SMT processing plant lead-free solder needs to meet these conditions

Date：2022-09-30 13:54:39Views：622

In lead solders, lead exists as a basic element. In lead-free solders, the basic elements do not contain lead. With the strengthening of people's awareness of environmental protection, the use of lead in various industries is becoming more and more cautious. Among them, in smt chip processing, customers in different industries will be asked whether there are lead-free requirements for the welding process, which means that electronic manufacturing has very strict requirements for lead-free assembly process.

First of all, when using lead-free solder in SMT chip processing, it should be able to truly meet the environmental requirements, and lead should not be removed blindly, in addition, new toxic or harmful substances should be added; In order to ensure the solderability of lead-free solder and the reliability after welding, many problems such as the cost borne by customers should be considered. In general, lead-free solder in smt chip processing should meet the following requirements as far as possible:

First, the melting point of lead-free solder used in smt chip processing should be low, as close as possible to the eutectic temperature of 63/37 tin lead alloy of 183 ℃. If the eutectic temperature of new products is only a few degrees higher than 183 ℃, it should not be a big problem, but there is no such lead-free solder that can be really promoted and meets the requirements of welding process; In addition, before developing lead-free solders with lower eutectic temperature, the temperature difference between melting intervals of lead-free solders should be reduced, that is, the temperature range between the solidus and liquidus should be reduced as much as possible, and the minimum solidus temperature should be 150 ℃, The liquidus temperature depends on the specific application (tin bar for wave soldering: below 265 ℃; tin wire: below 375 ℃; solder paste for SMT: below 250 ℃; generally, the reflow soldering temperature should be lower than 225 to 230 ℃).

Secondly, lead-free solder used in smt chip processing should have good wettability; In general, the lead-free solder stays above the liquidus for 30~90 seconds during reflow soldering, and the contact time between the solder pin and the base plate of the circuit board and the molten tin during wave soldering is about 4 seconds. After using lead-free solder, it is necessary to ensure that the solder can show good wettability within the above time range to ensure high-quality welding effect.

Why does SMT chip processing use lead-free soldering?

Lead free soldering is mainly about environmental protection. It will be more healthy for users to use the product, and its impact on the environment will also be reduced. However, the cost of lead-free soldering will be higher, and the unit price of chip processing will also be higher. Customers need to use lead-free soldering or lead soldering, which needs to be considered according to the product's use environment, product price and profit, rather than blindly pursuing lead-free soldering.

The above is the introduction of lead-free solder in SMT processing plant, and I hope it will be helpful to you. Chuangxin Testing is a professional testing agency for electronic components. At present, it mainly provides integrated circuit testing services such as capacitance, resistance, connector, MCU, CPLD, FPGA, DSP, etc. Specializing in electronic component function testing, electronic component incoming appearance testing, electronic component dissection testing, acetone testing, electronic component X-ray scanning testing, ROHS component analysis testing. Welcome to call, we will serve you wholeheartedly!