DE3221826A1 - Method of producing printed circuit boards used in microelectronic systems - Google Patents

Abstract

The essence of the method is that conductor tracks of the required configuration are formed on a substrate composed of a metal which can be etched selectively with respect to the metal of the conductors in such a way that the conductor tracks of both sides of the substrate are formed and the conductor tracks have at least a tapering section on the side of the substrate remote from the side on which a base is to be deposited. The base of the printed circuit board is then deposited on the appropriate side of the substrate and the substrate metal is etched selectively with respect to the metal of the conductor tracks over its entire thickness until its metal has been completely removed only under the tapering sections.

Description

MANUFACTURING PROCESS PURE IN MICROELECTRONIC

CIRCUIT BOARDS USED IN GENERAL SYSTEMS The present invention refers to technological processes for the production of microelectronic systems and particularly relates to manufacturing processes for in microelectronic systems used printed circuit boards.

The printed circuit boards produced in this way can be used as a basis for the creation of microelectronic systems of various constructive complications entity, including hybrid integrated circuits, puncture modules, units and apparatus implemented using integrated circuits will.

The manufacture of microelectronic systems requires a combination a large number of single crystals with integrated circuits with a large (from about a few dozen) number of connecting lugs led to the outside. These The task is made more complicated by the fact that the number of connection traps led to the outside of integrated circuits is growing in recent years, and this process continues until the microelectroxiic Systems have found widespread use. It won't be for the next few years to be expected, and the need to interconnect devices with many terminal lugs connecting is becoming more and more acute. To effectively solve this task it is necessary a circuit board with no less than two line levels.

The main points of each manufacturing process for the circuit boards with multilevel wiring are # creation methods for crossovers, i.e. for crossing conductors that cross in the structure of the connections, without them being connected to one another, and for contacts between individual ones Management levels, At present, the most widely used manufacturing processes used for circuit boards that allow at the crossover points to obtain separate managerial positions at different management levels through the lekt rikum, the at the required points by partially or completely with a conductive medium Filled holes in the dielectric are contacted.

This group includes manufacturing processes for double-sided and multilayered Printed circuit boards with metallized holes, processes of thick layer technology and multilayer ceramics as well as new technological processes that have appeared in recent years for the production of multilayer bases from thin layers of an organic Dielectric3, which is based on a metal substrate with a low coefficient of thermal expansion are pressed on (see e.g.

Ch. S Let. Edges: A New Interconnection Technology, pp. 113-121, Electronics, vol. 52, N 20, 1979).

Technology is one thing in common for this group of processes successive growth of layers on a dielectric base, in which with this or that method holes are made and with a conductive Medium to be filled. In the structure of the circuit board it is therefore necessary a large number (up to a few thousand) of holes at desired locations generate and use them in a respective process to create electrical contacts to be metallized between the individual line levels. The present process step is the most expensive and essentially determines the reject rate in production and the failure rate in operation because of the difficulty in obtaining high reliability to ensure the contacts between the levels. Even when exploited Such an advanced drilling process as laser drilling remains this operation most of all most ornamental, requires a high level of accuracy when positioning of the raw material and is realized with the help of expensive equipment.

If the execution of the holes and their metallization by group machining, as it is in multilayer ceramic structures and using screen printing processes to maintain conductive and dielectric layers is the case, can be achieved can ~ in a number of applications there are no high parameters for the conductor to the accuracy of the geometrical dimensions of the circuit board and the mutual arrangement of contact surfaces forfeited, the electrical Capacities and the number of mutual connections between the conductor trains to ts. for example M.L. Topfer, Thick-Film Microelectronics, Van Nostrand Reinhold Company.

New York, 1971).

Notwithstanding the fact that the circuit boards with beam webs on Metal supports varied thanks to their mechanical and electrical properties Demands on hybrid integrated circuits and other types of microelectronic Systems suffice, such crossovers are currently not widely used. This depends on specifics of the current manufacturing technology for the Bar webs, the twenty work steps (S. e.g. O.E. Jowett.

The Ingeneering of Microelectronic Thin and Thick Films, London, 1976) includes, together, such considerable complexity and labor this process are linked to the fact that the height of the crossovers by a an additional layer produced by vapor deposition and electrolytic deposition Titanium-copper-titanium structure is laid down above the main level nufgotrngen and later completely removed by etching will be carried, For the supports, holes are made in the additional layer by means of photolithography and etching then in a photoresist layer a window for a beam of a crossover and created the crossover itself by means of electrodeposition of gold. Such technology can only be used successfully to manufacture printed circuit boards inferior Surface on rigid bases are used, which severely limits their possible riding.

More extensive possibilities from the point of view of manufacturing circuit boards The metal substrate has a large area because the metal shrinks completely is alien to all types of flexible dielectric to one degree or another is own.

It is a manufacturing process for hybrid integrated circuits known that from a metal substrate (see. Japanese Patent 52-551, Cl. 99 (5.) C2I, 1977). In this process, the conductor tracks and circuit elements in the known layering technique on one side of a copper or iron substrate applied, added discrete elements, whereupon this side of the substrate with epoxy resin is potted, then the photolithography is done on the back of the substrate and the etching to create load-bearing elements is carried out in the following can be used as connections.

