DD281939A7 - METHOD FOR PRODUCING CONTACT PANELS ON ELECTRONIC COMPONENTS - Google Patents

Abstract

The method for contacting electronic components is used to produce wrap-around contacts for electronic components on flat substrates, preferably chip resistors. According to the present invention, by using plating masks in a lift-off process on a large-format substrate prestructured in one direction, the contact layer system is applied on the front by plasmatron sputtering, trenching is introduced in one direction, then trenching is introduced vertically, front side a mask is applied and then strips are broken. Thereafter, the remaining Teilflaechen the contact are applied using masks and broken into finished components. Fig. 1 {contacts; Electronic Components; Chip resistance; sputtering; Resist mask; liftoff Prozesz; plasmatron; Dig; Flat substrates}

Description

For this 3 pages drawings

Field of application of the invention

The invention relates to a method for producing so-called wrap-around contacts for electronic components on flat substrates, preferably SMD chip resistors. It is a process in which a layer system for the contacts in thin-film technology is produced by Plasrr.atron sputtering.

Characteristic of the prior art

Electronic components on flat substrates are often provided with wrap-around contacts to ensure their use as SMD components on circuit boards and wiring substrates. The contact surfaces must be arranged on areas of the front side with the electrical functional layers, on two end surfaces dos flat substrates and on areas of the back and conductively connected. The electrical functional layers, e.g. Widerr'andsschichten, are usually produced by Siebdruck- and Brennverfahr.jn (thick film technology) or by Vakuumverschichtungsverfahran (thin film technology).

In general, the preparation of the wrap-around contacting on the front side, front sides and back side of the substrates takes place in three separate coating processes. These differ in productivity. Depending on whether the coating is carried out on a large-area substrate carrying many components with a matrix arrangement of m rows and η columns of components, on stripes (Zoilon and η components) or on individual components, very different costs result for the individual coating steps. If the geometric conditions of components with wrap-around contacts are present, continuous processing of large substrates containing m × η components in a matrix-like arrangement is not possible. Even the preparation in strips of η devices is problematic, because in the final process of device isolation technical problems oderr high costs arise. If the deposition of the layers for contacting by Plasmatron sputtering, the coating must be done by changing masks or the layers must be subsequently structured. Change mask structuring is only feasible for very coarse structural dimensions due to the very low profile accuracy and the insufficient edge sharpness.

For this reason, in the case of thin-film contacts, structuring generally takes place by chemical etching in the subtractive method using resist masks. This procedure has a number of deficiencies. The large number of necessary process steps (application of the structured resist mask, etching removal, removal of the resist mask, washing processes) causes high costs in the structuring of the contact layer. Since thin film contacts generally consist of several sublayers of different materials, complicated selective etching processes are required. Because of the strongly acidic or basic nature of the etchants, residual allo residues must be removed, and high quality, low porosity substrates must be used to prevent etchants from entering pores. Otherwise, the long-term stability of the electrical functional layers will not be achieved.

There have also been proposals to perform the structuring in a so-called lift-off process, that is to say by completely coating substrates with resist masks in the places which are not intended for contacting, and then removing these resist masks including the overlying layer. The application of such lift-off methods is limited to contact layers with a thickness of a few hundred nanometers. The difficulties increase with the layer thickness and with increasing freedom from pores of the layers, since the concealed coating structures are not attacked by the solvent. However, the required contact layers for wrap-around contacts consist of several sub-layers, whereby gerftde a low porosity is achieved, and have a thickness in Boreich of a thousand nanometers. As a result, lift-off structuring is not possible. It has also been proposed to carry out the lift-off process with a combined metal paint mask having overhanging edges. Because of the high process costs, the application is limited to special components of microelectronics.

For the reasons given above, lift-off structuring methods for producing electronic components with wrap-around contacts have not hitherto been used in production.

Wrap-around contacts have to be easy to solder on all sides. In the deposition by separate coatings of three sides of the components successively by sputtering on the one hand, the connection or the overlap of Teilfiächen the wrap-around contact is inevitable, on the other hand, the solderability of already deposited layers on sub-surfaces is critically affected. Causes for this are litter steam, residual gas and plasma reactions.

Object of the invention

The object of the invention is to overcome the deficiency of the prior art in the production of wrap-around contacts in thin-film technology and to improve the economics of contacting electronic components on flat substrates.

