Strip-shaped substrate for producing chip carriers, electronic module with a chip carrier of this type, electronic device with a module of this type, and method for producing a substrate

Abstract

A strip-shaped substrate made from a film includes a plurality of units for producing chip carriers. Each unit has a chip island for fixing a semiconductor chip, electrodes for electrical connection of the semiconductor chip, and through-openings for structuring the unit. At least one through-opening forms an anchoring edge for a casting compound for encapsulating the semiconductor chip. A surface section of the film abutting the through-opening is chamfered to form the anchoring edge. The anchoring edge protrudes past the side of the film on which the chip island is arranged.

Claims

1. A strip-shaped substrate, the substrate comprising: a film; a plurality of units disposed on the film, the plurality of units for producing chip carriers, each unit comprising a chip island for fixing a semiconductor chip, a plurality of electrodes for electrically connecting the semiconductor chip, and a plurality of through-openings for structuring the respective unit, at least one through-opening forming an anchoring edge for a casting compound, the casting compound encapsulating the semiconductor chip; and a surface section abutting the at least one through-opening of the film is chamfered for forming the anchoring edge; wherein the anchoring edge protrudes beyond a side of the film on which the respective chip island is arranged; wherein a thickness of the film is between 15 m and 35 m; wherein the film is formed from austenitic stainless steel.

2. The substrate according to claim 1, wherein a chamfer angle between the surface section and a second surface of the film is between 30 and 60 or between 40 and 50.

3. The substrate according to claim 1, wherein the surface section is straight.

4. The substrate according to claim 1, wherein the surface section comprises a comb-like profile for reducing a mechanical stress or the surface section comprises a smooth outer edge.

5. The substrate according to claim 1, wherein a through-opening of the plurality of through-openings comprises a chamfer-free curve or a chamfer-free recess for reducing a mechanical stress.

6. The substrate according to claim 1, wherein a through-opening of the plurality of through-openings abutting the chip island comprises an anchoring edge or the through-opening of the plurality of through-openings abutting the chip island on an inside of the chip island comprises the anchoring edge.

7. An electronic module comprising: a chip carrier comprising a chip island and a semiconductor chip fixed on the chip island; a plurality of electrodes for electrically connecting the semiconductor chip; a plurality of through-openings for structuring the chip carrier, at least one through-opening forming an anchoring edge for a casting compound, the casting compound encapsulating the semiconductor chip; and a surface section of the chip carrier abutting the at least one through-opening is chamfered for forming the anchoring edge; wherein the anchoring edge protrudes beyond a side of the chip carrier on which the chip island is arranged; wherein a thickness of the chip carrier is between 15 m and 35 m; wherein the chip carrier is formed from austenitic stainless steel, wherein the anchoring edge is embedded in the casting compound.

8. An electronic device comprising, an electronic module of claim 7, wherein the chip carrier is formed as chip card, health card, bank card, public transport ticket, hotel card, identity document, passport, paper-foil-type card, or an admission card.

9. A method for preparing a strip-shaped substrate to be manufactured into an electrical module, the substrate comprising a film and a plurality of chip carriers disposed on the film, each chip carrier comprising a chip island and a semiconductor chip fixed on the chip island; a thickness of the film is between 15 m and 35 m and the film is formed from austenitic stainless steel; the method comprising: (a) punching a plurality of through-openings in the film; and (b) chamfering a surface section of the chip carrier to form an anchoring edge for a casting compound.

10. A strip-shaped substrate comprising: a metal foil comprising a plurality of units disposed on the foil the plurality of units for producing chip carriers, each unit comprising a chip island for fixing a semiconductor chip; a plurality of electrodes for electrically connecting the semiconductor chip; and a plurality of through-openings for structuring the respective unit, at least one through-opening forming an anchoring edge for a casting compound, the casting compound encapsulating the semiconductor chip; wherein the metal foil, the metal foil is comprises an austenitic stainless steel; wherein the metal foil comprises a thickness between 15 m and 35 m; wherein the metal foil is formed from austenitic stainless steel.

