Following on from our discussions of last time...
As you will recall from the previous post on this topic, My friend and colleague Chris Nash and I were discussing some puzzling results for low dip height found during testing of package-on-package (PoP) materials. The findings will be of interest to everyone who uses a dipping process in both SMT and flip-chip assembly.
As always, please contact me if you need to learn any more.
Cheers! Andy
Also: a final big THANK YOU to our friends at Nordson/Asymtek for showcasing the Indium halogen-free PoP paste Indium9.88-HF which was still dispensing after over 3 days of continuous usage at room temperature: proving its hard-earned reputation as the Energizer bunny of Pb-free (lead-free) dispense pastes. Here is a picture from the final day.
随着电子元器件组装微型化的趋势(miniaturization)，最近有越来越多的客户向我们咨询叠成封装的材料以及相关工艺(Package-on-Package；PoP)。
在向客户推荐PoP材料的时候，除非客户已经十分清楚自己要什么，我们一般会和他们详细介绍叠成封装焊锡膏PoP paste 和叠成封装助焊剂PoP flux具体是什么，分析各自的优缺点，然后让客户自己做决定。
Indium 公司的PoP paste (Indium9.88HF) 用的是5号金属粉，金属比重大概在80%-83%之间，根据是有铅还是无铅而定。 我们做过一系列的实验，和常规的SMT 3号粉和4号粉，各种金属比重的焊锡膏做比较，用5号粉在这个金属比重中做出来的PoP paste，各方面的性能最好。 Indium公司的PoP flux (Indium 89HF-LV) 也是根据各种实验结果都是最好的证实后， 才推出的。 通常检测PoP焊接材料， 可以做这三个实验： Transfer Test, Wetting Test, and Electrical Test. 具体的检测方法，Indium公司的Jim Hisert在他的论文中有详细描述。《Next Generation PoP Pastes for Electronics Assembly》
一般我个人比较喜欢推荐PoP paste，因为PoP paste能够提供extra solder。 PoP component本来就很薄，在焊接后回流的过程中十分容易“warpage 板翘”，那么component边缘部分就很有可能有一个上下之间很大的gap，导致根本无法形成良好的焊点。但是如果使用优良的PoP paste, paste中的extra solder metal 就能起到一个很好的“粘合剂”作用，即使有warage，也可以有一定的防御。 但是PoP flux在这方面就相对弱一点。
然而，PoP paste中的flux，因为要做很多功夫来清洗powder表面的氧化物，所以在回流过程中会有挺多的outgassing，这就很有可能导致空洞voiding 的产生。PoP flux相对而言，outgassing 就少很多，自然产生voiding的几率也小。
无论如何，优良的PoP paste and PoP flux，在防止wargage和voiding产生的defect方面，都是应该做得不错的。
Cheers!
Pic: Indium Corporation
Acknowledge to: Eric Bastow andJim Hisert with Indium Corporation
This week a customer in Asia asked why one of our new epoxy fluxes was not allowing the package-on-package (PoP) device to be picked up from the dipping tray. Obviously, the vacuum nozzle must have sufficient force to extract the PoP package from the PoP flux reservoir (yellow, below).
Those of you who know me also know that I am always trying to reduce things to numbers so, naturally I got thinking about how I would model this from a physical viewpoint and came up with the following:
If the downward force (weight of component plus tack force of epoxy flux) is greater than the upward force (air pressure on the bottom of the component), then the component could not be extracted from the epoxy flux. The figure shows the different variables. Expressing this mathematically, this comes out, in SI units, as:
Downward force = m.g + n.Ft.pi.(d/2)^2
where Ft is the tack force in units of mass per unit area, taken from the maximum tack force determined by the Solder Paste Tack Test from J-STD-005, ANSI/IPC TM 650:2.4.44
Upward force = 101000.A.pi.(D/2)^2
where A is the measure (fraction) of atmospheric pressure and denotes how good the vacuum is (zero vacuum is 0.0atm : hard vacuum is 1.0atm).
