SE459708B - PROCEDURE FOR MANUFACTURING PRINTED CIRCUITS AND APPLIANCES - Google Patents

Description

10 459 708 2 some complex developers or techniques, which means that after the car application or installation, all that is necessary is that the uncured liquid polymer is removed.

In the broadest sense, it has been discovered that one can cera images on (hereinafter used for simplicity) pressure "insert") liquid polymeric coatings on printed circuit board blanks, while present in the undried state, and still obtain very good definition. This is the case even if one air gap must be maintained between the photo tool, which carries the image of the printed circuit pattern, and the liquid polymer coating.

This coating can vary from a liquid liquid to a sticky viscous liquid.

During car painting, light passes from it does not -coherent collimated light source through the transparent ones areas of the photo tool, hits the liquid polymer and cures this liquid polymer to a solid. Where some light does not pass through the photo tool, the liquid polymer remains liquid, and it is removed from the printed circuit board blank for exposure or exposure of the underlying metal. Although the liquid polymer can be removed by physical means methods, such as by means of an air knife or by drying, are it is most effective to remove the liquid polymer by means of a liquid in which the liquid polymer is at least partially dissolved but in which the cured solid polymer has substantially no gon solubility. The main advantage is that such a technology completely exposes the metal beneath the liquid the polymer, which enables a more efficient etching of this pine in a subsequent step.

As discussed above, one of the disadvantages of imaging is laying of a liquid coating the need to establish maintain an air gap between the photo tool and the liquid coating ningen. The use of an air gap usually results in a desire for definition in the printed circuit. In the present process, However, this is not a problem. partly the result of the use of a non light beam for imaging, This is at least -coherent collimated process techniques for removing the uncured liquid polymer, the good adhesion thereof cured the polymer at the underlying metal, the resistance of the cured liquid polymer against etching solutions as well the ease of removal of the cured liquid polymer after 3 459 708 É etching. In other words, the cured polymer is not attacked by it solution, which was used to remove the uncured liquid powder. the lymer for exposing the underlying metal. About it cured polymer is also attacked, there will be a desire in terms of definition in the final circle and a possible loss of adhesion of the cured polymer to the underlying gande metals. Any loss of adhesion would make that excess metal was removed during the etching step. When a solution containing cations derived from a strong base contact with the cured polymer, however, it is effective then to remove the cured liquid polymer without using grab the underlying metal. The net result will be that some organic solutions are not required in the processing of the put the printed circuit board. This means significant cost Savings, because organic materials are more expensive, are flammable and gives rise to vapors and odors which, according to State or local bare regulations must be removed from the work area. That is where- too useful to be able to use water-based solutions in the commercial production of circuit boards.

The term "non-coherent collimated light" means light with a half angle of not more than 3 degrees and preferably not more than l, S degrees. In contrast, laser light is coherent light. Light collimated (formed into a beam) by means of lenses, parabolic reflectors or various mirror arrangements.

Briefly, the present invention consists in novelties etching and plate resistance processes for the production of printed circuit boards short using liquid polymers, a new process for the production of solder masks using liquid polymers as well as single and multi-station equipment for implementation of these processes. In each of these processes, images are displayed circuit board blanks having a liquid polymer coating, and each requires only aqueous solutions for the processing of after imaging. As a result, the same equipment can can be used for plate resistance, etching resistance and solder masking. This Versatility means several cost advantages and this specific for such manufacturers of the various types of printed circuit boards cards that work with smaller volumes. a In the etching and plate resistance processes of the present invention, In this case, the circuit board blank is first coated with the liquid polymer. 459 708 A photo tool of the desired circuit is then placed in the responsibility for it and over but not in contact with the liquid the lyme coating. The subject is pictured.then, whereby under the transparent areas of the photo tool the polymer hardens to a solid, while under the opaque areas it remains liquid.

This liquid polymer is then removed. preferably by reversal of a solution, wherein it is at least partially soluble.

After this step, the processes for producing plates differ. resistors and etch resistors from each other. In the manufacture of etching resist, the exposed metal is etched away using a aqueous acidic solution, and the cured liquid polymer is is then removed using an alkaline solution containing cations derived from a strong base. In the manufacture of plate resistors are coated with tin, nickel and / or similar metals the exposed metal after removal of the liquid polymer, on the cured liquid polymer is removed during use dning of a alkaline solution, containing cations derived from a strong , and the exposed metal layer is removed by etching.

Solder masks are formed by coating a printed circuit card with a liquid polymer, imaging of the coated card for producing cured polymer on certain parts of the circuit pattern while leaving the polymer uncured on other parts.

The uncured liquid polymer is then removed during use of a solution in which it is at least partially soluble, base and that exposed metal is coated with solder. The cured polymer is removed usually not but left on the card or disc as an insulation layer.

The single station equipment, which has been found to be a lot useful in implementing these processes, consists of a device for holding a printed circuit board or a blank for a printed circuit board in the set-up or start-up position, a retractable roller or roller coating device for coating one side of a card, a photo tool in accordance with the circuit board blank and bearing an image of a circuit and which can be pulled back to a point above, but in close proximity to the coated card and a non-coherent collimated light source, which are arranged to cause light to pass through the photographic tool. goat for curing liquid polymer. Different arrangements for these devices are possible. However, the preferred arrangement is to have lS ï 459 vøs the blank is held in place by means of a vacuum with a roller coating device horizontally retractable for coating card. The photo tool unit is vertically retractable and is located above the positioned circuit board. the substance and in the way of the non-coherent collimated light from the light source. During operation, the machine operator therefore arranges the card in position and activates the vacuum retaining means. Then start- step by step, the roller coating device, which passes over the occupy the card and return. After this step is lowered the photo tool unit to close connection with the coating, and at setting in the correct position, the light source is activated during a certain time period for curing of the polymer. When the light is turned off, it is turned off the photo tool unit back up and the card moves on one transport device to a spray bath .for removing the uncured liquid polymer. The equipment for the subsequent steps consists of per se known etching, metal plating and solder deposition devices. The multi- or multi-stage equipment is stands for separate coating and exposure units but is similar otherwise single-station equipment.

The present procedures and equipment will be discussed. race in more detail in connection with the following drawings: Fig. 1 is a stepwise diagram of the etching resistance process for production of printed circuit boards.

Pig. 2 is a step-by-step diagram of the plate resistance process for production of printed circuit boards.

Pig. 3 is a step-by-step diagram of the manufacturing process. soldering masks.

Fig. 4 is a side view of a circuit board blank arranged in position on a vacuum holding plate.

Pig. 5 is a side view of the circuit board blank under coating with a retractable roller coater.

Fig. 6 is a side view of the photo tool immersed in close tape with the coated circuit board blank.

Pig. 7 is a side view of the circuit board blank with the photo tool the backing feature, wherein a certain area of cured liquid poly- more is displayed.

