As the carrier of various components and the hub of circuit signal transmission, PCB postao najvažniji i ključni dio elektroničkih informacijskih proizvoda, njegova kvaliteta i pouzdanost određuju kvalitetu i pouzdanost cijele opreme. Međutim, zbog troškova i tehničkih razloga, postoji mnogo problema s kvarovima u proizvodnji i primjeni PCB -a.

Za ovu vrstu problema s kvarom moramo koristiti neke često korištene tehnike analize kvarova kako bismo osigurali kvalitetu i razinu pouzdanosti PCB -a u proizvodnji. Ovaj rad sažima deset tehnika analize grešaka za referencu.

Mehanizam i analiza uzroka kvara PCB -a

1. Vizualni pregled

Appearance inspection is to visually inspect or use some simple instruments, such as stereoscopic microscope, metallographic microscope or even magnifying glass, to check the appearance of PCB and find the failed parts and relevant physical evidence. The main function is to locate the failure and preliminarily judge the failure mode of PCB. Appearance inspection mainly checks PCB pollution, corrosion, the location of board explosion, circuit wiring and the regularity of failure, if it is batch or individual, whether it is always concentrated in a certain area, etc. 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. Rendgenska fluoroskopija

Za neke dijelove koji se ne mogu pregledati izgledom, kao i unutrašnjost PCB-a kroz rupu i druge unutarnje nedostatke, za provjeru moramo upotrijebiti sustav rentgenske fluoroskopije. Rendgenski fluoroskopski sustav je upotreba različite debljine materijala ili različite gustoće materijala za rentgensku higroskopnost ili prijenos različitih principa na snimanje. Ova se tehnologija više koristi za provjeru mjesta nedostataka u PCBA lemnim spojevima, kroz nedostatke rupa i nedostatke u BGA ili CSP uređajima s pakiranjem velike gustoće. 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. Section analysis

Slice analysis is the process of obtaining PCB cross section structure through sampling, Mosaic, slice, polishing, corrosion, observation and a series of methods and steps. 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; Istodobno, metoda zahtjeva za uzorke je visoka, vrijeme pripreme uzorka je također dugo, potrebno je dovršiti obučeno tehničko osoblje. For detailed slicing procedures, please refer to IPC standards IPC-TM-650 2.1.1 and IPC-MS-810.

4. Skenirajući akustički mikroskop

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. At this point, the scanning acoustic microscope shows its special advantage in nondestructive detection of multi-layer high-density PCB. The general obvious bursting plate can be detected by visual inspection.

5. Mikroinfrardeća analiza

Mikro infracrvena analiza je infracrvena spektroskopija u kombinaciji s metodom mikroskopske analize, koristi različite materijale (uglavnom organske tvari) na principu apsorpcije infracrvenog spektra, analizirajući složeni sastav materijala, zajedno s mikroskopom može napraviti vidljivo svjetlo i infracrveno svjetlo sa svjetlosnom putanjom, sve dok se nalazi pod vidnim poljem, može tražiti analizu organskih zagađivača u tragovima. In the absence of a microscope, infrared spectroscopy can usually analyze only large samples. 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. Analiza skenirajućom elektronskom mikroskopijom

Skenirajući elektronski mikroskop (SEM) jedan je od najkorisnijih velikih elektroničkih mikroskopskih sustava za snimanje za analizu kvarova. Njegov princip rada je formiranje elektronskog snopa promjera od nekoliko desetaka do tisuća angstrema (A) fokusiranjem elektronskog snopa emitiranog s katode ubrzanog anodom. Pod djelovanjem otklona zavojnice za skeniranje, Elektronski snop skenira površinu uzorka točku po točku u određenom vremenskom i prostornom redoslijedu. Visokoenergetski snop elektrona bombardira površinu uzorka i generira različite informacije koje se mogu prikupiti i pojačati kako bi se dobile različite odgovarajuće grafike na zaslonu. 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. Pobuđeni elektroni povratnog raspršenja generiraju se u rasponu od 100 do 1000 nm na površini uzorka i emitiraju različite karakteristike s razlikom atomskog broja tvari. Dakle, slika elektrona unatrag rasuta ima morfološke karakteristike i sposobnost razlikovanja atomskog broja, pa stoga slika rasutog elektrona može odražavati raspodjelu kemijskih elemenata. The present scanning electron microscope has been very powerful, any fine structure or surface features can be magnified to hundreds of thousands of times for observation and analysis.