The main drawbacks of this method are the complexity and the Labor involved in making crossovers because the process is fundamental only one level of management results and not a solution to the question of creating the crossovers bypassing the known technologies considered above.

There is also a manufacturing method for a lead frame of an electronic device known, which is a special version of a printed circuit board (see e.g.

Japanese Patent 48-36III, Cl. 99 (5) 021, 1974) This procedure consists in making traces of the circuit board more necessary Configuration can be created on a substrate from a metal facing each other the metal of the conductor can selectively etch one side of the substrate The basis of the printed circuit board is stacked and the substrate for its entire thickness is etched selectively with respect to the conductor tracks.

In this process, the metal substrate is related to the side facing away from the conductor tracks masking layers applied to the extended Sections of the conductor tracks are opposite, whereupon an etchant everything except the Conductor lines and the sections of the protected by the masking layers Wtetall substrate is etched off. As a result, those formed by the 0, metal substrate load-bearing elements separated from each other and with those from the deposited metal executed narrow Abach sections of the conductor tracks connected.

Disadvantages of this as well as of the previous method are the complexity and labor of making crossings and thus also of printed circuit boards, which are used to create modern microelectronic Systems are necessary.

So the known methods are mainly focused on one of the two Tasks oriented towards the creation of circuit boards for microelectronic systems: either on the creation of a large-area printed circuit board with a low one Integration density of interconnections in the wiring (appropriate Type of circuit board or on the creation of circuit boards small area, however with a high integration density of the interconnections in the wiring (appropriate Art the microcircuit). In this context, in the microelectronic systems of high structural complexity, at least two types of circuit boards widely used: integrated circuits are assembled into microcircuits, which are arranged with additional elements on the printed circuit board. Here are two manufacturing steps for microelectronic systems and their utilization two kinds of technology inevitable: printed manufacturing technology circuit board and hybrid layer technology, which is a major disadvantage from the current state of the egg-making technology for the interconnections overall results.

The invention is based on the object of a manufacturing process for circuit boards used in microelectronic systems to create the it Permitted circuit boards of a uniform type with at least two line levels while simplifying the technological process for their manufacture to manufacture.

This object is achieved in that in the production method for printed circuit boards used in microelectronic systems' in which one conducts conductors of the circuit board required configuration on a substrate from one against the metal of the conductor selectively etch metal produced, a basis of the printed circuit board is stacked on one side of the substrate and the substrate for the entire thickness of which is selectively etched with respect to the conductor tracks, according to the Invention generated the conductor tracks from both sides of the substrate and on the side of the substrate facing away from the side on which the foundation is laid is created, the conductor tracks are generated, the at least one tapering section have and the selective etching of the substrate lasts until be metal has only been completely removed under the tapered sections is.

The corresponding conductor runs can be used to generate crossing conductor runs on the side of the substrate on which the base is coated the sections of its surface that correspond to the corresponding tapering Sections of the crossing Ileiters are opposite.

Preferably, the conductor tracks are tapered with at least one Section created in such a way that the width of its narrowest section with the thickness of the metal substrate is consistent and more than twice smaller than the width of the sections of the conductor tracks at their junctures with others, is connected to them.

Prior to layering the base, the metal substrate is preferred selectively etched to a depth within the limits of 0.01 to 0.05 of the width of the conductor tracks is selected, the metal subatrate with the conductor tracks created on this are expediently annealed.

Copper, iron, aluminum or alloys can be used as the metal of the substrate on their basis and as the metal of the conductor tracks nickel, copper, tin, gold or their Combinations can be used.

Between the substrate and the base of the circuit board there is a Layering the former is at least one made of a dielectric material Layer generated, this layer preferably at the points of the circuit board is to be provided with holes where the heat-generating lSlexnentc of the microelectronic System and / or the connections are arranged with a subsequent layer.

It is most technologically appropriate to have the base itself made of metal, from a finished plate or from a metal substrate with on this in the invention Process to generate executed conductor tracks.

The inventive manufacturing method for printed circuit boards combine the manufacturing technology for microcircuits and printed circuit boards to a unified manufacturing technology for circuit boards with more than two management levels, while at the same time the manufacturing options this procedure can be extended.

The invention is illustrated with reference to the in the drawing Embodiments explained in more detail. It shows:.

1a, b, c, d, e, f, g, h show the step-by-step implementation of the invention Manufacturing process for printed circuit boards; 2a, b, c work steps for stratification a basis for a circuit board according to the invention; Fig. 3a, b, c, d, e the step-by-step Implementation of the manufacturing method according to the invention for printed circuit boards with a combined metal-dielectric base; Fig, 4a, b, c, d, e, f, g, h, i die. Step-by-step implementation of the manufacturing method according to the invention for printed circuit boards with a combined base that is a printed circuit board with wirings for "earth" and "feed" includes; Fig. 5a, b, c, d, e an embodiment of a circuit board in microelectronic systems with different design variants for after external and internal leads that are in the same working cycle of the wiring.

The manufacturing process for used in microelectronic systems Printed circuit boards consists in the fact that originally conductor tracks of the printed circuit board were required Configuration can be created on a substrate from a metal facing each other selectively etch the metal of the conductor.

