CSN33: Micron BGA Manufacturer`s User Guide
Contents
1. 0 65mm F4 Fine 0 50mm F5 Fine 0 40mm F6 Fine 0 30mm Table 2 BGA Maximum Package Height Profile J ESD30E Code Subcode Profile Description Profile Height B2 Extra thick gt 3 50mm B1 Very thick gt 2 45mm and lt 3 50mm B Thick gt 2 45mm Blank Standard gt 1 70mm and lt 2 45mm L Low gt 1 20mm and lt 1 70mm Thin gt 1 00mm and lt 1 20mm V Very thin gt 0 80mm and lt 1 00mm W Very very thin gt 0 65mm and lt 0 80mm U Ultra thin gt 0 50mm and lt 0 65mm X Extremely thin lt 0 50mm X1 Extra thin gt 0 40mm and lt 0 50mm X2 Super thin gt 0 30mm and lt 0 40mm X3 Paper thin gt 0 25mm and lt 0 30mm X4 Die thin lt 0 25mm BGA Coplanarity and Warpage Measurement Guidelines Coplanarity is the measure of deviation of the terminals solder balls from the seating plane Refer to JEDEC standard 22 B108B for more definitions and coplanarity measure ment methods Micron BGAs meet the coplanarity specifications documented in the package outline drawings provided in Micron component data sheets as follows e 100um for 1 0 0 80 0 65mm ball pitch packages 0 35 0 40mm ball diameter 80um for 0 50mm ball pitch packages 0 3 0 25 and 0 20mm ball diameter e This meets the standards described in JEDEC Design Guide 4 5 As part of the manufacturing process Micron measures coplanarity at room tempera ture on all BGA packages before2. Concave Convex JA Too ae Reference M plane easuring zone Measuring zone Moisture Sensitivity Plastic IC packages absorb moisture when exposed to atmospheric conditions During surface mount reflow absorbed moisture can vaporize and damage the package if not properly controlled To prevent damage to the package from internal stresses generated by the moisture vaporization process it is critical that strict adherence to floor life expo sure times be followed The allowable floor life exposure time for any given part is identi fied on the label for each moisture barrier bag of components contained in the shipment If the floor life exposure time is exceeded the components need to be baked dry before surface mount Refer to Micron s technical note TN 00 01 and IPC JEDEC standard J STD 033B 1 for recommended bake out conditions PDF 09005aef8479301f Source 09005aef84792f7e csn33_bga_user_guide fm Rev C 12 14 EN Micron Technology Inc reserves the right to change products or specifications without notice 3 2011 Micron Technology Inc All rights reserved Macron CSN33 Micron BGA Manufacturer s User Guide Surface Mount Design Materials and Process Recommendations C0 Surface Mount Design Materials and Process Recommendations Figure 3 BGA surface mount assembly typically follows the flow as shown in the Figure 3 Some of the guidelines at each step are provided and the signific
3. o O e Nondestructive X ray low dose electrical testing scanning acoustic microscopy visual or microscopic such as 10X inspections e Destructive Dye and pry and micro section Many manufacturers use a single rework station to incorporate multiple rework process steps such as component removal site redress solder paste flux application align ment component placement and reflow Characterizing and storing individual compo nent reflow profiles and the advancement of beam splitting imaging for alignment placement has simplified the rework process significantly One area of concern with rework is thermal separation of adjoining components during the rework process Some manufacturers have addressed this by designing hot gas nozzles that maintain the keep out zone around the reworked component to thermally isolate adjacent components during the reflow process Original equipment manufacturer OEM requirements differ when it comes to solder paste and flux only applications during the rework process For those requiring solder pastes microstencils and microsqueegees have been developed to correspond with multiple BGA sizes and ball array footprints The micro stencil is aligned using the same beam splitting imaging as component placement M icrosquee gees enable simple uniform solder paste coverage across the microstencil Some of the recommended instructions for the rework are listed below e Prior to rework parts must be free from mo
4. 09005aef84792f7e Micron Technology Inc reserves the right to change products or specifications without notice csn33_bga_user_guide fm Rev C 12 14 EN 11 2011 Micron Technology Inc All rights reserved
