WO2005081603A1

WO2005081603A1 - Method for producing substrates

Info

Publication number: WO2005081603A1
Application number: PCT/EP2005/050187
Authority: WO
Inventors: Thomas Cwik; Uwe Metka; Roland STÜTZER
Original assignee: Hitachi Via Mechanics, Ltd.
Priority date: 2004-02-17
Filing date: 2005-01-18
Publication date: 2005-09-01
Also published as: CN100518450C; CN1860835A; JP2007522662A

Abstract

The invention relates to a method for producing substrates (200) which are produced by successive planar process steps and which comprise a first layer (210) and at least one second layer (220) suited to the first layer (210). In a first step, a plurality of marks (211) is measured on the first layer (210) and a deviation of the actual position from the desired position is determined for every mark (211). These deviations are used to determine a transformation FTrans 1 for the position deviation from any grid point of the first layer (210) and a transformation FTrans 2 for any position deviation from grid points of the second layer (220). The transformation FTrans 2 is determined while taking into account known marginal conditions for a possible warping behavior of the second layer. When the second layer (220) is treated, a combined transformation from the two previously determined transformations FTrans 1 and FTrans 2 is taken into account. The inventive method allows for a reliable contacting of strip conductors despite different degrees of warping of the two layers (210, 220), thereby reducing the portion of refuse of defect circuit boards in the production of multilayer circuit boards.

Description

Besehreibung

Process for the production of substrates

The invention relates to a method for producing multilayer substrates which are produced by successive two-dimensional process steps with a first layer and at least one second layer matched to the first layer.

When building multilayer printed circuit boards, the individual layers of the printed circuit boards are pressed together several times. The applied temperature and pressure stress leads to unwanted distortions, such as shrinkage or expansion, for the materials used for printed circuit boards. The dimensions of the printed circuit boards can change several times until the finished state. Depending on the PCB layout, ie the-realized by copper surfaces interconnect structures in single layers, it can thereby auc _etc., lead to non-linear distortions in which the expansion or shrinkage in different directions to different extents fails.

In order to be able to selectively electrically connect different printed circuit structures formed in different layers to one another in a layered printed circuit board, one has to follow the distortions present in the starting layer both when applying layers and when making contact with different connection surfaces of different conductor structures perpendicular to the layer level. In order to follow these delays, markings are usually applied or exposed on the starting layer, which are measured by an optical system. The distortion of the starting layer is then determined from the deviations of the actual position from the target position of these markings. About this delay To determine for all grid points of the starting layer, a mathematical transformation is determined from the previously determined deviations, by means of which the distortion can be calculated for any grid point of the starting layer. The term lattice point is understood to mean any point in the starting layer, that is to say not only selected points which lie on a discrete lattice.

The transformation of a target position to an actual position can be in an xy coordinate system by the following equation 1 given: ^x i _t = a _l + b _l - x _soll + c _x ^• y _to + d _x ^■ x _should ^■ y _should yist ^{~ u} 2 ⁺ ^"2" y _s oll ^{^"*" C} 2 ^{^'+ X} to ^{"2" X} ^should' 'to

The parameters ai and a _{2 describe} a linear shift, the parameters bi, b ₂ , cj. and c ₂ describe an elongation or shrinkage as well as a rotation and the parameters di, d ₂ describe a possible shear of the starting layer. Since this system of equations has four parameters a, b, c and d to be determined for each coordinate, a total of four markings must be measured to completely determine these parameters, so that the resulting system of equations can be uniquely solved with a total of eight unknown parameters.

It is pointed out that for a number of applications, shear of the starting layer is negligible and thus the coefficients di and d ₂ can be set to zero. In this case, the measurement of three markings is sufficient to uniquely determine the remaining parameters ai, a ₂ , bi, b ₂ , ci and c ₂ .

However, different layers often have different warping behavior, or a subsequent layer can have a certain warping due to technical reasons do not follow the layer below. In such a case, when using the transformation described with equation 1, the connection areas of different printed circuit board structures are often arranged offset from one another, so that the overlap between the connection areas to be contacted is often not large enough to be reliable. to allow electrical contact of the relevant connection surfaces. Printed circuit boards produced in this way are therefore often defective and must be removed from the manufacturing process.