Such continuations can be created in two ways, from which the first in a selective removal of the over the entire substrate surface previously applied metal of the conductor tracks and the second in a selected electrolytic deposition of the metal of the conductor tracks over a substrate covering Protective mask required configuration exists. Advantage of the first method is the possibility of using finished bimetallic laminates on metallurgical Paths can be obtained by plating, only that the conductor parts obtained in the end have uneven edges and poor shape reproducibility. The second The method is more economical from the point of view of metal consumption for the ladder lines than the first and allows a greater density of the conductive pattern of the conductor plate to obtain. That is why this is precisely what will be kept in mind in the further presentation of the method keep.

A protective mask 2 is therefore required on a metal substrate 1 Configuration made, for example, from a photoresist by double-sided photolithography on the substrate 1 (Fig. 1;, a, b, c) is formed, the metal of the conductor tracks (Fig. 1'd) electrodeposited. The conductors are deposited on both sides carried out, wherein on one of the sides of the substrate 1, a conductor line 3 with a running tapered section 4, which gives him the ponl of a dumbbell. The conductor runs 5 and 6 of the main line level crossing the conductor run 3 become on the opposite side of the substrate 1 arranged and there, where the conductor tracks 6 are to connect to the conductor track 3, the width of the the latter enlarged not less than twice, with its ends for example a disc shape is added. The conductor runs electrically isolated from the conductor run 3 5 are at the crossing point opposite the tapered section 4 of the conductor run 3 'executed.

After the generation of the conductor tracks 3 to 6, the further is not more required protective mask 2 (Fig. Le) removed and on the substrate 1 side the conductor tracks 5 and 6 of the main line level a basis 7 (Fig. 1 "f) of the circuit board piled up.

The work process for layering the base 7 needs a more detailed one Consideration and is specified below; to understand the essence of the procedure it is assumed that the base 7 is a dielectric pressed onto the substrate 1 Represents plate.

The structure obtained as a result of this operation is used for the entire thickness of the substrate 1 is etched in a solution that is only selective on its metal acts. The electrical insulation of the conductor tracks 3 and 5 is affected of the etchant not only in depth, but also in terms of sides, i.e. through a lateral undercut, guaranteed. Thanks to the action of the etchant after those enclosed between the substrate 1 and the base 7 become the depth Additional lines 5 and 6 of the main line level are etched free and isolated from one another, while the lateral undercut protrudes beyond the surface of the base 7 the edges of the conductor run 3 of the second line level result. Because the width of the tapered section 4 of the conductor line 3 commensurate with the thickness of Substrate 1, 'is chosen ~ depends on the tapered section 4 after a predetermined time interval after the etching of the metal of the Substrate 1 ..

for the entire thickness over the surface of the base 7 (Fig, 1, g) which thereby separates the superfluous contacts at the crossover point will. At the same time, 3 load-bearing elements remain under the ends of the conductor run 8 are in the form of rods made of the metal of the substrate 1, which make the connections of the conductor run 3 with the conductor runs 6 of the main line level. As a result, the conductor runs 5 and 6 will cross over with the aid of the conductor run 3 executed.

It is preferred that the width of the tapered portion 4 of the conductor line 3 by r # e? Ir than twice smaller than its width at the Connection points with the conductor run 6, because otherwise there is no reproducibility the size of the supporting elements 8 secured.

As a result of the etching, the structure of the circuit board takes the form shown in Fig. the form shown.

If necessary, the air gap between the moves 3 and 5 in the hermetic sealing of the microelectronic system with a Dielectric to be filled.

In view of the fact that the conductor tracks 5 and 6 of the present Process manufactured circuit boards only by the forces of adhesion of their metal be adhered to the base 7 of the circuit board, the durability such a structure against thermal and mechanical loads for a Number of systems are not enough.

In order to increase the reliability and durability of the manufactured Printed circuit boards against external influences, the entire etching time for the metal substrate separated into two steps, the first step (undercut) before laying the foundation and the second step (etching for the whole Depth) after layering the foundation, taking into account the underetching time is carried out in the first step. The composition of the etchant and the Etching processes can be identical in the two steps.

In the first step, a relief-like elevation of all ladder lines, underneath the conductor tracks 5 and 6, over the surface of the D.letallßubstrtats 1 (Fig. 2a) guaranteed. The main thing is the appearance of outstanding gentle 9 at the conductor tracks 5 and 6, under which when the base 7 is layered, a liquid one Layer 10 of a dielectric material arrives, creating the edges of the corresponding Ladder trains (Fig. 2b) are recorded. After breathing; of the substrate 1 are the Conductor tracks 5, 6 on the surface of the circuit board not only due to the adhesive forces between the metal and the dielectric of layer 10, but also through the mechanical strength held by shafts 11 made of the same dielectric material, which as a result of its flow under the overhanging edges 9 of the conductor tracks 5, 6 (Fig. 2c) have formed. The second component of adhesive force is its nature according to volumetric and is therefore in much smaller dimensions than the first of the action exposed to external influences. In addition, it exceeds the adhesive force in terms of amount in the case of narrow ladder sections by a multiple. This creates a multiple Enlargement of the force achieved, the æum flaking of the conductor tracks 5, 6 from the, Surface of the circuit board is necessary.