There are some uncertainties with this approach: How does the vacuum vary across the nozzle diameter? Does the 5mm diameter probe used in the IPC test equate to a complex CSP (chip-scale package) bottom surface, with many rounded solder bumps or solderspheres? And so on. But, at least the model puts us in the right ballpark. Just to give you a feel for how this works, the second figure shows some results. Note that scenario (iv) is the only one showing problems (negative force balance).
The data implies that you are only likely to see an issue with inability to pick up components from a dipping flux tray if either:
For many of the newer applications, component sphere/bump immersion to just deeper than the bump height (say 100-110%) is desirable. If the customer dips the whole bottom of the component into a standard (non-epoxy) flux, this potentially opens up a lot of issues including reliability (SIR; electrochemical migration); component displacement (skewing) during reflow; as well as difficulty in picking up the component from the tray. The solution to this series of issues, is to choose either a standard flux with a high pre-reflow SIR, such as our PoPflux 30B, or a low-volatile content epoxy flux.
I'll have more to say on epoxy fluxes in a couple of months, as we are currently nearing the end of extensive testing at several customers in Europe and Asia.
最近小忙，少讀書了，也少和大家分享了；不過工作之餘，翻看了一下《A Seat at The Table》一書，覺得裏面有些道理也蠻有啓發的。比如説此書中一直圍繞這個主題來展開了論述“Today, the only thing your customer cares about is value.”
就這個觀點，再對照一下Indium公司的兩個主要系列產品：
² 電路板組裝焊接材料(Solder Materials): 這裡也要分產品而論。對於技術含量較高，工藝使用要求較多的焊錫膏(Solder Paste)材料，重視成品可靠性的客戶們會更多的關注產品帶來的“價值”。 如果只圖便宜的材料，但是用起來“錯漏百出”的，最後還是事倍功半：返工，復修，廢棄率高（特別是浪費貴的不能翻修的板子），產出率低，總體成本也自然高了。 對技術含量較低，工藝已經“模式化”的產品，像錫棒(Solder Bar)，錫綫(Solder Wire), 性价比會更關鍵……在目前日益高漲的金屬原材料市場中，Indium公司考慮到客戶們的成本壓力，也推出了性能可以和SAC305錫棒媲美的有成本優勢的Sn995錫棒。
² 半導體封裝材料(Semiconductor Materials): 整個半導體行業應該算是一個高成本，高投資，高回報（運營得好的話）的三高行業。半導體封裝材料也像是其中的經絡血脈吧，連接各個部分，讓整體最後順暢無阻的工作。半導體各個部分的材料都不便宜，設備更是不菲；對材料性能的表現要求和驗證都很嚴格，畢竟都投資那麽多，不能“功虧一簣”嘛。所以客戶們一般會十分重視產品的價值。 Indium 公司目前提供的半導體材料有：Wafer Flux, Wafer Paste, Micro Spheres, Flip-Chip Flux, Substrate Paste, Ball Attach Flux, Die-Attach Paste/Wire, PoP Fluxes, etc.
Indium公司還為大家提供散熱界面材料(Thermal Interface Materials)，工程焊料(Engineering Solders)，薄膜光付太陽能板製造材料&太陽能板組裝焊接材料(PV Solar Materials)，和銦金屬及其化合物等。 這些材料使用在比較領先的應用中，新興行業，或是細分市場中，客戶們都十分重視產品和服務能給自己帶來的價值。
Cheers!
