TWI712350B - Method of manufacturing printed circuit board assembly, method of clamping electronics boards for processing and carrier - Google Patents

Abstract

A method of manufacturing a printed circuit board assembly, comprises clamping an electronics board to a carrier by applying an electrostatic field to the electronics board and applying print medium, for example conductive print medium, to the electronics board using a printing process, the electronics board remaining clamped to the carrier by the electrostatic field during the printing process. Additional boards may be successively clamped to the carrier, enabling accurate placement of each board.

Description

Method for manufacturing printed circuit board components, method for holding electronic boards for processing And carrier

The invention relates to a method of manufacturing printed circuit board components, a method of clamping an electronic board for processing, and a carrier.

Industrial screen printers usually apply a pattern of conductive printing media (such as solder paste or conductive ink) through holes in a screen (sometimes called a foil or stencil) by using an angled blade or squeegee. The conductive printing medium is applied to a flat work piece (such as a circuit board or an electronic board). A surface mount technology (SMT) process for placing electronic components on solder paste pads on the board can then be used to make the resulting printed circuit board (PCB) filled with components to form printed circuit board components. The component can then be passed through a reflow oven to complete the soldering process, thereby ensuring the electrical and mechanical connection of the component to the substrate.

However, this known method has a problem that is the trend of miniaturization of components. As the size of components decreases, the solder paste pads required to attach the components must be reduced in size accordingly. In addition, circuit boards are becoming thinner and thinner, and flexible boards (so-called "Flex-PCBs" or "flexible printed PCBs") are becoming more common. All these trends require very precise printing, which puts pressure on productivity and manufacturing quality. PCB has related tolerances and distortions, so it is difficult to accurately align all necessary components.

As a specific example, a flexible PCB usually includes very small components in a "cluster" and also panelled, so that each panel contains at least one of these clusters. Each component has its own associated tolerance, and in addition, each cluster also has its own tolerance relative to clusters in other panels. Therefore, the tolerance may be higher than the accuracy required for successful printing in a cluster.

Currently, a vacuum carrier is used to support the plates during the printing process, thereby vacuum clamping each plate to the carrier. Using such a carrier, it is impossible to provide multiple alignments to the board, so it is only possible to print at an average position, that is, to align the board on the carrier at a position optimized for all clusters at the same time, rather than at the best for each cluster Realign between positions. Therefore, printing accuracy is impaired.

The present invention attempts to overcome these problems and provides as an example for clamping such a flexible PCB. Other objects of the present invention include providing a simplified and more accurate board assembly process.

According to the present invention, this object is achieved by using a new type of carrier that uses electrostatic clamping instead of vacuum clamping.

This solution is completely contrary to the traditionally recognized concept in the printing industry, which generally believes that it is necessary to avoid electrostatic charges in the printing press. However, it has been determined that in practice electrostatic fixation is a viable clamping option, because the generated field exists with significant strength only in the surface of the material or component being clamped.

If the non-conductive material has electrical polarization properties, the material can be clamped in this way. The external electric field applied to the dielectric material can cause displacement elements of the combined charged elements. These are elements that bind to molecules and cannot move freely around the material. The positively charged elements shift in the direction of the field, and the negatively charged elements are Shift in the opposite direction. The molecule can maintain a neutral charge, but still form an electric dipole moment.

The electrostatic field can be maintained for several days without the need for a power source, which allows the same carrier to be used in a variety of different processes, such as printing, placement, and reflow. In addition, the high temperature of the reflow oven does not affect the clamping force.

According to a first aspect of the present invention, there is provided a method of manufacturing a printed circuit board component, including the following steps: i) clamping the electronic board to the carrier by applying an electrostatic field to the electronic board; ii) using a printing process to print the printed medium Applied to an electronic board, where the electronic board remains clamped to the carrier by an electrostatic field during the printing process.