In addition to this effect, such a structure minimizes harmful phenomena the discharge and the electromigration between the conductor tracks 5, 6 of the conductor plate, because these processes take place intensely at the edges of the conductor tracks, where the largest Potential gaps are concentrated. In the structure shown in Fig. 2b, c the waves 11 made of the dielectric material counteract this process.

As a result, the limit voltage between the neighboring Ladder trains 5, 6 may be created.

The contribution of the spatial component to the resulting force of the Adhesion of the conductor tracks 5, 6 on the surface of the circuit board begins at a width of the overhanging edge not less than 0.01 of the width of the conductor line to make noticeable. Since it is difficult, the size of the overhang at the first step To keep the etching under control, there must be a connection between this and the Etching depth of the metal substrate 1.

When etching in a static solution, these quantities are very close together Therefore the above-mentioned figure can relate to the undercut depth that is much easier to control.

On the other hand, it is necessary that after the undercut the adhesion the conductor tracks 5X 6 on the substrate i is maintained to prevent their peeling and shifting to be avoided in subsequent operations. For this purpose, the undercut depth Do not exceed 0.45 times the minimum width of the conductor run. When etching in the resting Lojung a remains between the conductor tracks 5, 6 and the substrate 1 Get a web with a width of not less than 0.1 of the width of the conductor track, which is practically sufficient.

In the case of special etching processes, namely jet and emulsion etching where the relationship between the etching depth and the size of the lateral undercut in favor of the former changes, the upper limit can be shifted further However, it is not practical to set the sub-depth more than 0.5 times the width of the ladder line to enlarge.

With tough demands on the reliability of the contacts between the levels and to the mechanical strength of the crossings is that Metal substrate 1 with the conductor tracks 3 to 6 produced thereon (Fig. 2a) the layering of the base 7 to ensure diffusion welding of the metals of the substrate and the conductor tracks to anneal. A side effect are here one Improvement of the crystal structure and the elimination of mechanical stresses in the metal of the conductor tracks, whereupon it becomes more plastic. This also causes an increase the resistance of the circuit boards to thermal and mechanical influences, where due to a difference in thermal expansion coefficient the basis 7 and the ladder trains 3 requirements for a detachment of the latter from the supporting elements 8 are created.

An interruption of the conductor tracks 3 to 6 in the base material is caused by prevents an increased plasticity of your metal after annealing.

Second, it requires the increased plasticity of the tapered Section 4 of the conductor run 3 a gentler handling of the circuit board as long as the air gap between the crossovers is not filled with the dielectric material are. The short circuits between the line levels are avoided by that when the tapered sections 4 sag in the direction of the surface of the circuit board, they are not with the conductor tracks 5 of the main line level, but come into contact with the waves il made of the dielectric material 10 for the purpose additional. Reinforcement of Fixation of the load-bearing elements 8 in the layer 10 ground the ends of the conductor tracks 6 of the main line level extended and executed with holes 12 at their connection points with the conductor track 3. Under hemispherical depressions are formed in the holes 12 when the base is etched under 13 in the metal of the substrate 1 (Fig. 2a). When layering the base 7 flows the pressurized and liquid dielectric material 10 into the depressions 13, in which he as it were "rivets" 14 (Fig. 2b, c) forms. As a result, the load-bearing elements 8 as well as the conductor tracks evolve 5, 6 as connected to the dielectric material of the layer 10 to form a “lock”.

In compliance with all of the requirements listed above, a Printed circuit board of the highest reliability, capable of Heat conditions up to cryogenic temperatures and the strongest mechanical stresses without damaging the construction and maintaining all # electrical To withstand parameters of wiring in the required level. In such Printed circuit boards proves the reliability of the connections between the in different wiring levels in terms of reliability a uniform ladder run as not worse, what in the known design variants is not reachable.

As a material for the substrate 1 and the conductor trains 3 to 6 are widely used metals that meet the requirement of selective etching of the metal of the substrate compared to the metal of the conductor tracks. at In the manufacture of printed circuit boards of the highest reliability, it is advisable to that these metals form a continuous series of solid solutions with one another.

A good metal pair from a technical point of view is copper for that Substrate and nickel for the conductor tracks, the copper is compared to the nickel in Etching agents based on chromic anhydride and sulfuric acid or in ammonia solutions selectively etched. Instead of copper, various alloys can be used Base, especially brass and bronze, can be used.

For mass-produced items where the demands of the cost are paramount can occur, an iron substrate in the form of a sheet or band of low-carbon Steel can be used. Such a substrate can be compared to the conductor tracks made of copper or nickel in etchants based on oxalic acid or hydrogen peroxide selectively etch. The substrate can also be made of aluminum, only that then on the surface of the clining substrate prior to electrodeposition of the metal of the conductor trains a conductive conversion layer, for example a Fluoride-phosphate film must be produced, which ensures adequate adhesion of the conductor tracks on the substrate and the electrical contacts between the line levels slightly impaired.

The aluminum substrate does best in alkaline etchants etching.

The structure of the conductor tracks of the circuit board can be multilayered A Nickeigrund can be used, for example, to improve the weldability or the electrical conductivity gold-plated, tinned for soldering or in the case of particularly high demands on the conductivity of the wiring are silver-plated. Regardless of the fact that the silver in conventional printed circuit boards is on their Reliability and service life are negative due to its high ability to migrate affects, this effect is shown in Fig. 2b th structure minimized, and the silver can be used unhindered if necessary. this may be required in the manufacture of microelectronic systems that work at frequencies of a few hundred megahertz.

