• Home
  • About
  • Forums
  • Articles/Blogs
  • Ask the Guru
  • Profiling Guru Survey
You are here: Home / Archives for BGA Profiling

Tips on Cooking Both a Perfect Thanksgiving Turkey and a PCB

November 23, 2011 by Profiling Guru Leave a Comment

Tweet

Why does it take half a day to cook a Thanksgiving turkey?  The answer is simple ― you have 20 lb of bird that simply cannot just be nuked in a microwave like last night’s dinner.  If not properly thawed, prepared and monitored, you either have an overcooked, dried-out bird or worse: Salmonella. Strangely enough, as you will see in a moment, PCBs are not that much different.

Let’s say you skip the thawing process and in your haste stick a frozen bird in the oven.  What happens?  The bird may look properly cooked on the outside, but as soon as you try your skill with the carving knife, you either hit bedrock or the inside is completely raw. OK, I will admit I speak from personal experience on this one (please do not bring this up with my wife).  Are PCBs any different?  Well, your reflow profile has a preheat phase, with the purpose of bringing your PCB to temperature. In other words, the entire mass of the board with all its components is gradually brought to equilibrium. If you do not do this, you run the risk of thermally shocking your components when they hit reflow and peak.  Thawing your bird and preheating your PCB ― you have the same objective in mind.

So, for the vast majority of us, we really have no idea when the turkey is fully cooked until getting an internal reading. A PCB is no different. On the surface, both might look great, but upon closer inspection, you discover some components have defects due to improper reflow or, for that matter, when you cut into a turkey that is still pink it really hits home that you aren’t cooking a TV dinner.

turkey-in-Spec_SM01

Because of this, as we all know, a 20 lb turkey requires a thermometer. I will concede that some of you use the old “poke the bird and check for pink until done” trick. Let’s assume you are not as skilled, like me, for example. Would you seriously cook a turkey by relying solely on the oven’s temperature reading on your stovetop?  Of course not, but why do some of you profile your PCB by relying on your reflow oven’s reported readings? Are either situation that much different?  Actually, yes. Your nice self-contained turkey cooking oven is more of a steady state, but there remains a large difference between what is reported by the oven and the internal temperature of your turkey. In contrast, your PCB is exposed to anything but a steady state environment because it rides on a conveyor through different heated zones with blowers, extraction systems and both ends of the oven even open to the elements!  For this reason, any oven manufacturer will adamantly tell you to profile and with regularity. Alright, you may have learned how to cook a turkey in your Mama’s kitchen and, in fact, be skilled at not using a thermometer; however, I doubt any serious SMT manufacturer would take a similar approach, checking your PCBs regularly for “doneness” in your reflow process.

What about placing the fate of your Thanksgiving feast on the cheap-o plastic pop-up indicator that likely came with the turkey? Do not laugh. How many of us use the trailing wires that came with the reflow oven?  Now to be fair, both work in principal; otherwise, you would have the likes of Purdue Farms with food poisoning lawsuits on their hands, but they only give you ballpark readings in many cases. By design, the turkey is going to be a little overdone and dried out.  Your PCB, on the other hand, cannot afford to be a little overdone or it is simply OUT of spec.  You can get by with eating the overcooked turkey … the gravy and mashed potatoes are there to make up for less than a perfectly cooked bird. But your PCB will not be as forgiving.  Trailing wires, never mind being cumbersome to use, have a tendency to kink and stretch, which compromise their readings.  They also are susceptible to 50 or 60 cycle noise from some reflow oven environments, further questioning their accuracy in some cases.

So you want to cook the perfect bird. Who doesn’t? So you pony up for a stainless steel large-dial meat thermometer to accurately read the internal temperature of your 20 lb bird. You also pony up for a KIC Explorer with Navigator because you want to create the perfect deep-in spec reflow profile. It will not only tell you the specific temperature of the joints of your $500 BGAs, but it also will find a balance that does not overcook them or any of your other temperature-sensitive components on the PCB.  No pop-up indicator profiler needs to apply since the KIC Explorer with Navigator will go the extra mile and tell you not only if you are in-spec but how DEEP in-spec your profile is, along with what can you do to improve the profile in minutes, if not seconds.  Now do you know of any turkey thermometers that can do that?

So when you prepare your Thanksgiving turkey, and as you pause to give thanks, consider applying the same care and consideration that you have given to your family’s feast as you do to your PCBs.