Fig. 8 is a schematic diagram illustrating the non- -coherent collimated lights used. ' Pig. 9 is a front side view of a single station device. 6 459 708 * i containing the components of Figs. 4 and 7.

Pig. 10 is a side view of the single station apparatus from Pig. 9.

Pig. ll is a side view seen from the front of multi-station which gradually carries out the operations for Pig. 9 and 10.

Pig. the device according to 12 is a plan view of the aerial tool surface of the gap connection with the circuit board blank during imaging.

'Pig. 13 is a perspective view of the fixture voltage plate aggregate hole holding the circuit board blank in position.

Pig. 14 is a sectional view of the plate assembly of Pig. 13 taken along line 14-14.

Pig. 1 indicates the steps that apply to the production of a printed circuit board using etch resist technology. The process starts with an electrically conductive roll cladding blank. Such substances consist of a non-metallic substrate , usually a plastic containing reinforcing fibers , which on one or both sides have a net number layer with a thickness of from about 0.025 to 0.075 mm.

The substrate can be of any reasonable thickness but is usually gene from about 0.075 to 6.25 mm thick. Vanli gene are these substrates phenol or epoxy plastics reinforced with fiberglass or something similar with equivalent material. The metal plating is usually copper.

In the preparation of an ester resist according to the present invention the plated metal blank is coated on one side with polymer to a thickness of from about 2.5 to 250 microns or more. Preferably, the coating thickness is uniform throughout the substance, the thickness being from about 12.5 to 125 μm. The coating must be thick enough to be sure that there are no cavities but not so thick that it the polymer flows off at the edge of the blank or through the many small holes that cross the subject. The coating can be done by means of which any suitable technique, such as by spraying, brush or by roller coating. since it thereby sets aside one using Roll coating is preferred, however, smoother wet polymer film on skis van or card, and it has surprisingly been found that in rolling coating the liquid polymer tends not to flow into some of the heel through the substance even if vacuum is applied to the underside of the card. This can primarily be attributed to an interaction between this method of application and the surface tension of the liquid polymers. 459 708 rerna. These holes were later used in connecting the circuit components. to the finished cards. If polymer ran down into these holes, it would be necessary to remove the same before mounting of the circuit.

In the next step, a photo tool is placed, which carries the circuit pattern, in air gap interaction with the liquid polymer coating. It is it is desirable to have the photo tool as close as possible but not in rate with the liquid polymer coating. An air gap of from approx 0.13 to 13 mm was usually used. A unit pours photo the fabric in position and in accordance with the polymer coated the subject. According to the preferred method, the photo tool is held in place using a metal frame, and vacuum is applied to the edge of the photo- the tool. When the photo tool is an emulsion on a glass plate, read the glass plate in place mechanically. In cases where the photo tool is an emulsion on a plastic film, such as a polyester film having a thickness of from about 100 to 250 μm, a glass plate is arranged over the film to ensure that the film is kept in the same plane.

Regardless of whether an emulsion on a glass plate or a plastic film was used as a photo tool, it is the emulsion side that is in air gap connection with the liquid polymer coating.

The term "photo tool" is used in the broad sense of the word. any image-bearing medium and can be any silver emulsion or silver-free emulsion. This includes diazo- emulsions. This emulsion may be supported on a polymer film, glass or any other suitable medium. The expression "equivalent" or "in accordance with" was used to indicate give the location of the photo tool over the circuit board blank on one way that the desired circuit is placed in predetermined areas of the subject.

When the photo tool is in place, a non-coherent one is activated collimated light source, which is preferably a source of a radiating from 2000 to 5000 Ångström and which is located so that light is passed through the photo tool. Among suitable lighting Sources include carbon arcs, mercury arcs, mercury xenon lamps; tungsten halide lamps and argon light bulbs. Preferably is the light source a mercury arc or mercury zenone light beam.

The light passes through the transparent areas of the photo tool, hits the liquid polymer and cures this liquid polymer to a solid. A liquid polymer, which does not come into 1D ' 459 708 8 pace with some light, remains fluid. A time period of from approx to 120 seconds is usually sufficient to cure it the liquid polymer. If this is necessary, however, longer periods are used.

When the liquid polymer has solidified after contact with , the remaining uncured liquid polymer is removed liquid to expose the underlying metal. This can accomplish using an air knife to blow off the liquid polymer from the surface, by drying or by inversion of a liquid in which the liquid polymer is at least partially soluble. The preferred technique involves using an aqueous alkaline solution, at least partially soluble. are containing sodium, light wherein the liquid polymer is Suitable solutions are alkaline solutions. potassium or ammonium ions, such as natural sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium sulfite, sodium bisulfite, potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium sulfite, potassium bisulfite, ammonium hydroxide, ammonium carbonate and combinations of these materials. Alkaline detergents or even organic-water mixtures can also be used. as long as they do not attack the cured polymer.

After removal of the uncured liquid polymer, the exposed metal is removed by etching. Usually this is metal copper , and the etching solution can be any commonly used copper ore solution, such as an acidic chloride solution.

Commonly used copper solution are ferric chloride or salt acid solutions, which may also contain certain other components.

When this step is completed, the blank remains with the metal layer now only present under the cured liquid polymer.

The last step involves the removal of the cured the liquid polymer. This is accomplished by the cured fly the polymer is contacted with an alkaline solution, contains cations derived from a strong base. Sodium or potassium-containing compounds are preferred alkaline materials for preparation of such solutions. Other reagents basic cations, however, can also be used. 50111 , which gives strong Pig. 2 indicates the steps that apply to the production of one printed circuit board using plate resist technology. The first the four steps in the plate resistance process are essentially the same as those for the etching resistance process. After the step of removing the uncured ........ ...___ - .. fl- ... 9 459 708 the resulting liquid polymer results in the exposed medium the pine is present in a pattern identical to that of it final circuit pattern. The remainder of the metal is covered by it cured polymer.

The next step in the production of a plate resistor consists in tin, lead, nickel or combinations of these metals on the exposed metal. This is conveniently done by de-energizing plating or electroplating on the exposed metal. The the cured polymer is removed in the same manner as in the etch resist technology. niken. In other words, the card is washed with an alkaline solution containing holding cations derived from a strong base.

The final step in the production of the plate resistor is stands in the etching away of the metal, usually copper, that has been exposed upon removal of the cured polymer. This etching is the same as for etching resists where the cladding metal protects the horizontal metal. The final product is a printed circuit board with a circuit pattern coated with the plated metal.

Pig. 3 indicates the steps for applying solder masks printed circuit boards. In the manufacture of a solder mask, the a fully printed circuit board. In the first step, the printed circuit board is coated with the liquid polymer using any of the methods described in written in connection with the etching resistance process according to Pig. l. A photo- tools, which have opaque areas over the areas where plumbing is to be placed, then placed in exact conformity of the coated printed circuit board and light source.activated.-The liquid poly- hardens to a solid in all areas that have come in contact with the light, all other areas remaining liquid.