The expansion of the technical possibilities of the present procedure, on the applicability of the latter for the production of large-format printed circuit boards on any basis - may it be rigid, flexible, flexible-rigid and with a built-in heat dissipation - is achieved by the fact that the actual wiring separated from the base on a metal substrate is manufactured while the base itself is a combined structure can. - For this purpose it must be formed from at least two layers, of which at least one layer adjoining the base of the printed circuit board a dielectric material is carried out. The other layers can be made of metal, Dielectric or combinations thereof are carried out.

In the layer adjacent to the base, the Holes are created at the points of the circuit board where the heat develops Elements of the microelectronic systems and / or the connections with a subsequent Shift.

The structure considered above was treacherous. 2) illustrates one the most distinctive and practically important cases of a combined basis, in which the metal base 7 is placed on the layer 10 made of the dielectric material immediately follows. Such circuit boards have good heat dissipation and high mechanical strength.

With the rigid wiring of the components of the microelectronic System on the circuit board the base 7 must be made of a metal, whose coefficient of thermal expansion is adapted to that of the components, for example made of an iron-nickel alloy. If that is not necessary, it is best of all, a plate made of anodized aluminum or a special aluminum profile with elevations in the form of ribs or pins to improve heat dissipation to use.

If the layer 10 is produced in such a way that it extends beyond the boundaries of the Basis 7 goes beyond this, provided that there is sufficient flexibility a flexible-rigid construction, where the building elements are within the limits of the basis of the system can be assembled while the beyond the limits of the basis 7 outgoing layer 10 of the dielectric material for flexible loops Forms connection with external circuits.

The dielectric material layer 10 is convenient from an adhesive film between the base 7 and the metal substrate 1 is laid before the operation to build up the foundation 7 (Fig. 3a, c). Intermediate layers (Fig. 3b) are punched out of the adhesive film, except for the above-mentioned holes 15 have basic perforation holes to this with the metal substrate 1 better to match. The intermediate layers made of the dielectric material let after it between the metal substrate 1 with the conductor tracks 3 to 6 and the base 7 have been placed, stripped at the level of the holes 15 Sections of the metal base 7 free, on which in the following heat-generating Elements 16 of the microelectronic systems (Fig. 3d, e) are arranged. there the electrical contact with the metal of the base 7 can also be realized will. In Fig. 3e it is shown how the element 16 with the conductor tracks 6, 6a, 6b, 6c can be connected.

As adhesive films, rectangular positions on fiberglass or to use a polyamide base, which is impregnated or coated with an adhesive mass are in a solid but responsive state is located.

If the requirements on the electrical data of the circuit boards are not high and no strict operating conditions for them, the adhesive film can be one layer represent of glass fabric soaked by thermoset epoxy resin and after the impregnation is heat treated to a thermally reversible condition.

For circuit boards with a high density of the line pattern that operated under severe conditions, the adhesive film must be polyamide based have applied from both sides with an adhesive of high temperature is covered.

The temperature control when laying the foundation is based on from a transition of an adhesive mass to a thermally irreversible state (complete polymerization for epoxy adhesive compounds) or their softening is selected. The pressure applied here must ensure good gluing and flow of the adhesive compound under the overhanging edges 9 of the conductor tracks 5 to 6 of the main line level.

In complex microelectronic systems it is necessary to to have a circuit board that has more than two levels of wiring (Fig. 4).

This task can also be done by applying a combined basis be solved, which over the layer 10 of the dielectric material with the the required locations made holes 15 (Fig. 4a, d) on the metal substrate 1 is stacked with the ladder sections 3 to 6.

Three and more levels of management can be obtained when the on the dielectric layer adjacent to the base of the printed circuit board Layer is generated from a prefabricated printed circuit board. Of practical interest is the case for digital systems of great complexity, where in the combined basis a prefabricated printed circuit board is received, which can be one-sided and with a wiring area for the elements of the system (Fig. 4b) not even metallized holes needs.

The microelectronic digital system usually contains a considerable number of Number of integrated circuits with complicated wiring for logic circuits and simple wiring for a ground and a feed circuit.

It follows that a high density of the wiring pattern of the circuit board una several - at least one pair - of line levels only for the logic circuits are required, while other requirements are placed on the supply circuit and the grounding circuit be provided, namely a minimization of the ohmic resistance of the conductor tracks and the fulfillment of the functions of a shield. Therefore these circuits, without impairing the integration density of the system, on a one-sided basis Printed circuit board can be led out with wide conductor tracks, which is a maximum occupy the surface of the former.

The line pattern of the circuit board 17 for the ground and feed circuit (Fig. 4b, f) can represent two opposing comb structures 18 and 19, of which one is supplied with a supply voltage and the other is supplied with a zero potential. at ensuring sufficient electrical capacitance between these structures each of them is equivalent to the ground circuit for the logic circuits. That's why are ~ the logic circuits (Fig. 4c, d) on the earthed surface, which is advantageous from the technical circuit point of view.

