As the carrier of various components and the hub of circuit signal transmission, PCB elektron axborot mahsulotlarining eng muhim va asosiy qismiga aylandi, uning sifati va ishonchliligi butun uskunaning sifati va ishonchliligini belgilaydi. Biroq, xarajatlar va texnik sabablarga ko’ra, tenglikni ishlab chiqarish va qo’llashda ko’plab nosozliklar mavjud.

Bunday nosozlik muammosi uchun biz ishlab chiqarishda tenglikni sifatini va ishonchliligini ta’minlash uchun tez -tez ishlatib turadigan xatolarni tahlil qilish usullaridan foydalanishimiz kerak. Ushbu maqolada ma’lumot olish uchun xatolarni tahlil qilishning o’nta texnikasi umumlashtirilgan.

PCB buzilishining mexanizmi va sabablarini tahlil qilish

1. Vizual tekshirish

Tashqi ko’rinishni tekshirish – bu PCB tashqi ko’rinishini tekshirish va buzilgan qismlar va tegishli ashyoviy dalillarni topish uchun stereoskopik mikroskop, metalografik mikroskop yoki hatto kattalashtiruvchi oynalar kabi oddiy asboblarni vizual tekshirish yoki ulardan foydalanish. Asosiy vazifa – bu nosozlikni aniqlash va PCBning ishdan chiqish rejimini oldindan baholash. Tashqi ko’rinish tekshiruvi asosan PCBning ifloslanishi, korroziyasi, taxtaning portlash joyi, elektr simlari va ishlamay qolishining muntazamligini tekshiradi, agar u partiyali yoki individual bo’lsa, u har doim ma’lum bir hududda to’planganmi va hokazo. In addition, the failure of many PCBS was discovered after the assembly of PCBA. Whether the failure was caused by the influence of the assembly process and materials used in the process also requires careful examination of the characteristics of the failure area.

2. Rentgenli fluoroskopiya

Tashqi ko’rinishini tekshirib bo’lmaydigan ba’zi qismlar uchun, shuningdek, teshik va boshqa ichki nuqsonlar orqali PCBning ichki qismini tekshirish uchun rentgen floroskopiya tizimidan foydalanish kerak. X-nurli fluoroskopiya tizimi-har xil material qalinligi yoki har xil material zichligi rentgen gigroskopikligi yoki tasvirlashning turli printsiplarining o’tkazuvchanligi. Ushbu texnologiya yuqori zichlikdagi qadoqlangan BGA yoki CSP qurilmalaridagi teshik nuqsonlari va nuqsonlari orqali PCBA lehim bo’g’inlarida nuqsonlarning joylashishini tekshirish uchun ko’proq ishlatiladi. At present, the resolution of industrial X-ray fluoroscopy equipment can reach less than one micron, and is changing from two dimensional to three dimensional imaging equipment. There are even five dimensional (5D) equipment used for packaging inspection, but this 5D X-ray fluoroscopy system is very expensive, and rarely has practical application in the industry.

3. Bo’limni tahlil qilish

Bo’laklarni tahlil qilish – bu namuna olish, mozaika, tilim, abraziv, korroziya, kuzatish va bir qator usul va bosqichlar orqali tenglikni kesimining tuzilishini olish jarayoni. Abundant information about the microstructure of PCB (through hole, coating, etc.) can be obtained by slice analysis, which provides a good basis for the next quality improvement. However, this method is destructive, once the slice is carried out, the sample will inevitably be destroyed; Shu bilan birga, namuna talablari usuli yuqori, namuna tayyorlash muddati ham uzoq, o’qitilgan texnik xodimlarning bajarilishi zarur. For detailed slicing procedures, please refer to IPC standards IPC-TM-650 2.1.1 and IPC-MS-810.

4. Akustik mikroskopni skanerlash

At present, c-mode ultrasonic scanning acoustic microscope is mainly used for electronic packaging or assembly analysis. It makes use of the amplitude, phase and polarity changes generated by the reflection of high-frequency ultrasound on the discontinuous interface of materials to image, and its scanning mode is to scan the information in the X-Y plane along the Z-axis. Therefore, scanning acoustic microscopy can be used to detect various defects, including cracks, delamination, inclusions, and voids, in components, materials, and PCB and PCBA. Internal defects of solder joints can also be directly detected if the frequency width of scanning acoustics is sufficient. Of a typical scanning acoustic image in color red alert said defects exist, because a large amount of plastic packaging components used in SMT process, by a lead into the process of lead-free technology, a large number of moisture reflow sensitive problem, namely the moisture absorption of powder coating devices will be at a higher temperature reflow lead-free process occurs within or substrate layer cracking phenomenon, Under the high temperature of lead-free process, common PCB will often burst board phenomenon. Shu nuqtada, skanerlash akustik mikroskopi ko’p qatlamli yuqori zichlikdagi PCBni buzilmasdan aniqlashning o’ziga xos ustunligini ko’rsatadi. The general obvious bursting plate can be detected by visual inspection.