The uncured liquid polymer is then removed in the same manner as in the etching resistance process. The exposed metal areas are brought in contact with solder, which remains on the exposed metal. Wave- soldering methods can be suitably used. The weight in these selected areas the wires were then used to connect various electronic components. and threads.

In These are the three primary processes for the use of processes in which liquid polymer is used, for manufacture of printed circuit boards. Pig. 4 through 7 illustrations broadly outlines the preferred mechanisms used in the implementation of performing these steps by curing the liquid polymer. 459 708 In Fig. 4, the printed circuit board blank 10 is arranged scaffolding plate ll by means of guide and re which pass through hole 13 in on site at upp- registration pins 12, circuit board subject. This clamping plate has a series of small holes 14 drilled through it. Vakkum applied to the underside of this clamping plate the ice covered sufficient to hold the card load in position on the surface of the plate.

The pins 12 are then retracted below the card surface.

When the printed circuit board blank is now locked in position, illu- strerar Fíg. The coating with liquid polymer. The return the pullable roller coating device consists of the application roller 15 and control roller 16. A supply of liquid polymer is held ' 1 pinch between the rollers. Each roller is at least the same long as the width of the circuit board blanks. By means of the control roller is allowed a predetermined amount of liquid polymer to be taken u pp of applice- ring roller.

This predetermined amount regulates the thickness of it liquid polymer 17 on the blank. After the coating is rolled, laying device back.

Pig. 6 shows the short blank with liquid polymer with photovoltaic the fabric in place. Here, the blank 10 is completely coated with a layer 17 of liquid polymer. The air gap 18 , which is in the range from 0.13 to 13 mm , separates the liquid polymer from the photo tool.

The photo tool unit comprises a negative 19 and a flat glass plate 20 for holding. The negative is directly above 1 uftga- pet 18 , and preferably the emulsion side of the film is adjacent to the air. the gap. With the photo tool in place, a light source over the photo the tool. When light hits the liquid polymer, it hardens to a solid. This is illustrated7 solid polymer areas, while 2 of liquid polymer. uncured polymer. and Pig. 7, where 21 indicates 2 indicates the uncured areas The card is now ready for removal The card can be conveniently transported from the tension plate by means of a series of rollers 23 , which bears conveyor belt 23 (a) for transporting the card. Conveyor belts 23 (a) are recessed in the clamping plate and raised when the card is to be porters.

The non-coherent collimated light used for these processes, is defined as the angle of light at which the light strikes the resist material. This angle should preferably be a light with a half angle of not more than 3 degrees and preferably not more than 1.5 degrees. This light produces a photoresist, which has one x f * 459 708 deviation angle from the vertical line or plane of no more 11 than in 3 degrees and preferably not more than 1.5 degrees. In addition- deviation or deviation indicates a shoulder on the photoresist, then a negative deviation indicates an erosion. Furthermore, it applies that this light should not have an image dimensional deviation of more than 12 12.5 μm and preferably not more than f 6.25 μm. If liquidation then from the vertical plane or the image dimension deviation exceeds these values, the result is a lack of accuracy and / or uniformity in the dimensions of the resulting circuit.

This can result in a change in the resistance of the circuit, which may affect the overall performance of the final electronic the detail.

These factors, which define this light, are illustrated in the hoist in Fig. 8. In this figure, the incident light is denoted L.

The photo tool is designated 19, the circuit board 10, the liquid poly- the additional coating 17 and the air gap between the photo tool and the polymer area 18. The region 21 (a) of the photographic tool is a parent area, while area 22 (a) is an opaque area. After expo- light has solidified in the area Z1 of the maxi-liquid polymer, while in area 22 it remains a liquid. The light hits the photographic the fabric under substantially perpendicular conditions. Because this is an ideal state, and since all non-coherent light has one certain deviation, however, this is defined by means of angle A of the light. This half-angle A produces an angle for the deviation in the photoresist, resulting in either a shoulder B or a recess B 'in the photoresist. Deviation angle in photo- the resistor, which is the angle of the shoulder or of the recess, is the angle at which the vertical side of the photoresist deviates. from the absolute vertical line.

The dimensional deviation factor is also illustrated in connection with Pig. 8. This factor is the maximum deviation of the photoresist from the dimension of the circuit line on the photo tool. The light itself itself or the light hitting the edge of the opaque area the photo tool, can not be deflected or otherwise affected in a extent where the dimension of the polymerized polymer 21 differs from the dimension of the opaque area 21 (a) on the the tool 13 with not more than 3 12.5 μm and preferably not more than and 6.25 um. The purpose is to get the width dimensions for the area 21 so as much as possible to be identical to those for area 21 (a). 'zs 459 vos n This is shown by angle C.

This light should have a significant portion of its energy within it ultraviolet and visible bands, ie. in the field from 2000 to 5000 Ångström. Furthermore, this light should have an intensity of from about 4 to 30 milliwatts / cm 2 at the surface of the liquid polymer. clean. However, this is not a critical feature, because at lower intensities longer exposure time can be used.for achieving of the same result. A light source of this kind is sometimes called a actinic light source.

The other parameters that are important in terms of luminosity the source is its position in relation to the object to be receive light energy. The collimated light should be in a plane, which is parallel to the plane of the object to be received by the the energy. Thus, the collimated light emitted at an angular right to the plane of light, to be received perpendicular to the plane of the remål that receives the light. This ensures that it the final circuit and the circuit pattern on the photo tool are identical together. If this orientation is not maintained, will the circuit lines to be offset from those of the photo tool. The- take will cause problems, as a card must have different circuits on each side.

Pig. 9 and 10 illustrate single station equipment, which includes includes all the unit operations that have been discussed in connection with Pig. 4 through 7. By single station is meant that each of the steps in Pig. 4-7 are performed at the same area. The preferred the arrangement of the individual units is shown in each figure. The the upper part of the cabinet houses a light source 27 and has an outlet 28 for emissions of heat and vapors from the appliance. The light source is one mercury arc or mercury xenon lamp and is stationary and can thus be mounted or arranged in any way, provided which ensures stiffness. The lower section 26 of the cabinet houses a wake pump 29 and connecting pipes 30 and 31, the motor 47 which drives the conveyor system for removing illustrated cards to the station for removing uncured polymer and polymer pump and storage tank 48 with discharge pipeline 48 (a). The middle part of the cabinet is located on the operator's work level and contains the special equipment for the unit operations shown in Pig. 4 to 7.

Instead of a light source arranged in the upper part of 13 459 708 cabinet 25, the light source may be located in the lower part of the cabinet. pet with a series of mirrors in the upper part of the cabinet. These mirrors are placed so that they change the path of light so that this passes down through the photo tool. This can be accomplished through the use of two angled mirrors, each reflecting light angularly so that the direction of the light beam changes from the upward direction in a downward direction and through the photo tool.

