電(dian)子產品(pin)使(shi)用(yong)的(de)電(dian)路板的(de)最佳形狀為矩形。長寬比為3:2或(huo)4:3。當所(suo)設計的(de)電(dian)子產品(pin)使(shi)用(yong)電(dian)路板面尺寸需大(da)于(yu)200mm×150mm時，應考慮電(dian)路板所(suo)具(ju)有的(de)機械(xie)強(qiang)度。

印制電路板外形尺寸

印(yin)制(zhi)電(dian)路板外形尺寸(cun)首先要符合(he)電(dian)子產(chan)品整(zheng)機(ji)結構設(she)計的(de)(de)要求，即由電(dian)子產(chan)品結構設(she)計決定印(yin)制(zhi)板的(de)(de)外形尺寸(cun)和調整(zheng)、開關(guan)、顯(xian)示等元器件的(de)(de)位置；另一方面，機(ji)械強度決定印(yin)制(zhi)板的(de)(de)尺寸(cun)不(bu)能過大，在無支撐點的(de)(de)情(qing)況(kuang)下，一般尺寸(cun)不(bu)應超過200mm×150mm。

印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)路板(ban)(ban)的厚度(du)選(xuan)擇應根據印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)路板(ban)(ban)的功能及(ji)所(suo)安裝的元(yuan)器(qi)件質量、印(yin)(yin)制(zhi)(zhi)(zhi)板(ban)(ban)插座規(gui)格以及(ji)印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)路板(ban)(ban)外形尺(chi)寸所(suo)承(cheng)受的機械負荷來決(jue)定。

印制電路板翹曲度

印制(zhi)(zhi)電(dian)路(lu)板翹曲度(du)的(de)要(yao)求，就是印制(zhi)(zhi)電(dian)路(lu)板平整(zheng)度(du)的(de)要(yao)求，是表面安裝生產線(xian)上(shang)貼裝設備對(dui)印制(zhi)(zhi)電(dian)路(lu)板的(de)一種要(yao)求。一般(ban)對(dui)上(shang)翹曲度(du)要(yao)求小于(yu)1.2mm，下翹曲度(du)要(yao)求小于(yu)0.3mm。

印制電路板定位孔

印制(zhi)電(dian)路(lu)(lu)板(ban)定(ding)(ding)(ding)位(wei)(wei)(wei)(wei)孔(kong)(kong)(kong)主要用于(yu)焊膏或貼片(pian)膠(jiao)的(de)(de)絲網印制(zhi)、元器件組裝(zhuang)和在(zai)線測試(shi)過程中對(dui)(dui)PCB進行固定(ding)(ding)(ding)夾(jia)持(chi)定(ding)(ding)(ding)位(wei)(wei)(wei)(wei)之用，是(shi)一種非鍍層(ceng)孔(kong)(kong)(kong)。印制(zhi)電(dian)路(lu)(lu)板(ban)定(ding)(ding)(ding)位(wei)(wei)(wei)(wei)孔(kong)(kong)(kong)一般設置(zhi)在(zai)PCB對(dui)(dui)角的(de)(de)邊(bian)緣上，印制(zhi)電(dian)路(lu)(lu)板(ban)定(ding)(ding)(ding)位(wei)(wei)(wei)(wei)孔(kong)(kong)(kong)孔(kong)(kong)(kong)徑范(fan)圍為1.5~3.0mm，既可(ke)是(shi)圓孔(kong)(kong)(kong)，也可(ke)為橢圓孔(kong)(kong)(kong)。對(dui)(dui)批(pi)量印制(zhi)電(dian)路(lu)(lu)板(ban)，定(ding)(ding)(ding)位(wei)(wei)(wei)(wei)孔(kong)(kong)(kong)的(de)(de)最大孔(kong)(kong)(kong)經(jing)偏(pian)差不(bu)應(ying)超過0.07mm。如果在(zai)PCB上有相對(dui)(dui)應(ying)的(de)(de)裝(zhuang)配孔(kong)(kong)(kong)，則可(ke)用于(yu)代替印制(zhi)電(dian)路(lu)(lu)板(ban)定(ding)(ding)(ding)位(wei)(wei)(wei)(wei)孔(kong)(kong)(kong)。拼板(ban)定(ding)(ding)(ding)位(wei)(wei)(wei)(wei)孔(kong)(kong)(kong)通常設置(zhi)于(yu)PCB板(ban)的(de)(de)工藝夾(jia)持(chi)邊(bian)。

