Top 5 Ways to Mitigate Component Availability Problems

Most of the electronics design world is by now aware that we’re in a very serious period of components shortages. Hardest hit seem to be ceramic capacitors, but other passives as well as a variety of connectors and silicon parts are also caught up in the shortage storm. Allocation and shortages hit every few years, but this one seems to be the worst in recent memory. It could be a problem until 2020, and the supply chain and world of components manufacturers will likely be a different animal coming out of it.

So, you might ask, isn’t that just a problem for high volume producers? No, I would answer. It affects anyone regardless of volume. The exact way that it hits you and what you can do about it may differ, but it has or soon will hit all of us.

Here’s five things you can do to minimize the effects. I’m going to go backwards and starting with the most important thing for people who need low volumes manufactured:

1. Check the availability of all of your parts immediately before sending us your bill of materials.

The. very. last. thing. before sending us your BoM. It’s not uncommon for a part to be in stock one day and out the next. We’ve even seen cases where the part’s in stock in the morning and out by the afternoon. If you’re having us quote and order your parts, verify they are in stock as the last thing you do before sending your files to us.

Almost every BoM we see these days has one or more parts that are out of stock. We send you an email about the parts being out of stock. We can’t do anything else until we hear back from you. We can’t build without parts and we don’t know your design like you do, so we can’t guess at substitutions. A last-minute check can save days of delay.

2. Put one or two alternate part numbers in your BoM, especially for passives.

As I said above, we don’t know your project so we can’t pick a sub for you. Give us some alternates. Put them on the same line as the original part, to the right. And be sure to tell us in the special instructions that you’ve put alternates in the BoM.

 

 

 

 

 

 

 

 

3. Consider your parts values carefully. You may be able to pick something with better availability.

The 0.01?F capacitor is the hardest hit component. It’s the most commonly used bypass capacitor. Some designs need exactly that value, but many don’t. It may be easier to find a 0.022?F, a 0.0047?F, or something else close enough. If that’s the case, choose a close enough value that has better supply, or put one in as an alternate.

4. You might need a slight redesign to use a smaller package.

Since smaller packages can be used in more applications, many suppliers will be allocating more of their foundry capacity to smaller form factors like 0402 and 0201 sizes. Some component manufacturers have said they’ll be permanently discontinuing anything bigger than 0402 parts except when absolutely necessary.

Stick with 0402 size passives. It may be easier to find the parts you need in that package, and those size parts will be the first ones to come back in stock.

5. If we send you a message about a part we can’t find, respond as quickly as possible.

We do our best to avoid any delays in this process, but we can only do so much. Help us out by getting back to us as soon as possible, and don’t be afraid to give us more than one part number to try.

This can be a pretty annoying problem and it can cause delays and other problems. The good news is we’re having this problem because the design world is booming and technology is advancing. It will get better, and following these five tips can help prevent delays. Don’t forget to check your parts for availability right before sending your BoM in to us. I mean it!

Duane Benson
Parts, parts everywhere, but not an 0805 to solder

Embedded Passives

I recently participated in an Altium podcast where I discussed the origins of Screaming Circuits, some DfM hints and a few other topics. I was discussing some of the challenges everyone is having these days in procuring components, and the host asked if we see many people using embedded passives as a way to mitigate supply difficulties.

I told her that I don’t think we’ve seen very many embedded passives come through our shop; too late realizing that given that embedded passives are — embedded — inside — the PCB, we wouldn’t actually see them.

Then, somewhat coincidentally, yesterday I was visiting our San Diego PCB Design division and that very subject came up. It seems that our SDPCB layout group does sometimes use embedded passives in some of the boards they lay out. I need to have a conversation with them about the layout and fab implications of embedding passives.

I’m kind of guessing here at what they look like, so don’t take this representation as literal fact.

Originally embedded passives were invented primarily for space savings. Now with 0201 and 01005 components available, that’s less of a need these days, but embeddeds can still be advantageous for reduction of parasitic effects or in areas where even 01005s are impractical, like termination of large numbers of transmission lines.

What I’m wondering, is if embedded passives could be a viable solution to some of the supply chain issues we’re seeing lately? If you need a few dozen 0.01 uF bypass capacitors on your PCB, but can’t find them*, would embedded capacitors be a practical solution?

*It’s important to note, that in most cases, the term “embedded passives” refers to the process of using various resistive and dielectric materials to create the components within the layers of the PCBs. I’m not talking about embedding the currently hard-to-find discrete resistor and capacitors within the bare board.

Duane Benson
Sorry. I have nothing snarky to say, and as you know, if you don’t have anything snarky to say, you shouldn’t say anything.

What is Your Supply Chain Telling You about Packages?

Have you purchased any electronics components lately? Have you tried and failed to do so lately? Allocation is the word of the day and substitutions are your friend.

Many, many parts are in short supply, or unavailable with extraordinarily long lead times. Sure, that happens every now and then in this industry. It’s a periodic nuisance, but what should you do for the long term? We’re are getting some interesting stories from component suppliers that might help. 

What we’re hearing is that many passive manufacturers will be trying to move their customers to smaller sizes. They want to consolidate on as few packages as is possible. That means we may be seeing the end of 1206, 0805, and maybe even 0603 form factors for many passive values.

It kind of makes sense. Right now, there might be several dozen different varieties of 0.1uF, 16V capacitor. Does the industry need that? And if there isn’t enough fab capacity to make all of the variations, why not consolidate and run more of fewer variations? It won’t surprise me if we start seeing fewer voltage ranges as well. In most cases, a 16V part will be just fine if you’re calling for a 6V or 10V part.

