapsulating an electronic component according to the method of the present invention. The present invention also relates to a surface layer for detachably connecting to a metal mold substrate.

[0002] Encapsulating electronic components mounted on a carrier using an encapsulating material is a known technique. On an industrial scale, such electronic components have encapsulation parts, usually encapsulation parts of cured epoxy resin, with a filler material added. There is a trend in the market to encapsulate a large number of relatively small electronic components simultaneously. Electronic components such as semiconductors, which are generally getting smaller and smaller (chips, although LEDs are also considered semiconductors in this regard), can be envisaged here. Once the encapsulating material has been set, the collectively encapsulated electronic components are placed in an encapsulation part (package), which is provided on one side of the carrier and sometimes also on both sides of the carrier. The encapsulating material usually takes the form of a flat layer connected to the carrier, but it is also possible to mold an optional specific encapsulation part depending on the part to be molded and its application. The carrier can consist of a lead frame, a multi-layer carrier (also called a board or substrate, etc.) partially made of epoxy resin, or another carrier structure.

[0003] During the process of encapsulating an electronic component mounted on a carrier, a press with two half-molds is usually used according to the prior art, with at least one of the two half-molds being concave to form one or more mold cavities. After placing the carrier with the electronic component to be encapsulated between the half-molds, the movable half-molds, such as moving relative to each other, can clamp the carrier. Then, a usually heated liquid encapsulating material is typically fed into the mold cavity by transfer molding. As an alternative, the encapsulating material, such as granules, can also be brought into the mold cavity before closing the mold part, and then the part to be molded is pressed into the encapsulating material; this compression encapsulation process is an alternative to transfer molding. The encapsulating material used is epoxy resin (also called resin), usually provided with a filler material. After at least partial (chemical) curing of the encapsulating material in the mold cavity, the carrier with the encapsulated electronic component is removed from the encapsulation press, and the encapsulated products can be separated from each other during further processing. Foil can be used during the encapsulation process to shield or cover a part of the electronic component that does not require the encapsulating material to prevent that part of the electronic component from being covered by the encapsulating material. The foil can also be or alternatively used to shield the encapsulating material on the mold surface. Partially encapsulated products (products that are not fully molded or "overmolded" products are also called "die" or "naked mold" products) can be used for various applications; for example, various types of sensor components, ultra-low packaging, or heat dissipation components. The encapsulation method is suitable for large industrial scales and enables well-controlled encapsulation of partially uncoated electronic components.

[0004] During the encapsulation process and subsequent handling of the molded electronic component, there is a problem that contact between the foil and the electronic component causes local deformation of the foil, which varies with local lateral displacement of the foil material. The lateral displacement of the foil material may cause undesired changes in the dimensions of the encapsulation material after molding. The inaccuracy of the dimensions of the molded product cannot meet the increasing requirements for dimensional accuracy of molded electronic components in the market.

[0005] The object of the present invention is to provide an alternative method and device by which the advantages of the prior art electronic component encapsulation can be maintained, but an encapsulation with more precise dimensional control of the electronic component can be achieved.

[0006] The present invention provides a method for encapsulating an electronic component mounted on a carrier, the method comprising the following processing steps: A) at least partially covering the contact side of a mold part with a foil layer, the covered part of the contact side of the mold part comprising at least one recessed cavity; B) placing a carrier having an electronic component between at least two mold parts of the mold, at least one mold part of the mold being at least partially covered with a foil layer; C) moving the mold parts relative to each other and clamping the carrier having the electronic component between the contact sides of the mold parts to press the foil layer onto the electronic component, and the mold parts and at least one cavity enclosing the electronic component to be encapsulated; D) introducing an encapsulation material into the cavity; E) separating the mold parts from each other and removing the carrier having the molded electronic component from the mold parts, wherein the surface of the foil layer facing the electronic component is impermeable to the molding material, and at least part of the local displacement of the foil layer caused by the local pressure exerted on the electronic component by the foil layer is absorbed by the foil expansion space. The local displacement of the foil material (staying of the lateral foil material displacement) before and during the molding process may be caused by uneven pressure load distribution on the surface of the foil layer. One of the reasons for this foil material displacement may be that when the foil is pressed onto the electronic component, the foil is (constrained) compressed due to locally higher pressure applied to the foil from the opposite side. Another reason for the foil material displacement may be the irregular distance (height) of the electronic component protruding from the carrier end, or the change in the size of the carrier. The dimensional changes of the mounted electronic component and the carrier may cause (limited) height changes on the surface of the electronic component in contact with the foil, which also results in differences in the local pressure applied to the foil.