In more detail, when a circuit board subject has in the machine and placed in the position of the retraction only the pins (as shown in detail in Figs. 4 and 5), are applied vacuum on the underside of_pppspänningsplattan.ll using vacuum pump 29 and connecting pipe 30. This view shows the roller the coating device in the position it is in ír fi r_ fi bmæræ polymer is applied to a circuit board blank. Roller coating devices The application roller 15 and control roller 16 are mounted on one holder 32. The application roller is located in front of the control roller.

Each roller rotates cooperatively as shown in Figs. S.

The area between the rollers receives liquid polymer from the pump and tank 48 by means of the tube 48 (a). An electronic sensing mechanism maintains a constant level of liquid polymer in the nip between by starting the liquid polymer pump or actuating a valve so that the polymer flows back to the tank. A driving mechanism 33 drives the rollers. This drive mechanism is arranged on it mobile trolley and is an electric motor with chain or gear wheel drive for each roller. The drive mechanism 34 drives the roller the laying mechanism forwards and backwards on fixed screw grooves 35. This drive mechanism 34 consists of a stationary reversible electric motor, which is connected to each rotating screw by means of a chain drive device. In other words, the motor shaft and each screw have one sprockets and the chain runs over each sprocket. Preferred a spring-loaded non-driving sprocket was used for tensioning the chain that drives the screw. These screw grooves can both carry laying device and move it forwards and backwards in each coating cycle. However, it is advisable to use a separate carrier Sd to support the roll coating device. The roller 15 is usually in contact with the substance only at the forward or reverse ongoing movement on the subject. However, it may be in contact with the substance in both directions or at both passages. When coating in forward direction comes the application roller 15, due to 14 459 708 the location of the control roller 16 (behind the roller 15), to deposit one thicker film. in the forward movement this coating can vary from about 75 to 250 μm, while the coating at the the walking movement will be thinner and be between 12.5 and 125 um. Depending on the thickness of the desired the coating the application roller is held in contact or raised out of contact with the subject in the forward or backward movement over the subject. Solenoids were used to raise the rollers at the forward walking or recurring movement, depending on what is desired. Ask- the laying time is between 4 and 20 seconds, with about 8 seconds has been found to be an appropriate time. The rotating screw mechanism which drives the roller coating device can be operated at different speeds. named, because it uses another separate.reversible electric motor than that which regulates the rollers or rollers. This evidence can be changed if the need arises.

The application roller is constructed of a polyene or a mixture of polyenes. These materials are stable and unaffected appreciably of the liquid polymer. This roller has such a length that it occupies the largest circuit board blank that can be held on the clamping plate and is between approx. 5 and 15 cm in diameter.

The control roller can be of any material that does not of the liquid polymer and is suitably stainless steel or smiles chrome-plated steel. The diameter of this roller is smaller than that for the application roller. The degree of clearance between application choices sen and the plate, which holds the substance ring of two micrometer screws does not raise or lower the screw the subject. , is set by adjusting , which raises and lowers the rollers but the mechanism for feeding roller aggregates Pictured above the roller coating mechanism is the photo tool the unit 37. The photo tool unit contains the film 19 , as kept in a planar direction by means of glass pl attan 20. The lower side of the film is the emulsion side of the film and carries the image of the circuit the pattern. The photo tool unit is retractably mounted by means of a control console 38 and a carrier track 39, so that it can raised to an upper part of the cabinet, when the roller coating device is in a front position where liquid polymer is applied, and after lowered to set the photo tool in close air gap connection with the liquid polymer coating during imaging ngen. Photo- the tool can slide -up and down in a line determined by ZS 459 708 the support tracks 39. Chains 40 are connected to side brackets 49 on the power tool assembly and extends upwardly over sprockets 41.

These sprockets are rotated by a reversible motor 42 via a drive shaft 43. When these sprockets are caused to rotate, raise and lower the photo tool unit approx. 30 cm. These sprockets only need to have a circumference that is approximately equal to that distance as the photo tool unit is to be raised and lowered. On the wonder At the end of the photo tool assembly are adjustable pins 44, which are set to maintain the appropriate air gap between the photo- the fabric and the coated surface. At least four of these pins are used des. These pins come into contact with the surface of the clamping plate and supports the photo tool assembly during imaging. A pipeline 31 connects the photo tool assembly to the vacuum pump. The vacuum, which is applied to the photo tool, holds it in place at its edges. Registration or setting tabs can also so be used to facilitate the alignment of the photo tool. Also whether the return mechanism has been discussed in connection with use of a chain or a chain, a rotating screw, as used in for the roller coating device, be used. However, it is appropriate to use a chain or chain elevator type mechanism for to raise and lower the photo tool unit.

Once the photo tool unit is in place and resting on pins 44, the lamp 27 is activated, which emits a beam of non- -coherent collimated light down on the photo tool. This light appli- during S to 120 seconds and preferably for about 20 seconds seconds. As a light source ages and becomes weaker, sheep the light application time is extended. The light intensity can be measured and the time period is adjusted, or an integrator can used, which automatically records the intensity of the application light energy over time and adjusts the light source. Light- the source is then turned off and the power tool unit is raised its resting position. The clamping plate is then relieved applied the vacuum, the transport mechanism 45 is raised, and the card is automatically removed from the appliance for further processing.

The conveyor belt is raised by activating solenoids 46, which are raised is the holder 45, which in turn raises the rollers 23 and so on joined the conveyor belt Z3 (a) in the area of the clamping plate.

The motor 47 is activated simultaneously with the solenoids 46. Band 47 (a) from the motor drives rollers 23. 459 'ros m I The equipment can be operated on a manual or automatic basis.

In manual operation, the operator would regulate each step. One automatic operation is preferred, however, whereby after the the card has been placed in the position the steps are performed each after each other without any regulation by an operator. In addition to this provides better quality control, it allows safer operation of the armor. The control means shown in Fig. 9 are some of those which was used for automatic operation. That would generally be desirable to have measuring instruments that give a constant indication of vacuum in the clamping plate and the photo tool assembly. Switches would include a "Master On-Off" switch, a vacuum pump switches and a light timer device. These are all in and known per se, and other devices can also be used.

Fig. 10 shows a view of one side of the apparatus of Fig. 9, namely gen the side opposite the one where the circuit board blank comes out, i.e. from the left side of the apparatus according to Pig. 9. The various details are the same and have the same reference numerals as in Fig. 9, except that this view shows the use of an even possible unit with several chamber clamping plates. The upper section.25 contains the light source 27 and the outlet 28. The lower one section 26 contains the vacuum pump 29, the liquid pump and a tank 48 with continuous polymer supply pipes. 48 (a) and a motor 47 with associated belts 47 (a) for driving transport rollers 23. The middle section is operator's area of operation and contains the positioning mechanism circuit board, the roller coating mechanism and the photo tool the unit. Each of these has been described in connection with Fig. 9 but will now be described again in in connection with Fig. 10.

