PCB News - PCB multilayer board pressing production

1. Autoclave pressure cooker
It is a container filled with high-temperature saturated water vapor and high pressure can be applied. The laminated substrate (Laminates) sample can be placed in it for a period of time to force moisture into the board, and then taken out the sample again. Place it on the surface of high-temperature molten tin and measure its "delamination resistance" characteristics. This word is also synonymous with Pressure Cooker, which is commonly used in the industry. In the multi-layer board pressing process, there is a "cabin press method" with high temperature and high-pressure carbon dioxide, which is also similar to this type of Autoclave Press.

2. Cap Lamination method
It refers to the traditional lamination method of early multi-layer boards. At that time, the "outer layer" of MLB was mostly laminated and laminated with a thin substrate of single-sided copper skin. It was not until the end of 1984 that the output of MLB increased significantly. Copper skin types large or mass pressing method (Mss Lam). This early MLB pressing method using a single-sided copper thin substrate is called Cap Lamination.

3. Crease wrinkles
In multi-layer board pressing, it often refers to the wrinkles that occur when the copper skin is improperly handled. Such shortcomings are more likely to occur when thin copper skins below 0.5 oz are laminated in multiple layers. To

4. Dent depression
Refers to the gentle and uniform sag on the copper surface, which may be caused by the local point-like protrusion of the steel plate used for pressing. If there is a neat drop in the faulty edge, it is called Dish Down. If these shortcomings are unfortunately left on the line after copper corrosion, the impedance of the high-speed transmission signal will be unstable and noise will appear. Therefore, such a defect should be avoided as much as possible on the copper surface of the substrate. 

5. Caul Plate partition
When the multilayer board is pressed, in each opening of the press, there are often many "books" of bulk materials (such as 8-10 sets) to be pressed in each opening of the press, and each set of "bulk materials" ( Book) must be separated by a flat, smooth and hard stainless steel plate. The mirror stainless steel plate used for this separation is called Caul Plate or Separate Plate. At present, AISI 430 or AISI 630 are commonly used. To

PCB multilayer Board

6. Foil Lamination copper foil pressing method
Refers to the mass-produced multilayer board, the outer layer of copper foil and film is directly pressed with the inner layer, which becomes the multi-row board large-scale pressing method (Mass Lam) of the multilayer board, which replaces the early tradition of single-sided thin substrates Suppress legal.

7. Kraft Paper Kraft Paper
When laminating (laminating) multi-layer boards or substrate boards, kraft paper is mostly used as a heat transfer buffer. It is placed between the hot plate (Platner) of the laminator and the steel plate to ease the heating curve closest to the bulk material. Between multiple substrates or multilayer boards to be pressed. Try to reduce the temperature difference of each layer of the board as much as possible. Generally, the commonly used specifications are 90 to 150 pounds. Because the fiber in the paper has been crushed after high temperature and high pressure, it is no longer tough and difficult to function, so it must be replaced with a new one. This kind of kraft paper is a mixture of pinewood and various strong alkalis. After the volatiles escape and the acid is removed, it is washed and precipitated. After it becomes pulp, it can be pressed again to become rough and cheap paper. material.

8. Kiss Pressure, low pressure
When the multi-layer board is pressed, when the plates in each opening are placed in position, they will start to heat and be lifted up by the hottest layer of the bottom layer, and lifted up with a powerful hydraulic jack (Ram) to press each opening ( Bulk materials in Opening) are bonded together. At this time, the combined film (Prepreg) begins to gradually soften or even flow, so the pressure used for the top extrusion can not be too large to avoid slippage of the sheet or excessive outflow of the glue. This lower pressure (15-50 PSI) initially used is called "kiss pressure". However, when the resin in the bulk materials of each film is heated to soften and gel and is about to harden, it is necessary to increase to the full pressure (300-500 PSI), so that the bulk materials can be tightly combined to form a strong multi-layer board. 

9. Lay Up overlap
Before lamination of multilayer boards or substrates, various bulk materials such as inner laminates, films and copper sheets, steel plates, kraft paper pads, etc., must be aligned, aligned, or registered up and down for convenience. It can be carefully fed into the pressing machine for hot pressing. This kind of preparatory work is called Lay Up. In order to improve the quality of the multilayer board, not only this kind of "stacking" work must be carried out in a clean room with temperature and humidity control but also for the speed and quality of mass production, generally, those with less than eight layers use the large-scale pressing method (Mass Lam ) In construction, even "automated" overlapping methods are needed to reduce human errors. In order to save workshops and shared equipment, most factories generally combine "stacking" and "folding boards" into a comprehensive processing unit, so automation engineering is quite complicated. To
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10. Mass Lamination large pressure plate (laminated)
This is a new construction method that abandons "aligning tips" in the multi-layer board pressing process and adopts multiple rows of boards on the same surface. Since 1986, when the demand for four- and six-layer boards has increased, the pressing method of multi-layer boards has been greatly changed. In the early days, there was only one shipping board on a processing board to be pressed. This one-to-one arrangement has been broken through in the new method. It can be changed to one-to-two, one-to-four, or even more according to its size. The row boards are pressed together. The second new method is to cancel the registration pins of various bulk materials (such as inner sheet, film, outer single-sided sheet, etc.); instead, use copper foil for the outer layer, and pre-make "targets" on the inner layer board., To "sweep" out the target after pressing, and then drill the tool hole from its center, then it can be set on the drilling machine for drilling. As for the six-layer board or the eight-layer board, the inner layers and the sandwich film can be riveted first with rivets, and then pressed together at high temperature. This simplifies, fast, and enlarges the area of the pressing, and can also increase the number of "stacks" (High) and the number of openings (Opening) according to the substrate-based approach, which can reduce labor and double the output, and even automate. This new concept of pressing plate is called "large pressing plate" or "large pressing plate". In recent years, many professional contract PCB manufacturing industries have emerged in China. 