[0007] As a result, the foil material may bulge (alternate wording: pop out or protrude) at certain locations along the sides of the area (surface) where the foil contacts the electronic component. The bulging foil material may cause an undesired local immersion, resulting in measurement differences (variations) in the molded material portion of the molded electronic component. The "bulging effect" of such pressure-induced lateral foil material displacement can be prevented (or limited) by the method of the present invention, since the expansion space will absorb any lateral foil material displacement and thus will prevent (or limit) the bulging foil material. In addition to the bulging absorption effect of the expansion space, it can also play a positive role in equalizing the pressure applied to the mold part (mold) during the molding process. According to the prior art and depending on factors such as the size of the electronic component, the mold cavity, the mold part, the clamping force, and / or the pressure gradient of the molding material that may be generated on the mold part, this pressure gradient may affect the accuracy of the molding process. Since the expansion space can absorb any (lateral) foil material displacement, the present invention can reduce the occurrence of the pressure gradient during the molding process and thus can prevent (or limit) the pressure gradient. Therefore, the size of the molded electronic component can be better controlled.

[0008] The local foil layer displacement can be absorbed by the foil layer expansion space, and for this purpose, the expansion space can be provided in the contact side of the foil and / or the mold part. The expansion space must be "compressible", so the expansion space can be filled with gas, or filled with a porous material or any other material that can be compressed with a load smaller than the load that causes the foil material displacement. Thus, the compressibility of the expansion space may be related to the "softness" of the material it contains. Thus, preferably, the "softness" is obtained through a sufficiently low compression modulus (also known as the "bulk modulus"). On the other hand, preferably, the indentation hardness of the material is high enough to prevent material flow due to plastic deformation.

[0009] In the case where the expansion space is filled with gas, the expansion space can be open, but alternatively or additionally, the expansion space can also be closed and thus embedded in the foil material. When the expansion space is open, the expansion space can be open to the side of the foil opposite to the side in contact with the molding material. Thus, at least during the closing of the electronic component through at least one mold cavity, the expansion space can be closed so that the gas is contained in the expansion space and compressed and enclosed in the expansion space. Alternatively, the expansion space can also be open to the side where the foil contacts the molding material. In the case where the expansion space is open to the side where the foil contacts the molding material, the foil material can adhere to the epoxy resin during the molding process, such as by using a tapered hole.

[0010] In another alternative method, local foil displacement can be absorbed by a laminated foil having a surface layer facing the electronic component and a support layer including an expansion space, and the molding material is impermeable to the surface layer. For such a layered or laminated foil material, it is easier to optimize the various functions that the foil must achieve (impermeable coating of the molding material and dispersion of local foil displacement over the laminated layers).

[0011] As an alternative (or additional) option, local foil displacement can be absorbed by a foil expansion space provided in the surface layer of the foil contact surface of the mold part. The surface layer on the foil contact side of the mold part can be detachably connected to the metal mold part. The surface layer on the foil contact side of the mold part can alternatively be formed by a soft material surface layer, so the compression modulus of the soft material is generally lower than that of the metal mold part. As an alternative, the foil expansion space can be provided in the metal layer of the mold part or in an insert layer that is part of the mold part. Since the surface layer of the mold part is used to achieve the function of absorbing local foil displacement, this alternative allows the use of prior art foil materials. In addition, since the surface layer of the molded part is isolated from the molding material by the foil layer, the surface layer of the molded part can be used for multiple molding cycles, so this alternative will likely result in a reduction in variable molding costs. This alternative also has the advantage that thinner (and thus cheaper) foils can be used.

