How to choose FPC SMT

If you are looking for an excellent way to fix your FPC, this article can help you. This article will give you information about FPC SMT and how to fix it properly. We will discuss the composition of solder paste, the proper condition for soldering, and how to inspect your FPC. You will also learn the importance of testing your FPC after a successful fix.

Fixing FPC smt

When fixing FPCs, precise positioning is essential. Besides the proper carrier board, the other critical factors in selecting FPCs include printing, patching, and reflow soldering. Furthermore, strict production process management is necessary for FPC assembly. Therefore, engineers must enhance inspections and IPQC. They should also analyze abnormal conditions on the production line and correct them as soon as possible. In this way, they will be able to ensure that they appropriately assemble the FPC.

To ensure the correct placement of FPCs, the carrier board should be flat and temperature-resistant. In addition, the placement process needs to be highly controlled. The best way to perform this process is by using a high-speed placement machine with an optical positioning system. A high-speed placement machine can be helpful for rigid PCBs and a medium-speed one for flexible PCBs. After assembling FPCs, you should check the process for defects and proper positioning.

When fixing FPCs, you should use high-temperature double-sided tape. This tape will prevent the FPC from warping or offsetting when placed on a carrier board. The tape should have a moderate viscosity, be easily peeled off after reflow, and leave no residual glue. The best tape machines can cut the length of tape quickly and easily, increasing their efficiency.

Another type of tape is high-performance acrylic PSA. This kind of tape is suitable for fixing FPCs and other electronic components. It can withstand high temperatures, even when the components are subject to lead-free solder reflow. FPC also has various applications, such as electronic components and computers. It also has excellent adhesion properties and is suitable for various industries.

Solder paste composition


Regarding PCB assembly, lead-free solder paste is the preferred choice because it does not cause oxidation or deterioration. Lead-free solder paste consists of tin, silver, copper, and copper alloy. However, solder paste’s composition differs depending on the components used in PCB assembly. For this reason, it is crucial to choose the correct paste for the specific application.

You should control the temperature of the solder paste so that it does not overheat the components. Some solder paste manufacturers allow a little increase in the temperature during activation. A flat temperature curve is desirable for solderability and a longer processing window. The temperature of the active zone should be relatively constant, which is essential for FPC SMT assembly. However, some furnaces cannot maintain the solder paste temperature evenly.

The formulation of FPC SMT solder paste does not contain special requirements for the composition of the solder paste. However, the solder paste should have excellent printing properties. It should be easy to print and release, and it should be able to adhere firmly to the pads of the flexible PCB. Also, it should not cause the mold to collapse after printing or clog the steel mesh. Furthermore, it should be suitable for medium and high-speed placement machines.

As the solder paste consists of metals, it is susceptible to oxidation. This reduces the solder balls’ quality and defeats soldering’s purpose. Therefore, it is essential to store solder paste in an air-tight container and store it at a low temperature. Heat is harmful to the metals in solder paste and oxidizes the flux that holds the solder powder together.

Soldering conditions

Soldering FPC requires the use of lead-free reflow and a high temperature. Because FPC materials do not have the same thermal conductivity as PCBs, the solder paste must have a high printing performance. It must release from the mold quickly and adhere to the FPC surface. The paste should not cause the mold to collapse after printing, clog the steel mesh, or create poor mold release.

In this process, we mount the PCB and FPC at different heights. The height depends on the FPC’s thickness, the lever lock’s angle, and the actual equipment. When using a hot bar, the temperature should be higher than that of the ACF. The temperature and pressures should be different to ensure the best results. We should regulate the temperature and pressure separately. The process points for FPC soldering are similar to those for other materials, and we can perform it using the same equipment.

We fix the FPC with BGA into a cuboid with four screw bars in the first step. We then drop this cuboid from a height of 1.5 meters onto a concrete surface. The connection’s reliability depends on the BGA placement and the solder joint diameter. In practical drop reliability tests, there are six orthogonal drop tests. For the simulation, the FPC is a rectangle.


Inspecting PCBs for defects is an essential part of surface mount technology manufacturing. There are two main methods for this. The first is the SPI inspection, which reviews the printed circuit board after solder paste is applied. The second is the AOI inspection, which checks for components’ placement before reflowing. The results are compared to the reference spec to ensure compliance in both cases. A combination of both inspection methods is necessary for successful PCB production.

Visual inspection involves examining the product visually with the naked eye. It is a cheap, easy-to-implement method. However, it is unsuitable for 0603 or 0402 packages or fine-pitch components. Nevertheless, this method is a very accurate way to inspect the surface defect on an FPC. In addition, visual inspection is often helpful for reflow soldering and process validation, a critical stage in FPC SMT assembly.

Another way to check the integrity of FPCs is to use a microscope. A microscope can provide an insight into the condition of the lines on an FPC. For example, a three-meter probe is helpful if the line breaks or is too thick. A magnetic jig is also useful for this purpose. A magnetic jig used to fix the FPCs can provide an excellent way to fix the components to the carrier board.

A third method is a drill-through inspection. This method enables inspectors to see the drilling process. It also allows the manufacturer to see whether the drilled holes have failed to meet the required quality standards. Then, using an IPQC sample, a qualified FPC board is put into the production line. This process is not only fast and efficient but also accurate. The result is a better product that meets customers’ expectations.


The best SMT cleaning methods are the ones that don’t require expensive tools or new materials. But choosing the right one is critical. You should select the right cleaning process based on the built product type, cost, performance, and environmental impact. You need to understand the type of flux used in your production process and determine the best way to apply it. For this purpose, there are several options available. Let’s take a look at some of the most common options.

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