DE3144849A1 - Optoelectronic adjusting method in the production of multilayer circuits - Google Patents

Abstract

Contactless adjustment for the exposure operation in the production of multilayer circuits by means of an optoelectronic method. An optoelectronic sensor, e.g. an image dissector camera, measures by means of a multiplicity of radial scanning paths the distances DELTA R between in each case two dark circular rings on the glass master and two bore holes in the inner layer, each circular ring being assigned to a bore hole. Subsequently, the measured values are standardised with respect to a reference, and statistical spatial averaging is carried out for a multiplicity of radial directions.

Description

Opto-electronic adjustment process during manufacture

of multiple cha1tunen.

The invention relates to a method for automatic adjustment from printing tool to inner layers of multilayer in exposure to achieve an increased coverage accuracy Multi-layer printed circuit boards consist of several Layers of copper-clad on one or both sides, bearing the conductor pattern Foils that are pressed with unlaminated, insulating intermediate layers (prepregs) and After drilling, the chemical or galvanic contacts are made through the outer layers also consist of copper-clad foils, which only after Pressing and through-hole plating can be printed.

One of the most important work steps in the production of multilayer printed circuit boards is the drilling of the connection holes for the metal through connections. To the electrical function9 the electrical safety, as well as the reliability of the To ensure the product "multilayer printed circuit board", these holes must correspond to the internal connection surfaces (e.g. soldering eyes) on the signal layers as well as the internal ones Etchings on the potential layers are very much within specified tolerances Narrow tolerance ranges are particularly important for multilayer printed circuit boards to be demanded, since an exact alignment in the different positions is a prerequisite for their usability. The most accurate possible knowledge of the actual position of the internal An surfaces or etchings to a reference point (e.g.

Mounting hole) is a prerequisite for fulfilling this requirement.

In the production of multilayer printed circuit boards today, the registration accuracy of the individual layers during exposure and lamination through use a dowel pin system guaranteed.

For this purpose, there are two drill holes with a diameter in the inner layer from Z. B. 8 mm cut at a distance of about 300 to 400 mm, as a recording serve for the dowel pins. Two fitting sockets must be included in the glass master the same dimensions are introduced. Glass master and inner layer are then over the Alignment pins before exposure. The accuracy of this procedure is limited. Furthermore, the drill holes of the relatively soft epoxy material are deformed on.

When pressing the individual inner layers to form a multi-layer circuit board however, they will be in the correct position again using a dowel pin system with the same drill holes adjusted, so that this results in an additional reduction in the accuracy of the coverage Lamination process can occur.

Figures 1 and 2 show a dowel pin system during manufacture of multilayer circuit boards. In the figure 1 is the schematic arrangement of two Glass master 1, 2 with associated inner layers 3, 4 on fitting pins 5, 6 shown.

FIG. 2 shows schematically the process during lamination.

As shown in this picture, there are three inner layers 7, 8, 9 with two prepregs 10, 11 stacked. A dowel pin 12 is used for adjustment.

With the further reduction of the grid dimension and the conductor track widths are those with the well-known passport pin system achievable coverage accuracy no longer sufficient.

The invention is based on the object of the known dowel pin system with the described inadequacies as far as possible through precise, non-contact Adjustment process to replace 0 This object is achieved by using two adjustment marks on a glass master, two boreholes can be assigned in a single inner layer and optically electronically measured whether the radial distances between boreholes and alignment mark are the same.

This eliminates the need to attach the metal sockets in the glass master and the inaccuracy caused by the mechanical adjustment process by means of the dowel pins. In addition, with the method according to the invention, the deformability of the drill holes avoided in the inner layer during the exposure process Alignment mark preferably provided a dark circular ring, the outer diameter of which lies within the borehole of the inner layer.

Furthermore, the radial distances of this circular ring to the borehole are through an opto-electronic sensor coupled to a microcomputer system ist0 The optoelectronic sensor is preferably an image dissector amera with freely selectable scanning path (randomaccess) use. Such a sensor has a high point resolution and a freely selectable program-controlled scanning path. The use of such an optoelectronic sensor enables polar image scanning. The polar image scanning has no preferred direction in the pattern recognition (borehole circular ring).

In addition, the polar image scanning avoids tangential cuts would be with a conventional TV camera due to its rigid, line-by-line image scanning not possible 0 According to a development of the invention are for Compensation of the local linearity errors with respect to the measured radial distances a reference; e.g. the width of the circular ring, standardized. This is preferably done by detecting and evaluating the known circular ring width of the alignment mark the glass master.