[0012] Local foil displacement can be absorbed by uniformly distributed expansion spaces, here referring to the uniform distribution of the expansion spaces on the foil and / or the uniform distribution on the surface layer of the foil contact side of the mold part. However, local foil displacement can alternatively be absorbed by expansion spaces that are irregularly distributed on the foil and / or uniformly distributed on the surface layer of the foil contact side of the mold part. In the case of the irregular distribution, the expansion spaces are unevenly / grouped in terms of quantity and / or size, depending on, for example, the cavity position and / or the position of the electronic component. As an example, the density of the expansion spaces at the position where the foil contacts the electronic component may be greater than the density of the expansion spaces at the position where the foil does not contact the electronic component, thus generating more dimensional change absorption at the desired position or expected absorption amount. It is also possible to limit the density of the expansion spaces at the positions where the electronic component requires greater pressure during molding (such as at the position where the semiconductor is supported by the raised contacts). The expansion spaces can also be distributed in other ways, for example: related to the distance to the gate opening (feeding into the cavity) or adjusted to the position where the overflow will affect the tolerances of the mold.

[0013] The present invention also provides a foil for encapsulating an electronic component mounted on a carrier by the method of the present invention described above, wherein the foil has an expansion space, and the contact surface of the foil layer facing the electronic component is impermeable to the molding material. As described in the method for encapsulating an electronic component according to the present invention, the expansion space of the foil layer can be formed by a plurality of inflation holes. The expansion space can be further opened and / or closed, and the expansion space can be filled with gas or any other compressible material. In addition, the foil can be multi-layered with the expansion space in a layer separated from the layer configured to contact the electronic component and the molding material during molding. The expansion space can also be distributed uniformly or irregularly on the foil as described above. Regarding the foil for encapsulating an electronic component according to the present invention, all the features and advantages of various alternatives of the foil using the molding method described above are also incorporated herein.

[0014] The present invention also provides a mold part for encapsulating an electronic component mounted on a carrier by the method according to the present invention, wherein a foil layer expansion space is provided on the contact side of the mold part facing the foil layer during molding. As described in the method for encapsulating an electronic component according to the present invention, the foil layer expansion space can thus be formed by a plurality of inflation holes. The contact side of the mold part can include a surface layer detachably connected to the metal mold part substrate, and the surface layer is provided with a foil layer expansion space. The surface layer can also be formed of a soft material, and the compression modulus of the soft material is generally lower than that of the metal mold part substrate. In addition, the expansion space (in the surface layer) can be distributed uniformly or irregularly. Regarding the mold part according to the present invention, all the features and advantages of various alternatives of the foil using the molding method described above are also incorporated herein.

[0015] Finally, the present invention also provides a surface layer formed of a soft material for being detachably connected to the metal mold part substrate as part of the mold part according to the present invention described above, wherein the surface layer is provided with a foil layer expansion space distributed uniformly or irregularly. Similarly, regarding the mold part according to the present invention, all the features and advantages of various alternatives of the foil using the molding method described above are also incorporated herein.

[0016] The present invention is further illustrated according to the following non-restrictive clauses:

[0017] 1. A method for encapsulating an electronic component mounted on a carrier, comprising the following processing steps:

[0018] A) At least partially covering the contact side of the mold part with a foil layer, the covered part of the contact side of the mold part including at least one recessed mold cavity;

[0019] B) Placing a carrier having an electronic component between at least two mold parts of a mold, at least one mold part of the mold being at least partially covered with a foil layer;

[0020] C) moving the die parts relative to each other and clamping a carrier having electronic components between the contacting sides of the die parts to laminate a foil onto the electronic components, and the die parts and at least one cavity enclose the electronic components to be encapsulated;

[0021] D) introducing an encapsulation material into the cavity;

[0022] E) separating the die parts from each other and removing the carrier having the molded electronic components from the die parts,

[0023] wherein the surface of the foil facing the electronic components is impermeable to the molding material,

[0024] the local displacement of the foil layer caused by applying local pressure on the electronic components by the foil layer is at least partially absorbed by the foil layer expansion space.

