Printed circuit board marking points and printed circuit board tin spraying

Mark points are the position recognition points for PCBs used in automatic placement machines in circuit board design.The marking points can be on bare copper,which is protected by a transparent antioxidant coating.PCB board marking points,also known as reference points,provide a common measurement point for all steps in the surface installation process to ensure that SMT equipment can accurately locate PCB board components.Therefore,marking points are very important for SMT production.
The role of secondary standards
Marking points can be divided into single board marking points,puzzle marking points,and local marking points.The marking points on the board can locate the positions of all circuit features;Jigsaw boards can help locate the positions of all circuit features;Local marker points can locate reference point markers for individual components to improve placement accuracy,such as QFP,CSP,BGA,etc.Parts must have local markings,etc.
Marking points are points used for positioning when welding with machines.The PCB of surface mount components needs to set marking points because in the mass production of SMT SMT SMT factories,the SMT machine is manually or automatically searched for marking points for calibration.The selection of marking points directly affects the placement efficiency of the automatic placement machine.
1.PCBs with marked points,commonly referred to as"marked points"in SMT technology,to solve this problem,are the optical components of the machine correctly installed on the PCB placement machine and accurately positioned on the PCB?
2.Used to locate the marking points of the mobile placement machine.In fact,it is a single-layer special solder pad typically placed on the diagonal(asymmetric)of each side of the PCB.It must have a certain size and no components can be placed around it to contrast with the background and facilitate machine recognition.Introduction to PCB board tin spraying
PCB surface treatment technology,currently the most widely used is the tin spraying process,also known as hot air leveling technology,which sprays a layer of tin on the solder pads to improve their conductivity and solderability.
HASL is the most common surface coating form in circuit board surface treatment.It is widely used in circuit production.The quality of tin spraying will directly affect the quality of solder and the subsequent production of solder by customers.Solderability;Therefore,the quality of tin spraying has become a key focus of quality control for PCB production enterprises.
The difference between lead spray tin and lead-free spray tin
1.The lead content without lead tin does not exceed 0.5,and the lead content of lead tin can reach 37.
From the surface of the tin spray,lead and tin are relatively bright,while lead-free tin(SAC)is relatively dull.
3.Lead tin is brighter and lead-free tin(SAC)is darker,but the wettability of lead-free tin is slightly lower than that of lead tin.
During the welding process,lead will increase the activity of the tin wire.Lead wire is better than lead-free tin wire,but lead is toxic and long-term use is not good for the human body.The melting point of lead-free tin is higher than that of lead tin.In this way,the solder joints are much stronger.
5.Lead in lead is harmful to the human body,while lead-free is harmless.The eutectic temperature of lead is lower than that of lead-free.The specific content depends on the composition of the lead-free alloy.
6.Lead free tin spraying belongs to the environmental protection category,does not contain harmful substances such as lead,and has a melting point of around 218 degrees;The temperature of the tin spraying furnace needs to be controlled between 280-300 degrees;The peak temperature needs to be controlled at approximately 260 degrees;Everything is over.The reflux temperature is 260-270 degrees.
7.Lead tin spray does not belong to environmental protection category.They contain harmful substance"lead"with a melting point of about 183 degrees;The temperature of the tin spray furnace needs to be controlled between 245-260 degrees;The peak temperature needs to be controlled at approximately 250 degrees;Everything is over.The reflux temperature is 245-255 degrees.