11. The electronic module of claim 7, wherein at least one electrode of the plurality of electrodes is a bond wire.

12. The substrate of claim 1, further comprising the casting compound.

13. The substrate of claim 10, further comprising the casting compound.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be discussed in detail including further details, with reference to the attached schematic drawings by way of exemplary embodiments, in which

(2) FIG. 1 shows a strip-shaped substrate with a number of units for producing chip carriers according to the state of the art;

(3) FIG. 2 shows a cut-out from a strip-shaped substrate according to an embodiment of the invention with anchoring edges configured according to the invention;

(4) FIG. 3 shows a section through the substrate according to FIG. 2 along line A-A;

(5) FIG. 4 shows a section through the substrate according to FIG. 2 along line B-B;

(6) FIG. 5 shows a to view of a substrate according to an embodiment according to the invention with smooth anchoring edges without mould cap;

(7) FIG. 6 shows a perspective view of the top of the substrate according to FIG. 5;

(8) FIG. 7 shows a perspective view of the substrate according to FIG. 5 with semiconductor chip and mould cap;

(9) FIG. 8 shows a cut-out of the substrate according to

(10) FIG. 6; and

(11) FIG. 9 shows a variant of an anchoring edge.

(12) The basic structure of the strip-shaped substrate shown in FIG. 1 may also be realised in terms of the invention. The invention is different from the substrate shown in FIG. 1 in that a.o. the anchoring edges are shaped in a different manner not shown in detail in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(13) The invention is not limited to the basic structure shown in FIG. 1, in particular the structuring of the substrate. The invention also covers substrates, where the geometries are structured in a different way. For example further stress-relief slots may be provided in order to reduce mechanical stresses, which if arranged in the area of the moulding compound/casting compound, may be provided with anchoring edges formed according to the invention.

(14) The strip-shaped substrate shown in FIG. 1 is an intermediate product which is further processed to create a package or electronic module. The anchoring edges introduced into the substrate are also present in the further-processed module or in the end product, such as in a chip card or generally in the electronic device.

(15) In detail the strip-shaped substrate as per FIG. 1 is constructed as follows. The description which follows is explicitly disclosed in the context of the invention/in all exemplary embodiments of the application.

(16) The strip-shaped substrate is produced from a flexible film 1. The flexible film 1 is preferably a steel foil, in particular a foil produced from hard-rolled, austenitic stainless steel. The film or foil comprises a number of units 2 which are separated from each other in a later method step for producing electronic modules. The units are all constructed identically. Each unit 2 has a chip island 3 to which the semiconductor chip can be attached.

(17) The semiconductor chip may come in a variety of embodiments. These may be in the form of an electronic memory, random electronic circuits (integrated circuitsICs) or LEDs.

(18) In terms of the invention the strip-shaped substrate includes embodiments without and with semiconductor chips. In FIG. 1, as well as in FIG. 2, the substrate is shown in a fitted condition, i.e. fitted with semiconductor chips 17.

(19) The substrate comprises more than the units 2 shown in FIG. 1. Normally the substrate extends in transverse direction to the depicted three units 2. The substrate is or may be coated.

(20) Each unit 2 comprises electrodes 4 for electrical connection of the respective semiconductor chip 17. The electrodes 4 surround the chip islands 3 on both sides respectively. The chip islands are electrically neutral. Each electrode 4 is divided into two partial areas, i.e. into a bond pad 5/a bond connection surface 5, which is used to electrically contact the semiconductor chips with the aid of bond wires (not shown). Other electrical connections are possible. The second partial area of the respective electrode 4 is an outer contact surface, e.g. an antenna pad 6, to which an antenna (not shown) or a voltage supply (not shown) can be connected.

(21) The strip-shaped substrate is provided with through-openings 7, 8, 9, 10, with the aid of which the respective unit 2 is structured and the above-mentioned functional areas of the unit 2 are delimited from each other.