印制電路板基準定位標志

印(yin)制(zhi)電(dian)路(lu)板(ban)基(ji)(ji)準(zhun)定(ding)位(wei)(wei)(wei)(wei)標志(zhi)，是(shi)針對表(biao)面(mian)安裝(zhuang)技術組裝(zhuang)設備(bei)的(de)(de)(de)光(guang)學視覺(jue)定(ding)位(wei)(wei)(wei)(wei)系(xi)統的(de)(de)(de)需求(qiu)而設置(zhi)的(de)(de)(de)，依據基(ji)(ji)準(zhun)標志(zhi)對印(yin)制(zhi)電(dian)路(lu)板(ban)進行位(wei)(wei)(wei)(wei)置(zhi)確認。基(ji)(ji)準(zhun)定(ding)位(wei)(wei)(wei)(wei)標志(zhi)應設置(zhi)在(zai)含有表(biao)面(mian)貼裝(zhuang)元(yuan)件的(de)(de)(de)PCB表(biao)面(mian)(放置(zhi)于PCB任(ren)意(yi)兩對角的(de)(de)(de)空白區域內)，要考慮(lv)PCB材料顏色與環境的(de)(de)(de)反差，選擇適當的(de)(de)(de)單面(mian)焊盤(pan)圖(tu)(tu)(tu)形(xing)作(zuo)為基(ji)(ji)準(zhun)定(ding)位(wei)(wei)(wei)(wei)標志(zhi)。不可將線條(tiao)或填充(chong)圖(tu)(tu)(tu)形(xing)用作(zuo)印(yin)制(zhi)電(dian)路(lu)板(ban)基(ji)(ji)準(zhun)定(ding)位(wei)(wei)(wei)(wei)標志(zhi)圖(tu)(tu)(tu)形(xing)。因這(zhe)兩種圖(tu)(tu)(tu)形(xing)將在(zai)PCB制(zhi)造時，被阻焊膜覆蓋而使光(guang)學定(ding)位(wei)(wei)(wei)(wei)系(xi)統識別(bie)困(kun)難。

基準標志常用圖形有：■、●、▲、╂，大(da)小在0.5~2.0mm范圍內，標志(zhi)銅層阻焊區(qu)尺寸應為標志(zhi)外形尺寸的兩倍。

印制電路板局部基準定位標志

在印制(zhi)電路板上(shang)，對單(dan)個、多個細(xi)間距(ju)(ju)多引線、大尺寸(cun)表面安(an)裝器件的(de)(de)精確放置、拼板區域定(ding)(ding)位(wei)而設置的(de)(de)專門焊(han)盤(pan)圖形。局部基準(zhun)(zhun)定(ding)(ding)位(wei)標志一般靠近需(xu)精確定(ding)(ding)位(wei)的(de)(de)器件邊(bian)沿(yan)位(wei)置，一般在引腳(jiao)間距(ju)(ju)小于(yu)(yu)或(huo)等于(yu)(yu)0.5mm的(de)(de)QFP器件、BGA器件焊(han)盤(pan)的(de)(de)對角外側或(huo)內側設置局部基準(zhun)(zhun)定(ding)(ding)位(wei)標志。局部基準(zhun)(zhun)定(ding)(ding)位(wei)標志焊(han)盤(pan)圖形選(xuan)擇可參照4中(zhong)的(de)(de)方法處理。

印制電路板工藝夾持邊

為使電(dian)路板在(zai)裝聯設備(bei)上正常(chang)傳遞或在(zai)線測試系統(tong)的工藝(yi)(yi)夾具需求，在(zai)印制(zhi)電(dian)路板的元器件布局(ju)、布線區外邊(bian)(bian)預(yu)留4mm以上的空白區，即工藝(yi)(yi)夾持邊(bian)(bian)。如因電(dian)路板結構的約束，PCB本身不能留有工藝(yi)(yi)夾持邊(bian)(bian)，工藝(yi)(yi)夾持邊(bian)(bian)與PCB間用Ｖ形槽(cao)方(fang)式(shi)處(chu)理。