5. Mikro infraqizil tahlil

Mikro infraqizil tahlil – bu infraqizil spektroskopiya usuli bo’lib, u mikroskopni tahlil qilish usuli bilan birlashtirilgan bo’lib, u infraqizil spektrni yutish printsipi bo’yicha turli xil materiallardan (asosan organik moddalardan) foydalanadi, materiallarning murakkab tarkibini tahlil qilib, mikroskop bilan birlashganda ko’rinadigan yorug’lik va infraqizil nurni yaratadi. yorug’lik yo’li bilan, vizual maydon ostida bo’lganida, izli organik ifloslantiruvchi moddalarning tahlilini izlash mumkin. Mikroskop bo’lmasa, infraqizil spektroskopiya odatda faqat katta namunalarni tahlil qilishi mumkin. In many cases, trace pollution in electronic process can lead to poor weldability of PCB pad or lead pin. It can be imagined that it is difficult to solve the process problem without the matching infrared spectrum of microscope. The main use of microscopic infrared analysis is to analyze the organic pollutants on the welding surface or solder spot surface, and analyze the causes of corrosion or poor solderability.

6. Elektron mikroskop yordamida skanerlash

Skanerlash elektron mikroskopi (SEM)-elektron mikroskopik tasvirni ishdan chiqishini tahlil qilish uchun eng foydali tizimlaridan biri. Uning ishlash printsipi – anod bilan tezlashtirilgan katoddan chiqadigan elektron nurini yo’naltirish orqali diametri o’nlabdan minglab angstromlarga (A) teng bo’lgan elektron nurni hosil qilish. Skaner lentasining burilish harakati ostida, Elektron nuri namuna nuqtasining sirtini ma’lum vaqt va makon tartibida tekshiradi. Yuqori energiyali elektron nurlari namuna yuzasini bombardimon qiladi va turli xil ma’lumotlarni ishlab chiqaradi, ularni ekran ekranida mos keladigan turli xil grafiklarni olish uchun to’plash va kuchaytirish mumkin. The excited secondary electrons are generated within the range of 5 ~ 10nm on the surface of the sample. Therefore, the secondary electrons can better reflect the surface topography of the sample, so they are most commonly used for morphology observation. Orqa tarafga burilgan elektronlar namuna yuzasida 100 ~ 1000nm oralig’ida hosil bo’ladi va ular moddaning atom raqami farqi bilan har xil xususiyatlarni chiqaradi. Shuning uchun, elektronning teskari tasviri morfologik xususiyatlarga va atom raqamlarini ajratish qobiliyatiga ega, shuning uchun teskari elektron tasvir kimyoviy elementlarning tarqalishini aks ettirishi mumkin. Hozirgi elektron skanerlash mikroskopi juda kuchli, har qanday nozik tuzilish yoki sirt xususiyatlarini kuzatish va tahlil qilish uchun yuz minglab marta kattalashtirish mumkin.

In PCB or solder joint failure analysis, SEM is mainly used for failure mechanism analysis, specifically, is used to observe the surface morphology structure of the pad, solder joint metallographic structure, measurement of intermetallic compounds, solderable coating analysis and tin must be analyzed and measured. Different from the optical microscope, the scanning electron microscope produces electronic images, so it has only black and white colors. Moreover, the sample of the scanning electron microscope is required to conduct electricity, and the non-conductor and part of the semiconductor need to be sprayed with gold or carbon, otherwise the charge will gather on the surface of the sample and affect the sample observation. Bundan tashqari, skanerlash elektron mikroskopi tasvirining maydon chuqurligi optik mikroskopga qaraganda ancha katta, bu metallografik tuzilish, mikroskopik sinish va qalay mo’ylovini tahlil qilishning muhim usuli hisoblanadi.

7. X-ray energy spectrum analysis

Yuqorida aytib o’tilgan elektron mikroskopi odatda rentgen nurli spektrometr bilan jihozlangan. When the high-energy electron beam hit the surface, the surface material of the inner electrons in the atoms are bombarded escape, outer electrons to low energy level transition will inspire characteristic X ray, atomic energy level difference of different elements from different characteristic X ray is different, therefore, can send sample of the characteristics of X-ray as chemical composition analysis. Shu bilan birga, mos keladigan asboblar to’lqin uzunligi yoki rentgen signalini aniqlashning xarakterli energiyasiga ko’ra, mos ravishda spektrli dispersiyali spektrometr (qisqa uchun WDS) va energiya dispersiyasi spektrometri (qisqacha EDS) deb nomlanadi. Spektrometrning rezolyutsiyasi energiya spektrometridan yuqori, energiya spektrometrining tahlil tezligi esa energiya spektrometridan yuqori. Energiya spektrometrlarining yuqori tezligi va arzonligi tufayli umumiy SCANNING elektron mikroskopi energiya spektrometrlari bilan jihozlangan.