According to a second aspect of the present invention, there is provided a method for holding an electronic board for processing, including the following steps: i) providing a carrier including an electrostatic field generator, the electrostatic field generator is suitable for at least two spaces of the carrier The clamping electrostatic field is generated at the upper separated area; ii) the first electronic board is placed on the carrier at the first determined position in the first area of the carrier; iii) by generating the electrostatic field at the first area, the first An electronic board is clamped to the carrier; iv) the second electronic board is placed on the carrier at a second determined position in the second area of the carrier; and v) the second electron is removed by generating an electrostatic field at the second area The plate is clamped to the carrier.

According to the third party aspect of the present invention, a carrier for the method according to any one of the first aspect and the second aspect is provided.

As used in the present invention, the term "electronic board" is used to refer to flexible or rigid, printed or unprinted, used to carry electronic circuits, electronic components or electronic equipment. Printed boards, substrates or workpieces.

According to a preferred embodiment of the present invention, the electrostatic carrier can individually clamp a single, single circuit or cluster (for example, a flexible PCB). The corresponding board can be accurately placed on the carrier, for example, using a pick-and-place machine, and then the board can be clamped in place by turning on an electrostatic field. The board can be accurately held in this position throughout the manufacturing process (ie, printing, assembly, and reflow soldering). Additional circuits or clusters can be separately placed on the carrier and clamped separately, so that each circuit or cluster board can be clamped in an optimal position. At the end of the manufacturing process, the clamping can be released by discharging the electrostatic field.

Other specific aspects and features of the present invention are set out in the appended claims.

1: Electrostatic carrier

2: carrier base

3: Lower dielectric insulation layer

4: Electrode layer

5: Upper dielectric insulation layer

6a, 6b: electronic board

7: electrical contacts

8a-8c: anode structure

9a-9c: Cathode structure

10: Carrier benchmark

11: Board reference

Fig. 1 schematically shows a side view of an electrostatic carrier according to an embodiment of the present invention.

Fig. 2 schematically shows a cross-sectional view of the electrostatic carrier of Fig. 1 along the line A-A.

Fig. 1 schematically shows a side view of an electrostatic carrier 1 according to an embodiment of the present invention. The carrier 1 is formed as a layered structure with a flat top surface suitable for supporting at least one electronic board on top in use, two separate boards 6a, 6b being supported are shown in FIG. 1 . The lowest layer of the carrier 1 in use is the carrier base 2, which provides the carrier 1 with structural rigidity. The carrier base 2 may include various materials, such as glass, silicon, metal, or organic materials. In the illustrated embodiment, a lower dielectric insulating layer 3 formed by thin film technology is located on top of the carrier base 2. The lower dielectric insulating layer 3 is only required when the carrier base 2 is formed of a conductive material such as aluminum Al or other metals. The electrode layer 4 is placed on top of the lower dielectric insulating layer 3, which will be described in more detail below. If the lower dielectric insulating layer 3 is not present, the electrode layer 4 can be directly positioned on the carrier substrate 2. The upper dielectric insulating layer 5 is placed on top of the electrode layer 4, and the upper dielectric insulating layer 5 may be formed similarly to the lower dielectric insulating layer 3. The upper and lower dielectric layers may be formed of various materials, including, for example, polymers, such as polyvinyl chloride (PVC) or polycarbonate, or non-polymer materials, such as SiO ₂ . The individual layers can be formed separately and then attached together, for example, by using a small amount of adhesive or thin film technology.

The upper dielectric insulating layer 5 serves as a supporting surface for one or more electronic boards 6a, 6b. It should be noted that the thickness of the upper dielectric insulating layer 5 affects the clamping force available for electronic boards, and therefore, in order to ensure effective clamping, the upper dielectric insulating layer 5 should be kept as thin as possible. If PVC or polycarbonate is used as the upper dielectric insulating layer 5, a thickness of about 10 μm can currently be reached, while a layer thickness of about 50 nm is possible using thin film technology, for example, for SiO ₂ .

Although not shown in FIG. 1, the carrier can also be provided with identification marks, such as 2D or 3D barcodes or RFID tags, so that the carrier can be tracked in the subsequent manufacturing process.