The circuit board positioning mechanism consists of a clamping plate assembly 61, which has a series of holes 63 for application of vacuum on the upper side of the plate. The plate is here multi-chamber- the plate assembly from Figs. 13 and 14. In other words, there are four ready chamber in the plate unit. Vacuum.can be applied to which any of or all of these chambers. This plate was used when circuit boards of different sizes shall be produced. When used vacuum is applied only to the chamber or chambers, above which (s) a circuit board blank is positioned.

When locking the circuit board blank, first decide on which chambers in the clamping plate as a vacuum are to be applied. ”- 459 ma Valves S2 with connecting lines 53 to a vacuum manifold 51 is then opened for the chambers to which vacuum is to be applied. race. The other valves 52 remain closed. When the circuit board is fixed in position, the roller coating device is activated, so that it moves forward on screws 35 and coats the circuit board. the substance with liquid polymer. The application and control rollers are not visible in this view. The roll coating device then runs back, and the photo tool assembly 37 is lowered into position. The body 38 controls the photo tool on the carrier web 39. Chains 40 are connected side holder 49 and raises and lowers the photo tool unit. Photo- the tool is lowered until adjustable pins 44 come into contact with the in step with the upper surface of the plate 61. In the fully activated position the photo tool assembly is carried by these adjustable pins 44. By adjustment of these pins allows the air gap between the photo tool and the liquid polymer changes. When the photo tool unit is in place, an actinic light source is activated 27. When the light source is turned off, the photo tool unit is raised, and the transport rollers 23 and the associated bands 23 (a) are activated. The engine 47 and that the associated belt 47 (a) provides drive on the rollers 23.

At the time the photo tool has been raised to its storage position the transport bracket 45 is raised with solenoids 46. At the same time the motor 47 and the transport rollers 23 and the associated ones are activated the straps so that the circuit board can be lifted up from the plate of beer and transported from the equipment to the next workstation.

As already mentioned, it is advisable to operate this equipment automatically. Therefore, after switching operation of the main switch an operator, after the film is the bearing circuit pattern has been inserted into the photo tool assembly, that arrange the circuit board blank in position on the vacuum plate and apply vacuum on the plate to lock the circuit board blank. When this vacuum on the plate reaches a preset level, the roll coating the order of the liquid polymer to automatically advance and coat the back of the circuit board blank. The roller coating unit then withdrawn completely. When the roller coating device is in the storage position, the photo tool unit drops to a within the predetermined or preset air gap distance from the coated card. When the photo tool is in position, activate the light source automatically shuts off during the preset time. Light source lan is then turned off automatically, and the photo tool unit 459 708 ïs elevator mechanism raises the photo tool upwards by about 30 cm until then storage position. When the photo tool unit has been raised a position of about S cm, the transport mechanism is raised in the area of tension plate from about 1.3 to 2.5 cm so that it comes in con- pace with the underside of the illustrated card the device is started at the same time so that it bi transported to the next workstation. ready to repeat the cycle for roller coatings Pig. , and the whole transport replace the circuit board The equipment is then and imagery. ll illustrates the multi-station embodiment of the device implementation of the above processes. the single station embodiment according to Pig. the circuit board and the subsequent exposer place, these steps are performed at multiple stations ready places.

While at 9 and 10 the coating of no one is performed on the same the embodiment of the The main advantage of multi-station compared to the embodiment comprising a single station is that daily production can be doubled. This is the result of the fact that one can simultaneously coat a card with liquid polymer and exposes another card to the non-coherent package In more detail, 89 is the occupancy station laying the circuit board with liquid polymer. retractable coating device as in the rate according to Pig. 9 and 10 can be used. where the coating rollers are stationary and coated passes through the rollers, increased the light. for the The same type of single station device A coating device, the circuit board to be preferred, however. This is the case since the card can move continuously therethrough to the sec- exposure to non-coherent collimated light. Suitable coating devices are commercially available from than e.g. the Union Tool Company.

The illustrated coating device is of the preferred type.

The coating device consists of an input conveyor 81, which feeds the disc or card into rollers 83 and 84. Roller 83 is a support roll, while roll 84 is the coating roll. Roller 82 is The liquid polymer stock is maintained in lan rollers 82 and 84. When the card has passed through the and coated, it is transferred to the conveyor 86 enclosed. nypvalsen- nypet mel- ssa val- , which is completely This enclosure consists of a sheet metal enclosure or possibly it may have one or more sides of a parent plast. Conveyor 86 transports the coated card in in the exposure section 90. Immediately before the exposure section pzs 19 459 708 the card can be pre-exposed to a low light level for partial poly- merisation of the coating. This would be to use one low-level non-collimated light radiation, such as through use of fluorescent light with an output within the UV-visible range.

This pre-exposure section 88 (a) is shown in broken lines, followed by as this is an eventual component.

The conveyor 86 delivers the card to the clamping plate 89, which is the same as the clamping plate of single station devices. rates. In other words, a carrier transports the card in position over the clamping plate and it is then pulled back down whereby the clamping plate then carries the card. Control and input directional pins were used to place the card on the clamping the plate until vacuum is applied to lock the card on the plate. Instead of using guide and alignment pins can however, various other equivalent mechanical devices are used.

When the card is in place, the photo tool 93 lowers in place via guideways and an elevator or lift mechanism 94. This photo- tools are the same as for the single station apparatus and are described more in detail in Pig. 12. When the photo tool is in place and in accordance with the card, the non-coherent collimated is activated light source 97. This light source is the same as for single station devices. It may be located in the upper part 91 of this section. of the apparatus or in the lower area 92 with mirrors located in the upper section to change the direction of the light, so that that after passing upward via multiple reflections can be conducted down through the photo tool. Regardless of the arrangement, this one must light source have previously specified characteristics, such as detailed in connection with Fig. 8. The fan and outlet system 98 removes fumes and heat from the appliance.

The lower section 92 also contains the various accessories of the apparatus. accessories, such as a transformer, vacuum pump, electric motors, valves, switches and the like. These are arranged as space allows in this area.

When a card is exposed, the photo tool is retracted upwards, the vacuum holding the card on the plate is relieved and the plate conveyor moves upwards from its rest position in the plate and for the exposed card on the output conveyor 99, which eject the card from the device. Section 88 (b), marked with dashed lines, indicates a possible post-curing site. With ZS ' 459 708 2 ” in other words, there may be a source of non-collimated light with low intensity in this range, whereby the liquid polymer pure would be further polymerized on the card. The conveyor 99 outputs the card to the final processing line for the circuit board. This consists of an apparatus 100, which removes the polymer which does not has been exposed to the collimated light. Typically accomplished this using an alkaline washing solution. The card can then etched in section 101 to remove exposed metal, and in section 102 the liquid polymer which is polymerized exposed to the collimated light, during use of a strong alkaline solution. The latter three sections, which can be considered as a developing line, may consist of commercial available devices from Chemcut Corporation.