According to a further embodiment of the invention, the measured Radial distances of both boreholes in the microcomputer system according to a statistical Mixed methods and the adjustment variables Ax, äy and a y for the x, y adjustment evaluated with angular rotation of the relative position between the glass master and the inner layer and fed to a mechanical adjustment device for precise readjustment. By this statistical method allows local form errors to be reduced considerably and carry out a center compensation between the drill holes for the adjustment.

The invention is explained with reference to FIGS. 3 to 6.

The figures show: FIG. 1 the dowel pin system in the production of multilayer printed circuit boards with regard to the exposure process and FIG. 2 during pressing, FIG. 3 the automatic Adjustment with image processing for a borehole with a circular ring arrangement, FIG. 4 the drill hole of an inner layer with the circular ring mark underneath it on the glass master, FIG. 5 shows the measured radial distances as a function of the polar angle and figure 6 the normalization of the measured radial distances from the measured circular ring width.

In FIG. 3 there is an optical sensor 13 with a glass master 14 and an inner layer 15 can be seen. The glass master lies on the inner layer. The exploded view was only for the sake of clarity chosen. There is an adjustment mark in the form of a dark ring 16 on the glass master provided, which is smaller in diameter with respect to the borehole 17.

The direction of exposure is indicated by the arrows 18.

The lines 19 symbolize the optical image of the borehole and Annular mark on the sensitive layer of the sensor In Figure 4, # R is the distance. indicated between borehole 17 and circular ring mark 16. In the figure 5 is the distribution of the measured radial distances # R as a function of the polar angle - applied.

FIG. 6 shows enlarged the circular ring linear mark 16 in the borehole 17, where with is the measured value for the radial distance at the polar angle - and with this the measured value for the circular ring width at the polar angle G denotes the known The width of the circular ring is indicated with d and the polar angle with S. The radial The scanning path is symbolized by the reference symbol 20.

The Image Dissector camera measures through a variety of radial scan paths the distances # R of the circular rings. The polar image scanning avoids tangential Cuts and has no preferred direction. To compensate for local linearity errors of the Image-DissectorCamera, the measured radial distances # RMess still have to be related to a reference can be corrected. According to the exemplary embodiment, this reference becomes in the form of the known circular ring width d of the alignment mark on the glass master educated. If the alignment mark consists of a circular ring with a point in the middle, For example, the diameter of this point can also serve as a reference.

The actual radial distances iXR result from the measured Radial distances i Xess after the normalization = # Rmess x d / dMess this is included the measured annulus width on the respective scanning path and d the known width of the circular ring. This means that linearity errors in the camera can be almost completely eliminated compensate.

The invention does not apply to the application of the method in the manufacture of printed circuit boards limited. Rather, it can be used anywhere where dowel pin systems are contactless working adjustment procedures have to be replaced for further automation.

5 claims 6 figures

Claims (1)

Claims. 1. Procedure for automatic position detection and adjustment of the individual Layers of multilayers for printing tools in the photocopying process, d u r c h it is not shown that two adjustment marks (16) on a glass master (14) two drill holes can be assigned in a single inner layer and opto-electronically it is measured whether the radial distances (#R) between the drill hole (17) and the adjustment mark (16) The same are two methods according to claim 1 9 d a d u r c h g e -k e-n n z e i c h n e t p that a dark circular ring is preferably provided as the alignment mark (16) is, the outer diameter of which is within the borehole (17) of the inner layer (15) lies, and the radial distances of this circular ring to the borehole by an opto-electronic Sensor (13) are detected, which is coupled to a microcomputer system. 3 Method according to claim 2, d a d u r c h g e -k e n n z e i c h n e t that as opto-electronic sensor (13) with an image dissector camera Freely selectable scanning path (random access) use is made of 4 methods according to claim 3, d a d u r c h g e -k e n n n z e i c h n e t that to compensate for the local Linearity error the measured radial distances (R) still with respect to a reference, z. B. the width of the circular ring (d measurement), can be corrected. 50 The method according to claims 1 to 4, d u r c h e k e n It should be noted that the measured radial distances (ARMess) of both boreholes averaged in the Nikrocomputer system according to a statistical method and the adjustment variables #x, #y and ## for the x, y = adjustment with angular rotation of the relative position between Glass master (14) and inner layer (15) evaluated and a mechanical adjustment device be fed for exact adjustment.