Fig. 2 schematically shows a cross-sectional view of the electrostatic carrier of Fig. 1 along the line A-A. In this view, the internal structure of the electrode layer 4 is visible. The relative overlapping positions of the electronic boards 6a, 6b are shown in outline, and as explained in more detail below, various carrier fiducials 10 on top of the upper dielectric insulating layer 5 are also shown. The electrode layer 4 includes an electrostatic field generator having at least one (three in this embodiment) electrostatic field sub-generator in the form of an electrostatic clamping area defined by a capacitive interdigital comb electrode pattern. Each pattern is formed by an interdigital arrangement of anode electrode comb structures 8a-8c and cathode electrode comb structures 9a-9c. Each comb structure can be independently electrically connected to an external dc voltage source (not shown) through a corresponding electrical contact 7. When connected in this way, each sub-generator will generate an electrostatic field, which can be The electronic board on the top surface of the carrier 1 exerts a downward force or clamping force. To facilitate connection, each electrical contact 7 is conductively connected to a point on the outer surface (not shown) of the carrier 1 that is connected to an external voltage.

The electrode layer 4 can be formed in various ways obvious to those skilled in the art, such as by printing the desired electrode pattern on the dielectric substrate, by forcing a conductive paste through a suitable mask, or by using PCB manufacturing technology or thin film technology. .

The three patterns shown are spatially separated along the carrier 1, so in use, that is, when each pattern is connected to an external voltage source, three local areas of the carrier 1 with a relatively high electrostatic field will be generated Or district. As mentioned above, each pattern can be individually connected to an external voltage source, so each pattern and thus each field area can be individually and selectively actuated. In this way, different electronic boards 6 can be individually or sequentially clamped to the corresponding areas of the carrier 1 that generally correspond to the respective patterns. Figure 2 shows an embodiment in which one electronic board can be clamped to each area, but in other embodiments, more than one electronic board can be clamped to the same area, however such an embodiment would be Disadvantageously, this is because the two plates will be clamped at the same time, so it will not be possible to clamp the first plate, then locate and clamp the second plate.

FIG. 2 shows a plurality of carrier fiducial marks ("fiducials") 10, which are optically identifiable marks on the upper surface of the carrier 1. In addition, and as known in the art, each electronic board 6a, 6b is provided with a corresponding board reference 11. The carrier reference 10 and the board reference 11 can illustrate the precise placement of the electronic board 6 on the carrier 1, as explained in more detail below.

An exemplary method of manufacturing a printed circuit board component according to the present invention will now be described.

In the initial step, a carrier (such as the carrier shown in FIGS. 1 and 2) is provided and discharged so that the carrier does not generate an electrostatic field.

The first electronic board can then be placed on the carrier at a first determined position in the first area of the carrier. Such placement can be performed, for example, using a pick-and-place machine capable of highly accurate placement. The correct positioning of the electronic board can be achieved by positioning the board reference 11 on the electronic board relative to the carrier reference 10. Generally, the pick and place machine includes an optical position sensor, which is adapted to recognize these fiducials.

Then, by connecting the cathode and anode electrodes of each electrostatic field generator to a voltage source, an electrostatic field is generated at the first region, thereby clamping the first electronic board to the carrier.

If necessary, and when the first electronic board is clamped to the carrier, additional electronic boards may be sequentially placed on the carrier at various determined positions in various regions of the carrier in a similar manner to the first electronic board, and After positioning, it is clamped by generating an electrostatic field at the corresponding area.

It should be noted that this method allows each board to be optimally placed, which is impossible with the known vacuum clamping method. In particular, this method can place and clamp a single flexible PCB with high accuracy.

Once the electronic board is clamped to the carrier, the individual electrostatic field generators can be disconnected from the voltage source because the electrostatic field can be kept high enough to perform clamping in several days. This enables the electronic board to remain clamped on the same carrier during more than one manufacturing process, and the carrier can be transported between processes.

Therefore, after clamping as described above, for example, by aligning a carrier fiducial or a plate fiducial as known in the art, the carrier can be accurately positioned in the printing press. A printing process can then be used to apply a printing medium (for example, a conductive printing medium, such as solder paste) to the electronic board, usually including by sweeping a squeegee blade over an appropriately patterned stencil, forcing the printing medium through holes in the stencil. The printing medium is applied to the top surface of the electronic board.