It should, however observed , that the card does not have to pass through the entire developer line without it being possible to remove any intermediate processing and then returned to the developing line or removed for any other form of processing.

Pig. 12 shows the lower surface of the photo tool assembly, which years in close air gap relationship with the liquid the polymer coating during the shooting. The unit 55 , which is a metal, such as aluminum minium, has an inner area S9, where the photo tool is located.

Around this opening is a vacuum channel 56. openings 57 are in connection to the pipeline 31 on the upper surface. In this view is displayed six adjusting pins 44. The details 58 are magnets, which are embedded in the surface. These magnets hold a metal frame, which can also be used turned to hold the photo tool (film or sheet) in position.

There may be a set of alignment pins 60 for alignment of the photo tool on the unit. Such alignment losses couple passing through small holes in the photo tool. When using the the operator places the photo tool on the unit and places thin steel tape in the area of the embedded magnets, whereby the photo tool is arranged in a sandwich configuration between the surface and the bands. Vacuum- the system is then activated and the photo tool is further locked in place. The pins 44 are adjusted to provide the appropriate air gap between the polymer coated blank and the photo tool. Foot overkill the unit is then ready for use. L Pig. 13 and 14 are views of the vacuum embodiment. the plate with several chambers. Pig. 13 is a perspective view of the plate.

In this view, the multi-chamber plate has the same appearance as the single-chamber plate. 21 459 708 plate ll. In the single chamber plate according to Fig. 4, a sealing plate fitted to the shoulder 1l (a) to form the vacuum chamber with the vacuum line 30 connected to this sealing plate. The also have the same channels 62, where the conveyor belts are located when they not in use. Furthermore, both plates have a series of holes, which communicates from the upper surface and thereby to the inner chamber maren. In the single chamber plate these are named 14, while those at the multi-chamber plate is designated 63. Fig. 14 is a section through the multi-chamber plate. The side walls 64 also form part of the outer the chamber 67. The inner walls 65 form the walls of the chambers 68, 69 and 70. Openings pass through the lower surface and are connected to a vacuum manifold. The vacuum manifold and connecting pipe shown in Fig. 10. As discussed above, this is a multi- chamber plate assembly more efficiently when circuit boards of different sizes to be manufactured. In other words, you need a small card apply vacuum only to chamber 70, while for the largest the cards apply vacuum to all chambers in order to better keep the circuit board blank in place.

Instead of the vacuum plate with several chambers, you can use a plate where the holes in the upper position can each selectively opens or closes. One technique is to use holes with offset configuration as shown in Fig. 11 (a). The hole is offset and has a closure in the form of a ball. When the plate is made of aluminum or some similar material, magnetic spheres (attracted) to a magnet) is selectively placed in the holes to block them holes when vacuum is applied. To remove the bullets, it is then only necessary to move a magnet over the plate. If the plate is of a magnetic material, can be a magnetic or someone else bullet can be used, the removal being effected by means of a transfer pressure of air inside the plate. This would blow the bullets out of the len.

Any liquid polymer composition which is curable to a solid using non-coherent collimated light and strippable or removable in liquid systems, can be used reversed in the present proceedings. Suitable useful liquid polymer compositions are those described in U.S. Pat. Nos. 3,660,088 and 3,753,720. However, a preferred polymer is an acrylate with terminal unsaturation at one end of the polymer molecule and a terminal carboxyl group at the other end of the polymer molecule. 22 459 708 The terminal unsaturation is curable by free radical polymerization. while using non-coherent collimated light, while the terminal carboxyl group imparts stripped polymer to the cured polymer. solubility using concentrated alkaline solutions.

A polymer which has these characteristics and which is useful in the present processes are a polymer of the following formula: * H3 9? * H3 913% ” CH2 = C-C-O-R1-0-C-N-R2-N-C-O-éPEä; -0-C-C = C_C_OH wherein R 1 is an alkyl group having from 1 to 6 carbon atoms, R 2 the organic moiety in a diisocyanate and is an alic clay and aryl is it cyclic group el- , alkyl or arylalkyl group, and (PE) X is a poly- ester or polyether extension chain unit, where x is an integer of from 2 to SO.

This polymer can be used alone or in combination with one viscosity modifiers , such as a carboxy-terminated hydroxy ethyl methacrylate of the formula: H3 91: H c = c-c-o-ca -ca -o -o-c-c-c-cooa. 2 "2 2 0 By adding varying amounts of the carboxy-terminal the rade-hydroxyethyl methacrylate can increase the viscosity of the liquid the polymer composition changes.

Other viscosity modifiers can also be used.

Useful in the liquid polymer composition is also a photosensitizer, by way of non-limiting example may be mentioned benzophenone, acetophenone, acenaphthenic quinone, o-methoxybenzo phenone, dibenzosuberone, anthraquinone, hexanophenone or 2,2-dimethoxy- -2-phenylacetophenone- These substances improve free radical production ring and thus accelerates the curing process. Other photosensitizers motorizers can be used.

These are the primary additives in the preferred liquid polymer compositions- However, these compositions may also contain an epoxy acrylate, a multifunctional acrylate such as hexanediol diacrylate, a multifunctional thiol such as pentaerythritol tetra- kis (β-mercaptopropionate) and a phenolic stabilizer such as hydroquinone monomethyl ether or trihydroxybenzene. These additives agents stabilize the composition and also provide agents to combine the polymerized carboxy-terminated acrylic with itself and also with the carboxy-terminated hydroxy- - * - 459 708 the ethyl methacrylate. The bridging gives a harder cured polymer and one that generally has higher thermal stability. When e.g. solder masks are to be made, a bridging 23 or crosslinking agent, so that the polymer can better withstand it temperature of about 200 or 260 ° C that applies to tin-lead solder spray.

The present description has focused primarily on copying. pair-coated or roll-plated circuit boards, as these are currently the dominant printed circuit boards manufactured in mercilessly. However, the processes are useful for other metal coatings or claddings and should also be operational with non-metallic conductive coatings. Therefore, when is used, it is understood that this also includes vivalent (roll) plating.

The present description is directed to the use of non- -coherent collimated light. A light with the specifications used provided herein has been developed for the present use of the Optical Radiation Company. A laser light beam is a coherent collimated light beam and can not be used instead of the non-coherent collimated the light. If a laser beam is to be used, it must it is set via a computer system to scan the pattern of it desired circuit. Such a laser system would be very expensive. rafe than the arrangements for non-coherent collimated light and photo tools that have been discussed in detail in the present text and would_refer to a longer period of time in the exposure section, which to a production loss. Furthermore, a laser system would not meet the image deviation factor of not more than 12.5 μm.