5. Bs having both standard pitch and fine pitch components A step up stencil is one with an area higher and thicker than most of the stencil and step down stencils have areas that are lower and thinner than most of the stencil Some of the factors to consider during solder paste printing are listed below e Precise volume of solder paste e Stencil alignment and accuracy e Proper stencil cleaning for clogged apertures Device Pick and Place Guidelines As the component ball pitch decreases accurate component placement becomes more important There are many suppliers for pick and place equipment depending on the manufacturing requirements parts speed and so on Component placement with the PDF 09005aef8479301f Source 09005aef84792f7e Micron Technology Inc reserves the right to change products or specifications without notice csn33_bga_user_guide fm Rev C 12 14 EN 6 2011 Micron Technology Inc All rights reserved Macron CSN33 Micron BGA Manufacturer s User Guide Reflow Process Guidelines PCB is important to ensure high SMT yield Micron recommends a minimum of 80 of the ball diameter intersect with the PCB land This will help maximize the inherent self alignment properties of the BGA package during reflow Reflow Process Guidelines Figure 6 270 260 250 240 230 220 210 200 180 160 140 Temperature 120 100 80 60 40 20 The reflow temperature profile is one of the most importa
6. Micron CSN33 Micron BGA Manufacturer s User Guide Introduction Customer Service Note BGA Manufacturer s User Guide for Micron BGA Parts Introduction This customer service note provides information that will enable customers to easily integrate both leading edge and legacy Micron ball grid array BGA packages into their manufacturing processes It is intended as a set of high level guidelines and a refer ence manual describing typical package related and manufacturing process flow prac tices The recommendations and suggestions provided in this customer service note serve as a guideline to help the end user to develop user specific solutions It is the responsibility of the end user to optimize the process to obtain the desired results Because the package landscape changes rapidly and information can become outdated very quickly refer to the latest product specifications Contact your sales representative for any additional questions not covered within this guide An overview of a typical BGA package and its components are shown in Figure 1 Figure 1 Ball Grid Array Package Dual Die Wire Bonded Silicon die Wire bond typically gold Die attach layer or flip chip with solder bumps Mold compound PCB substrate Solder ball JEDEC Terminology This document uses J EDEC terminology J EDEC based BGA devices in the semicon ductor industry are identified by two key attributes e Maximum
7. ant factors affecting the yield through surface mount are also briefly discussed in this customer service note BGA Surface Mount Technology SMT Process Flow Solder printing and inspection process Cleaning optional with no clean paste Solder reflow Device placement inspection 7 Rework if needed Printed Circuit Board Design Guidelines PCB design guidelines depend on many variables including ball pitch ball diameter and PCB metal land pad type Solder mask defined SM D pads have a solder mask that partially overlaps each metal land pad and defines the pad diameter Non solder mask defined NSMD pads have a solder mask clearance area away from the metal land pads so that each metal land pad diameter is defined by the edges of the metal Figure 4 and Figure 5 illustrate the difference between SMD and NSMD pads With SMD pads the solder flow is restricted to the top of the metallization which prevents the solder from wetting the sides wall of the pad as in the case of NSM D Some of the advantages and disadvantages of the SMD and NSMD are listed below Application should determine selection of pad type e For NSMD definition and control of size and location is easier than SMD Cu etching has tighter control over the solder masking process e NSMD pads are smaller and offer more space for trace routing than SM D pads e For fi
8. change products or specifications without notice 7 2011 Micron Technology Inc All rights reserved o CSN33 Micron BGA Manufacturer s User Guide Macron PCB Cleaning Figure 7 BGA Ball Attribute Before and After Reflow Before Reflow After Reflow Weight of package Package gt substrate Solder _ gt Solder paste Solder mask gt PCB gt PCB Cleaning After the surface mount process some flux residues can be found on the PCB and around the solder joint which may damage the PCB or package if not cleaned If a no clean solder paste was used in surface mount the flux residues don t have to be cleaned after the soldering process For tighter pitch and low standoff BGA packages no clean solder paste is generally recommended because of the difficulty a cleaning solution would have reaching the underside of the package If a solder flux used during surface mount requires cleaning the choice of cleaning process and cleaning solution depend on the package PCB and flux Rosin aqueous based used in the solder paste Contact the solder paste suppliers for PCB cleaning recommendations Micron also recommends completely drying the PCB after the cleaning process to remove any residual solvents If no clean solder pastes are used during rework or manual soldering operations the remaining non activated flux can cause corrosion and the PCB should be carefully inspected Test and Inspectio