After this printing process, the printed electronic board can be equipped with one or more electronic components while the electronic board remains clamped to the carrier. Advantageously, the carrier can be transported to a pick-and-place machine, for example along a conveyor belt, and accurately positioned in the placement area of the machine. As is known in the art, the carrier and/or plate fiducials can again be used to ensure proper alignment.

After the assembly process, the assembled electronic board can be subjected to a reflow soldering process, while the electronic board remains clamped to the carrier. Advantageously, the carrier can be transported, for example, along a conveyor belt to a reflow oven for heat treatment, as is well known in the art. The electrostatic clamping function of the carrier is not affected by the high temperature in the furnace.

After reflow soldering, the or each electronic board can be released from the carrier by discharging the corresponding electrostatic field (for example, by short-circuiting the anode and cathode electrodes of each pattern).

In all these steps, the carrier can be tracked by correctly reading the carrier identification mark of each machine so that the board or each board on the carrier can be processed correctly. The above-mentioned embodiments are only exemplary, and in this case Other possibilities and alternatives within the scope of the invention will be obvious to those skilled in the art. For example, the interdigital comb electrode pattern shown in FIG. 2 can be replaced with any capacitive electrode pattern. Each carrier can be equipped with one or more patterns, the upper limit being determined by the physical size of the carrier in question. The carrier is capable of holding various materials, clusters, and components, including thin glass (e.g., about 150 μm thickness) for microstructuring.

4: Electrode layer

6a, 6b: electronic board

7: electrical contacts

8a-8c: anode structure

9a-9c: Cathode structure

10: Carrier benchmark

11: Board reference

Claims (11)

A method of manufacturing a printed circuit board component includes the following steps: i) clamping an electronic board to a carrier by applying an electrostatic field to the electronic board; ii) applying a printing medium to the electronic board using a printing process, wherein The carrier includes an electrostatic field generator for generating the electrostatic field, and the electronic board is kept clamped to the carrier by the electrostatic field during the printing process. According to the method described in item 1 of the scope of patent application, the electrostatic field generator includes at least two spatially separated and individually actuable electrostatic field generators, and the electrostatic field generators are suitable for A clamping electrostatic field is generated in the corresponding area of the carrier. The method described in item 2 of the scope of patent application, wherein step i) includes clamping the electronic board to the carrier at a first determined position in the first region of the carrier, and While the board is clamped to the carrier, the second electronic board is clamped to the carrier at a second determined position in the second area of the carrier. The method described in item 1 of the scope of the patent application, wherein step i) includes placing the electronic board on the carrier using a pick-and-place machine. The method described in item 1 of the scope of the patent application includes the step of assembling one or more electronic components for the electronic board printed during the printing process, wherein, during the entire printing and assembling process, the electronic board Keep clamped to the carrier. The method described in item 5 of the scope of patent application, wherein the electronic board is assembled using a pick and place machine. The method described in item 5 of the scope of patent application includes the step of performing a reflow soldering process on the assembled electronic board, wherein the electronic board remains clamped during the entire printing, assembly and reflow soldering process To the carrier. A method for holding an electronic board for processing includes the following steps: i) providing a carrier including an electrostatic field generator adapted to generate a clamping electrostatic field at at least two spatially separated areas of the carrier; ii) in a first area of the carrier Place the first electronic board on the carrier at the first determined position; iii) Clamp the first electronic board to the carrier by generating an electrostatic field at the first area; iv) Placing a second electronic board on the carrier at a second determined position in the second area of the carrier; and v) clamping the second electronic board to the carrier by generating an electrostatic field at the second area The carrier. The method according to item 8 of the scope of patent application, wherein the carrier includes at least one fiducial, so that the first electronic board and the second electronic board can be positioned relative to the carrier. The method according to item 8 or 9 of the scope of patent application, wherein the first electronic board and the second electronic board are placed on the carrier by a pick-and-place machine. A carrier used in the method described in item 8 or 9 of the scope of the patent application includes an electrostatic field generator adapted to generate a separate Controlled clamping electrostatic field.

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