In the process of PCB board design and circuit board production, engineers not only need to prevent accidents during PCB board manufacturing and processing, but also need to avoid design errors. Below, the editor of Shenzhen senyan Circuit Board Factory will let you know about it, and summarize and analyze the PCB board problems of the eight major factors common to circuit board manufacturers, hoping to bring some help to everyone's design and production work.
Problem 1: Circuit board short circuit: For this kind of problem, it is one of the common faults that will directly cause the circuit board to fail to work. There are many reasons for this board problem. The following editor will take you to understand and analyze them one by one. The biggest cause of short circuit on the PCB is improper pad design. At this time, the circular pad can be changed to an oval shape to increase the distance between points to prevent short circuit. Improper design of the direction of the PCB proofing parts will also cause the board to short circuit and fail to work. For example, if the pin of SOIC is parallel to the tin wave, it will easily cause a short circuit accident. At this time, the direction of the part can be appropriately modified to make it perpendicular to the tin wave. There is also a possibility that it will cause a short-circuit failure of the PCB, that is, the automatic plug-in bends the feet. Since IPC stipulates that the length of the wire pin is less than 2mm and the parts will fall off when the angle of the bent pin is too large, it is easy to cause a short circuit, so the solder joint should be separated from the wire by more than 2mm.
Problem 2: PCB solder joints turn golden yellow: Generally, the solder of PCB circuit boards is silver-gray, but occasionally golden solder joints appear. The main reason for this problem is that the temperature is too high. At this time, it is only necessary to lower the temperature of the tin furnace.
Problem 3: There are dark and granular contacts on the circuit board: Dark or small granular contacts appear on the PCB, most of which are caused by solder contamination and too much oxide mixed in the molten tin to form a solder joint structure that is too brittle . Care must be taken not to confuse it with the dark color caused by the use of solder with low tin content. Another reason for this problem is that the composition of the solder used in the manufacturing process changes. If there are too many impurities, pure tin or solder needs to be added. Stained glass has physical changes in fiber lamination, such as separation between layers. But this situation is not a bad solder joint. The reason is that the substrate is overheated, and it is necessary to reduce the preheating and soldering temperature or increase the speed of the substrate.
Problem 4: Loose or misaligned PCB components: During the reflow process / small parts may float on the molten solder and eventually break away from the target solder joint. Possible reasons for shifting or tilting include vibration or bouncing of components on the soldered PCB due to insufficient board support, reflow oven setup, solder paste issues, human error, etc.
Problem 5: Circuit board open circuit: An open circuit occurs when the trace is broken, or when the solder is only on the pad and not on the component lead. In this case, there is no adhesion or connection between the component and the PCB. Just like short circuits, these can also occur during production or during welding and other operations. Vibrating or stretching boards, dropping them or other mechanical deformation factors can damage traces or solder joints. Likewise, chemicals or moisture can cause solder or metal parts to wear away, causing component leads to break.
Problem 6:Soldering Problems: Here are some problems that can arise due to poor soldering practices: Disturbed solder joints: Solder moves before it solidifies due to external disturbances. This is similar to a cold solder joint. But for a different reason, it can be corrected by reheating and keeping the solder joint cool without external disturbance. Cold Soldering: This occurs when the solder does not melt properly, resulting in rough surfaces and unreliable connections. Cold solder joints can also occur due to excess solder preventing complete melting. The remedy is to reheat the joint and remove excess solder. Solder Bridge: This occurs when solder crosses over and physically connects two leads together. These have the potential to form unintended connections and short circuits that can burn components or blow traces if the current is too high. Insufficient pad, pin or lead wetting. Too much or too little solder. A raised pad due to overheating or rough soldering.
Problem 7: The badness of the pcb board is also affected by the environment: due to the structure of the PCB itself, when it is in an unfavorable environment, it is easy to cause damage to the circuit board. Extreme temperatures or temperature fluctuations, excessive humidity, high levels of vibration, and other conditions are all factors that can cause board performance to degrade or even be scrapped. For example, changes in ambient temperature can cause deformation of the board. This will destroy the solder joints, bend the shape of the board, or possibly cause an open circuit in the copper traces on the board. On the other hand, moisture in the air can cause oxidation, corrosion and rust on metal surfaces such as exposed copper traces, solder pads and component leads. Accumulation of dirt, dust or debris on the surface of components and boards can also reduce air flow and cooling of components, leading to overheating and degraded performance of the PCB. Dropping by vibration, hitting or bending the PCB will deform it and cause cracks, while high current or overvoltage will cause the PCB board to be broken down or cause rapid aging of components and pathways.
Problem 8:Human errors: Most of the defects in PCB manufacturing are caused by human errors. In most cases, wrong production processes, wrong placement of components and unprofessional manufacturing specifications are responsible for up to 64% of the defects. Avoid product defects appearing. The possibility of defects increases with circuit complexity and production process due to the following reasons: densely packed components; multiple circuit layers; fine traces; surface soldered components; power and ground planes. Although every manufacturer or assembler hopes to produce PCB boards that are free of defects, there are several problems in the design and production process that cause PCB board problems. Typical problems and results include the following: poor soldering can cause shorts, open circuits, cold solder joints, etc.; misalignment of board layers can cause poor contact and overall poor performance; Arcing occurs between copper traces and vias; placing copper traces too tightly to vias risks short circuits; and insufficient thickness of the board can lead to bending and breaking. In addition to the reasons mentioned above, there are also some reasons that can lead to short-circuit faults on the PCB, such as too large a hole in the substrate, too low temperature of the tin furnace, poor solderability of the board surface, failure of the solder mask, contamination of the board surface, etc. , are relatively common causes of failures, and engineers can compare the above reasons and the occurrence of failures one by one - to eliminate
