# New Excel Software Tools to Practice for SMTA Certification #1: Line Balancing

I recently developed some Excel-based software to help those who are planning to take the SMTA certification exam to practice.

In this post, I will discuss the tool that performs line balancing. In a typical SMT assembly line, the placement machines are the “gate” in the cycle time of the line. To assure that their cycle time is the lowest, the placement machines must be time balanced. For example, suppose a simple SMT assembly line has one chip shooter and one flexible placer. Let’s say that the chip shooter takes longer to place all of the chips than the flexible placer takes to assemble the simple and complex integrated circuits. So, in this case, chips should be removed from the chip shooter and be placed on the flexible placer. But how many should be moved to the flexible placer? Determining the number requires algebra, and to understand how to do it, we need a numeric example.

Let’s do an example. In an assembly line, the “gate” in the cycle time is component placement.

• The chipshooter (CS) places passives at 60,000/hr and Simple ICs (SICs) at 4,000/hr
• The flexible placer (FP) places complex ICs (CICs) at 3,000/hr and SICs and passives at 8,000/hr
• The bill of material (BOM) is 354 passives, 12 SICs, and 4 CICs
• If the FP takes less time to place the CICs and SICs than the CS takes to place all of the passives, then move some of the passives to the FP to time balance the line
• Let’s check the situation that the FP takes: (4 CICs / 3,000/hr) + (12 SICs / 8,000/hr) = 0.001333 + 0.0015 = 0.002833hrs
• The CS takes: 354/60,000/hr = 0.0059hrs
• So, move chips to the FP—but how many? Let’s call the number x. The times should be equal, so:
• 0.002833+x/8000 = (354-x)/60,000.  Solve for x to time balance the line.
• 0.002833+x/8000 = (354-x)/60,000, multiply each side by 60,000
• (60,000*0.002833) + (60,000x/8000) = 354 – x
• 170 + (60/8)x = 354 – x,  gather x terms
• 170 + ((60/8) +1)x = 354, gather numbers
• (68/8)x = 354-170 = 184, solve for x
• x = (8/68)*184 = 21.65 or 22 passive moved to FP

Let’s see if the times on each machine are the same.

• CTCS= 332 passives/60,000 passives/hr =0.005533 hrs or 19.92 secs

Is the FP the same?

• CTFP = 0.002833 + 22/8,000 = 0.005583 hrs or 20.10 secs

Why the difference?

The times can’t be exactly the same as we rounded the number of passives moved to the FP.

Figure 1 shows the calculations from the Excel® software tool I developed called “Line Balancer.”  Note the answers are the same. If you would like a copy, send me an email at [email protected].

Here is a problem for you to solve:

• The chip shooter (CS) places passives at 50,000/hr and Simple ICs (SICs) at 3,000/hr
• The flexible placer (FP) places Complex ICs (CICs) at 4,000/hr and SICs and passives at 7,000/hr
• The bill of material (BOM) is 390 passives, 14 SICs, and 6 CICs

How many components need to be moved, and to which placement machine? What is the cycle time?

To the first person that sends me the answer, I will send them a Dartmouth hat.

# Early Placement Tales

Some comical reminisces on an early (50 years old!) attempt to machine-assemble a printed circuit board. The program was written on punched paper tape and feed into a robotically controlled “placement machine.” Hijinks ensure.

# Hitachi’s SMT Exit

And then there were … 27?

Hitachi’s board today announced plans to exit the SMT component placement business, selling off certain parts of the division and closing the rest. In a press release, the firm said it would transfer the sales organization to Yamaha and cease its development and manufacturing activities.

Japan has always been the major provider of the world’s component mounters, headed such major conglomerates as Fuji, Yamaha, Juki, Sony and Panasonic. And while Hitachi’s competitors will welcome one fewer player in the market, this in all likelihood won’t shake up the industry.

Over the years it’s been widely assumed consolidation was inevitable, yet it’s taken more than a decade since the Great Tech Recession of 2001-03 for any major moves to be made.

There have been several transactions and reshufflings, of course: ASM bought Siplace (Siemens), Universal was acquired by a private equity group, as was Assembleon. Mydata was acquired by a fellow Swedish OEM. And earlier this week Dima, a small European player, was snatched up by Nordson. None of these deals has truly changed the shape of the market.

In fact, the June 2013 merger of Juki and Sony was the first major deal in which a serious player ceased to exist. Hitachi’s will be the second.

The 27 (at least) remaining players will welcome the chance to grab Hitachi’s roughly \$68 million in equipment sales now in play as result of this decision. Someone’s bottom line will look at least marginally better in the coming year. But more moves will be needed before the SMT market can truly regain the types of margins needed to inspire significant commitments to innovation that were standard fare in the 1990s.

# It (0.3mm) Finally Happened

Back in January of 2012, I wrote about the possibility of 0.3mm pitch BGAs being used here and there. I predicted that in a year, we’d see some 0.3mm pitch BGAs showing up. I was about three months off. Almost to the day.

