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PCB Tech

PCB process elaborate on the myth of Micro-USB structure and insufficient welding strength
2021-10-06
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Author:Aure

PCB process elaborate on the myth of Micro-USB structure and insufficient welding strength




I believe that many friends have encountered the problem of insufficient strength of the Micro-USB connector, and the contact is unstable. In the worst case, the entire USB connector may fall.


Regardless of whether the Micro-USB is prone to drop or short-circuit charging, have you ever wondered why the Micro-USB connector can be so small and can achieve most of the purposes of use? And now almost most of the mobile phone charging and data transmission interfaces are completed by Micro-USB, except for Apple products, but Apple’s connectors are not easy to weld, and now there is a new USB Type-C. I don’t know if it can be solved. this problem?


In short, from the perspective of the organization, the main structure of the entire Micro-USB connector is roughly divided into the following two parts:

Black plastic: This black plastic piece should be regarded as the core of the Micro-USB connector, because all the signal contact points, including the tongue used to contact the USB flat cable and the signal pins connected to the circuit board, are in this black piece On plastic.

Metal shell: The purpose of the metal shell is to protect the black plastic, and its shell will be connected to the ground line of the circuit board, which can effectively guide and eliminate the impact of static electricity (ESD) on the product. Another purpose of using a metal shell is to tightly fix the USB flat cable on the connector without loosening.

So if there is no other special design, when the USB flat cable is inserted into the Micro-USB connector, the black plastic will directly bear the insertion force of the flat cable. At this time, the black plastic will directly retreat to support the power of the black plastic. It comes from the five ultra-fine pins that have been soldered on the circuit board behind it. I believe that as long as the user inserts the solder joints of these pins a few more times, it will not stand the impact and fall apart.


PCB process elaborate on the myth of Micro-USB structure and insufficient welding strength



It is of course not strong enough to rely on the soldering of these thin pins as a support. The most common thing is that the pins are pushed away from the solder pads or the pins are broken directly. So smart connector manufacturers think that they can use metal outer iron shells. Behind the black plastic to lift it to withstand the impact of the flat cable insertion.


However, in this way, the insertion force of the entire USB flat cable is indirectly transferred to the metal iron shell, so the force of the metal shell welded to the circuit board must also be strengthened. Please remember that there are two main points to enhance the soldering strength of the parts without considering the replacement of the solder paste and the surface treatment of the circuit board:

Increase the contact area of solder.


It's not volume! So adding a large mass of solder will have almost the same strength as just filling the solder pins with solder. If you look closely, you should see that most of the Micro-USB connector suppliers make a fuss on the soldering feet of the metal shell. Some punch holes on the soldering feet, and some increase wrinkles. The purpose is to increase the soldering tin. The contact area to improve the welding strength of the metal shell. Using structural design, the force is transmitted to other institutions to bear.


The most common thing is to make the pins of the Micro-USB metal shell into an upright perforated design, so that the force can be transmitted to the hole wall of the PCB to withstand it.


For Micro-USB connectors with no through-hole design, some manufacturers will design more round or semi-circular shapes on their soldering pins to increase the soldering area.


So far, most of the Micro-USB connectors have a great improvement in their resistance to plugging and dropping, and they are also sufficient for general use. It’s just that, after all, this Micro-USB connector will fall into the hands of all kinds of people. Some will use it carefully, and some will use it casually. Even if it is plugged in the wrong direction, it will be hard-plugged in, similar to Yu Yan. The problem of poor contact or falling of the lower Micro-USB connector is also heard from time to time.


The solution is to put an iron frame on the outside of the Micro-USB connector, and then switch to a Micro-USB connector with a stopper design. This stopper is a very clever design. Use the original iron frame to block it in black. Before the plastic, it can block the force of the flat cable plug directly hitting the black plastic. The biggest advantage is that it can extend the life of the signal pin. ipcb is a high-precision, high-quality PCB manufacturer, such as: isola 370hr pcb, high-frequency pcb, high-speed pcb, ic substrate, ic test board, impedance PCB, HDI PCB, Rigid-Flex PCB, buried blind PCB, advanced PCB, microwave PCB, telfon pcb and other ipcb are good at PCB manufacturing.