[0025] 2. The method for encapsulating electronic components according to clause 1, characterized in that the local foil layer displacement is absorbed by the foil layer expansion space provided in the foil.

[0026] 3. The method for encapsulating electronic components according to clause 1, characterized in that the local foil layer displacement is absorbed by a laminated foil layer having a surface layer facing the electronic components that is impermeable to the molding material and a support layer including an expansion space.

[0027] 4. The method for encapsulating electronic components according to any one of the foregoing clauses, characterized in that the local foil layer displacement is absorbed by the foil layer expansion space provided in the surface layer of the foil contact side of the die part.

[0028] 5. The method for encapsulating electronic components according to clause 4, characterized in that the local foil layer displacement is absorbed by the surface layer of the foil contact side of the die part formed by a soft material surface layer detachably connected to the metal die part.

[0029] 6. The method for encapsulating electronic components according to any one of the foregoing clauses, characterized in that the local foil layer displacement is absorbed by uniformly distributed expansion spaces.

[0030] 7. The method for encapsulating electronic components according to any one of clauses 1-5, characterized in that the local foil layer displacement is absorbed by irregularly distributed expansion spaces.

[0031] 8. The method for encapsulating electronic components according to clause 7, characterized in that the density of the expansion space at the position where the foil contacts the electronic components is greater than the density of the expansion space at the position where the foil does not contact the electronic components.

[0032] 9. A foil for encapsulating an electronic component mounted on a carrier by the method according to any one of the preceding clauses, wherein the foil is provided with an expansion space, and the molding material is impermeable to the contact surface of the foil layer facing the electronic component.

[0033] 10. The foil for encapsulating an electronic component according to clause 9, characterized in that the expansion space is closed.

[0034] 11. The foil for encapsulating an electronic component according to clause 9 or 10, characterized in that the foil layer is of a laminated type, having: the surface of the foil layer facing the electronic component is impermeable to the molding material, and a support layer including the expansion space.

[0035] 12. A mold part for encapsulating an electronic component mounted on a carrier by the method according to any one of clauses 1 to 8, wherein a foil layer expansion space is provided on the contact side of the mold part facing the foil layer.

[0036] 13. The mold part for encapsulating an electronic component mounted on a carrier according to clause 12, characterized in that the foil contact side of the mold part includes a surface layer formed of a soft material, the surface layer is detachably connected to the metal mold part base body, and the surface layer is provided with a foil layer expansion space.

[0037] 14. The mold part for encapsulating an electronic component according to clause 13, characterized in that the expansion space in the surface layer is irregularly distributed according to the position of the mold cavity.

[0038] 15. The mold part for encapsulating an electronic component according to any one of clauses 12 to 14, characterized in that the expansion space in the surface layer is irregularly distributed according to the position of the electronic component.

[0039] 16. A surface layer formed of a soft material, for being detachably connected to the metal mold part base body as part of the mold part according to any one of clauses 13 - 15, wherein the surface layer is provided with a foil layer expansion space.

[0040] The present invention is further illustrated based on the non - restrictive exemplary embodiments shown in the following drawings. It is shown here:

[0041] Figure 1 is a side view of a cross - section of a mold for encapsulating an electronic component mounted on a carrier in the prior art;

[0042] Figure 2 is Figure 1 a detailed view of the cross - section of the shown mold.

[0043] Figure 3Is a detailed view of a cross-section of a mold for encapsulating an electronic component mounted on a carrier according to the present invention.

[0044] Figures 4A - 4C Are various alternative embodiments of the foil according to the present invention.

[0045] Figure 5A And 5B Is a detailed view of a cross-section of a mold part for encapsulating an electronic component according to the present invention.