It is therefore an object of the invention to provide a method for producing multilayer substrates in which reliable contact between selected areas of different layers is ensured in spite of delays occurring and thus a lower rejection rate is achieved in the production of circuit boards built up in layers.

This object is achieved by a method for producing multi-layer substrates with the features of independent claim 1.

According to the invention, a plurality of markings applied to this layer are first measured on a first layer and subsequently a deviation of the measured actual position from a previously known target position is determined for each marking. On the basis of the determined deviations, two different transformations are determined for the determination of the position deviations of lattice points of the first layer, with previously known boundary conditions for possible position deviations of lattice points of the second layer being taken into account when determining at least one of the two transformations. The boundary conditions are suitably predetermined by corresponding relationships between parameters a, b, c and d of equation 1 above. Then the two identified transformations combined with each other and the first layer is processed taking into account the combined transformation.

The invention is based on the knowledge that when processing the second layer, not only the

Warping of the initial layer is taken into account, but rather that possible process-technical restrictions in the compensation of this warping when applying the second layer are at least partially taken into account in advance. So you take when editing the first

Layer deliberately not optimal compensation of the delay of the output layer in purchase. This disadvantage, which is only apparent in most applications, is more than compensated for when the second layer is applied.

It is pointed out that, for measuring the markings, a camera can be used, for example, which is present in any case in the production of layered substrates and is usually used to determine the position of the substrate to be produced.

According to claim 2, holes are drilled through the first layer, taking into account the combined transformation. Subsequent application of the second layer to the first layer machined by drilling can then be applied either indirectly taking into account the drilling positions or directly taking into account the combined transformation. The drilled holes, which are either blind holes or through holes, are used in particular for contacting different connection surfaces in different layers. Electrical contact is achieved by metallizing the corresponding borehole.

According to claim 3, the holes are preferably produced by means of laser beams. This has the advantage that when using modern laser processing machines for laser drilling Multi-layer substrates both a high yield, ie a high number of holes drilled per unit time can be achieved. Furthermore, the spatial dimensions of the holes can be kept so small that a high packing density of electronic assemblies can be realized on printed circuit boards built up in layers.

According to claim 4, taking into account the combined transformation when processing the first layer (210), an intermediate layer is formed between the first layer (210) and the second layer (220). This has the advantage that a maximum overlap between selected areas of all layers can always be achieved perpendicular to the layer plane.

According to claim 5, the number of markings measured can vary. When measuring only two markings, only a displacement and additionally either an expansion or shrinkage or alternatively a rotation can therefore be taken into account by means of the two transformations. When measuring three markings, in addition to shifting the starting layer, expansion or shrinkage and rotation can also be taken into account. When measuring four markings, a shear generated by the influence of shear forces can also be taken into account in comparison to the measurement of three markings.

It is pointed out that more than the minimum number of brands to be measured can of course also be measured. The consequence of this is that an equation system with an over-determination of the transformation parameters can be set up, which can advantageously be used for a more precise determination (in particular by averaging) of the individual transformation parameters. It can be based on well-known procedures to solve over-determined systems of equations.

The method according to claim 6, in which shear is excluded for the second layer, is of great practical importance, since the layer-by-layer construction of substrates generally has an exposure to form a conductor track structure. Process-related exposures of this type are usually carried out using a mask, in which only one (possibly different in the x and y directions) expansion or shrinkage of the first layer can be taken into account. The inside angles of a usually rectangular mask are fixed at 90 °. Such a transformation, in which the parameters di and d ₂ given above are equal to zero, is therefore also referred to as a so-called orthogonal transformation.

According to claim 7, a weighted superposition of the two transformations is used as a combination. A weighting factor z is used, which is the proportion of the second

Transformation determined on the overall transformation. The weighting factor z preferably results from the size of the areas which are used in each case for the selected areas of the first layer divided by the sum of the size of the areas which are in each case for the selected areas of the first layer and for the selected areas of the second layer be used. Selected areas are, in particular, connection areas formed on the first layer and / or on the second layer for producing electrical contacts between individual layers.