(22) First through-openings 7 are formed laterally of the chip island 3. The first through-openings 7 are essentially rectangular, in particular square. Other geometries are possible.

(23) The unit 2 comprises second through-openings 8 which limit the chip island 3 and essentially determine its form and size. The second through-openings 8 are arranged mirror-symmetrically on both sides of the chip island 3. The second through-openings 8 are essentially shaped in the form of a U. Each second through-opening 8 comprises a transverse shank, which is arranged transversely to the longitudinal direction of the unit 2 and which determines the width of the chip island. The two longitudinal shanks of the through-openings 8 arranged in longitudinal direction of the unit 2 are shorter than the longitudinal side of the chip island 3, so that the ends of the longitudinal shanks of the second through-openings 8 are spaced apart from each other.

(24) The first through-openings 7 are arranged between the second through-openings 8.

(25) The substrate shown in FIG. 2 further comprises third and fourth through-openings 9, 10, which separate the bond pad from the antenna pad 6. Between the third and fourth through-openings 9, 10 connecting webs 24 are formed, which form the electrical connection of the bond pad 5 and the antenna pad 6.

(26) The third through-openings 9 are curved in sections and extend in the area of the corners of the second through-openings 8.

(27) The fourth through-openings 10 are arranged parallel to the transverse shank of the second through-opening 8. Instead of the single fourth through-opening 10 shown in FIG. 2 two through-openings 10 respectively may be provided on the respective side of the chip island 3, as shown for example in FIG. 1.

(28) The unit 2 shown in FIG. 2 further comprises through-openings 23, which are arranged outside the casting compound and therefore do not comprise any anchoring edges. The through-openings 23 without anchoring edges delimit the antenna pads 6 from the remaining areas 19 of the foil shown in FIG. 1. A web 20 respectively is formed between the through-openings 23 which is removed prior to the function test and is used for handling the substrate during processing. The same applies to the webs 20 between the second and third through-openings 8, 9.

(29) The remaining areas 19 of each unit surround the electrodes 4 as well as the chip island 3 and ensure the mechanical bond of the substrate during processing. The electrodes 4 and the chip islands 3 form part of the electronic modules produced from the substrate. The remaining areas 19 and the conveying strip 21 are removed during manufacture. The manufacturing process is described in detail in DE 20 2012 100 694 U1 in paragraphs [0078] to [0084] to which express reference is made at this point.

(30) In order to protect and fix the semiconductor chip 17 this is embedded into a casting compound 18. The casting compound 18 surrounds the semiconductor chip 17 and the bond wires and extends at least partially over the electrode 4, in particular over the bond connection surface/the bond pad 5. In order to ensure reliable operation of the modules/the components produced therefrom, it is crucial that the casting compound 18/the mould cap formed therefrom is firmly connected to the strip-shaped substrate/the chip carrier after separation of the respective units 2.

(31) To this end the through-openings 7, 8, 9, 10 comprise anchoring edges 11 which interact with the casting compound during encapsulation of the semiconductor chips. The construction of the anchoring edges 11 is shown in FIGS. 3, 4 and 8. A variant with a profiled anchoring edge is shown in FIG. 9. As clearly revealed in FIGS. 3, 4 and 9, the anchoring edges 11 are formed by chamfering the surface sections 12 abutting the respective through-openings 7, 8, 9, 10.

(32) Chamfering is understood to mean a reshaping of the foil (film), where the rim area of the foil limiting the respective through-opening 7, 8, 9, 10 is bent over. Specifically the adjacent surface section 12 is bent upwards/chamfered in such a way that the anchoring edge 11 protrudes past the side of the foil 1, on which the chip island 3 is arranged. The anchoring edge 11 protrudes somewhat beyond the surface of the surrounding foil 1. This arrangement can be clearly recognised in FIGS. 3, 4 and 9.