Pic: Indium Corporation
PS: 前些日子看了中央4台的《第三屆漢語橋在華留學生漢語比賽》，感慨不已！除了感嘆這些留學生們對“那麽難”的漢語的精湛掌握，對中國文化和歷史的了解，甚至對中國的熱愛；更感慨的是，這些活動也説明了祖國的強大！現在越來越多的留學生們來中國學習，想進一步了解中國，和中國人民交流；中國話也在慢慢傳播到全世界！以前中國學子們苦讀英語，考TOFEL, 雅思，GRE什麽的；現在金髮碧眼的學生們也在場上比拼誰更了解我們的“四書五經”了，哈哈！
上週在美國的拉斯韋加斯(Las Vegas), IPC舉辦了美國地區行業的盛會APEX. Indium公司一如既往的在展會中心安排展位，和業界各位舊友新友交流，與大家分享最新的產品和技術，傾聽大家的反饋和聲音。
除此，在人山人海的技術會議交流中心(paper presentation, educational workshop)，Indium公司的五位大將還為大家做了精彩的演講：
² Lead-Free Flux Technology and Influence on Cleaning.
² Selection of Dip Transfer Fluxes and Solder Pastes for PoP Assembly.
² Achieving High Reliability Low-Cost Lead-Free SAC Solder Joints Via Mn or Ce Doping.
² Achieving High Reliability for Lead-Free Solder Joints – Materials Consideration
² Addressing the Challenge of Head-in-Pillow Defects in Electronics Assembly.
² Challenges for Implementing a Halogen-Free Process
² Understanding SIR
² Stencil Printing Transfer Efficiency of Circular vs. Square Apertures with the Same Solder Paste
Cheers!
Click here for a description and video that shows a nozzle design from FINETECH which clamps down onto PoP components during rework.
“The PoP soldering head is an easy-to-use tool for reworking stacked devices as a whole in a single reflow process. It uses vacuum-actuated mechanical clamping tweezers which avoid separating the single layers of a PoP during component removal. The PoP soldering head can be easily adapted to different component thicknesses. Furthermore it is possible to adjust the width of the clamping tweezers prior to the process when the rework arm is swiveled down to avoid affecting other components on the PCB (e.g. accidental shifting of neighboring small passives).”
Sounds like this would be great for combating “PoP Quicksand”. That nasty problem that large components have when the vacuum provided by the nozzle isn’t strong enough to lift the package-on-package component back out of the PoP solder paste or dipping flux. Okay, I just made up that term – but it’s pretty descriptive, right?
Conceptually it seems to make a lot of sense, please comment if you have any experience with it!
7:40am
Just got in, fired up the laptop, and made some hot chocolate. This is the best time to get a jump on the day. I clear out my spam that rolled in overnight and prioritize the emails in my inbox. The first tasks that I cleared were:
- Connected a new potential solar materials rep with the right people at Indium Corporation
- Recommended the optimal reflow profile for Indium9.88HF PoP solder paste
- Activated an online Vapor Deposition course
- Helped specify tabbing ribbon and solder wire for a college student working on a lunar rover project
- Planned underfill testing for today.
10:00am
After rounding up materials, components, and equipment, Brandon Judd and I assembled some BGAs on a customer's test board. Later today we’ll underfill, and rework some of the components to demonstrate the yield of a reworkable underfill. Each board had 18 components of 2 types. One of them is a very large, coarse pitch BGA. The other one (you guessed it) is exactly the opposite, a small, fine pitch BGA.
Noon
Took a drive and ate lunch.
1:00pm
When I returned to my desk, I noticed a few emails that needed attention. One was regarding the PoP solder paste reflow profile I mentioned earlier. It looks like that will work for the particular application. Another email regarded a barcode design that I am working on for a customer.
1:30pm
Took a call regarding solder sphere attachment. WS3622 was recommended to ease flux cleaning in place of an older tacky flux.
2:00pm
Answered an interesting call regarding thermal management for a cavity CPV assembly. The coolest part – he found my contact information on this blog.
2:45pm
Worked on editing an interview for Global Solar Technology magazine. I had a chance to discuss many of our solar products in detail, while explaining the advantages of each.
3:00pm
The schedule for the day shifted, so we will reconvene the underfill testing early next week. This gives me some time to begin the Interfacial Engineering course mentioned earlier. Looks pretty interesting so far. Spent some time going through the course material and learning some new things.