9. cil Guidelines As a general design guide the aperture size should have a 1 1 ratio to the board land size For BGA applications a stencil with round or square apertures is recommended To improve paste release a positive taper 5 angle with a bottom opening larger than the top can be used To achieve good BGA print characteristics maintain a diameter to stencil thickness ratio of at least 3 1 larger openings provide better print quality Stencil design should follow the IPC stencil guideline PC7525B as shown in Table 3 on page 6 PDF 09005aef8479301f Source 09005aef84792F7e Micron Technology Inc reserves the right to change products or specifications without notice csn33_bga_user_guide fm Rev C 12 14 EN 5 2011 Micron Technology Inc All rights reserved o CSN33 Micron BGA Manufacturer s User Guide GA icron Solder Paste and Stencil Printing Guidelines _ aw OO Table 3 General Aperture Design Guideline for BGA from IPC 7525B Standard Land Stencil Footprint Aperture Thickness Area Ratio Part Type Pitch Dimension Dimension Range Range Solder Paste BGA 1 25 Circle 0 55 Circle 0 52mm 0 15 0 20mm 0 65 0 86 Type 3 Fine pitch BGA 1 00 Circle 0 45 Square over 0 115 0 135mm 0 65 0 76 Type 3 print 0 42mm Fine pitch BGA 0 50 Circe 0 25 Square over 0 075 0 125mm 0 56 0 93 Type 3 print 0 28mm Fine pitch BGA 0 40 Circle 0 20 Square over 0 075 0 100mm 0 56 0 75 Type 3 prin
10. isture as per supplier labels e Under board preheating is required e Thesame profile must be used for removal and replacement The number of times a part can be removed and replaced should be kept to a minimum to prevent internal thermal damage to the printed circuit board While the use of flux only attachment has been a common practice for BGA packages in component rework solder paste is recommended for the best BGA package attachment results Before implementing flux only attachment it is important to note that because this process reduces the amount of solder within the solder joint BGA stand off is reduced and solder joint reliability may be compromised Manufacturers must evaluate flux only versus solder paste attachment to determine the most suitable process for their specific application Reballing BGAs is not recommended for production applications This is primarily due to the various techniques used to remove excess solder from the bottom side of the BGA following removal from the PCB Excessive heat during the redress process can damage the BGA However when properly controlled reballing can be executed successfully Special reball fixtures and tools are available to simplify and help control this process PDF 09005aef8479301f Source 09005aef84792f7e csn33_bga_user_guide fm Rev C 12 14 EN Micron Technology Inc reserves the right to change products or specifications without notice 9 2011 Micron Technology Inc Al
11. l rights reserved o CSN33 Micron BGA Manufacturer s User Guide IA icron Storage and Handling of Components and Boards Storage and Handling of Components and Boards References All parts components and boards should be stored in an oxygen free environment to prevent oxidation The product manufacturer s specifications should always be followed Some of the practices to avoid when handling electronic assemblies are listed below e Avoid touching or pressing on component leads e Avoid smashing leads don t coin stack units e Avoid putting excessive force on any part of the assembly e Avoid introducing foreign material to any part of the assembly BGA components are particularly susceptible to mechanical damage from mishandling All processes where bending flexing impacting or dropping the BGA or where stresses could potentially be transferred to a component when loading it into tooling test fixtures sockets cases packaging for shipment and so on should be closely scrutinized and included in routine preventative maintenance checks Use of ESD safe trays and moisture barrier bags for storage and shipping is recommended 1 JESD30 B Descriptive Designation System for Semiconductor Device Packages 2 JEDEC IPC J STD 020D 01 3 JESD22 B108A Coplanarity Test for Surface Mount Semiconductor Devices 4 J STD 033B 1 Joint PC JEDEC Standard for Handling Packing Shipping and use of Moisture Reflow Sensitive S