Explanation of the essence of the invention

The invention has for its object to provide a method for applying well-rotatable wrap-around contacts by Plasmatron sputtering. This method should be highly productive and do not place high demands on the absence of pores of the substrates.

According to the invention, the object of applying the contact layer system to areas of the front side, the rear side and two end faces of the component as wrap-around contact on a flat substrate of dimension 1 χ b χ d by means of Plasmatron sputtering using resist masks in a lift-off Process solved in that the contact layer system in a first Plasmatron sputtering process over the entire surface and from the front on large-sized, pre-structured in one direction only provided on this front side with a glaze layer and provided on the non-contacting surfaces of the front with a resist mask substrates is applied. It has a matrix-like arrangement of m rows and η columns of components and thus has the dimension ml χ nb χ d, whereby the preliminary structure takes the form of trenches of depth T ₂ and width B; has evenly spaced at the distance I parallel on the front of the substrate and the grunts of the later components in one direction with 0.2 d <T? <0.5 d and with B *> 0.25 Tj form. Subsequently, trenches of depth T ₅ and width Bs running parallel to each other at a distance b perpendicular to the preliminary structure on this front side of the substrates, with Ts>T; and B ₅ = » Bz incorporated, which form the boundaries of the later components in the second direction. Thereafter, the lateral dimensions of the contact surfaces on the front side of the substrates are generated by a lift-off process. After performing further processing steps in the overall process of device fabrication such as annealing, patterning and trimming the functional layers, applying protective layers, etc. on the front side and applying a resist mask to the non-contacting surfaces on the back side of the large format substrate dimension nb χ ml χ d including the regions on the back, in which the trenches of the depth T ₅ and the width B _s are located on the front side, the substrate is separated into strip-shaped sub-substrates of dimension I χ nb χ d, preferably by breaking. Thereafter, the contact layer system on all other faces of the later wrap-around contact in a second

Plasmatron Sputterproze. "Applied to these strip-shaped sub-substrates, these sub-substrates in a plane next to each other, but each with a free space S with S> 1.5d are arranged, with a direction of vapor incidence in this sputtering process, which inclines against the direction of incidence in the first sputtering process During this second coating, the front side of the sub-substrates is covered to the edges, and in a subsequent second lift-off process, the lateral dimensions of the contact surfaces are produced on the rear side of the strip-shaped sub-substrates The dimensions of the large substrates ml x nb xd or of the sub-substrates I x nb χ d are the net Abrnessungon of the dimension I xb χ d only after the soldering of all contact surfaces on the strip-shaped sub-substrates In "handling strips" for handling the substrates during the manufacturing process, the gross dimensions are larger by the corresponding amounts.

The sub-steps of the process according to the invention in their sequence and configuration make it possible to deposit the contact layer system on areas of the front side, two front sides and the back side of flat substrates in only two plasmatron sputtering processes. Furthermore, the method provides the ability to apply lift-off processes for lateral patterning despite the large thickness in the range of one thousand nanometers and the pore poverty of the multilayer contact layer system for wrap-around contact. For the economy of the process, first of all the small number of required sub-processes is decisive. However, it is crucial that the method for producing the wrap-around contact allows the implementation of the majority of the process steps on the large-format substrates for m χ η components. This applies to the entire process sequence for component manufacturing. The application of the lacquer masks and protective layers takes place without difficulty with standard screen printing processes. In particular, the patterning and trimming of the electrical functional layers, for. As the resistance layers, on the large format substrates possible. Only a coating, a lift-off and the Belotungsprozeß are performed on strip-shaped sub-substrates, which still allow the integrated processing of η components. The implementation of the majority of the sub-processes on the large-format substrates drenched drastically the expenses for handling and adjustment and thus has a decisive influence on the process economy in the production of devices with wrap-around contacts.