The integrated digital circuits 20 with carriers made of plastic or ceramics are at the level of a dividing line between structures 18 and 19 mounted, making the corresponding connections of each of the integrated circuits 20 via the holes 15 in the layer 10 of the dielectric material both with the structure 18 as well as with the structure 19 (Fig. 4g, i, h) can be connected.

The wiring for the logic circuits is described in the above Process carried out on a metal substrate (Fig. 4c, d). After assembling the integrated circuits, the printed circuit board is coated with a layer of varnish 21. In the Endelßekt there is a circuit board with three levels, which thanks to a differentiated Density of the line pattern for the line levels and a uniform manufacturing technique is optimal for a digital system. The uniformity of technology is through the identity of the basic operations for manufacturing both the wiring of the logic circuits as well as the printed circuit board for wiring the grounding and supply circuit. The integration density of the digital system on such a circuit board can are not lower than in a thin-film microcircuit, although here they are not expensive Materials are required and the Hert + manufacturing process involves working in the Vacuum included, if necessary, can be screen printed on the circuit board Load and adaption, xswidere3t ~ other with the help of low temperature - resistance pastes be generated.

The manufacture of the complex microelectronic digital system on such circuit boards requires a minimum of technological equipment and Equipment because in the integrated circuits of a series as components of the system, the earth and feed connections are usually arranged in the same way. This allows the same type of printed circuit board and the same type of adhesive layer with the holes to create the layer of dielectric material use to make, with the whole variety of circuit boards for different logic units of the system by replacing only one metal substrate with the conductor tracks for wiring of the logic circuits is obtained.

The combined basis can be a second system of ladder tracks on the metal substrate similar to the first in the above described Technology is executed. This is a circuit board with a wiring Obtained in four levels, based on a two-sided assembly of components of the system is oriented. Such a printed circuit board is of interest for complex microelectronic Systems with a minimum of size and mass and with a low power requirement.

There are also other combinations of structures and materials in the composition of the basis of the circuit board possible, starting with their selection on the specifics of the component range and the integration density of the microelectronic System takes place, 'to use the present circuit board for its production is intended.

For example, if the system contains a significant number of in the thin-film or thick-film technology implemented passive elements, so can the prefabricated printed circuit board that goes into the foundation is a ceramic or glass plate represent the elements of a choice of the layer belonging to the system contains. When the power dissipation level is high, one is preferred for these purposes Insert plate made of anodized aluminum.

In the digital systems it is possible to use pre-made double-sided printed Printed circuit boards with metallized holes or even multi-layer printed circuit boards are used in those for the production of outer layers by the technique described above Use is made.

Such a construction is not a simple combination of several Types of circuit boards, but they do not represent a circuit board with qualitative new possibilities which are not inherent in their individual components. This is also a special case of a uniform type of printed circuit board Building blocks and hybrid #chicht-microcircuits that the possibilities of both Constructions united and from the main disadvantage of each one, i.e. from the difference is free in the technological equipment and facilities involved in their manufacture be applied.

Specific exemplary embodiments of the inventive Procedure.

The examples of a concrete implementation of the The method described above is divided into two groups, with the first group Examples 1 to 3, which focus on creating a structure with two levels of wiring on a metal substrate, and the second Examples 4 to 8 for the Manufacture of finished circuit boards based on this structure and for their application includes.

Example 1 creation of a printed circuit board with two line levels using photolithographic processes.

The substrate made of 0.05 mm thick copper foil with a prepared (Purified from oxides and rescued) surface becomes in one Immersion process with a 0.004 to 0.006 mm thick poto resistance layer on both sides overdrawn. Then it is between two otosschablonen previously brought to convergence placed on a flexible film or glass plate and with it from both sides irradiated ultraviolet light, one being the type of photoresister applied appropriate exposure is guaranteed. The pattern on the poto templates corresponds the attachment of conductor tracks of the main line level with a width of 0.025 mm with distances between the conductor tracks of 0.05 mm. The tapering sections the further trains of the second management level are also 0.025 wide mm and are in the contact points with the main line level with washers completed by 0.1 mm in diameter.

The photoresist is developed and cured, followed by the substrate is placed in a galvanic nickel-plating bath with a sulfamine electrolyte, that for the preservation of plastic, tension-free residues and for a high speed of application cares. The nickel is deposited up to a thickness of the conductor tracks of 0.015 mm, Then the now superfluous photoresist is removed and the substrate in an etchant based on chromic anhydride and sulfuric acid for a Undercut depth of 0.01 mm. The annealing of the substrate takes place in an inert Gas medium at a temperature of 8500C in the course of 15 minutes.

The base is made from an anodized aluminum plate with a Thickness of 0.5mm made. A polyamide film is used for their coating, which are covered on both sides with layers of a fluorinated adhesive is. The coating is applied under a pressure of 50 to 75 kp / cm2 at a temperature performed by 4500C. The final etching takes place in an etchant based on Chromic anhydride and sulfuric acid for the full thickness of the substrate to the full Removal of the copper under the crossover points.

After etching, the circuit board is immersed in deionized water using ultrasound, rinsed and dried through, infrared rays. Now the circuit board for the assembly of components with connecting wires is in one Thermocompression or ultrasonic welding processes ready. In a constructive way represents the microelectronic system, in the manufacture of which this printed circuit board is used, a hybrid integrated circuit with a high degree of integration represent.