12. n Some of the common defects encountered with BGA in the SMT assembly process are listed below e Head in pillow Poor wetting between the solder paste and solder balls e Solder voids Voids are cavities or air pockets formed in solder joints that seriously affects the reliability Voiding can be caused by poor selection of materials processes and designs e Pad crater Crack formation within the laminate below the solder pad due to mechan ical stress during in circuit testing board depanelization connector insertion or other stresses such as shock and vibration e Tombstoning Component tilt during reflow producing an open solder joint e Popcorning Moisture evaporation that creates high pressure leading to delamination within a plastic package In the most extreme cases the pressure may produce crack and release through the body of the package referred to as out gassing Common inspection techniques to identify defects in SMT assembly can be classified as destructive and nondestructive testing Some of these techniques are listed below The user is responsible to identify suitable techniques depending on the application PDF 09005aef8479301f Source 09005aef84792f7e Micron Technology Inc reserves the right to change products or specifications without notice csn33_bga_user_guide fm Rev C 12 14 EN 8 2011 Micron Technology Inc All rights reserved Macron Rework CSN33 Micron BGA Manufacturer s User Guide Rework
13. ne pitch applications with NSMD there is increased risk of bridging and so maintaining the solder mask webbing becomes difficult e SMD pads have larger surface area attachment to the laminate which can prevent pad cratering e SMD solder joints have higher standoff which makes the joints more robust during shock or drop events e Use of underfill may effect the choice between SM D and NSMD pads depending on application Micron recommends PCB land pad designs maintain a 1 1 2 to 1 1 ratio size between the PCB land pad and the package land pad Refer to IPC publication 7351B PCB Design PDF 09005aef8479301f Source 09005aef84792f7e csn33_bga_user_guide fm Rev C 12 14 EN Micron Technology Inc reserves the right to change products or specifications without notice 2011 Micron Technology Inc All rights reserved IA ICro n CSN33 Micron BGA Manufacturer s User Guide Stencil Guidelines EEE Ee Guidelines for additional details regarding metal land pad dimensions and other PCB design considerations Additional board design factors to consider for maintaining high SMT yields are e Land pads need to be planar and clean from any foreign materials e Solderability performance finish shall meet ANSI J STD 003 solderability require ments e Proper selection of pad surface finish materials Figure 4 NSMD and SMD PCB Land Pad Layouts NSMD SMD Figure 5 BGA Solder Ball Attach in NSMD and SMD Pads NSMD SMD Da ui Sten
14. nt factors in surface mount and must be fine tuned to establish a robust process for solder joint formation The actual temperature of the board or components will be different from the reflow oven setting and is dependent on several factors including board size thermal mass compo nent density oven type solder type reflow oven and so on The other reflow parameters such as heating ramp rate dwell time and cooling rate should be selected depending on the flux activity chemistry being used and should closely follow the paste manufac turer s recommendations It is the responsibility of the user to properly measure the temperature at different locations on the PCB and components to ensure the desired temperature is reached at all locations for complete reflow of solder joint Typical exam ples of reflow profile are shown in the Table 6 with peak temperatures of 260 C 235 C and 220 C depending on the application and solder paste type Refer to Micron s tech nical note TN 00 15 for additional soldering and surface mount recommendations Reflow Profiles 260 C am m m m m m m Umbrella profile Preheat Flux activation Reflow Cooldown O OIl MAX time approximately 9 minutes Time i pproxi y inu 1 Contact solder paste suppliers for specific reflow profile recommendations PDF 09005aef8479301f Source 09005aef84792f7e csn33_bga_user_guide fm Rev C 12 14 EN Micron Technology Inc reserves the right to
15. package height profile e Ball pitch For example TFBGA 1 2mm package height and less than 1 0mm ball pitch Package descriptors F 1 through F6 have been added to provide more detailed ball pitch information for devices with a ball pitch of less than 0 8mm Within the industry many memory manufacturers continue to use only the F descriptor for any ball pitch of 1 0mm or less see J EDEC J ESD 30E for additional information Maximum package height profile and ball pitch codes based on the EDEC standard are shown in Tables 1 PDF 09005aef8479301f Source 09005aef84792f7e Micron Technology Inc reserves the right to change products or specifications without notice csn33_bga_user_guide fm Rev C 12 14 EN 1 2011 Micron Technology Inc All rights reserved Products and specifications discussed herein are for evaluation and reference purposes only and are subject to change b Micron without notice Products are only warranted by Micron to meet Micron s production data sheet specifications All information discussed herein is provided on an asis basis without warranties of any kind IA ICro n CSN33 Micron BGA Manufacturer s User Guide BGA Coplanarity and Warpage Measurement Guidelines and 2 Table 1 Ball Pitch Dimensions and Code J ESD30E Code Name Dimension E Enlarged gt 1 50mm Blank Standard gt 1 00mm and lt 1 50mm F Fine lt 1 00mm F1 Fine 0 80mm F2 Fine 0 75mm F3 Fine