The following examples describe the invention in more detail.

EXAMPLE 1 This example describes a process for the preparation of one of the preferred liquid polymer compositions.

A resin cooker is equipped with a stirrer, thermometer, drying tube and additive funnel. methyl ether, 5.8 g of triphenylphosphite and 0.15 g of dibutyltin dilaurate 185 g of toluene diisocyanate, 0.63 g of hydroquinone mono- added to this boiler. When heating the mixture to -35 ° C, 189 g of hydroxypropyl acrylate are added dropwise, wherein the mixture is allowed to form an exotherm to 65 ° C.

The temperature is kept between 60 and 6S ° C for 1 hour, after which in the main essentially all hydroxy groups are consumed, and the NCO content reaches the 1.77i 0.1 meq / g, which is determined by titration with dibutyl- 459 708 24 amine. Then 785 g of molten poly (diethylene glycol) are added. adipate) with a molecular weight of 1000 together with 0.15 g of di- butyltin dilaurate catalyst. The reaction mixture is maintained 65-70 ° C for approximately 6 hours until the isocyanate group the perna are consumed. 385 g of hydroxyethyl methacrylate and 0.42 g of hydroquinone are added then to this mixture. When the reaction mixture has been white homogeneous and the temperature has dropped below 65 ° C 248 g of solid maleic anhydride and 8 g of dibutyltin dilaurate.

Slowly (for about 1 hour) the reaction mixture is heated to S5 ° C to dissolve the maleic anhydride. The heating continues and the temperature is maintained at 75-80 ° C for about 6 hours, until its that the maleic anhydride is completely reacted, which is evident from the absence of peaks at 1845 and 1975 cm-1 in an IR spectrogram. The final product thus obtained is a viscous liquid with a viscosity of 5700 cP at 2S ° C and an acid group content of 1.4 meq / a. ' The prepolymer has the following composition: 9 9 9 ° 9 9 9 9 9 9 9 n _ H2C = C- C-O-Clíz-CP- (IN- NC-üf fi üízüízOCl-IZÜ-Iz-O-C-C 41-18 -C-Ošt-SC-IFFC-C-OH CH3 _ ' 9 0 HIKO ' 'll d} ¶C-ïïäík flfl O Eígë g {H ti sæmwnsnæ 2 J ZGE - - EXAMPLE 2 The following composition is prepared from the resin product from Example 1 and used in a printed circuit board: Component The resin product from Example 1 etching resistance processes for the production of Weight percent 79.93 Epoxy acrylate ("Bpocryl 370") 6.93 "Irgacure S51" 0.92 Benzophenone 2.76 Hydroquinone monomethyl ether 0.046 Pyrogallol 0.023 Modaflow 2.30 "chrømophral small" (ciba-Geigy) o, fi4 Pentaerythritol tetrakis- (B-mercapto- propionate) 6.46 '2 1 5 459 708 This composition has a Brookfield viscosity of 3450 cP at z4 ° c.

A substance for a printed circuit board and consisting of epoxy fiberglass and roll-plated copper were cleaned by water scrubbing with pumice stone using a "Scotch Brite" sponge to remove corrosion and foreign materials. The subject was then coated with the above composition to about 63 μm for 60 seconds through a photographic negative with a 0.63 mm air gap to the coating on the card using a mercury vapor lamp of medium pressure at a distance where the radiation intensity is about 25 milliwatts / cmz. The exposed card is then spray washed. using a 5% sodium carbonate solution at room temperature for 10 seconds followed by rinsing with water and air drying, whereby the cured photoresist material is left as an image with high accuracy and resolution.

The washed card with the circuit pattern is then exposed etching with hydrochloric acid cupric chloride for 60 seconds at S2 ° C to solution of the copper metal in the uncoated areas. The cured po- the lyme resistance remains intact and provides good protection for the person in question copper against the etchant. The cured polymer is then removed using a 5% sodium hydroxide solution at 55 ° C. About 30 seconds are required for this removal. The copper left on the card turns out to be excellent in question on detail and integrity. The circuit board cables are well shaped with sharp edges and have side walls, which are substantially perpendicular against the substrate. In continuity and resistance testing shows that there is no short circuit and that the the punch for a similar circuit is essentially constant. Furthermore, the liquid polymer did not penetrate into any of the holes through the card.

EXAMPLE 3 This example illustrates the production of plate resistors using the liquid polymer of Example 2. A circuit board blank (copper plating of 304 g / m2) is then coated with the liquid polymer composition used in Example 2 by reverse or backing. The coating thickness was nomi- nellt 48 um. A collimated mercury-zenon light from Optical Radiation Company was used as an energy source. The distance of the photo tool taps were set to give an air gap of about 750 pm Cfotoverktg- the goat consisted of opaque areas in the same pattern as the desired one 459 708 = 26 the circuit. The liquid polymer was exposed to mercury. -zenon source _i_ 30 seconds. The card was then transported to a Chemcut spray washer, in which it was introduced contact with sodium carbonate at a pH of 10.5 for 10 seconds.

The exposed copper metal is then electroplated with tin-lead and the cured polymer are removed in a spray bath below use of a 5% sodium hydroxide solution at S4-60 ° C.

The stripping is completed in 30 seconds and the card is rinsed with water. The exposed copper plating is then removed through etching with a SN hydrochloric acid-cupric chloride solution at 52 ° C. The etching is completed in 60 seconds and the card rinses ten. The circuit had high resolution and in EXAMPLE 4 then with water gave short circuits.

This example illustrates the production of solder masks using the liquid polymer of Example 2.

A pre-printed copper circuit board was fastened to one clamping plate and by means of a roller coating device coated by reversing rollers a continuous layer of it the liquid polymer composition of Example 2 on the circuit board. Ask- the laying was about 38 μm thick on the circuit and from about 100 to 125 μm thick in the non-circuit bearing areas. A photo tool, which is transparent with the exception of in the circuit surfaces where the solder is to be set aside, placed in the exact direction with the circuit board. It used the air gap was 500 μm. A mercury-zenon light source with collimated light, from the Optical Radiation Company, was used to cure poly- lakes. The light went out after 60 seconds and the card was spray washed with an aqueous sodium carbonate solution at 10.5 Spray washing was continued for 30 seconds. dried. in pH.

The card was removed and The circuit board was then placed in a wave soldering apparatus, where solder was applied to the exposed or exposed copper surface.

No damage to the cured polymer occurred due to con- rate with molten solder. The cured polymer left the card as a protective layer.

EXAMPLE S es on circuit The procedure of Example 2 was repeated but in use as a photo tool of a circuit pattern, where the circuit lines or the lines shall be 150 μm wide and the distance between the the conductors are 150 pm. The photo tool was a polyester film with a series 150 μm wide opaque areas separated from each other by 27 459 708 150 μm wide transparent areas. A mercury-zenon light source with collimated light from the Optical Radiation Company was used for the imagery. The other steps were the same as in Example 2. It obtained circuit board had well-defined copper circuit lines, which had side walls that were perpendicular to the card. None of the circuit the wires had a short circuit. The circuit lines were nominal 150 pm wide, the distances between them also being nominally 150 pm.