Example 2 Production of a printed circuit board with xei line levels without the use of photolithographic processes with direct transfer of the line pattern onto a metal substrate In the manufacture of small series of very complicated circuit boards with a large number of modifications, the application is the photolithographic Procedure inexpedient. An optimal use of the possibilities of the computer-aided The topology is designed with an immediate utilization of the design data to transfer the line pattern to a basic substrate.

For this purpose, a substrate similar to the one in the example 1 is described by drawing from the solution with layers of a chemically resistant Lacquer covered on both sides to a thickness of 0.04 to 0.06 mm.

In the following, the lacquer is tinted by a sharp laser beam using the reflective properties of the metal substrate from both sides selectively baked out, which frees up a surface for future conductor tracks. Thereafter the substrate is blown with a cleaned compressed air in a deionized one Rinsed water under the action of ultrasound, and all subsequent operations, starting with an electrolytic deposition of nickel, are analogous for example 1 performed.

Example 3 Production of a printed circuit board with two line levels without the application of photolithographic processes using offset printing.

This process is expediently larger in production Series of circuit boards of low and medium complexity with none very to apply a high density of the wiring pattern.

The creation of a protective mask on a metal substrate is similar that described in Examples 1 and 2 takes place here by way of transfer a chemically indestructible color from a printing form onto the substrate with the help a rubber plate and in the following by analogy for example 1 #.

Since with the transmission a loss of accuracy in relation to the geometric dimensions of the conductor tracks in comparison to the printing form the width of any sections of the conductor tracks is generally not less than 0.1 mm lie. If this restriction applies, the present procedure is based on its highest productivity preferred.

Example 4 Manufacture of a circuit board on a flexible Basis with two management levels.

After producing a metal substrate using one of the examples 1 to 3 conductors produced on both sides are based on a polyamide film, those on one side with a layer of a weldable organofluorine polymer is covered.

If the metal substrate is in the form of a strip, then the layering is expedient while moving the substrate and that facing it with the weldable layer Realize polyamide tape between heated rollers.

The laminate obtained undergoes selective etching in the metal substrate and subjected to a rinse, which is the duty cycle for manufacturing the circuit board is terminated on the flexible basis.

Example 5 Manufacture of a circuit board on a flexible Basis with four management levels.

The process is carried out in the same way as in example 4, only that a perforated polyamide film is used as the basis, which is covered on both sides with Layers of a weldable organofluorine polymer is covered. On this slide are metal substrates from both sides with one on both sides any of Examples 1 to 3 produced conductor lines are stacked. The line pattern the Lletallsubstrate is made according to the topologies of the first and the second Pair of management levels generated.

Example 6 Manufacture of a circuit board on a flexible Basis with three line levels, of which the third level is an earth or feed line represents.

The process is the same as in Example 5, only that instead of of the second metal substrate with conductor tracks generated on both sides thereof 0.05 to 0.1 mm thick metal strip is used, which consists of one against one on the Substrate einwirlcenue etching resistant metal is carried out.

This metal band is referred to below as earth or Feed line used, the contact with this via perforation holes in the polyamide film comes about.

Example 7 Manufacture of a circuit board on a combined flexible-rigid base with built-in heat dissipation.

The process is the same as in Example 6, only that instead of of the metal strip 0.5 to 2.0 mm thick aluminum plates are used, their Dimensions are smaller than those of the polyamide film.

Within the limits of these boards, on the whole flexible circuit boards a rigid heat-dissipating section can be generated, which is used for mounting components of the system is provided.

In the case of high power dissipation, it is advisable to take the place of the aluminum plates a special rolled aluminum with an enlarged Surface to use on one of its sides.

Example 8 Application in systems.

The main focus of the application of a circuit board in the systems is the production of connection lugs to the outside and inside, what a Connection of the circuit board with external circuits is crucial and certain Makes demands on the technical equipment of the system.

A partial view of one on the present circuit board with various types of outward and inward connections microelectronic system is shown in FIG.

The main peculiarity of this system is that all types the connections used in this in the same operation as the management levels are established, and for their establishment and connection needed there are no auxiliary operations. The configuration of the connections is the same as for the conductor tracks 3 to 6 simultaneously from both sides of the metal substrate 1 (Fig. 5a, b) carried out.

The rod-shaped inner connections 22 are in the form of individual disks executed from the side of the metal substrate 1 which is facing away from the side which the foundation 7 is piled up.

The outer tape connectors 23 are in the form of identical figures on the sides of the substrate 1 facing away from each other, whereby they slightly Reach beyond the base 7 (Fig. 5c).

The special internal connections 24 that allow an interruption of contact on corundum an always existing mismatch of the coefficient of thermal expansion of the materials of Basis 7 and the components of the system Executed in a comb shape on the side of the metal substrate 1. that facing away from that on which the base 7 is stacked. The width of the comb teeth will be equal to the width of the tapering sections 4 of the conductor tracks 3 generated. on the connections 22 are furthermore a sub-plate 25 and on the connections 24 a building element 26 (Fig. 5c, d) mounted after the foundation 7 and the selective etching of the substrate 1 are formed under the disks of the connections 22 rods 27 made of the metal of the substrate 1, which form the supporting elements 8 are similar, which realize a contact between the line levels. the Band connections 23 gain mechanical strength thanks to bands 28 made from the metal of the substrate 1, which are located in the central part thereof. Above load-bearing elements 29, which consist of the metal of the substrate 1 under the edges of the particular inner Form connections, the teeth of the combs 24 remain after the etching hang freely.