With the consequence of the method steps, in particular the electrical conductivity of the wrap-around contact on the end faces of the flat substrates and the good solubility are ensured. This is particularly noteworthy in view of the fact that both the separation of the large-sized suostrate into strip-shaped sub-substrates and the separation into individual components preferably takes place by breaking, whereby rough break edges with steps are unavoidable. The secure contacting in spite of these conditions is ensured on the one hand by the execution of the first coating on one side vors'.rukturierten substrates with trenches dor arneführung design rule. They are executed only in the area of the edges on the end faces of the wrap-around contact. Prestructuring the substrates in both directions would make the first lift-off process impossible. It has been found that the minimum quality for the surface topology of the breaklines is ensured by making the trenches narrow and deep. This specified geometric design ensures by the ratio of width and depth in addition to the possibility of breaking and a partial covering of the end faces by utilizing scattering effects in the first Plasmatronsputterprozeß. Only in conjunction with the much more effective scattering effects in the second sputtering process as a result of the changed in this sub-process geometric conditions of the arrangement, the required thickness of Kontakschichtsystems is achieved in the critical edge region of depth T ₂ . In addition, the effect is effective that the effective layer thickness in the edge region of the depth T ₂ under the same sputtering conditions is comparatively higher than on the fracture surface, because the pre-structuring is carried out by means of a grinding process, resulting in a low average surface roughness in these areas.

The possibility of making the lateral structuring of the contact surfaces despite the contradictory requirements with respect to thickness and freedom from pores of the contact layer systems also has a decisive influence on the process economy. Surprisingly, the well-known difficulties Deim lift-off process on thick layers could be overcome by close-meshed mechanical scribing of the metal and lacquer layers. Obviously, such scratches create points of attack for the solvent of the lift-off lacquer and create critical changes in the metal layers and lacquer layer to allow their removal. It is particularly advantageous if the solvent used is a substance which leads to the swelling of the paint. A peculiarity of the method according to the invention is that such a close-meshed scoring of the metal and lacquer layers in the second partial process results in the creation of the preliminary structure which forms the boundaries of the later components in the second direction, ie without a separate process step. It can be seen that the distance b, which is in the range of one to two millimeters, is sufficient to achieve the tonal effects ι ir the lift-off process. The geometrical dimensions of the trenches of depth T ₅ and width B _s not only ensure the lift-off process and the subsequent breakage of the substrates, but also ensure complete electrical isolation of the columns of the device array on the large area substrate prior to singulation. Thus, only the leadership of measuring and trimming processes with enpor Toloranz on the large-area substrate is made possible. While the lift-off process on the substrate surface, which is provided with a glaze layer with relatively low roughness, is ensured by the sub-steps of the method according to the invention, such sub-processes are not required for the lift-off process on the substrate back. The attack of the source un-f solvent for the paint is secured by selecting the material for the substrates and by the prior creation of broken edges of metal and lacquer layer in the fourth Toilprozoß the process of the invention. For the substrate material this means a minimum porigkoit and Mindost roughness requirement, ie the use of cost-saving materials.

During the implementation of the second Plasmatron sputtering process, the cover of the front of the sub-substrate is carried out by a screen-printed resist mask, which consists of the same paint that is used for the two lift-off processes or by resiliently pressing ebenon support surface on the front of sub-substrates , Both Verfahronsvarianten ensure that the applied in the first sputtering layer system on the Vordorseite the substrate to the edge dor strip-shaped sub-substrates is protected from the action of scattered vapor and high-energy particles of the plasma sputtering, while the don on the front side applied layers remain free and influenced by the plasma become. However, the geometrical conditions of the second plasmatron sputtering process ensure that the

Condensation with high growth rate of the layer on the critical areas of the face overcompensates the disturbing plasma influences. On the other hand, by leaving these areas free, the required overlap of the In the two Plasmatron sputtering processes is formed. Achieved layer systems and thus achieved a good conductive connection. It is expedient that the second Plasmatron sputtering process is performed so that the direction of vapor incidence is inclined exactly 180 ° against the direction of vapor incidence of the first Plasmatron sputtering process, so the coating takes place from the substrate back. The faces of the later components are coated by scattered vapor.

It may also be expedient, particularly in the case of a substrate material which forms very coarsely crystalline fracture surfaces, that the vapor incidence directions in the two plasmatron sputtering processes are inclined by 90 °, that is to say the coating proceeds in the second plasmatron sputtering process from the end faces of the later components. The coating of the substrate back side takes place in this case by scattering processes. In this procedure, several opposing plasmatron sputtering beads are required.