16. shipment to the customer Warpage is the deformation and deviation from a package s initial flat surface that occurs during reflow Package warpage during board assembly can cause the package terminals solder balls to have open or short circuit connections after reflow soldering Warpage is largely driven by the coefficient of thermal expansion CTE mismatch between the constituent materials of the BGA package and can also be affected by mois PDF 09005aef8479301f Source 09005aef84792f7e Micron Technology Inc reserves the right to change products or specifications without notice csn33_bga_user_guide fm Rev C 12 14 EN 2 2011 Micron Technology Inc All rights reserved Macron CSN33 Micron BGA Manufacturer s User Guide Moisture Sensitivity ture absorption The warpage signature can be either concave or convex see Figure 2 Refer to JESD22 B112A or J EITA ED 7036 standards for more information and warpage measurement methods Warpage requirements vary depending on the applications and package dimensions Micron s BGA products meet a variety of customer requirements and industry standards Some BGA products for example package on package PoP require tighter warpage control than others across the reflow temperature range Refer to Micron customer service note CSN 34 PoP User Guide for additional information on PoPs and warpage Figure 2 Package Warpage Convention J EITA ED 7036 Reference J B plane
17. t 0 23mm Solder Paste and Stencil Printing Guidelines The quality of the solder paste is an important factor in producing high yield assem blies Water soluble or no clean paste can be used for the surface mount assembly Some of the important paste properties are alloy composition melting point of the alloy solder powder type size clean no clean flux flux activity rheology and solder paste shelf stencil life Solder paste should be stored at the manufacturer s recommended temperature and used before the expiration date The solder paste types their typical solder powder size and their classifications are shown in the Table 4 Proper selection of solder paste should be made depending on the application and BGA pitch Micron has had good surface mount results using Type 3 low residue or no clean paste meeting the ROL 0 per J STD 004 Table 4 Solder Paste Types and Particle Size Paste Type Mesh Size lines per inch Particle Size jum Type 2 200 4352 75 45 Type 3 325 500 45 25 Type 4 400 635 38 20 Type 5 500 25 25 Type 6 635 15 5 To ensure good contact between the solder ball and the PCB pad optimum solder paste volume is required in the printing step Some of the important parameters at the printing steps are squeegee speed force snap off and so on A stencil with different thicknesses in specific areas either the top or bottom side s can be used to control the paste deposits on PC
18. urface Mount Devices 5 J STD 020D 01 Joint PC J EDEC Standard for Moisture Reflow Sensitivity Classifica tion for Nonhermermetic Solid State Surface Mount Devices IPC 7526 Stencil and Misprinted Board Handbook IPC 7525B Stencil Design Guideline IPC 7351 PCB Design Guidelines IPC 7095B Design and Assembly Process Implementation for BGAs 10 JEITA ED 7306 Measurement methods of package warpage at elevated temperature and the maximum permissible warpage 11 Craig Hillman Challenges with Package on Package PoP part 1 Manufacturability DfR Solutions Oo CON DD PDF 09005aef8479301f Source 09005aef84792f7e 10 Micron Technology Inc reserves the right to change products or specifications without notice csn33_bga_user_guide fm Rev C 12 14 EN 2011 Micron Technology Inc All rights reserved IA ICro n CSN33 Micron BGA Manufacturer s User Guide Revision History Revision History e Changed PCB land pad opening and the package land pad solder mask opening to PCB land pad and the package land pad e Updated all sections e Initial release 8000 S Federal Way P O Box 6 Boise ID 83707 0006 Tel 208 368 3900 www micron com productsupport Customer Comment Line 800 932 4992 Micron and the Micron logo are trademarks of Micron Technology Inc All other trademarks are the property of their respective owners PDF 09005aef8479301f Source
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