4:30pm
Posted this blog entry. After looking at the things I’ve mentioned here, I noticed I could tweet all the little parts of my day. If you’re interested, check: http://twitter.com/SolderNinja
After just finishing her department’s monthly activity report, Patty took a break to stare out of her window, admiring the beauty of last night’s fresh snowfall. Her mind quickly went to the events of the past week. Rob had “popped the question” and Patty had quickly said yes. Her and Rob’s mothers were ecstatic. Both Patty and Rob liked and enjoyed each other’s parents. Patty recognized this as a blessed situation, but both mothers were now spending 10 hours each day planning the wedding. A result, Patty and Rob were both fielding 3 or 4 calls a day from each mom. Patty decided to go “with the flow” and count her blessings that both she and Rob had great parents.
She briefly looked down at the ring Rob had given her. It was a striking two carat emerald with 0.4 carat diamonds on either side. Rob was concerned that Patty might not like an emerald, but he explained that the price of diamonds is controlled and that “you could pave your driveway with diamonds for each equally good sapphire, ruby and especially emerald that exists in nature.” He went on to tell her that “all of the emerald mines of Colombia produce only one or two good 2 carat emeralds per year.”
Well one of them was right there on her finger. In addition to the uniqueness of emerald, the setting was in rhodium, the hardest and rarest of the precious metals. “Five hundred times more rare than gold,” Rob told her. She was especially impressed when she looked up rhodium on the internet and found this quote: “Rhodium has been used for honours, or to symbolize wealth, when more commonly used metals such as silver, gold, or platinum are deemed insufficient.” Gold and platinum insufficient!?
Rob was really secretive about how he found such an apparently rare ring. But it was consistent with his many other successes in life. She was thrilled to have him as a future hubby, even if she did beat him at golf.
These happy and a little stressful thoughts were interrupted, by Pete coming to her door.
“Hey, kiddo, get packed, looks like will be going on another trip. Guadalajara, this time. Como es su espanol?” Pete said with gusto.
“Mi espanol es muy bueno. Why do you think we will go to Guadalajara?” Patty asked.
“Well, I just talked to Pedro and he said that they performed our productivity audit. Uptime is 29%, and all lines are time balanced to +/- 2%, about as best as could be hoped.”
Patty and her team developed a “Productivity Audit” from what they learned with The Professor in their recent adventures together.
“So then what is the problem?” Patty inquired.
Pete responded, “Jane, the finance exec we met on our trip to South Carolina, implemented a company-wide profitability software program. It was implemented and Guadalajara is 10% too low. No one can figure out why. I think we’ll want The Professor for this one.”
Patty called and was stunned that The Professor was again available. Apparently this was his off term teaching at Ivy University, as he teaches over the summer.
When our trio arrived at ACME’s Guadalajara facility they all spoke in Spanish. Patty had taken Spanish starting in 4th grade through high school, Spanish was one of the 7 or 8 languages The Professor spoke and Pete was second generation from Puerto Rico. They were surprised that the site GM, Harry Hopkins, asked them to speak in English.
“Give me a break, I grew up in Boston, I can barely speak English,” he joked in his heavy Boston accent. “We want you to help us find that lost 10%, we must be doing something wrong. Help us find it,” Harry implored. “One thing I can tell you is that I am really proud of my team, they are really working hard, you can tell by all of the product that is out there. It makes me proud just to walk out on the shop floor and see all of the product!”, he went on.
Patty was relieved that Harry was so supportive. Apparently Jane had sent the “good word” about how the trio had helped ACME’s South Carolina plant.
As the trio went on a tour, one thing immediately struck Patty, there was hardly room to walk around. There were partly assembled boards all over the place.
At the end of the tour Patty spoke up, “This facility is striking in how much partially completed product is on the shop floor.”
“And there-in lies the problem,” responded The Professor.
How can profits be off when uptime and line balancing are so good? Could it be that Guadalajara uses poor performing solder paste, fluxes, or performs? Will our illustrious trio find the problem? Does Patty really like her emerald engagement ring? Stay tuned for the latest.