Elektron nurlarini skanerlash rejimining har xilligi bilan energiya spektrometri sirtning nuqtasini, chizig’ini va tekisligini tahlil qilishi va elementlarning har xil taqsimlanishi haqida ma’lumot olishi mumkin.Point analysis yields all elements of a point; Chiziqni tahlil qilish har safar belgilangan satrda bitta elementli tahlil o’tkaziladi va barcha elementlarning chiziqli taqsimoti ko’p skanerlash orqali olinadi. Yuzaki tahlil – ma’lum bir sirtdagi barcha elementlarning tahlili. O’lchangan element tarkibi sirt o’lchovlari oralig’ining o’rtacha ko’rsatkichidir.

In the analysis of PCB, energy dispersive spectrometer is mainly used for the composition analysis of pad surface, and the elemental analysis of contaminants on the surface of pad and lead pin with poor solderability. Energiya spektrometrining miqdoriy tahlil aniqligi cheklangan va tarkibini 0.1% dan kam aniqlash odatda oson emas. Energiya spektri va SEM kombinatsiyasi sirt morfologiyasi va tarkibi haqidagi ma’lumotlarni bir vaqtning o’zida olishlari mumkin, shuning uchun ular keng qo’llaniladi.

8. Fotoelektron spektroskopiya (XPS) tahlili

Rentgen nurlanishidan olingan namunalar, atomning ichki qobiq elektronlari yuzasi yadro va qattiq sirt hosil bo’lishidan qochib, uning kinetik energiyasini o’lchaydi Ex, atomning ichki qobiq elektronlari bog’lanish energiyasini olish mumkin Eb, Eb har xil elementlardan va har xil elektron qobig’idan farq qiladi, bu atom identifikatsiya parametrlarining “barmoq izlari”, spektral chiziqning shakllanishi fotoelektron spektroskopiyasi (XPS). XPS namuna yuzasining sayoz yuzasida (bir necha nanometr) elementlarni sifatli va miqdoriy tahlil qilish uchun ishlatilishi mumkin. Bundan tashqari, elementlarning kimyoviy valentlik holatlari haqida ma’lumotni bog’lanish energiyasining kimyoviy siljishidan olish mumkin. U sirt qatlamining valentlik holati va uning atrofidagi elementlar orasidagi bog’lanish haqida ma’lumot berishi mumkin. The incident beam is X-ray photon beam, so insulation sample analysis can be carried out, without damaging the analyzed sample rapid multi-element analysis; Ko’p qatlamlarni, shuningdek, energiya spektriga (EDS) qaraganda ancha sezgirroq bo’lgan argon ionlarini ajratish (pastdagi holatga qarang) yordamida uzunlamasına tahlil qilish mumkin. XPS asosan payvandlashning yomon sababini aniqlash uchun PCB qoplamasining sifatini tahlil qilish, ifloslanish tahlili va oksidlanish darajasini tahlil qilishda ishlatiladi.

9. Differential Scanning Calorim-etry

Dasturlashtirilgan harorat nazorati ostida harorat (yoki vaqt) funktsiyasi sifatida modda va mos yozuvlar moddasi o’rtasidagi quvvat kiritishidagi farqni o’lchash usuli. DSC is equipped with two groups of compensation heating wire under the sample and reference container, when the sample in the heating process due to the thermal effect and reference temperature difference δ T, through the differential heat amplifier circuit and differential heat compensation amplifier, so that the current flowing into the compensation heating wire changes.

The temperature difference δ T disappears, and the relationship between the difference of the thermal power of the two electrically compensated samples and the reference material with temperature (or time) is recorded. According to this relationship, the physicochemical and thermodynamic properties of the material can be studied and analyzed. DSC is widely used in PCB analysis, but is mainly used to measure the curing degree of various polymer materials used in PCB and glass state transformation temperature, these two parameters determine the reliability of PCB in the subsequent process.

10. Thermomechanical analyzer (TMA)

Thermal Mechanical Analysis is used to measure the deformation properties of solids, liquids and gels under Thermal or Mechanical forces under programmed temperature control. Commonly used load methods include compression, pin insertion, stretching, bending, etc. Tekshirish moslamasi kontsentrli nurga va spiral kamon tayanchiga o’rnatilgan yukning dvigateli orqali, namuna deformatsiyasi yuz berganda, o’zgarishni aniqlash uchun differentsial transformatordan, shuningdek harorat, stress va zo’riqish kabi ma’lumotlarni qayta ishlashdan iborat. materialni harorat (yoki vaqt) bilan ahamiyatsiz yuk deformatsiyasi munosabatlari ostida olish mumkin. Deformatsiya va harorat (yoki vaqt) o’rtasidagi munosabatlarga ko’ra, materiallarning fizik -kimyoviy va termodinamik xususiyatlarini o’rganish va tahlil qilish mumkin. TMA PCB tahlilida keng qo’llaniladi va asosan PCB ning ikkita eng muhim parametrlarini o’lchashda ishlatiladi: chiziqli kengayish koeffitsienti va oynaga o’tish harorati. Kengayish koeffitsienti juda katta bo’lgan PCB ko’pincha payvandlash va yig’ishdan keyin metalllashtirilgan teshiklarning sinishiga olib keladi.