PCB News - Analyze the production process of PCB multi-layer board proofing and pressing

With the continuous development of technology, single and double panels can no longer meet the needs of most electronic products. Multilayer boards have been greatly developed. Multilayer boards have more laminating processes than double panels. The following editor will introduce PCB Multi-layer board proofing and pressing production process.

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 take 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 PCB boards. At that time, the "outer layer" of MLB was mostly laminated and laminated with a single-sided copper thin substrate. It was not used until the end of 1984 when the output of MLB increased greatly. The current copper-skin type large-scale or mass pressing method (Mss Lam). This early MLB pressing method using a single-sided copper thin substrate is called Cap Lamination.

3, Crease

In the multi-layer board lamination, 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.

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 of 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.

6, Foil Lamination method

Refers to the mass-produced multilayer board, the outer layer of copper foil and film are 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

When laminating (laminating) multilayer boards or substrate boards, kraft paper is mostly used as a heat transfer buffer. It is placed between the hot plate (Platern) 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 co-cooked with a mixture of pine wood 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 and positioned, they will start to heat up and be lifted up by the hottest layer of the lowest layer, and lift up with a powerful hydraulic jack (Ram) to compress the openings ( 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 stacking

Before lamination of multilayer circuit boards or substrates, various bulk materials such as inner layer boards, films and copper sheets must be aligned with steel plates, kraft paper pads, etc., to complete the up-and-down alignment, alignment, or registering work. Then 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 the automation engineering is quite complicated.

The above is an introduction to the production process of PCB multi-layer board proofing and pressing. Ipcb also provides PCB manufacturers and PCB manufacturing technology.