According to claim 8, the selected areas are connection areas for contacting the first layer with the second layer, so that interconnect structures formed on different layers can be made to contact one another in a targeted manner by contacting made perpendicular to the layer plane. Further advantages and features of the present invention result from the following exemplary description of a currently preferred embodiment.

FIG. 1 shows a schematic representation of a production of a printed circuit board known from the prior art with two different conductor track structures, which are contacted with one another by means of laser drilling, and

FIG. 2 shows the manufacture of a printed circuit board according to an exemplary embodiment of the invention, reliable drilling of different interconnect structures being achieved by laser drilling at drilling positions determined by a combination of different transformations.

At this point it should be noted that in the drawing the reference numerals of corresponding elements differ only in their first digit.

Figures la and lb illustrate the production of a layered printed circuit board 100 according to the prior art. The construction of the printed circuit board 100 begins with a first layer 110, on which four markings 111 are applied. The positions of these markings are measured and a transformation according to equation 1 is determined from the deviations from the actual positions to the respective desired positions, by means of which the distortion is determined for all grid points of the first layer 110. This delay can generally be determined very well for all grid points.

According to the exemplary embodiment shown here, the conductor track structure formed on the first layer 110 has a total of six first connection areas 112, which are arranged in two groups with three first connection areas 112 each. are divided. The connection areas 112 of each of the two groups are connected to one another by two first conductor tracks 113.

Since the distortion of each lattice point of the first layer 110 can be calculated very well using equation 1, the first layer 110 can be drilled in such a way that the holes 114, 114a are essentially in the middle of the hole by a corresponding control of a laser drilling machine, not shown First connection surfaces 112 shown are attached. The distortion of the first layer 110 is thus almost optimally compensated for by a targeted selection of the drilling positions.

Subsequently, a second layer 120 is applied to the first

Layer applied, wherein the first layer 110 and the second layer 120 are separated from each other by an insulation layer, not shown. According to the exemplary embodiment shown here, the second layer 120 has a total of twelve connection areas 122, 122a which, together with the second conductor tracks 123, represent the conductor track structure of the second layer 120. For the construction of this conductor track structure an exposure, not shown, is used, in which an exposure mask is used, in which the expansion or shrinkage can be freely selected, but the corner regions of the mask are, however, predetermined by a 90 ° angle. The second layer 120 can thus be adapted to the conductor track structure of the first layer 110 only by means of a displacement 130, a rotation 131 and an expansion or contraction (not shown) of the mask used for the exposure. The consequence of this is that, in particular, the bores 114a only meet the outer region of the connection surfaces 122a and thus only poor or even an interrupted contact is formed between the connection surfaces 112 and 122a, which are displaced relative to one another. It is pointed out that, in view of the small contact holes that are possible with modern laser drilling machines, even a slight difference between the unwanted first warping of the first layer 110 and the desired second warping of the second layer 120 can lead to such a large offset between contact surfaces to be contacted that contact perpendicular to the layer level is no longer possible.

Figures 2a and 2b show a manufacturing process of a layered printed circuit board according to a currently preferred embodiment of the invention. This manufacturing process differs from the known manufacturing process shown in FIGS. 1a and 1b in that the drilling positions 214, 214a are not only based on the

Pads 212 of the first layer 210 can be optimized. Rather, when selecting the drilling positions, the limited warping options of the second layer 220 are also taken into account. In the exemplary embodiment shown here, the warping possibilities of the second layer 220, which are limited by the orthogonality of the exposure mask, are already taken into account when selecting the drilling positions 214, 214a. This means that when selecting the drilling positions 214, 214a, optimal centering relative to the connection surfaces 212 is deliberately dispensed with. This disadvantage, which is generally only apparent, is more than compensated for in any case by a better overlap of the connection areas 222, 222a of the second layer 220 with the bores 214, 214a.

An overall transformation G, which is described by the following equation 2, is used to determine the bores 214, which are generally not arranged centrally to the connection surfaces 212, and in particular the bores 214a:

F _Tr ans _{I is} a transformation in which the transformation parameters ai, a ₂ , bi, b ₂ , Ci, c ₂ , di and d ₂ described above are used. The orthogonality of the exposure mask is taken into account in F _{Trans 2} in that this transformation only has the transformation parameters ai, a ₂ , bα, b ₂ , ci and c ₂ . The total transformation G is determined from a weighted combination of the two transformations F _Trans j. and F _r ans i _ι where the weighting factor z can be chosen between 0 and 1. A weighting factor of z = 1 means processing the manufacturing process after only the orthogonal transformation Fτ _r ans 2- Selecting the weighting factor z = 0 means processing only according to the algorithm F _Tr ans ι- for z = 0.5 for the total transformation G, both transformations F _Tra ns I and F _r ans 2 weighted equally.