Characterized in that the resist mask on the llückseito of the substrates before the second Plasmatron sputtering process is also on the areas on which are located on the front trenches of depth T ₈ and width B ₅ , it is ensured that after the pelota on the back the stripe-shaped sub-substrates the desired breaking lines during separation are free of contact and Lotschichton. In this way, the required tolerances of the device dimensions can be maintained without the strip-shaped substrates have to be separated by dicing saws. Obviously, stress states are generated which prefer to break towards the uncoated regions of the substrates.

embodiment The accompanying drawings show in 1: a contacted chip resistor, 2: a large-sized substrate with pre-structure, 3a to 3f: the individual ancestor steps on a substrate or sub-substrate to fertigon component.

The device, a chip resistor, is supported by a flat substrate 1 of dimension 1 × b d. The front also carries an electrical functional layer, here a resistance layer 2, which has been given its final electrical paramot by a stabilization and trimming process. There is a glaze layer 3 between the Widorstandsschicht 2 and the substrate 1. The device carries the wrap around contact 4. It consists of the contact surfaces 4.1 on the front, which contact the Widorsjandsschicht, from contact surfaces 4.2 on the end faces of the device and from Contact surfaces 4.3 on the back, all of which are conductively connected. The contacts 4 are bolotet and thus allow an automatable assembly of the components wahlwolse from the front or back of the device in SMD technology.

FIG. 2 characterizes the starting substrate for carrying out the partial steps of the method according to the invention for producing the wrap-around contacts 4. The method uses a large-format substrate provided with a voistic structure in only one direction and has the dimensions nb χ ml χ d and FIG allows matrix-like arrangement of nm devices. Optionally, the substrate is still larger in its length and width in each case around the botag 2a. By the edge strips of the width a, which are later rejected, the handling of the large-sized substrates 1 in the production process is facilitated.

In Fig. 3a, the substrate is shown in partial section after the first process step. It carries the glaze layer 3 and the resistance layer 2. On the front side of the substrate, that is to be applied to the contact surfaces 4.1, extending trenches 5 with the depth T _z and the width B _{2 in} parallel at a distance I to the lugs, in one direction form the Gronzon of the later individual components. The substrate 1 has the thickness of 0.6 mm, the trenches 6 have a depth of T; = 0.15mm and a width of Bz = 0.05mm. The substrate 1 further supports, at the locations on the side which are not provided (the contacting, a lacquer mask 6 with the orforcinal lateral structure, which is applied by screen printing.) In a first plasmatron sputtering process occurs over the whole area and from This layer system consists of a 0.03 μm thick adhesive layer, for example of chromium, of a 0.8 pm thick, highly conductive layer, for example of chromium, on the substrate front grain, illustrated by the arrows B. of copper, and another 0.4 pm thick well-aerosolizable layer, which dissolves less in the solder, for example, copper-nickel, which are deposited sequentially in time.The trenches 5 are also coated.

Fig.3b illustrates the next step Var. In the substrate 1 coated in accordance with FIG. 3 a, trenches 7 with a depth of 0.2 mm and a width of 0.05 mm are incorporated perpendicularly to the preliminary structure, likewise on the substrate front side parallel to one another and at a uniform spacing b. They form the boundaries of the later components in the second direction. Through the trenches 7 electrically isolated portions are created in one direction. The lacquer layer covered by the preceding coating process and the contact layer system are traversed by a network of separating cutons extending at a distance b from each other.

FIG. 3 c shows the schematic section of the large-format substrate after carrying out the third method step. By swelling and solvent has been achieved that the lacquer layer has been attacked from the direction of the trenches 7 and such conditions of tension on the edge of the paint in don contact layer systems causes that a lift-off process could be performed and the required lateral structure of the contact surfaces 4.1 on the Front of the substrates 1 has been achieved. FIG. 3 d illustrates the fourth method step. After carrying out process steps which are necessary for the overall production process of the component fabrication, but do not affect the production of the wrap-around contact 4, eg Temporn, trimming of the functional layers, application of protective layers on the large-format substrate, the coating layer 8 was applied to the not for the contacting provided areas on the substrate back including the areas 9, in which are located on the front of the trenches 7 of the depth Ts and the width B _s . Weitorhin every large-format substrate of the dimension ml χ nb χ d, preferably by breaking, in mreifförmige sub-substrates of the dimension I χ nb xd gotrennt, wherein dio fracture surfaces in the region of the trenches 5 extend.