[0046] Figure 1 Shows a cross-section of a mold 1 for encapsulating an electronic component 2 mounted on a carrier 3. The mold 1 includes two mold parts: a top mold part 4 and a bottom mold part 5 that can be displaced relative to each other. In Figure 1 The case shown, the mold parts 4, 5 are moved relative to each other to clamp the carrier 3 having the electronic component 2 between the mold parts 4, 5. The top mold part 4 has a concave mold cavity 6 for receiving the electronic component 2. A foil layer 7 is placed against the contact side of the top mold part 4, and the foil layer 7 has the function of facilitating the demolding of the electronic component 2 to be molded and keeping the top side of the electronic component 2 free of the molding material 8. The molding material 8 is introduced between the mold parts 4, 5, especially into the idle space in the mold cavity 6 (the space existing between the electronic components 2 and optionally below the electronic components 2).

[0047] Figure 2 Shows Figure 1 A detailed view of the cross-section of the mold 1 shown, in which a part of the top mold part 4 and a part of the bottom mold part 5 clamp the carrier 3, the electronic component 2 and the foil layer 7. When the pressure on the foil layer 7 above the electronic component 2 is higher than the pressure at the position where the molding material 8 is provided, a limited amount of the foil layer 7 material above the electronic component 2 will be pushed away (in the direction of arrow P1). Pushing the material of the foil layer 7 laterally (transversely) may cause a bulge 9 (swelling) to appear at the position where the foil material 7 is adjacent to the electronic component 2. As a result, a pit 10 appears at the position corresponding to the bulge 9 in the foil material 7 in the molding material 8. These pits 10 (or grooves / slots / depressions) cause undesirable dimensional errors in the molded electronic component 2.

[0048] Figure 3 Shows Figure 1 A detailed view of the cross-section of the mold 1 shown, but now in combination with the foil material 11 according to the present invention. At this time, the top mold part 4 and a part of the bottom mold part 5 clamp the carrier 3, the electronic component 2 and the foil layer 11. As Figure 2As shown, at this time, the pressure on the foil layer 11 above the electronic component 2 is higher than the pressure at the position where the molding material 12 is provided. However, the foil material 11 is provided with a foil layer expansion space 13, and this foil layer expansion space 13 can absorb the material of the foil layer 11 above the electronic component 2 that is pushed to one side. The expansion space 13' above the electronic component 2 is smaller than the expansion space 13 beside the electronic component 2 because the expansion space 13' above the electronic component 2 absorbs the local foil layer displacement and thus its size shrinks. As a result, no material of the foil layer 11 is pushed to the side of the electronic component 2, so there is no Figure 2 protrusion as shown in the prior art. Due to the adoption of the foil layer 11, the upper surface of the molding material 12 is flatter than Figure 2 the upper surface as shown in the prior art.

[0049] Figure 4A A foil 20 for encapsulating an electronic component is shown. The foil 20 is a single-layer soft film, and the single-layer soft film has a contact surface 21 that is impermeable to the molding material and faces the electronic component and the molding material. Open expansion spaces 23 (holes) are uniformly distributed on the opposite side 22 of the impermeable contact surface 21 and are used to absorb local foil layer expansion.

[0050] Figure 4B A foil 25 for encapsulating an electronic component is shown. The foil 25 is formed by two material layers 26, 27. At this time, the harder molding material-impermeable contact layer 26 is combined with the softer layer 27, and the softer layer 27 has uniformly (evenly) distributed open expansion spaces 28 (holes).

[0051] Figure 4C A foil 30 for encapsulating an electronic component is shown. The foil is formed by two material layers 31, 32. At this time, the molding material-impermeable contact layer 31 is combined with a support layer 32 provided with irregularly distributed open expansion spaces 33 (holes). The expansion spaces 33 can be provided, for example, at the positions where the foil 30 contacts the electronic component to be molded.