(33) The chamfer angle between the chamfered surface section 12 and the further surface 13 of the foil 1 surrounding the chamfered surface section 12 is approx. 45 in FIGS. 3, 4 in the case of the non-profiled, i.e. flat anchoring edge. The chamfer angle may be in the range between 30 and 60, in particular between 40 and 50. In FIG. 4 the chamfer angle is denoted with the reference symbol a. The further surface 13 of the foil 1 extends in the horizontal in the views of FIGS. 3, 4. Relative to the further surface 13 of the foil 1, the chamfered surface section 12 is upwardly inclined/generally inclined.

(34) The maximum chamfer angle of a profiled anchoring edge may be approx. 90, as shown in FIG. 9. Here also an angle range is possible, wherein the lower limit may be e.g. 40 or 45 or larger.

(35) The width of the chamfered surface section 12 is dimensioned such that a sufficient anchoring effect is achieved during encapsulation of the semiconductor chip 17 in the casting compound 18. As can be recognised in FIGS. 3, 4 the width of the chamfered surface section 12 may be roughly dimensioned such that the upper edge of the chamfered surface section 12 is arranged roughly at the height of the upper edge of the semiconductor chip 17 or slightly below it.

(36) As can be clearly recognised in FIGS. 2 and 5, the chamfered surface sections 12 are straight, i.e. they are formed on straight sides of the through-openings. The chamfered surface sections 12 extend along the straight sides of the through-openings. Generally only straight sides of the through-openings are chamfered.

(37) Surface sections which lie adjacent to curved areas of the through-openings, extend flush with the further surface 13 of the foil 1. That is, the curves 14 of the through-openings are chamfer-free. In other words the surface sections 14 in the curved areas, in particular in all curved areas, are not chamfered or bent over.

(38) In addition, as can be seen in FIGS. 2 and 5, chamfer-free recesses 16 are formed at the corners of the second through-openings 8, which relieve mechanical stresses in the area of the chip island 3. The recesses 16 form roundings, which lie on the inside respectively, of the longitudinal shanks of the second through-openings 8 extending in longitudinal direction of the unit 2. In the exemplary embodiment shown in FIGS. 2 and 5 respective chamfer-free recesses 16 are provided at four corners of the second through-openings 8.

(39) As can be clearly seen in FIGS. 2 to 4, the anchoring edges 11 are formed only in the area of the casting compound 18.

(40) To stabilise the chip island 3 chamfered surface sections are formed on the insides 15 of the second through-openings 8. Due to this profiling of the foil the chip island 3 is stabilised. The curved areas of the insides 15 of the second through-openings 8 are chamfer-free.

(41) As can be clearly recognised in FIGS. 2 and 5 chamfered surface sections 12/generally anchoring edges 11 are provided on the inside of the fourth through-opening 10. The anchoring edges 11 are formed in the straight areas of the inside of the third through-openings 9. The second through-openings 8 comprise respective anchoring edges 11/chamfered surface sections 12 both in the straight areas of the inside 15 and in the straight areas of the outside. The same applies to the first through-opening 7.

(42) In contrast to the view in FIG. 2, where the semiconductor chip 17 is encapsulated, the semiconductor chip 17 in the view shown in FIG. 2 is exposed. In FIG. 5 the position of the anchoring edges can be clearly seen.

(43) A further difference between the embodiments shown in FIG. 2 and FIG. 5 consists in that in FIG. 2 the anchoring edges 11 have a comb-like profile. The comb-like profile as per FIG. 2 extends in longitudinal direction of the anchoring edges 11. The chamfered surface sections 12 comprise a profiled outer edge. The profiled outer edge is formed by a plurality of uniform notches or cut-outs, which are arranged along the outer edge. The result is the comb-like profile. The notches shown are essentially rectangular. Other geometries are possible.

(44) In the example in FIG. 5 the anchoring edges are smooth. They comprise a continuous straight outer edge. The outer edge is not interrupted as in FIG. 2. A combination of the examples as per FIGS. 2 and 5 is possible.

(45) FIG. 6 corresponds to the intermediate state as per FIG. 5. Due to the perspective view as per FIG. 6 the arrangement of the chamfered surface sections 12 can be clearly seen. In FIG. 7 the semiconductor chip as per FIG. 6 is cast into the casting compound 18, which forms a mould cap.

