設(shè)計(jì)電路板需要的因素很多,例如線間矩、焊接、過(guò)孔、線路走線等問(wèn)題,合理布局線路板需要根據(jù)客戶提出的要求來(lái)設(shè)計(jì),不同產(chǎn)品應(yīng)用領(lǐng)域?qū)τ趐cb產(chǎn)品要求也有所區(qū)別,本章簡(jiǎn)單介紹關(guān)于設(shè)計(jì)電路板需要知道的四個(gè)知識(shí)點(diǎn):
(1) 正常情況下,信號(hào)線寬為0.3mm(12mil),電源線寬為0.77mm(30mil)或1.27mm(50mil);線與線之間和線與焊盤之間的距離大于等于0.33mm(13mil),實(shí)際應(yīng)用中,條件允許時(shí)應(yīng)考慮加大距離; 布線密度較高時(shí),可采用IC腳間走兩根線,線的寬度為0.254mm(10mil),線間距不小于0.254mm(10mil)。特殊情況下,當(dāng)器件管腳較密,寬度較窄時(shí),可按適當(dāng)減小線寬和線間距;
(2) 焊盤(PAD) 焊盤(PAD)與過(guò)渡孔(VIA)的基本要求是:焊盤直徑比孔的直徑要大于0.6mm;例如:通用插腳式電阻、電容和集成電路等,采用盤/孔尺寸1.6mm /0.8mm(63mil/32mil),插座、插針和二極管1N4007等,采用1.8mm/1.0mm(71mil/39mil),實(shí)際應(yīng)用中,應(yīng)根據(jù)實(shí)際元件的尺寸來(lái)定,在條件允許情況下,可適當(dāng)加大焊盤尺寸; PCB板上設(shè)計(jì)的元件安裝孔徑應(yīng)比元件管腳的實(shí)際尺寸大0.2~0.4mm(8-16mil)左右;
(3) 過(guò)孔(VIA) 一般為1.27mm/0.7mm(50mil/28mil); 當(dāng)布線密度較高時(shí),過(guò)孔尺寸可適當(dāng)減小,但不宜過(guò)小,可考慮采用1.0mm/0.6mm(40mil/24mil);
(4) 焊盤、線、過(guò)孔的間距要求 PAD and VIA :≥ 0.3mm(12mil) PAD and PAD :≥ 0.3mm(12mil) PAD and TRACK :≥ 0.3mm(12mil) TRACK and TRACK :≥ 0.3mm(12mil) 密度較高時(shí): PAD and VIA :≥ 0.254mm(10mil) PAD and PAD :≥ 0.254mm(10mil) PAD and TRACK :≥ 0.254mm(10mil) TRACK and TRACK :≥ 0.254mm(10mil)