Happy Thanksgiving – Profilingguru

Share

Filed Under: Featured, Improve, Reflow, TC's Tagged With: AOI, BGA, BGA Profiling, ceramic packages, cost-based tools, electronics manufacturing services, energy efficiency, flip chip, maximize throughput, Process monitoring, Process Window, profiling, profiling software, Reflow, reflow oven, reflow ovens, reflow process, reflow profiling, SMT, SMT and standards, SMT Reflow, soldering, SPI, surface mount technology, Thermal Management, thermal process, thermal profiling, thermocouple attachment

Reducing Reflow Product Changeover Time

November 7, 2009 by Profiling Guru Leave a Comment

Tweet

2009 Presentation at SMT Long Island on how to reduce the changeover time from one reflow profile recipe to another.  If you ever opened up your reflow oven to dump all its heat to lessen downtime, this 4 min video is for you!!!

To view the complete video series (click here).

To subscribe to my Podcast for iTunes (click here).

https://profilingguru.com/podcasts/Product_Changeover.m4v

Podcast: Play in new window | Download (Duration: 3:40 — 16.9MB)

Share

Filed Under: Improve, Podcasts, Process Window, Reflow Tagged With: AOI, BGA, BGA Profiling, ceramic packages, cost-based tools, electronics manufacturing services, energy efficiency, flip chip, maximize throughput, Process monitoring, Process Window, profiling, profiling software, Reflow, reflow oven, reflow ovens, reflow process, reflow profiling, SMT, SMT and standards, SMT Reflow, soldering, SPI, surface mount technology, Thermal Management, thermal process, thermal profiling, thermocouple attachment

Across the Belt Uniformity and Reflow Profiling

October 13, 2009 by Profiling Guru Leave a Comment

Tweet

I am often asked the question about how to handle components that are close to the outer edge of a PCB.   Today a question came in on Circuitnet to highlight this problem:

Title: Issues with BGA Components Near PCB Edges

What issues are we likely to see when we place BGA components very close to PCB edges?

What impact might it have on reliability?

Will equipment (screening, placement, reflow, etc.) require modification?

T. B.

I leave it to the screen printer, pick and place and reflow oven guys to answer the equipment part of the equation, but I can answer how one can determine with a profile if your BGA is getting what it needs as well as how other aspects of your PCB are impacted.

Across the Belt Uniformity:

There can be anywhere from a 2 – 5+C variation in temperature across the belt.  For example, BTU uses this homemade fixture to test for uniformity.  The idea is fairly simple.  With a set of type K calibrated thermocouples, you can easily monitor 6 TCs across the belt.  You want obviously to see the least amount of variation (if you were wondering the front TC is for measuring air temperature which is also used for automatic mapping of the profile to the oven zones with KIC2000 software).

BTU tool

Profiling for Reflow:

BGAs typically require more heat to reach their peak temperatures than smaller massed components like electrolytic capacitors.   For example, your BGA might have a peak temperature of 245C.

PCB2

While your electrolytic capacitors cannot tolerate as high as a peak temperature, therefore you want to set their maximum peak temperature lower, for example to 235C (this is just a relative example).

PCB3

With KIC2000 software, you can define each component in isolation.  If the BGA is off on the edge, I might need to bump up even further my peak temperature spec since in many reflow ovens, the outer edge near the rail is the coolest.  This is why you see some ovens with heat tape running along the rails!  Keep in mind of course as you crank up your oven to reach higher temps to reflow your outer edge BGAs, everything else on your board is also going to be impacted.   More the reason you better be hooking up thermocouples to temperature sensitive components to ensure they do not get fried while you are focusing your attention on your BGAs.  Profiling software that can “balance” the board is a must.  If there ever was a case where software can help solve complex problems in profiling, here you go!

I had a webinar back in July talking about BGA profiling.  There is also a video that illustrates what I explained above.  You can find this in an earlier posting:  https://profilingguru.com/reflow/profiling-bga-webinar/

Share

Filed Under: Characterization, Define, Improve, Measure, TC's Tagged With: BGA, BGA Profiling, cost-based tools, efficiency, electronics manufacturing services, profiling, profiling software, Reflow, reflow oven, reflow ovens, reflow process, reflow profiling, SMT, SMT and standards, SMT Reflow, surface mount technology, Thermal Management, thermal process, thermal profile, thermal profiling

Why are you replacing BGAs?