Cheers,
本來的初衷，是希望能給這傢ODM, 它的上游OEM（原始設備製造商）公司，下游EMS（製造加工廠），提供Indium公司性能穩定良好的SMT焊接材料(如錫膏solder paste，錫綫solder wires)等，並為他們提供及時的技術服務和一系列解決方案，協助他們做到最好。
但是在相互交流的過程中，我們了解到這傢公司還做IC設計，芯片曡層封裝等(Package on Package; PoP)。其實，在曡層封裝應用中，的Indium 公司也有的很成熟的半導體技術和材料。比如説for BGA/CSP的solder balls, dispensing paste/flux, transfer paste/flux, PoP paste/flux, etc.
站在客戶端的角度，他們也應該希望有供應商能提供這一整套的解決方案，以對内外材料/技術的洞悉，幫助他們順利完成這個（些）大項目。
站在我們自己的角度，在協助客戶時，也最好有發現“交叉銷售Cross Selling”機會的眼睛， “发现销售不同产品或向不同部门（或客户）销售的机会，从而帮助客户，满足客户需求，达到销售目的。”
Cheers!
PS: 小帆這兩天在博客中寫到“操作系统的改进更新目前来讲都是小步前行。如若想像windows95/98那样革命性的变化，那就要看未来人机交互方式的变化。从某种意义上讲，硬件技术而不是软件技术将是未来变革到来的动力。比如，如果你能把电脑做成手表；如果你的输入设备能凭空展开或投射虚拟。。。”他的話語也讓我立刻想起現在電子行業的微型化(miniaturization)，芯片的曡層封裝，3D Dimension, etc. ….. 科技以人爲本。很幸運，能生活在高科技的今天，享受各種高科技帶來的服務和便捷！
Source: Amkor
The new TVM™ PoP components have gotten a lot of press, and soon we should be able to get our hands on TMV PoP daisy chain parts for material testing. I would love to evaluate next generation PoP solder pastes with these new components. Lee Smith (Vice President of Business Development at Amkor) had this to say about obtaining parts for testing:
LS: “We have significant direct and end customer demand for our TMV technology in next generation high density PoP applications. Amkor has qualified the technology for high volume production and we are now completing customer ramp readiness and SMT validations.
In addition to our customer specific work, we have presented 3 TMV joint project studies on SMT stacking and board level reliability at industry conferences over the past 2 years. We have demonstrated robust SMT stacking with standard dipping flux, paste and BGA underfill materials. We plan on offering a 14x14mm daisy chain TMV PoP test vehicle through Practical Components sometime in Q2 2010. Prior to that we will entertain joint projects with this test vehicle under non-disclosure agreements to validate compatibility with new SMT materials.”
Click here to learn more about the Amkor’s TMV and PoP package family.
TMV is a trade mark of Amkor Technology, Inc.
Solder Basics... If I needed to pick my favorite flux for hand soldering, it would easily be PoP Flux 030B. I know it’s probably never going to find itself in household soldering toolkits, it’s a semiconductor packaging material – most people never need that good of a flux around the house, but I said it was my favorite, not the most practical.
This is why PoP Flux 030B is the best choice around the house:
1) It has proven it’s solderability to ENIG, silver, oxidized copper, OSP, and nickel with Pb free and Sn/Pb alloys (which I’d choose any day for my personal soldering applications).
2) It is a halogen free, no-clean flux, so you can just leave it on the pipes, connectors, or stereo wires you’re connecting.
3) It is safe to use even if it isn’t completely heated and cured – this is rare for a no-clean flux.
4) The airless packaging process gives it a unique tack/viscosity ratio and a smooth texture that you just don’t get with cheapo off-the-store-shelf fluxes.
5) It activates at a relatively low temperature but can endure ~300degC reflow. Hand soldering is not accurate, so I like the widened process window.
6) I think it’s pretty cool to use such an advanced flux for low-tech soldering, it’s overkill at its finest.