When the components 26 are assembled, these teeth bend against each other the basis of the printed circuit board, on which they get the properties of springs, the changes in size of rigid limbs when the system is exposed to heat take up. The resistance of such connections to impact and vibration loads is made possible by a layer of lacquer 21, which on the one hand is stiff enough to be glued on of the components 26 be on the surface of the circuit board and on the other hand a must have a certain elasticity so that the connections 24 retain the flexibility. These conditions are best met by compounds based on silicone rubber satisfied.

In addition to the types of connections mentioned, the one according to the mentioned Circuit board produced by technology always has a second wiring surface, expediently to realize the contact by means of thermocompression or ultrasonic welding is to be used. An implementation example for this The second wiring area is shown in FIG. 3.

The main advantage of the method according to the invention is elimination inevitable in the known methods of creating multilevel wiring Operations for the production and metallization of contacts between the levels as well as the U # berführun ## - of printed components and hybrid microcircuits a uniform construction and technological basis. This gives the possibility: - the amount of work involved in creating the system depending on the degree of its Decrease complexity by 35 to 75 / #; - the component density in the system 5 to 10 times that of printed wiring and 1.5 to 2 times as much compared to thick-film technology increase; - the reliability to increase the system; - the use of precious metals and deficient materials excluded or reduced to a minimum.

The cost of the actual circuit boards can be taken into account different types of printed circuit boards, which by one in the invention Technique manufactured circuit board can be replaced by more than twice be lowered.

Another important advantage of the process according to the invention is that The fact that virtually any of the existing types of circuit boards not only excluded, but also completed with qualitatively new possibilities which can be realized by the new printed circuit board with a combined basis will.

Since the present method is based on the operations for electrolytic Deposition and chemical etching builds up, it requires working with liquids chemical reagents, but has compared to those used in hybrid technology "Dry" processes have greater technical possibilities and can be used universally. In the fiction, according to the method, a qualitatively new circuit board can be obtained that of the printed circuit board only according to the manufacturing technology and after the low cost comes close and after the technical possibilities with the same size of incomparably more expensive precision plates for integrated Hybrid circuits are closely adjacent.

Claims (11)

PATENTMNSPRUCff # Manufacturing process for in microelectronic Systems used printed circuit boards, in which - on a metal substrate conductor tracks The required configuration of the printed circuit board is made up opposite the substrate selectively etched lvietall produced, - a basis of the printed circuit board one side of the substrate is stacked and - the substrate for the whole of it Thickness is etched selectively with respect to the conductor tracks, which is not possible æ e i c h n e t that the conductor tracks are generated from both sides of the substrate and - On the side of the substrate which is turned away from the side on which the base is located is piled up, the conductor tracks are generated, the at least one tapering Have section and - the selective etching of the substrate lasts until only completely removed its metal under the tapered sections has been. 2. The method according to claim 1, d a d u r c h g e k e n n z e i c N e t that to generate crossing conductor tracks the corresponding conductor tracks on that side of the substrate on which the base is layered the sections of its surface are created which are tapered to the corresponding Sections of the crossing conductor tracks are opposite. 3. The method of claim 1, d a d u r c h g e k e n n z e i c n e t that the conductor tracks with at least one tapered section in in such a way that - the width of its most scinal section with the Thickness of the metal substrate grain-tolerable and - more than two times smaller than the width of the sections of the conductor tracks at their junctures with others is connected to them. 4. The method according to any one of claims 1 to 3, d a d u r c h g e does not indicate that the metal substrate is used prior to piling the base with respect to the conductor tracks selectively for a depth that is within the limits of 0.01 to 0.05 of the width of the conductor tracks is selected, is etched. 5. The method according to any one of claims 1 to 4, d a d u r c h g e no indication that the metal substrate with the conductor tracks generated on it annealing before the foundation is built up. 6. The method according to any one of claims 1 to 5, d a d u r c h g e no indication that - as the metal of the substrate a) copper, b) iron, c) Aluminum or d) alloys based on them and - as the metal of the conductor tracks a) Nickel, b) copper, c) tin, d) gold or e) combinations of these are used. 7. The method according to any one of claims 1 to 6, d a d u r c h g e does not indicate that #between the substrate and the base of the circuit board when stacking the former, at least one made of a dielectric material executed layer is generated. 8. The method according to claim 7, d a d u r c h g e k e n n z e i c h n e t that the layer of dielectric material with holes in the places The printed circuit board is produced where the heat-generating elements of the microelectronic System and / or the connections are arranged with a subsequent layer. 9. The method according to claim 7 or 8, d a d u r c h g e k e n n z e i c.h n e t that the base is made of metal. 10. The method according to claim 7 or 8, d a d u r c h g e k e n n z e i n e t that the basis is generated from a prefabricated circuit board will. 11. The method according to claim 7 or 8, d a d u r c h g e k e n n z e i c h n e t that the base consists of a metal substrate with on this according to claim 1 executed conductor runs is generated.