As the carrier of various components and the hub of circuit signal transmission, PCB imekuwa sehemu muhimu na muhimu ya bidhaa za habari za elektroniki, kiwango chake cha ubora na uaminifu huamua ubora na uaminifu wa vifaa vyote. Walakini, kwa sababu ya gharama na sababu za kiufundi, kuna shida nyingi za kutofaulu katika uzalishaji wa PCB na matumizi.

Kwa aina hii ya shida ya kutofaulu, tunahitaji kutumia mbinu kadhaa za uchambuzi wa kutofautisha zinazotumiwa kuhakikisha kiwango cha ubora na uaminifu wa PCB katika utengenezaji. Jarida hili linafupisha mbinu kumi za uchambuzi wa kutofaulu kwa kumbukumbu.

Utaratibu na uchambuzi wa sababu ya kutofaulu kwa PCB

1. Ukaguzi wa kuona

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. Ukaguzi wa mwonekano huangalia hasa uchafuzi wa PCB, kutu, eneo la mlipuko wa bodi, wiring ya mzunguko na utaratibu wa kutofaulu, ikiwa ni kundi au la mtu binafsi, ikiwa kila wakati hujilimbikizia katika eneo fulani, nk. 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. X-ray fluoroscopy

Kwa sehemu zingine ambazo haziwezi kukaguliwa na muonekano, na vile vile ndani ya PCB kupitia shimo na kasoro zingine za ndani, lazima tutumie mfumo wa X-ray fluoroscopy kuangalia. Mfumo wa fluoroscopy ya X-ray ni matumizi ya unene tofauti wa nyenzo au wiani tofauti wa nyenzo ya mseto wa X-ray au upitishaji wa kanuni tofauti kwa picha. Teknolojia hii inatumiwa zaidi kuangalia eneo la kasoro kwenye viungo vya solder vya PCBA, kupitia kasoro za shimo na kasoro katika vifaa vya BGA au CSP vilivyo na ufungaji mkubwa. 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; Wakati huo huo, njia ya mahitaji ya sampuli ni kubwa, wakati wa kuandaa sampuli pia ni mrefu, hitaji la wafanyikazi wa kiufundi waliomaliza kukamilisha. For detailed slicing procedures, please refer to IPC standards IPC-TM-650 2.1.1 and IPC-MS-810.

4. Inachunguza darubini ya sauti

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. Kwa wakati huu, darubini ya acoustic ya skanning inaonyesha faida yake maalum katika kugundua uharibifu wa PCB yenye safu nyingi. The general obvious bursting plate can be detected by visual inspection.

5. Uchunguzi wa Microinfrared

Uchunguzi mdogo wa infrared ni infrared spectroscopy pamoja na njia ya uchanganuzi wa darubini, hutumia nyenzo tofauti (haswa vitu vya kikaboni) kwa kanuni ya ngozi ya wigo wa infrared, kuchambua muundo wa vifaa, pamoja na darubini kunaweza kufanya nuru inayoonekana na nuru ya infrared na njia nyepesi, maadamu iko chini ya uwanja wa kuona, inaweza kutafuta uchambuzi wa athari za uchafuzi wa kikaboni. Kwa kukosekana kwa darubini, uchunguzi wa infrared kawaida unaweza kuchambua sampuli kubwa tu. 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. Kuchunguza uchanganuzi wa hadubini ya elektroni

Kuchunguza darubini ya elektroni (SEM) ni moja wapo ya mifumo muhimu sana ya upigaji picha ya elektroni kwa uchunguzi wa kutofaulu. Kanuni yake ya kufanya kazi ni kuunda boriti ya elektroni na kipenyo cha makumi kwa maelfu ya angstroms (A) kwa kuzingatia boriti ya elektroni iliyotolewa kutoka kwa cathode iliyoharakishwa na anode. Chini ya hatua ya kupotoka kwa coil ya skanning, Boriti ya elektroni inatafuta uso wa sampuli kwa hatua kwa wakati fulani na mpangilio wa nafasi. Boriti ya elektroni yenye nguvu nyingi hupiga uso wa sampuli na hutoa habari anuwai, ambazo zinaweza kukusanywa na kukuzwa ili kupata picha anuwai zinazofanana kwenye skrini ya kuonyesha. 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. Elektroni zilizosisimka zilizorudishwa nyuma hutengenezwa kwa kiwango cha 100 ~ 1000nm juu ya uso wa sampuli, na hutoa sifa tofauti na tofauti ya nambari ya atomiki ya dutu hii. Kwa hivyo, picha ya elektroni iliyorudishwa nyuma ina sifa za kimofolojia na uwezo wa ubaguzi wa nambari za atomiki, na kwa hivyo, picha ya elektroni iliyorudishwa nyuma inaweza kuonyesha usambazaji wa vitu vya kemikali. Skrini ya sasa ya elektroni ya skanning imekuwa na nguvu sana, muundo wowote mzuri au huduma za uso zinaweza kukuzwa kwa mamia ya maelfu ya nyakati za uchunguzi na uchambuzi.

