The core board is an electronic main board that packs and encapsulates the core functions of the MINI PC. Most core boards integrate CPU, storage devices and pins, which are connected to the supporting backplane through pins. Because the core board integrates the common functions of the core, it has the versatility that a core board can be customized for a variety of different backplanes, which greatly improves the development efficiency of the single-chip microcomputer. Because the core board is separated as an independent module, it also reduces the difficulty of development and increases the stability and maintainability of the system. Especially in urgent and important projects, there are uncertainties in the development time and risk of high-speed hardware and low-level driver development from IC-level R&D. Using the core board as the master control is the first choice.
Of course, due to the numerous parameters of the core board and the limited space of this article, we will only talk about the packaging of the core board this time. The packaging of the core board is related to the convenience of future product production, production yield, the stability of field trials, the life of field trials, the convenience of troubleshooting and positioning of faulty products, and so on. Below we discuss two commonly used core board packaging forms.
1. Stamp hole type package
The stamp hole type package is loved by electronic engineers because of its IC-like appearance, and the ability to use IC-like soldering and fixing methods. Therefore, many types of core boards on the market use this type of package. This type of package is very firm due to the connection and fixation method of the base plate with welding, and it is also very suitable for use in high humidity and high vibration sites. For example, island projects, coal mine projects, and food processing plant projects. These types of use occasions have the characteristics of high temperature, high humidity, and high corrosion. The stamp hole is especially suitable for these types of project occasions due to its stable connection point welding method.
Of course, stamp hole packaging also has some inherent limitations or shortcomings, such as: low production welding yield, not suitable for multiple reflow welding, inconvenient maintenance, disassembly and replacement, and so on.
Therefore, if it is necessary to choose the stamp hole package because of the requirements of the application, the issues that need to be paid attention to are: full manual welding is used to ensure the welding product rate, and machine welding should not be used for the last time to paste the core board, and the scrap rate is high. Preparation. In particular, the last point needs to be specifically stated, because most of the stamp hole core boards are selected to obtain the polar repair rate after the product arrives on site, so it is necessary to accept the various production and maintenance inconveniences of stamp hole packaging, and the scrap rate and overall cost must be accepted. High features.
2. Precision board-to-board connector packaging
If the inconvenience of production and maintenance caused by stamp hole packaging is really unacceptable, perhaps precision board-to-board connector packaging is a better choice. This kind of package adopts the male and female sockets, the core board does not need to be welded during the production process, and it can be inserted; the maintenance process is convenient to plug out and replace; the troubleshooting can replace the core board for comparison. Therefore, the package is also adopted by many products, and the package can be plugged in, which is convenient for production, maintenance and replacement. Moreover, due to the high pin density of the package, more pins can be drawn in a small size, so the core board of this type of package is small in size. It is convenient to be embedded in products with limited product size, such as roadside video stakes, handheld meter readers, etc.
Of course, it is also due to the relatively high pin density, which makes it slightly more difficult to solder the female base of the bottom plate, especially in the sample stage of the product. When the engineer is performing manual welding, many engineers have already grasped the manual welding process of this kind of package. mad. Some friends melted the plastic of the female socket during welding, some caused a piece of pin collective adhesion due to the high pin density during welding, and some seemed to be welded perfectly but the measured pin was short-circuited.
The female socket based on this package is difficult to solder, so even in the sample stage, it is best to ask professional soldering personnel to solder it, or to solder it with a placement machine. If it is indeed unconditional machine welding, here is also a manual welding procedure with a relatively high welding success rate:
1. Spread solder evenly on the pads (note that not too much, too much solder will make the female seat high, and not too little, too little will lead to false soldering);
2. Align the female seat with the pad (note that when purchasing the female seat, choose a female seat with a fixed post for easy alignment);
3. Use a soldering iron to press each pin one by one to achieve the purpose of welding (note that it is pressed separately, mainly to ensure that each pin is not short-circuited, and to achieve the purpose of welding).
