Covering layer of board copper range is opposite printed circuit to nod structural influence without plumbic solder

0 %Ag - 0.

Per cent of quality of 5 %Cu () , the stannum do not have lead that aids welding flux to be colophony creams, 1.

The printed circuit with thick 2 Mm board with ball bar embattle BGA component, stick outfit technology craft to undertake weld manages according to the surface, namely vacuum-packed printed circuit board unseal, cream through stannum pattern plate pressworks, cross circumfluence solder furnace again. Printed circuit board cupreous range uses two kinds of different covering layer, namely organic covering layer and dip silver-colored layer. The temperature of heat preservation area in circumfluence solder process is 218 ℃ , peak value temperature is 235 ℃ . The BGA /Cu that lead makes after be being handled through circumfluence solder solders sample. The method that uses tensile test BGA and printed circuit board detached, observe below scanning report lens solder dot ruptures next the metabolic circumstance of means and fracture surface, rupture in order to decide what solder nods cupreous range covering layer is right means influence, drawing rate is 0.

5 Mm /min. To decide cupreous range covering layer is right solder nods structural influence, in printed circuit board same position office solders BGA /Cu sample cut, after passing polishing, use φ (φ of HNO3) 5 % + (φ of HCl) 2 % + (H2O2) 0.

5 % mixes acerbity solution to undertake cankerous handling, reoccupy bulk mark is small corrode of solution of alcohol of 25 % nitric acid. Solder to after the course corrodes processing, differring sample, the lens of JEOLJSM6360 scanning report that uses accessary INCA EDS (SEM) undertakes observation and analysis. After the site of the solder that do not have lead that 2 tests result and analysis use organic covering layer to protect passes tensile test, many solder dot is standing by cupreous range place to if what graph 1 (A) shows,rupture, the strength that shows drop of the solder that do not have lead under cupreous range and printed circuit board combinative strength; nods fracture surface observation to show to the solder that rupture, the more stomatic 1 (B) that be like a graph appears in solder dot, these stomatic size are differ, and welding flux of the conduce in air hole is residual. And after the site of the solder that do not have lead that uses protection of dip silver-colored layer passes tensile test, most copper range is pulled out to be like graph 1 (C) , the side of copper of intensity prep above that shows solder drop and printed circuit board combinative strength; nods observation to show the 1 (D) that be like a graph to the solder that rupture, fracture surface is behaved relatively level off, occurrence air hole is less. Does organic covering layer appear in solder dot does stomatic main reason depend on: ? Thank  ; Because these gas of? of  of  of  of Liao of paper of  of ⑸ of Bei of  of Jie of Qi of  of げ Qiao  have not enough time eduction and air hole is formed around the interface. When solder the dot suffers when outside force action, in stomatic place generation stress is centered and form micro-crack, micro-crack happens to expand and be brought up next, bring about solder dot finally to rupture, because this reduced the intensity of solder dot. The analysis of lens of report of fracture surface scanning that the graph orders without plumbic solder after 1 tensile test solders to different covering layer sample, use deep corrode processing, enclothe the stannic alloy on cupreous range to be corroded, if the graph is shown 2 times,SEM observation shows appearance of form of pebble form grain, can chart test shows, these grain are Cu6 Sn5 photograph, this and photograph of solder having lead are similar. But statistical analysis makes clear, after using organic covering layer, the average diameter of grain of photograph of the Cu6 Sn5 in solder dot is amounted to 2.

696 μ M, the average diameter of the grain in dot of solder of more silver-colored than using dip layer (it is on average 1.

945 μ M) raised 30 % . Graph after solder of appearance of look of look of the Cu6 Sn5 on 2 copper range nods section to experiment, analysis of scanning report lens shows, solder all is put in chip shape in bit or dendritic Ag3 Sn is shown 3 times like the graph. Chip shape Ag3 Sn basically receives nucleus of the form on interfacial layer to be brought up in solder, but if what 3 (D) of graph 3 (C) , graph shows,many chip shape Ag3 Sn appears on facing of abutment of solder of dip silver-colored layer. On the solder abutment facing that this makes clear to in dip silver is protected, ag3 Sn more be not even form nucleus to be brought up easily. Can chart analysis shows solder abutment facing by the compound between the metal (photograph of IMC) Cu6 Sn5 and Cu3 Sn composition, the ply of solder abutment facing that uses organic covering layer is 10 μ M on average, ply of facing of abutment of solder of silver-colored layer of dip of apparent prep above (it is 5 μ M) on average. Additionally the analysis also shows, solder in organic covering layer if what 3 (B) of graph 3 (A) , graph shows,is stomatic generation on the interface, this confirmed the result that fracture surface observes further. Graph lens of report of scanning of structure of section of 3 solder dot pursues printed circuit board after passing circumfluence solder furnace, below the action of high temperature, organic covering layer happens decompose, stannic silver-colored copper alloy fuses and with copper face happening reaction generates Cu6 Sn5, as reaction undertake, the Cu on cupreous range and the Sn in stannic silver-colored copper alloy produce each other to diffuse further, make the Cu6 Sn5 phase that nears cupreous range to go up chemical composition happening changes and form Cu3 Sn photograph finally, and the Cu6 Sn5 phase that nears solder to order end is brought up further. When covering layer is dip silver-colored layer, as a result of Ag stop action, of the Cu on cupreous range and the Sn in stannic silver-colored copper alloy diffuse each other speed is reduced, grown speed reduces Cu6 Sn5 photograph, the ply growth rate of interfacial layer also reduces; with respect to corresponding ground additional, because the Ag on cupreous range is when furnace of course circumfluence solder,happen to fuse and adhere to go up in photograph of certain Cu6 Sn5, the Cu6 Sn5 photograph that these surfaces contain Ag is become be not dot of even form nucleus, as reaction undertake, the Cu in be not even form nucleus to nod diffuses outwards, and the Ag in solder dot, Sn nods medium form nucleus dot to diffuse to solder, if what graph 3 (D) shows,be brought up further, because Ag3 Sn photograph has specific be used to,becoming a shape to be brought up as to Ag3 Sn photograph may be practice area, the characteristic with low nuclear energy of these materiality of mask of be used to of be used to, make Ag3 Sn reviews along be used to the face is brought up easily. Covering layer of board copper range was opposite 3 conclusion printed circuit to produce an effect without the construction that plumbic solder orders. Stomatic size and amount exceed dip silver-colored layer apparently in the site of the solder that do not have lead that uses organic covering layer. The solder dot that organic covering layer protects basically is standing by cupreous range place to rupture. Interfacial analysis shows the ply of solder interface layer that uses organic layer protection exceeded solder of dip silver-colored layer to nod. The solder abutment that uses dip silver-colored layer has the compound between metal of many chip shape Ag3 Sn on the face, this kind of compound grows into chip shape. CNC Milling