[0052] Figure 5A A top mold part 40 for encapsulating an electronic component 41 mounted on a carrier 42 is shown. Among them, the contact side 43 of the top mold part 40 facing the electronic component 41 is provided with a softer support layer 44 connected to the metal mold part base body 45. Expansion spaces 46 are provided in the top mold support layer 44 for the local expansion of the foil layer 47 located between the mold support layer 44 and the electronic component 41. In Figure 5A the shown case, the mold part 40 has not applied pressure to the electronic component 41.

[0053] Figure 5B Also shown Figure 5AThe top die member 40 shown, but now in the position where the die member 40 applies pressure to the electronic component 41. Since the local pressure on the top die support layer 44 is compensated, at this time, the expansion space 46' is smaller than the space before the pressure is applied. When the expansion space 46' is "absorbed", the material of the foil 47 is not pushed laterally (transversely), so there will be no (or less) protrusions as in the prior art shown in Figure 2 The contact surfaces of the position of the foil 47 facing the electronic component 41 and the position of the surface of the foil 47 not facing the electronic component will only have a slight height difference.

Claims

1. A method for encapsulating an electronic component mounted on a carrier, comprising the following processing steps: A) At least partially cover the contact side of the mold part with a foil layer, and the covered part of the contact side of the mold part includes at least one recessed cavity; B) Place a carrier with electronic components between at least two mold parts of a mold, at least one mold part of the mold being at least partially coated with a foil layer; C) Move the mold parts relative to each other and clamp the carrier with electronic components between the contact sides of the mold parts to press the foil layer onto the electronic components, and the mold parts and at least one cavity enclose the electronic components to be encapsulated; D) Introduce encapsulating material into the cavity; E) Separate the mold parts from each other and remove the carrier with the molded electronic components from the mold parts, wherein the surface of the foil layer facing the electronic components is impermeable to the molding material, The local foil layer displacement caused by the local pressure exerted on the electronic components by the foil layer is absorbed by the foil layer expansion spaces provided in the foil; wherein the foil layer expansion spaces are formed by a plurality of inflation holes.

2. The method for encapsulating an electronic component according to claim 1, characterized in that The local foil layer displacement is absorbed by a laminated foil layer having a surface layer facing the electronic components that is impermeable to the molding material and a support layer including expansion spaces.

3. The method for encapsulating an electronic component according to any one of the preceding claims, characterized in that The local foil layer displacement is absorbed by the foil layer expansion spaces provided in the surface layer on the contact side of the mold part.

4. The method for encapsulating an electronic component according to claim 3, characterized in that The surface layer on the contact side of the mold part is detachably connected to the metal mold part substrate.

5. The method for encapsulating an electronic component according to claim 1 or 2, characterized in that The local foil layer displacement is absorbed by uniformly distributed expansion spaces.

6. The method for encapsulating an electronic component according to claim 1 or 2, characterized in that The local foil layer displacement is absorbed by irregularly distributed expansion spaces.

7. The method for encapsulating an electronic component according to claim 6, characterized in that The density of the expansion spaces at the position where the foil contacts the electronic components is greater than the density of the expansion spaces at the position where the foil does not contact the electronic components.

8. The method for encapsulating an electronic component according to claim 1 or 2, characterized in that The expansion spaces are formed by a plurality of inflation holes.

9. The method for encapsulating an electronic component according to claim 8, characterized in that The holes are closed at least during the process of enclosing the electronic components through at least one cavity.

10. A foil for encapsulating an electronic component mounted on a carrier by the method according to any one of the preceding claims, wherein the foil is provided with an expansion space, and the molding material is impermeable to the contact surface of the foil layer facing the electronic component; wherein the foil layer expansion space is formed by a plurality of inflation holes.

11. The foil for encapsulating an electronic component according to claim 10, characterized in that The expansion spaces are closed.

12. The foil for encapsulating an electronic component according to any one of claims 10 - 11, characterized in that The foil layer is of a laminated type and has: a surface layer facing the electronic components that is impermeable to the molding material, and a support layer including expansion spaces.

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