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. Kwa kuongezea, kina cha uwanja wa picha ya darubini ya elektroni ni kubwa zaidi kuliko ile ya darubini ya macho, ambayo ni njia muhimu ya uchambuzi wa muundo wa metaligraphic, kuvunjika kwa microscopic na ndevu za bati.

7. X-ray energy spectrum analysis

Skrini ya elektroni iliyotajwa hapo juu kawaida huwa na vifaa vya kupimia nguvu vya eksirei. 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. Wakati huo huo, vifaa vinavyolingana vinaitwa mtawanyiko wa utawanyiko wa wigo (WDS kwa kifupi) na mtawanyiko wa usambazaji wa nishati (EDS kwa kifupi) kulingana na urefu wa tabia au nguvu ya tabia ya utambuzi wa ishara ya X-ray. Azimio la kifaa cha kupimia macho ni kubwa kuliko ile ya mwangaza wa nishati, na kasi ya uchambuzi wa mtazamaji wa nishati ni haraka zaidi kuliko ile ya mtazamaji wa nishati. Kwa sababu ya kasi kubwa na gharama ya chini ya viwambo vya nishati, microscopy ya jumla ya skanning ina vifaa vya kupima nguvu.

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. Uchambuzi wa uso Uchambuzi wa vitu vyote kwenye uso uliopewa. Yaliyomo ya kipimo cha vitu ni wastani wa anuwai ya vipimo vya uso.

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. Usahihi wa uchambuzi wa upimaji wa kipimo cha nishati ni mdogo, na yaliyomo chini ya 0.1% kwa ujumla si rahisi kugundua. Mchanganyiko wa wigo wa nishati na SEM inaweza kupata habari ya mofolojia ya uso na muundo wakati huo huo, ndiyo sababu wanatumiwa sana.

8. Uchambuzi wa picha ya elektroni ya picha (XPS)

Sampuli za miale ya X ray, uso wa elektroni za ndani za chembe zitatoka kwenye utumwa wa kiini na kutengeneza uso mgumu, kupima nishati yake ya kinetic, Ex elektroni za ndani za chembe zinaweza kupatikana nishati inayofunga ya Eb, Eb ilitofautiana kutoka kwa vitu anuwai na ganda tofauti la elektroni, ni “alama za vidole” za vigezo vya kitambulisho cha atomu, uundaji wa laini ya macho ni picha ya picha ya picha (XPS). XPS inaweza kutumika kwa uchambuzi wa ubora na upimaji wa vitu kwenye uso wa kina (nanometers kadhaa) za uso wa sampuli. Kwa kuongezea, habari juu ya hali ya kemikali ya valence ya vitu inaweza kupatikana kutoka kwa mabadiliko ya kemikali ya nguvu inayofunga. Inaweza kutoa habari ya dhamana kati ya hali ya valence ya safu ya uso na vitu vinavyozunguka. 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 hutumiwa hasa katika uchambuzi wa uchambuzi wa ubora wa mipako ya PCB, uchambuzi wa uchafuzi wa mazingira na uchambuzi wa kiwango cha oksidi, ili kujua sababu ya kina ya kulehemu duni.

9. Differential Scanning Calorim-etry

Njia ya kupima tofauti ya uingizaji wa nguvu kati ya dutu na dutu ya kumbukumbu kama kazi ya joto (au wakati) chini ya udhibiti wa joto uliowekwa. 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.