I delivered a session at PCB West last month and asked if anyone had used a part with that pitch yet. One hand went up. That actually surprised me. What surprised me even more was when one of them (a 0.3mm pitch BGA, not a hand) arrived on our shipping dock in a parts kit earlier this week.

For comparison, the land pattern for an 0402 passive component is about one millimeter long. This specific part is just shy of a millimeter square. Even as small as it is, this part can supply 750 mA continuous. The olden days are so very long gone.

We do many, many complex parts and PCBs. We’ve put 5,000 parts on a single PC board. We’ve built boards to be shot up in rockets and dunked way down in the ocean. Some very crazy stuff has come though our shop, but we don’t do everything. We don’t do 01005 passive components at the moment. Our machines have the technical capability, but we don’t rework them, which has to go along with the assembly capability, so we don’t support that form factor for now. The 0.3mm pitch components pretty much fall into that camp. Our machines can physically pick up and place the component, but until we’ve developed to process to assemble those parts with the quality people expect from us, we won’t be supporting them.

I expect we’ll be getting more and more requests for the form factor, so we’ll be looking at it. Keep checking back. One of these days, we’ll have the process down and reliable.

Duane Benson
It’s (Huey mm, Dewey mm, and Louie mm)/10

http://blog.screamingcircuits.com/

# Centroid/XYRLS/Pick-and-Place

Call it what you may, but surface mount assembly robots need this magic file to determine where to place your components and how to orient them. We call it a centroid. Others may call it something else, but it’s all basically the same. In our case, the basic format is comma delimited, in mils:

Ref designator,     Layer,     LocationX,     LocationY,     Rotation
C1 ,                       Top ,           0.5750  ,       2.1000  ,           90

That’s not too difficult. Most CAD programs will automatically create this file for you. Eagle doesn’t natively, but we have a ULP to do it for you in Eagle (downloaded here). Again, no problems here. Mostly…

I say mostly because, at this point, you are at the mercy of the person who created the CAD library part. Provided they center the origin and follow the IPC for orientation, everything should come out just fine. Unfortunately, we do find parts that don’t follow those rules. We’ll do our best to catch and correct such things here, but for maximum reliability, check you library components to make sure. We find the problem crops up most commonly with passives.

IPC says that zero orientation for two pin passives is horizontal, with pin one on the left. For polarized capacitors, pin one is (+). For diodes, pin one is the cathode. They note that pin one is always the polarity mark pin or cathode. Pin one is also on the left for resistors, inductors and non-polarized capacitors, but left vs. right doesn’t matter so much with non-polarized things. The most common orientation error we see is to have the “zero rotation” 270 degrees off from the IPC standard.

Every now and then we’ll find that someone assumes that since usually the anode on a diode tends to be on the positive side, that the anode should be pin one. Nope. Nope. Nope.

Duane Benson
Is it pulling electrons of pushing holes?

http://blog.screamingcircuits.com/

# Little Chippy Challenges

And “chippy,” in this context, refers to chip caps and any other tiny two-connector components. When considering surface mount, most people think of the many-connector parts, like BGAs and QFNs as the challenging components. That’s mostly true. However, the little passives can be big bears too if not treated properly.

You could have tombstoning problems. This can be caused by unequal sized pads, unequal sized traces going to the pads or inequality in copper plane in a different layer. A big part on one side can cause tombstoning too — the big part’s thermal mass may slow the solder paste melt on one side of the part, leading to tombstoning.

Via-in-pad is still a problem too. Open vias can lead to unreliable connections, tombstoning or crooked  parts.

Solder mask can cause problems too. Too thick a solder mask can prevent the part from reaching the solder and can cause tombstoning. Too think a solder mask can also interfere with outgassing in the reflow oven which can cause solder ball splatter. (A = okay, B = not okay).

Duane Benson
It just goes to show you…
It’s always something.

http://blog.screamingcircuits.com/

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# An Era Ends at Siemens

We have been noting for years that, with almost all the world’s major component placement equipment makers on the block, sooner or later, someone was going to be bought (or shut down).

Today, that day came, as semiconductor equipment OEM ASM said it would acquire Siemens’ Electronics Assembly Systems business unit.

“Acquired” is a delicate term: Siemens will actually pay ASM 29 million euros (roughly\$37.9 million) to take the money-losing unit off its hands.

Hong Kong-based ASM thinks it can do what Siemens could never master: develop a profitable channel in Asia. Siemens’ highly engineered machines are  generally expensive relative to its Japanese competitors, and attempts to develop a model whereby it could compete on price as well as technology haven’t yet managed to break the string of several successive quarters of (big) losses.

With tens of thousands of machines in place around the world, Siemens’ place in the pantheon of electronics assembly equipment  manufacturers is secure. Today we salute the legacy of the thousands of its engineers who designed some of the best machines the industry has ever seen, and we hope that under ASM’s management, the unit might again return to its former glory.