11. Platen hot plate
It is a movable platform that can be lifted and lowered in the laminating machine required for multilayer board laminating or substrate manufacturing. This kind of heavy hollow metal table is mainly to provide pressure and heat source to the plate, so it must be flat and parallel at high temperatures. Usually, each hot plate is pre-buried with steam pipes, hot oil pipes, or resistance heating elements, and the outer edges of the surroundings also need to be filled with insulating materials to reduce heat loss, and a temperature sensing device is provided to enable temperature control. 

12. Press Plate steel plate
It refers to the substrate or multilayer board used to separate each set of loose books (referring to a book composed of the copper board, film, and inner board) when the substrate or multi-layer board is laminated. This kind of high-hardness steel plate is mostly AISI 630 (hardness up to 420 VPN) or AISI 440C (600 VPN) alloy steel. The surface is not only extremely hard and flat but also after careful polishing to a mirror-like surface, the flattest substrate or PCB board. Therefore, it is also called Mirror Plate and Carrier Plate. This kind of steel plate has strict requirements. There should be no scratches, dents, or attachments on its surface, the thickness should be uniform, the hardness should be sufficient, and it should be able to withstand the corrosion of chemicals produced during high-temperature pressing. After each pressing and dismantling of the board, it must be able to withstand strong mechanical brushing, so the price of this kind of steel plate is very expensive. To
13. Print Through is pressed through, excessively squeezed
The pressure strength (PSI) used when the multilayer PCB board is pressed is too large, so that a lot of resin is extruded out of the board, causing the copper skin to be directly pressed on the glass cloth, and even the glass cloth is also flattened and deformed, resulting in insufficient board thickness, Poor dimensional stability, and lack of internal lines such as compression and aliasing. In severe cases, the line foundation is often in direct contact with the glass fiber cloth, burying the "anode glass fiber filaments" leakage concerns (Conductive Anodic Filament; CAF). The fundamental solution is the principle of scaled flow. The large-area pressing should use a large pressure strength, and a small plate surface should use a small pressure strength; that is, use 1.16PSI/in2 or 1.16Lb/in4 as the benchmark. Calculate the pressure intensity (Pressure) and total pressure (Force) of the on-site operation. To

14. Relamination (Re-Lam) multi-layer PCB board lamination

The thin substrate used for the inner layer is made by the substrate supplier using the film and the copper sheet to press. Laminates are often called "re-compression" or Re-Lam for short in some occasions. In fact, this is just a kind of "sniff" term for multi-layer board pressing, and it has a no deeper meaning. To

15. Resin Recession resin sinks, resin shrinks
Refers to the resin in the B-stage film or thin substrate of the multilayer board(the former is even worse), which may not be completely hardened after pressing (that is, the degree of polymerization is insufficient). When performing a section inspection, it was found that some under-polymerized resin behind the copper hole wall would shrink from the copper wall and appear voids, which is called "resin sinking". This kind of shortcoming should be classified as the overall problem of the manufacturing process or the board, and the degree is more serious than the poor craftsmanship such as the scratch on the surface of the board, and the cause needs to be investigated carefully. 

16. Scaled Flow Test Proportional flow test
It is a method for detecting the amount of glue flowing in the film (Prepreg) when multi-layer boards are laminated. It is a test method for the "Resin Flow" (Resin Flow) exhibited by resin under high temperature and high pressure. For details, please refer to section 2.3.18 of IPC-TM-650, and for the explanation of its theory and content, please refer to P.42, Issue 14 of PCB Board Information Magazine.

17, Temperature Profile temperature curve
In the PCB board industry, the pressing process, or downstream assembly of infrared or hot air welding (Reflow), and other processes, all need to find the best "temperature curve" that matches the temperature (vertical axis) and time (horizontal axis). In order to improve the yield of solderability in mass production. 

18. Separator Plate, steel plate, mirror plate
When the substrate board or multi-layer PCB board is laminated, the hard stainless steel plate (such as 410, 420, etc.) in each opening (Daylight) of the press is used to separate the books (Books). In order to prevent sticking, the surface is specially treated to be very flat and bright, so it is also called Mirror Plate.