Tom qab tooj liab clad laminate yog ua tiav los tsim PCB pawg thawj coj saib, various through holes, and assembly holes, various components are assembled. After assembling, in order to make the components reach the connection with each circuit of the PCB, it is necessary to carry out the Xuan welding process. Brazing is divided into three methods: wave soldering, reflow soldering and manual soldering. The socket-mounted components are generally connected by wave soldering; the brazing connection of surface-mounted components generally uses reflow soldering; individual components and components are individually manual (electric chrome) due to installation process requirements and individual repair welding. Iron) welding.

1. Solder resistance of copper clad laminate

Copper clad laminate yog cov khoom siv substrate ntawm PCB. Thaum lub sij hawm brazing, nws ntsib kev sib cuag ntawm cov khoom kub kub hauv ib qho instant. Yog li ntawd, Xuan vuam txheej txheem yog ib qho tseem ceeb ntawm “thermal shock” rau cov tooj liab clad laminate thiab ib qho kev ntsuam xyuas ntawm lub tshav kub tsis kam ntawm tooj liab clad laminate. Copper clad laminates xyuas kom zoo ntawm lawv cov khoom thaum lub sij hawm thermal shock, uas yog ib qho tseem ceeb nam ntawm kev ntsuam xyuas cov tshav kub tsis kam ntawm tooj liab clad laminates. Nyob rau tib lub sijhawm, kev ntseeg tau ntawm tooj liab clad laminate thaum Xuan vuam kuj tseem cuam tshuam rau nws tus kheej rub tawm lub zog, tev lub zog nyob rau hauv qhov kub thiab txias, thiab noo noo thiab kub tsis kam. Rau cov txheej txheem brazing yuav tsum tau ntawm tooj liab clad laminates, ntxiv rau cov pa immersion kuj cov khoom, nyob rau hauv xyoo tas los no, txhawm rau txhim kho kev ntseeg siab ntawm tooj liab clad laminates hauv Xuan vuam, qee qhov kev ntsuas kev ua tau zoo thiab cov khoom ntsuas tau raug ntxiv. Xws li kev nqus dej noo thiab kev ntsuas kub tsis kam (kev kho rau 3 h, tom qab ntawd 260 ℃ dip soldering test), noo noo nqus reflow soldering test (muab tso rau ntawm 30 ℃, txheeb ze av noo 70% rau lub sijhawm, rau reflow soldering test) thiab lwm yam. . Ua ntej cov khoom siv tooj liab clad laminate tawm hauv lub hoobkas, cov chaw tsim khoom siv tooj liab clad laminate yuav tsum ua kom nruj dip solder tsis kam (tseem hu ua thermal shock blistering) kuaj raws li tus qauv. Cov neeg tsim khoom lag luam luam tawm yuav tsum tau kuaj xyuas cov khoom no hauv lub sijhawm tom qab cov tooj liab clad laminate nkag mus rau hauv lub Hoobkas. Nyob rau tib lub sijhawm, tom qab cov qauv PCB raug tsim, qhov kev ua tau zoo yuav tsum tau sim los ntawm kev simulating yoj soldering tej yam kev mob hauv cov khoom me me. Tom qab lees paub tias hom substrate no ua tau raws li tus neeg siv cov kev xav tau ntawm kev tiv thaiv rau immersion soldering, PCB ntawm hom no tuaj yeem tsim ntau thiab xa mus rau lub tshuab ua tiav.

The method for measuring the solder resistance of copper clad laminates is basically the same as the international (GBIT 4722-92), the American IPC standard (IPC-410 1), and the Japanese JIS standard (JIS-C-6481-1996). The main requirements are:

①The method of arbitration determination is “floating soldering method” (the sample floats on the soldering surface);

② Cov qauv loj yog 25 hli X 25 hli;

③Yog qhov ntsuas qhov ntsuas kub yog qhov ntsuas mercury, nws txhais tau hais tias qhov sib npaug ntawm lub taub hau thiab tus Tsov tus tw hauv lub solder yog (25 ± 1) mm; tus qauv IPC yog 25.4 hli;

④The depth of the solder bath is not less than 40 mm.

It should be noted that: the temperature measurement position has a very important influence on the correct and true reflection of the level of dip solder resistance of a board. Generally, the heating source of soldering tin is at the bottom of the tin bath. The greater the (deeper) the distance between the temperature measurement point and the surface of the solder, the greater the deviation between the temperature of the solder and the measured temperature. At this time, the lower the temperature of the liquid surface is than the measured temperature, the longer the time for the plate with dip solder resistance measured by the sample float welding method to bubble.

2. Wave soldering processing

In the wave soldering process, the soldering temperature is actually the temperature of the solder, and this temperature is related to the type of soldering. The welding temperature should generally be controlled below 250’c. Too low welding temperature affects the quality of welding. As the soldering temperature increases, the dip soldering time is relatively significantly shortened. If the soldering temperature is too high, it will cause the circuit (copper tube) or the substrate to blistering, delamination, and serious warpage of the board. Therefore, the welding temperature must be strictly controlled.

Peb, reflow vuam ua

Generally, the reflow soldering temperature is slightly lower than the wave soldering temperature. The setting of reflow soldering temperature is related to the following aspects:

① Hom khoom siv rau reflow soldering;

②The setting conditions of line speed, etc.;

③The type and thickness of the substrate material;

④ PCB loj, thiab lwm yam.

Lub teeb kub ntawm reflow soldering yog txawv ntawm PCB nto kub. Nyob rau tib lub teeb kub rau reflow soldering, qhov kub thiab txias ntawm PCB kuj txawv vim hom thiab thickness ntawm cov khoom siv substrate.

Thaum lub sij hawm reflow soldering txheej txheem, lub tshav kub tsis kam ntawm lub substrate nto kub qhov twg cov tooj liab ntawv swells ( npuas) yuav hloov nrog lub preheating kub ntawm PCB thiab lub xub ntiag los yog tsis muaj noo noo nqus. Nws tuaj yeem pom los ntawm daim duab 3 tias thaum qhov kub thiab txias ntawm PCB (qhov kub ntawm lub substrate) qis dua, qhov ntsuas kub tsis kam ntawm qhov kub ntawm lub substrate qhov chaw qhov teeb meem o tshwm sim kuj qis dua. Nyob rau hauv cov xwm txheej uas qhov kub thiab txias tau teem los ntawm reflow soldering thiab preheating kub ntawm reflow soldering yog tas mus li, qhov kub thiab txias ntog vim qhov nqus dej ntawm substrate.

Four, manual welding

Hauv kev kho vuam lossis cais kev sib txuas ntawm cov khoom tshwj xeeb, qhov kub ntawm hluav taws xob ferrochrome yuav tsum tau qis dua 260 ℃ rau daim ntawv-raws li tooj liab clad laminates, thiab qis dua 300 ℃ rau iav fiber ntau daim ntaub-raws li tooj liab clad laminates. Thiab kom deb li deb tau kom luv lub sijhawm vuam, cov kev cai dav dav; daim ntawv substrate 3s lossis tsawg dua, iav fiber ntau daim ntaub substrate yog 5s lossis tsawg dua.