ELECTRICAL COMPONENT WITH THIN SOLDER RESIST LAYER AND METHOD FOR THE PRODUCTION THEREOF

Abstract

An electrical device and a method for the manufacture of an electrical device are specified. The device has a carrier with an upper side and a metallized contact surface arranged on it as well as a solder mask layer which covers a part of the upper side but not the contact surface. The solder mask layer has a thickness of 200 nm or less, thereby facilitating subsequent process steps for encapsulating the device.

Claims

1. An electrical device (EB) comprising a carrier (TR) with an upper side (O), a metallized contact surface (MK) on the upper side (O), a solder mask layer (LSS) that covers part of the upper side (O) but not the contact surface (MF), wherein the solder mask layer (LSS) has a thickness of 200 nm or less.

2. Device according to the preceding claim, wherein the solder mask layer (LSS) has a thickness between 30 nm and 80 nm.

3. Device according to the preceding claim, further comprising a bump ball (BU) on the metallized contact surface (MK).

4. Device according to any one of the preceding claims, further comprising an electrical component (EK) with a contact surface (KF) on the underside and a bump joint (BU) that connects the two contact surfaces (MK, KF).

5. Device according to the preceding claim, further comprising a molding compound that covers at least parts of the upper side of the carrier (TR) and the electrical component (EK).

6. Device according to the preceding claim, wherein the molding compound also fills the intermediate space (Z) between the electrical component (EK) and the carrier (TR).

7. The component according to any of the preceding claims, furthermore comprising a first signal line (SL) on the upper side (O) of the carrier (TR) and interconnected with the contact surface (MK), a second signal line (SL) on the upper side (O) of the carrier (TR), wherein both signal lines (SL) are at least partially covered by the solder mask layer (LSS), and the electrical resistance between the two signal lines (SL) is 100 M or more.

8. Device according to any one of the preceding claims, wherein the solder mask layer (LSS) has silicon as its main constituent or is made of silicon.

9. Device according to any one of the preceding claims, wherein device structures are arranged on the upper side (O) of the carrier (TR) which have heights of 40 m or more.

10. A method for producing an electric device (EB), comprising the steps Provision of a carrier (TR) with an upper side (O) and a metallized contact surface (MK) on the upper side (O), Arranging a lacquer layer (FL) on the upper side (O) and structuring the lacquer layer (FL) in such a way that material of the lacquer layer (FL) remains on the contact surface (MK) and the areas of the surface (O) with no contact surface (MK) are free of the material of the lacquer layer (FL), Depositing a solder mask layer (LSS) on the upper side (O) of the carrier (TR), Removing the remaining material of the lacquer layer (FL) together with the material of the solder mask layer (LSS) over the contact surface (MK).

11. Method according to the preceding claim, wherein the solder mask layer (LSS) is given a thickness of 200 nm or less.

12. Device according to the preceding claim, wherein the solder mask layer (LSS) is given a thickness between 20 nm and 80 nm.

13. Method according to any one of the three preceding claims, wherein the solder mask layer (LSS) includes silicon as its main constituent or is made of silicon.

14. Method according to any one of the four preceding claims, wherein the electrical device (EB) has a further solderable metal surface (LO) on the upper side and the solder mask layer (LSS) is directly deposited on the further solderable metal surface (LO).

15. Method according to any one of the five preceding claims, wherein the solder mask layer (LSS) is applied by means of PVD or CVD.

16. Method according to any one of the five preceding claims, further comprising the steps Arranging solder paste (LP), at least on the contact surface (MK), Arranging an electrical component (EK) with a contact surface (MK, KF) on its underside on the upper side (O) of the carrier (TR), Reflow soldering the device (EB) and connecting the two contact surfaces (MK, KF) by means of a bump joint (BU).

17. Method according to the preceding claim, further comprising the step Encapsulating the electrical component (EK) with a molding compound (MM), wherein the molding compound (MM) also fills the area between the component (EK) and the carrier (TR).

Description

[0048] The main ideas and principles of operation underlying the device and manufacturing method and also schematic examples are outlined in the figures.

[0049] Shown are:

[0050] FIG. 1: a cross-section through an electrical device,

[0051] FIG. 2: a cross-section through a device with further encapsulation,

[0052] FIG. 3: a cross-section through a device with a bump ball on the contact surface,

[0053] FIG. 4: a first intermediate step in the manufacture of a device,

[0054] FIG. 5: a second intermediate step,

[0055] FIG. 6: a third intermediate step,

[0056] FIG. 7: a fourth intermediate step,

[0057] FIG. 8: a first intermediate result in the manufacture of a complex electrical device,

[0058] FIG. 9: a further intermediate step,

[0059] FIG. 10: a further intermediate step after heating,

[0060] FIG. 11: a cross-section through a simple embodiment of the device,

[0061] FIG. 12: a cross-section through an alternative embodiment,

[0062] FIG. 13: a cross-section through a device with a thin solder mask layer and with a molding compound which fills the intermediate spaces between the electrical component and the carrier.