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. In addition, the depth of field of the scanning electron microscope image is much larger than that of the optical microscope, which is an important method for the analysis of the metallographic structure, microscopic fracture and tin whiskers.

7. X-ray energy spectrum analysis

Gore spomenuta skenirajuća elektronska mikroskopija obično je opremljena rendgenskim spektrometrom energije. 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. Istodobno, odgovarajući se instrumenti nazivaju spektrometrom za raspršivanje spektra (skraćeno WDS) i spektrometrom za disperziju energije (skraćeno EDS) prema karakterističnoj valnoj duljini ili karakterističnoj energiji detekcije signala X-zraka. Rezolucija spektrometra veća je od one energetskog spektrometra, a brzina analize energetskog spektrometra je brža od one energetskog spektrometra. Zbog velike brzine i niske cijene energetskih spektrometara, opća elektronska mikroskopija za skeniranje opremljena je energetskim spektrometrima.

With the different scanning mode of electron beam, the energy spectrometer can analyze the point, line and plane of the surface, and obtain the information of different distribution of elements.Point analysis yields all elements of a point; Line analysis One element analysis is performed on a specified line each time, and the line distribution of all elements is obtained by multiple scanning. Analiza površine Analiza svih elemenata na određenoj površini. Sadržaj izmjerenog elementa prosjek je raspona površinskih mjerenja.

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. Točnost kvantitativne analize energetskog spektrometra je ograničena, a sadržaj manji od 0.1% općenito nije lako otkriti. Kombinacijom energetskog spektra i SEM -a mogu se istovremeno dobiti podaci o morfologiji i sastavu površine, što je razlog zašto se oni široko koriste.

8. Analiza fotoelektronske spektroskopije (XPS)

Samples by X ray irradiation, the surface of the inner shell electrons of the atom will escape from the bondage of the nucleus and solid surface forming, measuring its kinetic energy the Ex, the inner shell electrons of the atom can be obtained the binding energy of Eb, Eb varied from different elements and different electron shell, it is the “fingerprints” of the atom identification parameters, formation of spectral line is the photoelectron spectroscopy (XPS). XPS se može koristiti za kvalitativnu i kvantitativnu analizu elemenata na plitkoj površini (nekoliko nanometara) površine uzorka. In addition, information about chemical valence states of elements can be obtained from chemical shifts of binding energy. It can give the information of the bond between the valence state of the surface layer and the surrounding elements. 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; Multilayers can also be analyzed longitudinally by argon ion stripping (see the case below) with far greater sensitivity than energy spectrum (EDS). XPS is mainly used in the analysis of PCB coating quality analysis, pollution analysis and oxidation degree analysis, in order to determine the deep reason of poor weldability.

9. Differential Scanning Calorim-etry

Metoda mjerenja razlike u ulaznoj snazi ​​između tvari i referentne tvari u funkciji temperature (ili vremena) pri programiranoj kontroli temperature. 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. Test probe consists of fixed on the cantilever beam and helical spring support, through the motor of the applied load, when the specimen deformation occurs, differential transformer to detect the change, and together with the data processing, such as temperature, stress and strain after the material can be obtained under the negligible load deformation relations with temperature (or time). According to the relationship between deformation and temperature (or time), the physicochemical and thermodynamic properties of materials can be studied and analyzed. TMA is widely used in PCB analysis and is mainly used in measuring the two most critical parameters of PCB: linear expansion coefficient and glass transition temperature. PCB with too large expansion coefficient will often lead to fracture failure of metallized holes after welding and assembly.