With the rapid development of modern electronic technology, PCBA udvikler sig også mod høj densitet og høj pålidelighed. Although the current PCB and PCBA manufacturing technology level has been greatly improved, the conventional PCB welding process will not be fatal to the product manufacturability. However, for devices with very small pin spacing, the unreasonable design of PCB welding pad and PCB blocking pad will increase the difficulty of SMT welding process and increase the quality risk of PCBA surface mount processing.

I betragtning af de potentielle fremstillings- og pålidelighedsproblemer forårsaget af urimeligt design af PCB -svejsepude og blokeringspude, kan fremstillingsproblemerne undgås ved at optimere enhedens emballagedesign baseret på det faktiske procesniveau af PCB og PCBA. Optimization design mainly from two aspects, first, PCB LAYOUT optimization design; For det andet PCB engineering optimering design. Pakkedesign i henhold til IPC 7351 standardpakkebibliotek og henvises til den padstørrelse, der anbefales i enhedsspecifikationen. For hurtigt design bør layoutingeniører øge størrelsen på puden i henhold til den anbefalede størrelse for at ændre designet. Længden og bredden på PCB -svejsepladen skal øges med 0.1 mm, og længden og bredden af ​​bloksvejsepuden skal øges med 0.1 mm på grundlag af svejsepuden. Conventional PCB resistance welding process requires that the edge of the pad should be covered by 0.05mm, and the middle bridge of the two pads should be larger than 0.1mm. In the design stage of PCB engineering, when the size of solder pads cannot be optimized and the middle solder bridge between the two pads is less than 0.1mm, PCB engineering adopts group solder plate window design treatment. Når de to pads kantafstand større end 0.2 mm pude, i henhold til den konventionelle pad emballage design; Når afstanden mellem kanterne på de to puder er mindre end 0.2 mm, er DFM -optimeringsdesignet nødvendigt. DFM -optimeringsdesignmetoden er nyttig til optimering af pudernes størrelse. Ensure that soldering flux in soldering process can form a minimum barrier pad when PCB is manufactured. Når kantafstanden mellem de to puder er større end 0.2 mm, skal det tekniske design udføres i henhold til de konventionelle krav; When the distance between the edges of two pads is less than 0.2mm, DFM design is needed. The DFM method of engineering design includes design optimization of welding resistance layer and copper cutting of welding aid layer. The size of copper-cutting must refer to the device specification. The copper-cutting pad should be within the size range of the recommended pad design, and the PCB blocking welding design should be single-pad window design, that is, the blocking bridge can be covered between the pads. Ensure that in PCBA manufacturing process, there is a blocking welding bridge between the two pads for isolation, to avoid welding appearance quality problems and electrical performance reliability problems. Welding resistance film in the process of welding assembly can effectively prevent welding bridge short connection, for high-density PCB with fine spacing pins, if the open welding bridge between the pins is isolated, PCBA processing plant can not guarantee the local welding quality of the product. For PCB isolated by open welding of high-density and fine spacing pins, the current PCBA manufacturing factory determines that the incoming material of PCB is defective and does not allow online production. In order to avoid quality risks, PCBA manufacturing factory will not guarantee the welding quality of products if the customer insists on putting the products online. It is predicted that welding quality problems in the manufacturing process of PCBA factory will be dealt with through negotiation.

Casestudie:

Enhedsspecifikationsbogstørrelse, enhedsstiftens mellemrum: 0.65 mm, pinbredde: 0.2 ~ 0.4 mm, pinlængde: 0.3 ~ 0.5 mm. Størrelsen på loddepuden er 0.8 * 0.5 mm, størrelsen på loddepuden er 0.9 * 0.6 mm, enhedsunderlagets midterafstand er 0.65 mm, kantafstanden på loddepuden er 0.15 mm, kantafstanden på loddepuden er 0.05 mm, og bredden af ​​ensidig loddepude øges med 0.05 mm. According to the conventional welding engineering design, the size of unilateral welding pad should be larger than the size of welding pad 0.05mm, otherwise there will be the risk of welding flux covering the welding pad. Som vist i figur 5 er bredden af ​​ensidig svejsning 0.05 mm, hvilket opfylder kravene til svejseproduktion og -behandling. Afstanden mellem kanterne på de to puder er imidlertid kun 0.05 mm, hvilket ikke opfylder de teknologiske krav til svejsebroen med minimum modstand. Engineering design directly design the whole row of chip pin design for group welding plate window design. Make board and finish SMT patch according to engineering design requirement. Gennem funktionstesten er svejsningsfejlfrekvensen for chippen mere end 50%. Again through the temperature cycle experiment, can also screen more than 5% of the defective rate. The first choice is to analyze the appearance of the device (20 times magnifying glass), and it is found that there are tin slag and welding residues between the adjacent pins of the chip. For det andet viste fejlen i produktanalysen, at fejlen i chipstiftens kortslutning brændte. Refer to IPC 7351 standard package library, the design of the help pad is 1.2mm * 0.3mm, the design of the block pad is 1.3 * 0.4mm, and the center distance between adjacent pads is 0.65mm. Through the above design, the size of unilateral welding 0.05mm meets the requirements of PCB processing technology, and the size of adjacent welding edge spacing 0.25mm meets the requirements of welding bridge technology. Increasing the redundancy design of welding bridge can greatly reduce the welding quality risk, so as to improve the reliability of products. Bredden på hjælpesvejsepuden er kobberskåret, og størrelsen på modstandssvejsepuden justeres. Ensure that the edge between the two pads of the device is greater than 0.2mm and the edge between the two pads of the device is greater than 0.1mm. The length of the pads of the two pads remains unchanged. Det kan opfylde kravene til fremstilling af PCB -modstandssvejsning med enkelt pladevindue. In view of the above mentioned pads, pad and resistance welding design are optimized by the above scheme. The edge spacing of adjacent pads is greater than 0.2mm, and the edge spacing of resistance welding pads is greater than 0.1mm, which can meet the requirements of resistance welding bridge manufacturing process. Efter optimering af svejsemodstandsdesign fra PCB LAYOUT -design og PCB -konstruktionsdesign skal du organisere for at levere det samme antal PCB igen og fuldføre monteringsproduktionen i henhold til den samme proces.