[0063] FIG. 1 shows a cross-section through a simple embodiment of the electrical device EB. The electrical device EB has a carrier TR, on which a metallized contact surface MK is structured. The metallized contact surface MK is intended to be connected to an electrical component via a bump joint. On the upper side O of the carrier TR, a solder mask layer LSS is arranged which covers those areas of the upper side of the carrier TR which should not come into direct contact with solder material.

[0064] Here the metallized contact surface may be a so-called under-bump metallization, UBM, and have a readily wettable surface.

[0065] FIG. 2 shows a cross-section through a form of an electrical device with a relatively thick solder mask layer LSS. The solder mask layer LSS reliably protects sensitive areas on the upper side of the carrier TR from being wetted with solder, provided the upper side of the carrier TR is sufficiently flat. If the device is to be encapsulated by a molding compound MM, a thick solder mask layer will, however, be an obstacle to filling the intermediate space Z between the carrier TR and the underside of the electric component EK, which is joined and connected to the carrier TR via the bump joints BU.

[0066] FIG. 3 shows a cross-section through an electrical device in which a bump ball BU has already formed on the metallized contact surface MK. Due to the surface tension of the solder, a ball-like shape forms during the course of the reflow process. The thickness of the solder mask layer LSS is very small compared to the height of the bump ball or the subsequent bump joint connection to an electrical component.

[0067] A material with a solderable surface LO, for example, a signal line SL, is arranged on the surface of the carrier and can include nickel, copper, gold or silver. Without a solder mask layer LSS, there is a danger that the material of the bump ball BU does not accumulate on the contact surface MK, but attacks the signal line and possibly shorts out the signal line and a further circuit element on the upper side of the carrier.

[0068] FIG. 4 shows a cross-section through a first intermediate result in the manufacture of the electrical device. The contact surface MK and the signal conductor SL as examples of elements to be protected are arranged on the upper side of the carrier TR.

[0069] FIG. 5 shows a cross-section through a further intermediate step, in which the entire surface, including the areas to be protected and the areas to be wetted subsequently by the solder, is covered by a photoresist FL.

[0070] FIG. 6 shows a cross-section through a further intermediate step, in which the photoresist FL is so structured that only the areas MK, which should later on remain free of the material of the solder mask layer, remain covered by the material of the photoresist FL.

[0071] To this end photoresist can be selectively exposed and developed.

[0072] FIG. 7 shows the result of a further intermediate step, in which the entire upper side of the previous electrical device is covered by the material of the subsequent solder mask layer LSS. The sensitive areas are directly covered by the material of the solder mask layer LSS. Where solder is subsequently to be disposed is where the remaining photoresist FL is found between the material of the solder mask layer LSS and the contact surface.

[0073] FIG. 8 correspondingly shows the result of a further process step, wherein the remaining remnants of photoresist FL have been removed together with the segments of the material of the solder mask layer LSS deposited on them, so that the surface to be wetted lies exposed without being covered by the solder mask layer.

[0074] FIG. 9 shows the result of a further step, namely, of applying a solder paste LP to areas which mainly correspond to the areas of the contact surfaces MK. Due to the precise defined edges of the solder mask layer LSS, lateral positioning need not be overly precise during application of the solder paste LP as long as a substantial area of the contact surface MK is covered by the solder paste LP.

[0075] FIG. 10 shows the result of a further intermediate step in the manufacture of the electrical device, wherein following heating the material of the solder paste LP has concentrated into a ball at the position of the contact surface MK.

[0076] FIG. 11 shows a cross-section through an electrical device wherein the contact surface MK on the underside of the electric component EK and the contact surface MK on the upper side of the carrier TR are connected via a bump joint which developed from the bump ball in FIG. 10.

[0077] FIG. 12 shows a cross-section through a further embodiment in which the electrical component EK and the carrier TR are joined and connected via a plurality of bump joints BU. In addition to the solder mask layer LSS on the upper side of the carrier TR a solder mask layer LSSpreferably equally thincan be arranged on the underside of the electric component EK.

[0078] Finally, FIG. 13 shows a cross-section through an encapsulated electric device in which a molding compound MM encloses the electrical component on the upper side of the carrier TR and fills the intermediate spaces Z between the electrical component EK and the carrier TR.

LIST OF REFERENCE SIGNS

[0079] BU: Bump joint [0080] EB: Electrical device [0081] EK: Electrical component [0082] FL: Photoresist [0083] KF: Contact surface [0084] LO: Solderable surface [0085] LP: Solder paste [0086] LSS: Solder mask layer [0087] MK: Metallized contact surface [0088] MM: Molding compound [0089] O: Upper side of the carrier [0090] SL: Signal line [0091] TR: Carrier [0092] UBM: Under-bump metallization [0093] Z: Intermediate space