(46) FIG. 8 shows a detailed cut-out from FIG. 6. Here the shape of the anchoring edges can be clearly recognised. The anchoring edges, as seen in the context of the first through-opening 7, may comprise flat faces. Other forms of anchoring edges 11 are possible, as depicted in the context of the second through-opening 8. Here it can be seen that the anchoring edge 11 has a curved face, which continually transitions into the inside 15 of the through-opening 8.

(47) FIG. 9 shows a variant of the anchoring edge 11. The anchoring edge 11 is profiled transversely to the longitudinal extension of the anchoring edge 11. The chamfered surface section 12 comprises a first shank 25, which extends vertically to the further adjacent surface 13 of the foil, which is not bent over. The first shank 25 transitions into a second shank 26 which extends vertically to the first shank 26 and forms an outer edge of the chamfered surface section 12. This results in an L-shaped profile of the anchoring edge 11. If you add the further surface 13 of the foil, an overall Z-shaped profile results. The profile extends along the side of the respective through-opening. The profile extends along the side of the respective through-opening. The profile allows secure anchoring of the casting compound 18.

(48) Other profiles are possible. Various profiles can be combined.

(49) Manufacture involves a reshaping tool 27, as shown in FIG. 9. During the process the material is deep-drawn (set-down). The material thickness is reduced.

(50) The foil used in the context of the embodiments is a metal foil consisting of a hard-rolled, austenitic stainless steel. The thickness of the foil is between 15 m and 35 m, specifically approx. 20 m. As a result the overall thickness of the package/the electrical module can be reduced to 200 m. Secure fixing of the casting compound 18 is achieved by the upwardly chamfered surface sections 12.

(51) Manufacture of an electronic module using a carrier substrate as per FIGS. 2 to 8 is effected as follows: To start with a semiconductor chip 17 is placed on the top of the respective chip island 3 of each unit 2 and fixed there. The semiconductor chip 17 may for example be glued on. Subsequently the semiconductor chip 17 is connected via bond wires (not shown) to the bond pad 5. Then the semiconductor chip 17 and the bond wires are fixed in that a moulding compound or casting compound 18 such an epoxy resin, is applied. The casting compound flows underneath the chamfered surface sections 12, thereby embedding them. After hardening of the casting compound 18 this is firmly anchored in the substrate.

(52) The structure devised in this way is shown in FIGS. 2 to 4 and 7.

(53) Subsequently the structure is electronically punched out. This involves removing the webs 20, which mechanically connect the electrodes 4 to the remaining areas 19 in an electrically conductive manner. This relates to the webs 20 between the through-openings 23 and the webs 20 between the second and third through-openings 8, 9. The connecting webs between the third and fourth through-openings 9, 10 remain standing.

(54) The webs 20 between the first and second through-openings 7, 8 cause the structure of the substrate to remain sufficiently stable and cohesive, enabling it to be processed further. Subsequently the functional test is carried out in order to remove defective modules.

(55) Thereafter the modules are separated from the foil 1 in that the webs 20 between the first and second through-openings 7, 8 are removed. The electronic modules produced in this way can then be installed in that, for example, wires or conductor tracks are connected as antennas or electric power lines to the outer connection surfaces/antenna pads 6.

LIST OF REFERENCE SYMBOLS

(56) 1 film (metal foil) 2 unit 3 chip island 4 electrodes 5 bond pad 6 antenna pad 7 first through-openings 8 second through-openings 9 third through-openings 10 fourth through-openings 11 anchoring edge 12 chamfered (first) surface section 13 further surface of the film 14 (second) surface section 15 insides of the through-openings 16 chamfer-free recesses 17 semiconductor chip 18 casting compound 19 remaining areas 20 webs 21 conveying strip 22 conveying opening 23 through-openings without anchoring edges 24 connecting webs 25 first shank 26 second shank 27 reshaping tool