拼板

拼(pin)板(ban)(ban)(ban)(ban)(ban)(ban)是一種提高生產(chan)效率(lv)的制板(ban)(ban)(ban)(ban)(ban)(ban)形(xing)式(shi)，它僅限于(yu)(yu)印(yin)制電(dian)路(lu)(lu)板(ban)(ban)(ban)(ban)(ban)(ban)外(wai)形(xing)尺寸小于(yu)(yu)50mm×50mm。當(dang)產(chan)量較(jiao)大時，將4~8塊(kuai)(kuai)相同(tong)的印(yin)制電(dian)路(lu)(lu)板(ban)(ban)(ban)(ban)(ban)(ban)拼(pin)在一起而形(xing)成(cheng)一塊(kuai)(kuai)較(jiao)大的印(yin)制電(dian)路(lu)(lu)板(ban)(ban)(ban)(ban)(ban)(ban)。對于(yu)(yu)拼(pin)板(ban)(ban)(ban)(ban)(ban)(ban)，由(you)于(yu)(yu)模板(ban)(ban)(ban)(ban)(ban)(ban)沖壓偏(pian)差，可能(neng)形(xing)成(cheng)板(ban)(ban)(ban)(ban)(ban)(ban)與板(ban)(ban)(ban)(ban)(ban)(ban)之間間距不一致(zhi)，最好(hao)在每(mei)塊(kuai)(kuai)拼(pin)板(ban)(ban)(ban)(ban)(ban)(ban)上都設有(you)基(ji)準(zhun)標志(zhi)，讓機器將每(mei)塊(kuai)(kuai)拼(pin)板(ban)(ban)(ban)(ban)(ban)(ban)當(dang)作單板(ban)(ban)(ban)(ban)(ban)(ban)看待(dai)。拼(pin)板(ban)(ban)(ban)(ban)(ban)(ban)的分離一般采用Ｖ型糟或銑外(wai)形(xing)留筋工藝(yi)，在拼(pin)板(ban)(ban)(ban)(ban)(ban)(ban)的邊(bian)沿加設工藝(yi)夾持邊(bian)，在工藝(yi)夾持邊(bian)上要設置(zhi)定位(wei)孔(kong)和印(yin)制電(dian)路(lu)(lu)板(ban)(ban)(ban)(ban)(ban)(ban)基(ji)準(zhun)定位(wei)標志(zhi)。

防振動、抗沖擊設計

印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)板上(shang)(shang)裝(zhuang)有上(shang)(shang)百個(ge)元器件或幾十個(ge)集成電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，而印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)板又(you)和機(ji)箱聯系在(zai)(zai)一(yi)(yi)起，因而它們所構(gou)成的振動(dong)(dong)系統是相(xiang)當復雜的，每個(ge)元器件、結構(gou)件都有自身的振動(dong)(dong)特性，兩個(ge)元器件或結構(gou)件裝(zhuang)配(pei)在(zai)(zai)一(yi)(yi)起又(you)會(hui)呈現第三(san)種振動(dong)(dong)特性，組(zu)裝(zhuang)方(fang)式不(bu)同(tong)，其振動(dong)(dong)特性也各異(yi)。為(wei)了(le)防止上(shang)(shang)述現象的產生，必須采用(yong)倍(bei)頻(pin)(pin)定律(lv)。倍(bei)頻(pin)(pin)定律(lv)是指(zhi)：在(zai)(zai)串聯的彈(dan)(dan)(dan)簧-質(zhi)(zhi)量(liang)系統中，任何一(yi)(yi)組(zu)彈(dan)(dan)(dan)簧-質(zhi)(zhi)量(liang)系統的固(gu)有頻(pin)(pin)率(lv)至(zhi)少是前面一(yi)(yi)組(zu)彈(dan)(dan)(dan)簧-質(zhi)(zhi)量(liang)系統固(gu)有頻(pin)(pin)率(lv)的兩倍(bei)。例如：假設機(ji)箱的固(gu)有頻(pin)(pin)率(lv)是100Hz，那么印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)板的固(gu)有頻(pin)(pin)率(lv)應該(gai)在(zai)(zai)200Hz以上(shang)(shang)，才能(neng)防止因印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)板的共振放大而引起機(ji)箱發生共振。為(wei)此，必須提高(gao)印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)板的結構(gou)剛(gang)度，或進(jin)一(yi)(yi)步在(zai)(zai)印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)板上(shang)(shang)采取減振措(cuo)施來削(xue)弱印(yin)(yin)制(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)板的振動(dong)(dong)。

常用的防振動和抗沖(chong)擊(ji)設(she)計措(cuo)施有以下幾種：

1. 增加印制板的厚度，從而提高印制電路板的結構剛度；
2. 在不能增加印制板厚度的情況下，可在印制板上附加加強筋，以提高其剛度。為滿足熱設計要求而采用的導熱條(板)，不僅增強了散熱能力，還提高了印制電路板的隔振及緩沖能力；
3. 把橡膠減振器聯結在印制電路板上作為附加的結構支撐，從而減小振動時印制電路板中心的振幅，使其在安全的范圍內；
4. 用機械方法增加印制電路板邊緣與支承界面間的接觸壓力，通過改變邊界條件來降低板中心的振幅，從而防止印制電路板上元器件的疲勞損壞。