This is a rare photo taken in the underground Structural Solder Joint Test Facility (SSJTF) nearly 5 miles below a small farming town in Central NY. The light that you see is not really just a cellar window…
Dr. Andy Mackie recently put together a model to determine the probability that a component can be successfully dipped in solder paste or flux. Here is a little more from him on this subject:
"A customer in Asia was asking why one of our no-clean package-on-package fluxes, the ultralow residue NC510, was not allowing the PoP device to be picked up from the dipping tray. It turned out that the customer was allowing the flux to coat the whole of the bottom of the component, not just the solder bumps, so the vacuum nozzle had insufficient force to extract the PoP package from the flux . I got thinking about how I would model this from a physical viewpoint.
If the downward force (weight of component plus tack of flux) is greater than the upward force (air pressure on the bottom of the component), then the component could not be extracted from the flux. The figure shows the different variables. Expressing this mathematically, this comes out, in SI units, as:
Downward force = m.g + n.Ft.pi.(d/2)^2
where Ft is the tack force in units of mass per unit area, taken from the maximum tack force determined by the Tack Test Method from J-STD-005, ANSI/IPC TM 650:2.4.44
Upward force = 101000.A.pi.(D/2)^2
where A is the measure (fraction) of atmospheric pressure and denotes how good the vacuum is (zero vacuum is 0.0 : hard vacuum is 1.0).
There are some uncertainties with this approach: How does the vacuum vary across the nozzle diameter? Does the 5mm diameter flat IPC probe equate to a much smaller sphere? and so on, but it at least puts us in the right ballpark.
Just to give you a feel for how this works, the second figure shows some data. Note that scenario iv is the only one showing problems (negative force balance). The data implies that you are only likely to see an issue with inability to pick up PoP components from a dipping PoP flux tray if either:
- Components: Heavy and have many large PoP solder bumps
- Vacuum Nozzle: Too small and the vacuum is weak/poor
- Flux: Very tacky (high tack force)
and certainly, if the customer dips the whole bottom of the component into the flux, this opens up a lot of issues, including reliability (SIR); component displacement during reflow; as well as inability to pick up the component from the tray. This is why we always recommend a flux dipping height of 40-50% of the PoP bump height, to eliminate these issues."
I have found this model not only interesting, but useful for technicians to use when asked why components are 'only dipped 50%'. As a technician, it is good to have a scientific reason to refer to - even though experience may have already proven the theory to us personally.
A passage from Metals Handbook, Volume 6, 1983Ӕ
According to the Encarta Dictionary that popped up on the left side of my screen a moment ago, "inextricably" is defined as:
1) impossible to get free from
2) impossible to disentangle or undo
3) hopelessly involved or complex
The interaction of flux and alloys/surface finishes is involved and complex. I think we've gotten to the point where we can take "hopeless" out of the description of flux though.
It is still widely thought that a flux is 'more powerful' or 'more active' than another. That's like saying "John is better than Joe" – John is better at what?!? Part of the confusion with fluxes came from the very chemical nature of the fluxes. Since certain chemicals react with certain oxides better over different temperature ranges, it would only be accurate to say that Flux A is better than Flux B for soldering alloy "X" to surface finish "Y" with "Z" profile. And even then you'd still be discounting the effects of Oxygen level during reflow, reflow equipment type, and other lesser variables.
When I began testing different fluxes to examine the effect surface finish had on solderability, I expected each flux to solder to copper differently. For example - lets call the wetting a function of that flux (f), and the difficulty of the surface a nominal value copper=1. It made sense to me that for a given alloy "A", the result would be 1A(f), soldering to nickel would be something like 0.5A(f). That's just not the way fluxes work though. Yes, it is more complicated than a simple formula, but flux activity is known through experience. Extensive testing has shown what works, and to what degree. There is no longer an excuse to guess at a preferred flux for ball-attach applications.