As for the preferred class of polymers which can be used used in accordance with the present invention, the contents of U.S. Patent Application 06/225,809, filed January 16, 2006 nuari l98l (corresponds to the Swedish patent application 19069 in horizontal text.

Claims (27)

10 15 20 25 30 35 459 'los 48 PATENTKRAV A method of making printed circuit boards, comprising: (a) providing or providing a circuit board substrate; (b) coating at least a portion of the substrate with a liquid polymer composition which is curable by non-coherently collimated light radiation; "(c) forming an air gap by placing a photo tool in close cooperation with the liquid polymer coated surface; (d) contacting the photo tool with non-coherent collimated light radiation with a half angle of not more than about 3 degrees and an image dimension deviation factor of not more than about 13 .mu.m, whereby said light selectively passes through parts of the photographic tool, comes into contact with the surface coated with liquid polymer and causes the liquid polymer to harden into a solid polymer when it comes into contact with the light (e) interrupts the application of said light radiation and removes the substantially uncured liquid polymer, leaving a solid cured polymer in the circuit board substrate. Method according to claim 1: characterized in that the air gap between the photographic tool and the surface coated with liquid polymer, while the photographic tool is kept in contact with the light radiation, is maintained at from about 0.13 to 13 mm. in A method according to claim 1 or 2, characterized in that the circuit board substrate has a metal plating on at least one side and that the liquid polymer, which has remained liquid after the step where the photographic tool has been brought into contact with the light radiation, is removed by contact with an aqueous solution, in which the polymer is at least partially soluble, whereby the metal plating is partially exposed. k á n n e - in that the liquid polymer composition is coated on the substrate in a thickness of from about 2.5 to 250 .mu.m by roll coating. A method according to any one of claims 1-3, wherein 10 15 20 ZS 30 35 40 Qq 459 708 A method according to claim 4, characterized in that the roll coating is a reverse roll coating, wherein the coating has a thickness of from about 13 to 125 .mu.m. A method according to any one of claims 1-S, characterized in that the non-coherent collimated light radiation has a half-angle of not more than about 1.5 degrees and a car deviation of not more than about 6 .mu.m. A method according to any one of claims 1-6, characterized in that in addition (f) treating the areas not covered with said cured liquid polymer, to form a defined circuit; and (g) removing the cured liquid polymer from the substrate. A method according to claim 7, characterized in that the cured polymer is removed by contact with an aqueous solution containing cations derived from a strong base. 9. A method according to claim 8, characterized in that the cations derived from a strong base are selected from the group consisting of sodium, potassium and ammonium cations. 10. A method according to any one of the preceding claims, characterized in that the liquid polymer consists primarily of a urethane molecule with terminal unsaturated at one end and a terminal carboxy group at the other end. ll. Process according to claim 10, characterized in that the liquid polymer consists primarily of: H 0 OHHO 0 HHO 1 H 'II IH II: 1 H CH 2 = CCO-R1-OCN-R2-NC-O- {PE} k0-CC = CC-OH wherein R 1 is an alkyl group having from 1 to 6 carbon atoms, R 2 is the organic moiety of a diisocyanate and is an alicyclic group or an aryl, alkyl or arylalkyl group and (PE) X is a chain extending polyester or polyether unit, where x is an integer from 2 to S0. A process according to claim 11, characterized in that the liquid polymer composition contains a carboxy-terminated methacrylate and a photosensitizer. 13. A method according to claim 12, characterized in that the liquid polymer composition contains a crosslinker containing terminal unsaturated groups. A method according to claim 12, characterized in that the liquid polymer composition comprises a crosslinker containing terminal thiol groups. A method according to any one of claims 7-14, characterized in that the treatment in step (f) is carried out by plating metals on areas of the circuit board substrate from which the liquid polymer has been removed; then removing (g) the cured liquid polymer; and (h) treating the areas not covered by the plated metal to form a defined circuit. Apparatus for producing printed circuit boards according to any one of claims 1 to 15, characterized in that it comprises: (a) means for coating at least a part of one side of a printed circuit board blank (10) with a liquid polymer (l7); (b) means for holding the liquid polymer coated circuit board holder in the set or start position; (c) a non-coherent collimated light source (27, 97) having a half angle of not more than about 3 degrees and an image dimensional deviation factor of not more than about 13 mm arranged so that the light therefrom comes into contact with the means for holding (d) a photographic tool assembly (37, 90, SS) located above the holding means for the circuit board blank and in the path of the non-coherent collimated light beam, so that a photographic tool (19, 93) in said assembly is not in contact with the liquid an air gap (18) is provided therebetween; and (e) means for activating the light source for a selected period of time. Apparatus according to claim 16, characterized in that the printed circuit board blank (10) is held by means of retractable guide pins (12, 44) and that the means for holding in the setting position is a plate (11, 61). holes (14, g of the circuit board blank; the polymer and so on, 89) with a plurality 63, S7) in the upper surface, through which vacuum is applied to hold the printed circuit board blank Apparatus according to claim 17, that the plate has an inner multiple chamber, on the upper surface. k a n n e t e c k n a d of which vacuum can be selectively applied to the plurality of holes (14, 63, 57) which traverse the upper surface of the plate (11, 61, 89). Apparatus according to any one of claims 16-18, characterized in that the coating means is a rolling device (15, 16; 83, 84) which may be a coating device 10 15 20 25 30 '37 459 708 Apparatus according to claim 19, characterized in that the roller coating device (15, 16; 83, 84) is arranged to pass back over the printed circuit board name. (10). Apparatus according to claim 19, characterized in that the roller coating device (15, 16; 83, 84) is stationary and that the printed circuit board name (10) passes through the roller coating device. Apparatus according to any one of claims 16-21, characterized in that the photo tool assembly (37, 90, 55) comprises vacuum means for holding the photo tool (19, 93) in position. Apparatus according to any one of claims 16 to 22, characterized in that it comprises means for moving the sensor - the photographic tool assembly (37, 90, SS) in and out of close cooperation with the holding means for the circuit board blank. Apparatus according to claim 19, characterized in that the coating means is a roller coating device (15, 16; 83, 84), which is retractably located next to the coating means for the circuit board blank (10) and which coats the printed circuit board frame while this blank is held. ZS. Apparatus according to claim 16, characterized in that the coating means is stationary and that the printed circuit board blank (10) passes through the coating means for the purpose of coating. Apparatus according to any one of claims 16-25, characterized in that the light source (27, 97) is a mercury arc source. Apparatus according to any one of claims 16-25, characterized in that the light source (27, 97) is a mercury xenon source. k å n n e -