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Answers to questions related to tin points when soldering lead-free tin wires

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Update time : 2022-08-30 16:02:24
Lead-free tin wire is a tin wire that meets environmental protection standards. In fact, there are standards in the industry for what effect the tin point achieves during the soldering process. Below we summarize the judgment standards and related issues for soldering tin points as follows:
1. First, the judgment of the standard tin point, the solder point must meet the following conditions to meet the standard:
Soldering criteria for tin point and related questions during lead-free solder wire soldering
(1) The tin point is formed into an inner arc;
(2) The tin point should be complete, smooth, without pinholes, and without rosin stains;
(3) There should be wire legs, and the length of the wire legs should be between 1-1.2mm;
(4) The shape of the part feet shows that the tin has good dispersibility;
(5) The tin surrounds the entire upper tin position and the foot of the part.
Soldering criteria for tin point and related questions during lead-free solder wire soldering
2. The solder point is a non-standard tin point when the following conditions occur:
(1) Welding: It seems that it is welded, but it is not welded, mainly because the pads and pins are dirty or the flux and heating time are not enough.
(2) Short circuit: The footed parts are short-circuited by excess solder between the feet and the feet. Another phenomenon is that the feet and feet are short-circuited due to improper operation of tweezers, bamboo sticks, etc. by the inspector, including residual Solder dross shorts foot to foot.
(3) Offset: The pins are not in the specified pad area due to inaccurate positioning of the device before soldering, or errors during soldering.
Soldering criteria for tin point and related questions during lead-free solder wire soldering
(4) Less tin: Less tin means that the tin point is too thin to fully cover the copper skin of the part, which affects the connection and fixation effect. The reasons for this phenomenon are that the wire diameter of the tin wire is too thin, the size of the soldering iron tip is improper, and the operation of the operator Inexperienced and so on.
The lead-free tin wire is composed of 99.3 tin and 0.7 copper and flux components. The solder joints of the lead-free tin wire will be shown in the following aspects:
1. Yellow solder joints are produced after tinning on the lead-free tin wire: This phenomenon is caused by the high temperature of the soldering tin. You should immediately check the temperature of the soldering iron tip and whether the thermostat is faulty. (Special note: It is normal for the solder joints of lead-free tin wires to be slightly yellowish compared to those with lead tin wires.)
Soldering criteria for tin point and related questions during lead-free solder wire soldering
2. When soldering components with lead-free tin wire, the solder joints are uneven after tinning: the main phenomenon is that the overall shape of the solder joints does not change, but the surface of the solder joints has a sandy protruding surface; at this time, we must pay attention to the crystal: it must be regularly inspected For the metal components in the solder, you can ask the supplier or entrust a third-party inspection agency to conduct a product sampling inspection to see if the tin and copper ratio of the solder wire is out of balance in the production process. The second is to check the tin slag: during the soldering process, the surface of the solder joint has a sand-like protrusion due to the tin slag contained in the tin liquid of the lead-free tin wire. Pay attention to foreign substances, which may be hidden by leftovers and insulating materials on the PCB board. In the foot of the part, it will be affected by the presence of impurities during the welding process.
3. The dim solder joints after tinning are manifested in the following two aspects:
(1) It has been a period of time after tinning, and the darkening of the color of the solder joints is mainly due to the normal oxidation of the solder joints.
(2) The solder joint is dark after tinning. In this case, it is necessary to regularly check whether the metal composition in the lead-free tin wire meets the standard; in addition, the organic acid-based flux will have a certain degree of residue on the hot surface or for too long. It is recommended to clean immediately after soldering
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