FIG. 3e explains the implementation of the fifth method step. To carry out a second plasmatron sputtering process, the sub-substrates were arranged in a plane next to each other, but each with a free gap i ° 1 mm. The vapor incidence direction, as illustrated by the arrows, forms an angle of 180 "against the direction of vapor incidence in the first sputtering process, thus coating directly from the back of the substrate During this second coating, the front of the substrates 1 is covered to the edges For this purpose, a coating system on the contact surfaces 4.2 and 4.3, which consists of the same partial layers as in the first plasmatron coating process, has been deposited on the end surfaces and the substrate back side by direct coating and by scattered vapor deposition It is ensured by the lacquer layer 10 that the contact surfaces 4.1 on the front side of the substrate are not unfavorably influenced by scattered vapor and plasma effects with respect to the ability to be soldered ight electrically conductively connected.

Fig. 3f shows schematically in section the sub-substrates after performing a second lift-off process for generating the lateral structure of the contact surfaces 4.3 on the substrate back. If the substrate 1 is made of glass-ceramic with a certain porosity and it only has a glaze layer 3 on the front side, then this lift-off process is probably directly possible owing to film defects and defects in substrate irregularities. If the substrate 1 has low porosity or also has a glaze on the back of the substrate, then the contact layer with the underlying lacquer layer 8 must be scribed in an intermeshed manner by means of an additional process. In the example, a substrate material is used, which allows a direct lift-off process on the substrate back. To further carry out the method, the strip-shaped Teilsubströli the dimension I χ nb χ d are soldered by a dip soldering or Schwallötprozeß. The boundary areas between the later individual components do not carry any solder on the substrate front surface since the contact layer has been removed home to generate the trenches 7. Also dio substrate back is lot-free due to the design of the resist pattern 9. The solder layer on the sub-substrate generates a mechanical stress state with extreme values in the region of the areas intended for separation. As a result of this substrate distortion separating the sub-substrates in individual components of the dimension I χ b χ d is possible by breaking, whereby the orörmlichon tolerances of the components of a maximum of ± 0.15 mm can be maintained.

Claims (1)

Method for producing contacting surfaces on electronic components, preferably chip resistors, which are provided in cap-like fashion at two end faces with a contiguous contact layer covering part of the front and back side, by plasmatron sputtering and using resist masks in a lift-off Process, characterized that the contact layer system in a first Plasmatron sputtering process over the entire area from front to large, pre-structured only in one direction, provided only on this front side with a glaze layer and provided on the non-contacting surfaces of the front with einor resist mask substrates, whose size is the matrix-like arrangement of m rows and η columns of components and thus has the dimension ml x nb xd, is applied, as a pre-structure trenches of depth T ₂ and the width Bz, evenly spaced parallel to the front of the Substrate and the boundaries of the later components form in one direction, with the dimensions 0.2 d <T ₂ <0,5dundmit B _z > 0.25Tz are introduced - That then on this front side of the substrates perpendicular to the preliminary structure at a distance b parallel trenches of depth Ts and the width Bs with T _s > Tz and B _s »B ₂ , which form the boundaries of the later components in the second direction, incorporated become, that subsequently the lateral dimensions of the contact surfaces on the front side of the substrates are produced by a lift-off process, - That after performing further Proz6ßschritte in the overall process of component manufacturing such as annealing, structuring and trimming the functional layers, applying protective layers, etc. on the front of a resist mask on the non-contacting surfaces on the back of said large format substrates of dimensions nb x ml xd including the areas in which the trenches of depth T _s and width Bs are located on the front side, _t - That subsequently the substrates are separated into strip-shaped sub-substrates of dimension I χ nb χ d by breaking, - That then the contact layer system on all other faces of the contact in a second Plamatron sputtering process, wherein the direction of vapor incidence is inclined against the direction of incidence in the first sputtering process, the sub-substrates in a plane next to each other with a free space <? > 1.5 d, is applied to the strip-shaped (egg) substrates, while the front of the sub-substrates is covered to the edges, - That subsequently in a second lift-off process, the lateral dimensions of the contact surfaces are generated on the back of the strip-shaped sub-substrates - And that after the Belotung all contact surfaces on the strip-shaped sub-substrates, the individual flat substrates of dimension I χ b x d are broken.