You are probably familiar with assembling PCB, but do you know the process in two-sided PCB assembly? To start things off, one must ensure that working environment is clean to avoid contamination. Proper humidity as well as high quality components should both be present in double-sided PCB assembly.
Below are the next few steps:
1. Preparing the substrate
An epoxy resin is sprayed or applied on a glass fiber. When the glass fiber is fully covered with epoxy resin, it will be rolled to remove the excess resin. It will also be thinned out to a specific size.
After that, this substrate will be placed in an oven. It will then be cut into panels which will be piled up in layers. Each layer contains copper foils with adhesive. When the layers are done, they’re subjected to very high temperature and pressure for about an hour. By the time this is finished, the layers are solidly bonded.
2. Drilling the holes
Now that you have the panel, the next step for PCB assembly is drilling the holes. Remember that a panel is huge enough that one panel can actually produce several circuit boards. These several panels will be piled up and placed in a CNC machine. CNC machine is responsible in drilling the holes as specified in the board pattern.
Holes in PCB are either conductive or non-conductive. For conductive holes, they are plated with copper to ensure that current will flow from one board to another. As for non-conductive holes, they will be covered while the rest of the holes are plated with copper. Sometimes, non-conductive holes are drilled only after the conductive holes are plated.
3. Creating a pattern for the PCB
During this phase in PCB assembly, there is a need to create a mask that will create a pattern for the PCB. This mask will ensure that only the necessary parts are plated with copper while the rest of the board remains untouched.
4. Attaching and plating of contact fingers
Contact fingers refer to the internal connectors plated with gold and copper. They are resistant to wear and tear, corrosion, and high temperature. These contact fingers will be attached to the ends of the substrate. Contact fingers act as a bond to connect the substrate with the PCB. To cover these contact fingers, plate them with tin-lead, nickel, and then gold metals.
Note that at this point, the exterior of the printed circuit pattern is still prone to corrosion. To resolve this, the entire panel goes through a reflow process where it is subject to a high temperature. This will allow the tin-lead to melt and reflow creating a shiny exterior.
6. Cutting the panels
Remember that panels can create several circuit boards. Once the reflow is done, the panel is cut into individual PCBs. The sides of the board are also smoothened out to create a nice finish.
7. Placement of Components
Now that the PCB is ready, it will pass through different machines. These machines make placing electrical components on the board easier and faster. Some technicians who do their own PCB assembly can manually do the placement themselves. But in cases where the amount of PCB produced is numerous, the use of machines and technology is highly essential.
When the placement phase is done, everything needs to be soldered onto the board. Depending on the amount of boards that need to be soldered, they can be done manually or through the use of a reflow oven.
Before the products are packaged for delivery, they have to be examined for quality. Through an optical inspection machine, flaws such as solder errors, misplaced components, and shifted boards are easily identified.
Without a doubt, manufacturing double-sided PCBs is quite challenging. Nonetheless, if you’re really serious about making your very own boards, you should keep everything you’ve learned in mind and persevere.
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