October 2, 2009 by Profiling Guru Leave a Comment

Tweet

There is a great post today in Circuitnet titled “BGA Replacement Limits,” that can be found under Circuitmart.  Panelists answer the following question:

How many times can a BGA component be replaced at the same location on the same PCB and retain reliability?

Mark McMeen of STI Electronics suggests that the answer may be as little as two times!

…most companies err on the cautious side and only replace twice at the same location after the initial build which is normally 2 thermal cycles for top and bottomside reflow thermal cycles.

I think a broader question needs to be asked, why are you replacing BGAs in the first place?  In my experience, often the answer is due to poor reflow profiling.  Often there is nothing wrong with the oven, PCB or BGA.   Why is it so hard to properly profile a BGA?  I believe the reason is most folks don’t have the option of placing a thermocouple underneath the BGA nor sacrificing a board in drilling a hole on the underside for TC placement.   In the old days, you could get away with snaking a TCs under the BGA, but with micro BGAs this is just not an option.  So what do people do?  They stick a TC on top of the BGA or along side it.  Many do nothing at all which is kind of scary and wind up asking question like how many times can I redo my board.

To go to show how hot of topic this is, I held a series of webinars a couple months ago with a turnout in the hundreds.  I shared some ideas, here is an abridged 8 min version of the session for those of you that missed it. Part of the answer is proper TC attachment which by the way is currently under study at RIT to see the most reliable method as well as determine if there is a non destructive methods that is both valid and repeatable.

The other part of the equation is profiling your PCB not only for your BGAs but also those components that cannot tolerate as high of temperatures. I’ve seen plenty of manufacturers so focused on a $500 BGA, ignoring pretty much what else is going on with other components on their PCB.   Certainly having the ability to define separate specifications, for example a peak temp for a DIP while addressing the special needs of your BGAs will lead to fewer BGAs having to be reworked in the first place.

After all, which is better, to treat the symthoms or the root cause?

Share

Filed Under: Define, Measure, TC's Tagged With: BGA, BGA Profiling, profiling, Reflow, reflow ovens, reflow process, reflow profiling, thermal profile, thermal profiling, thermocouple attachment

SMT related Links to know

September 30, 2009 by Profiling Guru Leave a Comment

Tweet

RSS feeds, Tweets, blogs and newsletters, how do you keep up?   Well here is the latest on what’s available in the SMT industry.   I subscribe to all of these newsletters and regularly pick out areas of interest related to profiling for you.   I also comb the blogs though I only know of two, not including profilingguru, which is quite remarkable considering other industries have hundreds if not thousands.   The SMTA group forum on LinkedIn yields on occasion a nugget, but you need to build a profile to join.  SMTnet has always been a jewel.  Lastly, Twitter is a new phenomenon for many of us.   I am still trying to get the knack of it myself but it does have some value no doubt and will continue to grow.

On-line Newsletters:

Circuitnet

Electronics Production World

EMS Now

GlobalSMT

PCB Update

SMT Week

Blogs:

Circuits Assembly

SMT Editorial Blogspot

Forums:

SMTA on LinkedIn

SMTnet

Twitter:

Circuit Assembly

Global SMT

SMT Magazine

Share

Filed Under: Links Tagged With: AOI, BGA, BGA Profiling, ceramic packages, cost-based tools, electronics manufacturing services, energy efficiency, flip chip, maximize throughput, Process monitoring, Process Window, profiling, profiling software, Reflow, reflow oven, reflow ovens, reflow process, reflow profiling, SMT, SMT and standards, SMT Reflow, soldering, SPI, surface mount technology, Thermal Management, thermal process, thermal profiling, thermocouple attachment

Next Page »

Search Bar

Recent Posts

  • Profiling Guru Survey
  • Profiling Dual Lane Variable Speed Reflow Ovens
  • Tips on Cooking Both a Perfect Thanksgiving Turkey and a PCB
  • 2011 Profiling Guide
  • Man versus Forno de Refusão

Interesting Blogs

  • Circuits Assembly Blog
  • Rick Short – Indium Blog
  • SMT Editorial Blogspot

Resources

  • SMTnet
March 2023
M T W T F S S
 12345
6789101112
13141516171819
20212223242526
2728293031  
« Aug    

Return to top of page
Copyright © 2023. Corporate Child Theme on Genesis Framework · WordPress · Log in