DFM設(shè)計(jì)與制造

1、Design For Manufacturing生產(chǎn)方式零件正確選擇板子大小尺寸光學(xué)點(diǎn)的需求標(biāo)示及識(shí)別說(shuō)明資料吃錫的考慮零件方向零件空間距離銅泊,錫墊, 孔徑大小治具孔維修重工測(cè)試點(diǎn)折板與連板的考量線路與導(dǎo)通孔測(cè)試著想而設(shè)計(jì)導(dǎo)入工業(yè)標(biāo)準(zhǔn)偏 移Pad 設(shè)計(jì)不良易造成偏移(往吸熱較多處)Component spaceFor wave soldering components, must be spaced sufficiently far apart to avoid bridging. This is less important for reflow soldering but suffici

2、ent space must be allowed to enable rework should it be required.Component spaceFreeAreaTest Pad5.00mmFixture0.5mm MinDepanelizationDefects can still occur much further away from the board edge if the board is large and flexible or if components are perpendicular to stress gradients. Components need

3、 to be isolated from connectors, mounting holes, pots, etc. to minimize damage from those sources of deflection.NGNGComponent OrientationDip FlowOKNG減少 ShortDip Flow增加拖錫點(diǎn)將錫留在特定位置，減少短路避免造成短路盡量將PAD與大銅箔隔離，避免受熱不均Change to1.5 mm採(cǎi)用短腳作業(yè)，避免引腳間短路IC Alignment在四邊的PAD加大，利用熔錫時(shí)的內(nèi)聚力作位置校正板彎(1) PCB設(shè)計(jì)不合理，元件分布不均會(huì)造成PCB

4、熱應(yīng)力過(guò)大，外形較大的連接器和插座也會(huì)影響PCB的膨脹和收縮，乃至出現(xiàn)永久性的扭曲。(2)雙面PCB，若一面的銅箔保留過(guò)大(如地線)，而另一面銅箔過(guò)少，會(huì)造成兩面收縮不均勻而出現(xiàn)變形。 合理設(shè)計(jì)PCB，雙面的鋼箔面積應(yīng)均衡，在沒(méi)有電路的地方布滿鋼層，并以網(wǎng)絡(luò)形式出現(xiàn)，以增加PCB的剛度，在貼片前對(duì)PCB進(jìn)行預(yù)熱，其條件是1054h；調(diào)整夾具或夾持距離，保證PCB受熱膨脹的空間；焊接工藝溫度盡可能調(diào)低；已經(jīng)出現(xiàn)輕度扭曲時(shí)，可以放在定位夾具中，升溫復(fù)位，以釋放應(yīng)力，一般會(huì)取得滿意的效果。避免板彎Add dummy circuitToo many empty area1.利用治具挾持2.增加空銅箔達(dá)

5、到熱均勻3.減少V-Cut，以機(jī)器切板Fillet Lifting How to avoid:Use silver-rich alloys. Silver contents of 3.5 % are recommended. Process Qualification VoidHow voids are formed:Voids are the result of solder shrinkage during solidification. Poor wetting can case voids.Outgassing in the plated through holes during so

6、ldering may produce holes in the solder.Sources of gas are moisture in the laminate and incomplete curing of the laminate.Incomplete outgassing can be caused by gas from flux chemistry of the solder paste or the flux for wave soldering.Improper amount of solderProcess Qualification Stencil CHIP元件，按1：1開(kāi)口 P=0.5mm，IC&QFP，開(kāi)口寬 0.25mm P=0.635mm，IC&QFP，開(kāi)口寬 0.35mm P0.635mm， IC&QFP， 開(kāi)口寬為55%PITCH P=0.8mm，BGA ，開(kāi)0.45mm 的圓。 P=1.27mm，BGA ，開(kāi)0.7mm 的圓。Lead Fre