An optimal yield of reliably contacted oiling surfaces can be obtained if the weighting factor z is determined according to the following equation 3:

Tolerance Layer1 Z - - Tolerance Layer1 + Tolerance Layer 2

The tolerances of layer 1 or layer 2 are determined by the size of the respective connection areas in layer 1 or layer 2. For example, in the case of very large-area connection areas in the first layer 1 in comparison with the connection areas in the second layer 2, a value of z is obtained which is only insignificantly smaller than 1. This means that the overall transformation is mainly determined by the transformation F _{Trans 2} .

In summary, it can be stated: The invention creates a method for producing substrates 200, which by successive two-dimensional process steps with a first layer 210 and at least one second layer 220 matched to the first layer 210 are produced. First, a plurality of markings 211 are measured on the first layer 210 and a deviation of the actual position from the target position is determined for each marking 211. From these deviations, a transformation F _Trans ι is determined for the position deviations of any grid points of the first layer 210 and a transformation F _{Trans 2} for possible position deviations of grid points of the second layer 220. When determining the transformation F _Tran s ₂ , known boundary conditions for a possible behavior of the distortion of the second layer are taken into account. When the second layer 220 is subsequently processed, a combined transformation from the two previously determined transformations F _Tra ns ι and F _Tran s 2 is taken into account. In this way, despite different warping of the two layers 210, 220, reliable contacting of conductor tracks can be ensured, so that a small amount of defective printed circuit boards is generated in the production of multilayer printed circuit boards.

LIST OF REFERENCE NUMBERS

100 printed circuit board 110 first layer 111 marking 112 first connection surface 113 first conductor track 114 bore 114a bore 120 second layer 122 second connection surface 122a poorly contacted connection surface 123 second conductor track 130 displacement 131 rotation

200 circuit board 210 first layer 211 marking 212 first connection area 213 conductor track 214 hole 214a off-center hole 220 second layer 222 second connection area 222a securely contacted connection area 223 conductor track 230 displacement 231 rotation

Claims

claims

1. A method for producing substrates (200), which is carried out by successive two-dimensional process steps with a first layer (210) and at least one on the first

Layer (210) matched second layer (220) are produced, in which

A plurality of markings (211) applied on the first layer (210) are measured on the first layer (210),

• for each marking (211) a deviation of the actual position from a previously known target position is determined, which is predetermined by a layout design of the first layer (210), • a first transformation for the determination of the from the previously determined deviations Positional deviations from any lattice points of the first layer (210) are determined,

A second transformation for possible positional deviations of lattice points of the second layer (220) is determined from the previously determined deviations, with previously known boundary conditions for behavior of the distortion of the second layer being taken into account when determining the second transformation, • the two transformations with one another can be combined, and

• the first layer (210) is processed taking into account the combined transformation.

2. The method of claim 1, wherein holes (214, 214a) are drilled through the first layer (210) during processing of the first layer (210).

3. The method of claim 2, wherein the holes (214, 214a) are drilled using laser beams.

4. The method according to any one of claims 1 to 3, in which an intermediate layer is formed between the two layers (210, 220).

5. The method according to any one of claims 1 to 4, in which two, three or at least four markings (211) are measured.

6. The method according to any one of claims 1 to 5, in which the previously known boundary conditions for possible position deviations of grid points of the second layer (220) consist in the fact that shear of the second layer is excluded.

7. The method according to any one of claims 1 to 6, in which a weighted superposition of the two as a combination

Transformations is used, with a corresponding weighting factor resulting from the flat dimensions of the selected areas of the two layers (210, 220).

8. The method according to any one of claims 1 to 7, wherein the _... , the selected areas are connection areas (212, 222, 222a) for contacting the first layer (210) with the second layer (220).