1, tin dipping effect

When hot liquid solder dissolves and penetrates the metal surface of the PCB ni soldered, o ti wa ni a npe ni irin imora tabi irin imora. The molecules of the mixture of solder and copper form a new alloy that is part copper and part solder. This solvent action is called tin-bonding. It forms an intermolecular bond between the various parts of the PCB, creating a metal alloy compound. Ibiyi ti awọn ifunmọ intermolecular ti o dara jẹ ipilẹ ti ilana alurinmorin PCB, eyiti o pinnu agbara ati didara ti awọn aaye alurinmorin PCB. Tin can be stained only if the copper surface is free of contamination and oxide film formed due to PCB exposure to air, and the solder and the working surface need to reach the appropriate temperature.

2. ẹdọfu dada

Gbogbo eniyan ni o mọ pẹlu aifokanbale omi ti omi, agbara ti o ṣetọju awọn omi tutu ni iyipo lori awo irin PCB nitori pe, ni idi eyi, adhesion ti o duro lati tan kaakiri omi lori dada to fẹẹrẹ kere ju isọdọkan rẹ. Wash with warm water and detergent to reduce surface tension. The water will saturate the greased PCB metal plate and flow outward to form a thin layer, which occurs if the adhesion is greater than the cohesion.

Tin-lead solder is even more cohesive than water, making the solder spherical to minimize its surface area (for the same volume, the sphere has the smallest surface area compared to other geometries to meet the requirements of the lowest energy state). The effect of flux is similar to that of detergent on the PCB metal plate coated with grease. In addition, the surface tension is also highly dependent on the cleanliness and temperature of the PCB surface. Only when the adhesion energy is much greater than the surface energy (cohesion), the PCB can have the ideal tin adhesion.

3, with tin Angle

A ṣe agbekalẹ meniscus kan nigbati a ba fi ju ti ataja sori aaye ti PCB ti o gbona, ṣiṣan ṣiṣan ni iwọn 35 ° C loke aaye eutectic ti solder. Si iwọn kan, agbara ti irin irin ti PCB lati lẹẹ tin le ṣe iṣiro nipasẹ apẹrẹ meniscus. The metal is not solderable if the meniscus has a clear bottom cut, looks like droplets of water on a greased PCB metal plate, or even tends to be spherical. Only the meniscus stretched to a size less than 30. The small Angle has good weldability.

4. The generation of metal alloy compounds

The intermetallic bonds of copper and tin form grains whose shape and size depend on the duration and strength of the temperature at which they are welded. Less heat during welding can form a fine crystal structure, which makes the PCB form an excellent welding spot with the best strength. Akoko ifura gigun, boya nitori akoko alurinmorin PCB gun ju, iwọn otutu ti o ga pupọ tabi awọn mejeeji, yoo ja si ni ilana okuta ti o ni inira ti o jẹ okuta wẹwẹ ati brittle pẹlu agbara rirẹ -kuru kekere.A lo Ejò bi ohun elo ipilẹ irin ti PCB, ati pe a lo tin-asiwaju bi alloy solder. Asiwaju ati bàbà kii yoo ṣe eyikeyi awọn akopọ alloy irin, ṣugbọn tin le wọ inu idẹ. Isopọ intermolecular laarin tin ati bàbà ṣe awọn akopọ alloy irin Cu3Sn ati Cu6Sn5 ni tita ati isunmọ irin.

Layer alloy irin (n +ε alakoso) gbọdọ jẹ tinrin pupọ. Ni alurinmorin laser PCB, sisanra ti fẹlẹfẹlẹ alloy irin jẹ 0.1mm ni kilasi nọmba. Ni ṣiṣan igbi ati titọ Afowoyi, sisanra ti ifunpọ intermetal ti awọn aaye alurinmorin ti o dara ti PCB jẹ diẹ sii ju 0.5μm. Nitori agbara rirẹ -kuru ti awọn alurinmorin PCB dinku bi sisanra fẹlẹfẹlẹ irin ti pọ si, igbagbogbo ni igbidanwo lati tọju sisanra fẹlẹfẹlẹ irin ni isalẹ 1μm nipa titọju akoko alurinmorin ni kukuru bi o ti ṣee.

Awọn sisanra ti irin alloy Layer da lori awọn iwọn otutu ati akoko ti lara awọn alurinmorin iranran. Apere, alurinmorin yẹ ki o pari ni iwọn 220 ‘t 2s. Labẹ awọn ipo wọnyi, ifesi kaakiri kemikali ti bàbà ati tin yoo ṣe agbekalẹ awọn ohun elo abuda alloy ti o yẹ Cu3Sn ati Cu6Sn5 pẹlu sisanra ti nipa 0.5μm. Isopọ intermetal ti ko pe jẹ wọpọ ni awọn isẹpo solder tutu tabi awọn papọ ti a ko gbe soke si iwọn otutu ti o yẹ lakoko alurinmorin ati pe o le ja si gige ti dada PCB alurinmorin. Ni ifiwera, awọn fẹlẹfẹlẹ alloy irin ti o nipọn pupọ, ti o wọpọ ni apọju pupọju tabi awọn papọpọ fun igba pipẹ, yoo ja si ni agbara fifẹ pupọ ti awọn isẹpo PCB.