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Learn PCB Breadcumb Introduction Breadcumb Lamination


Lamination is the process by which the core(s) of a printed circuit board (PCB) are melted together through heat and pressure with copper layers and prepreg layers (in multi-layer PCBs). This process requires specific heating and pressure for specific periods of time based on materials used to ensure the PCB is made properly.

Core of a PCB A lamination profile maps the temperature, pressure, and time when a board undergoes the lamination process. When the board is laminated, it starts of being gradually warmed up to reach the optimum temperature, left to dwell at the high temperature for a certain amount of time to ensure all the layers melt and stick together, and allowed to gradually cool down.

The boards are in a press the whole time to ensure the board doesn't warp and that it heats up and cools down uniformly.

The temperature and pressure needed for each board varies depending on the height of the stackup and the materials used. These are called press cycles.

During the lamination process, the layers of the PCB shift and move. In order to avoid pads and traces and other parts moving too far from where they should be, predictions of how and where things will shift and move are made. This is called scaling images. After lamination, vias are drilled. With scale images, the vias will not be too far off from where they should be. You can learn more about vias on our via page. After the vias are drilled, the surfaces and the vias are plated.

Types of Laminations

Single Side Lamination

One layer PCBs, that is, one copper layer is laminated to a PCB core substrate. The core is made of fiberglass impregnated with epoxy and stuck together with one copper sheet through the process of lamination. The board goes through the lamination process only once.

Two Sided Lamination

Two Sided Lamination

In a two sided PCB, copper layers are on both sides of the PCB core substrate. Both sides of the board can have traces and pads, and vias are drilled after the lamination process. The board goes through the lamination process only once.

Multi-Layer Lamination

In multi layered laminations, the PCB consists of more than just the core and copper. A four-layer board would consist of a core (which already has a copper layer on both sides), prepreg (which has no copper layer), and copper layers outside the prepreg. The inner layers are etched, then the outer layers are added and etched, and so on.

Multi-Layer Lamination

All of the layers are then laminated together all at once. During the lamination process, prepreg will melt out the sides in order to get the PCB to a predetermined thickness. The post-lamination thickness, or press out thickness, is determined before the lamination process. The board goes through the lamination process only once.

HDI: Sequential laminations

In sequential laminations for HDI boards, the PCB undergoes the lamination process multiple times. This limits the material, traces, and pads from shifting too much and causing annular breakouts when drilling vias. Depending on the types of vias in the board, they will be drilled at different times. For example, a buried via would be laser drilled before a blind via and through hole. If a through hole is buried, blind vias are drilled after the through hole has been laminated.

Cost implications

Quickturn HDI orders cost more because the board has to stay in the lamination press longer, and the length of time depends on the material used. Because HDI boards require sequential laminations, the board has to make its way through the shop multiple times to be imaged and etched, laminated, drilled, and plated multiple times.

Things That Can Go Wrong

Warpage from improper lamination heat profiles.

If the process is rushed, anomalies and inconsistencies will appear and possibly render the board useless. For example, if the board is heated too quickly and not left to dwell at the temperature long enough, the board will warp and and longer be flat.

Misaligned features

Make sure to ask your manufacturer about scale imaging to ensure they are prepared for any shifting and moving features on your board when it undergoes lamination. This can help you determine whether design changes need to be made, and can help you design better boards in the future.