A lot has changed in the world of package-on-package in the last few years. The most obvious change that I have seen is the development of specialized pastes for component dipping. If you haven’t tried one of these pastes, here are 8 reasons why you should:
8) More consistent transfer over time
7) Head-in-pillow elimination
6) Better wetting to a range of alloys
5) Optimized metal loading
4) Specially designed powder distribution
3) Halogen-free flux formulations
1) Higher possible yields
Don’t’ expect a simple answer – that depends on your application.
If you are looking for a solder paste, NC-SMQ80 is the flux vehicle of choice. For spray applications 5RMA has a strong following on Au substrate applications. For niche ball attach or specialty processes needing a tacky flux, WS-363 delivers the best wetting on ENIG (see attached chart), but WS-575 has a more useable rheology for pin-transfer. PoP Flux 030B is your ticket in no-clean applications at these low temperatures.
Did I mention all these options are Halogen-Free?
Are you looking for information on semiconductor packaging materials? Send your request to jhisert@indium.com. It’s all fair game – released, experimental, or competitor materials. Flux characteristics, paste properties, application methods…
Inquire about any of the following topics:
From a mechanical perspective, larger solder joints are generally preferred when assembling package-on-package (PoP) components. Just as a large set of gears can handle more power, fortified interconnects add a measure of reliability to BGAs and CSPs. That is why in many cases, dipping paste is used instead of PoP flux for package-on-package stacking and BGA rework - to increase solder joint volume. The added volume of solder helps keep the solder spheres in contact with interconnect pads throughout the reflow cycle, combating the effects of warpage. This will help you increase the solder reliability and the final yield of your PoP assemblies.
Here are some links to learn more about the PoP solder paste process:
Control Your Materials, or They Will Control You (part 1)
Control Your Materials, or They Will Control You (part 2)
Package-on-Package Paste Leveling (1/5)
Package-on-Package Component Dipping (2/5)
Package-on-Package Transport (4/5)
Package-on-Package Reflow (5/5)
Package-on-Package (PoP) use in the SMT process is slowly creeping from a niche application into mainstream use. From experience, I know that some customers are using off-the-shelf Wireless Local Area Network (WLAN) and Bluetooth Personal Area Network (PAN) integrated into their current PCB designs. Systems that already exist suddenly become user friendly with the addition of easy Bluetooth, such as portable navigation systems or even my new motorcycle helmet. So, with that, I'd like to try something different, and post an interview with our Semiconductor Application Engineer, Jim Hisert, and resident Package-on-Package expert. Jim, what is the biggest issue facing the widespread use of PoP's in the world today? Well, Mario, it is a different process. I would say component dipping is "easier" than standard SMT into solder paste, because customers are just so accustomed to paste printing. There is also a limited material set and knowledge base for this process, so I find many people feel they are pioneering and become uncomfortable. We try to provide as much knowledge as we can up-front to shorten the learning curve. Lets talk about the component dipping process. Can you diagram the process of PoP use in the SMT world? There are actually two different process sequences that are mainstream. Process "A" -Stencil print solder paste on the entire board (this will be used for all standard SMT components and the bottom component in the PoP stack). -Place standard SMT and bottom PoP components. -Dip second level PoP component in PoP solder paste or flux. -Place second PoP component on top of bottom PoP component. -Repeat if necessary for +2 level component stacks. -Reflow. Process "B" -Stencil print solder paste on the entire board. -Place a pre-assembled PoP stack along with standard SMT components (They can be purchased pre-assembled by the manufacturer in some cases, although this limits the modular application flexibility of separate PoP components). -Reflow. Based on your experience, what can we do to help existing and theoretical processes? There are so many things to do! We need to evaluate existing materials, new materials, and competitor materials. We should keep track of new process developments and possible issues to share with our customers to make their life easier. It is important to help customers select materials, and then be there on the line to help set up the process and get the equipment settings dialed in. I feel that many customers take too much on by themselves; why "re-create the wheel"? Thank you to Jim Hisert, Semiconductor Application Engineer for Indium Corporation. More information may be found at Jim's Semiconductor Blog or Online Help: Indium Knowledge Base.
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