The chip industry has been doing this for a while. Many of the newer components just come in BGA or QFN packages. Fewer and few leading edge parts come in large through-hole or SOIC packages.

Consider using smaller components, like standardizing on 0402 parts. I know it can be a pain to use smaller parts, but any potential for future proofing your design now can prevent delays or otherwise unnecessary redesign cycles. You might just be able shrink your board size and save some money on the board fab too.

Keep approved substitutions close by, and look for newer chips that are more likely to stay in production. For microcontrollers, pick parts that have multiple memory capacity or speed range variants all in the same package.

This looks to be a pretty extreme allocation cycle, and I have a feeling that the industry will be different when we come out of it.

Duane Benson
Which is worse
Being the missing link or the weakest link?

 

A Question on Schematic Style

Just a quick question here…

I’m placing the components for my TinyFPGA based stepper motor controller board (see the prior articles here firsthere next, and here last). Specifically, I’m finding places for all of the capacitors. That’s where the question of schematic style comes in. 

When I first started using CAD software, sometime shortly before the stegosaurus roamed the land, I would position component symbols on the schematic near the chips they belonged with. Doing so made it easy, come layout time, to remember which capacitors go where.

Since then, though — and I don’t remember when I started this — I’ve started following the practice of grouping capacitors on the schematic, as I’ve done on this sheet to the right. All of the capacitors are up at the top, shown connected to V+ and ground rails.

That’s not a problem when they’re all 0.1uf bypass capacitors and each chip just takes one. However, with higher speed and more complex chips, multiple bypass caps or different values are often required on each chip.

Now, when I go to layout, I need to go find my component data sheets again (they really should never be very far away) and re-figure out what combinations of bypass capacitors go to which pins on what chips.

I like the cleaner schematic that results from grouping bypass caps, but it’s adds pain and a bit of opportunity for error during layout.

What style do you use and why? Am I an idiot for doing it this way? Wait. Don’t answer that last question.

Duane Benson
Six of one and 12 × 5 × 10-1 of another

5 Traps to Avoid When Changing from Hand to Machine Assembly

In the past, it was usually pretty easy to find chips in both surface mount and through-hole packages. Somewhere in the past decade or so, component manufacturers stopped introducing through-hole versions of their newest chips as standard practice. In many cases, new components can only be found in tiny QFN (quad flatpack, no leads), or wafer-scale BGA (ball grid array) packages.

The maker community, never shying away from a good hack, found ways to work with many of these parts while still hand building. There are very few components used in the pro-design world that are still unusable by a creative DIY maker.

But what happens when a maker has a great design and wants to mass-produce it?

Sometimes the techniques that make things work when hand soldering, will completely break a machine assembly process. To cure that ailment, I’ve compiled five common traps to avoid when moving from hand to robotic assembly.


5. Consider moisture sensitivity. 
It may not seem logical, but plastic does absorb moisture. And, it doesn’t have to be dropped in the sink for it to happen. Just sitting around exposed to the air, plastic chips will absorb humidity. In a reflow oven, these parts can end up acting a bit like popcorn. The moisture turns to steam, and if it can’t outgas fast enough, may split the chips open. Often, the damage isn’t visible to the naked eye, but with show up as an unreliable product in the field.

When we DIY folks hand-build boards, we tend to open the component packages and then just let the parts lie around without giving thought to proper storage. If you are going to send your project off to be machine assembled, you can do two things with moisture sensitive parts.

First, order the parts when needed, not before, and keep the packages sealed. Alternately, you can send in parts that have been exposed to the air; if you inform your assembly house that the parts are moisture sensitive, and ask that they be baked prior to assembly. Prebaking will remove the moisture safely.

4. Don’t skimp on solder mask. Some board fabricators offer reduced prices if you order your boards without soldermask or silkscreen. That’s not a problem when you’re hand building — you can regulate the amount of solder by eyeball.

However, when a stencil is used to apply solder paste and the board is run through a reflow oven, the solder will spread back on the exposed copper traces. This may leave your parts without enough solder on the pins to create a reliable connection.

Solder mask may add a bit of cost up front, but will increase reliability and reduce cost in the long run. Creative choice of solder mask color can also add some personality to your boards.

3. Silkscreen is important too. Lack of sIlkscreen isn’t a reliability issue, but it can make accuracy of assembly more difficult to achieve. In a perfect word, the CAD files would tell the assembly machines exactly where each part is supposed to go and what angle and orientation it needs.

Unfortunately, we don’t live in a perfect world (who knew?). It’s far too common to have footprints with errors in them, or components with ambiguous marking, to depend on the CAD files alone. Clear silkscreen will help to ensure that any errors in the data are caught visually.

If you don’t want to clutter your PCB with reference designators and polarity markings, put the designators and any other important markings in the document layer in your layout software. Then, tell your assembly house to look on that layer for the information.

2. No need to fear surface mount. One of the easiest ways to ensure that a board can be hand-built is to stick with through-hole parts. But doing so puts many limits on a design, and rules out a lot of new technologies.

Little breakout boards — a small surface mount chip pre-mounted on a PCB, with hand-solderable headers — are available for a lot of new parts, but not all. That’s helpful, but they take up a lot of extra board real estate and cost more that the part alone.

If you’re hand building a prototype, or a small number of boards for your own use, go ahead use a breakout board. But, when it’s time to get a thousand built up to sell, re-layout your PC board to use the chip without the breakout board. Just don’t forget the bypass capacitors or any other required support components.

As a bonus, many breakout boards are open source, so you may be able study and use a proven schematic and layout for that part of your design.

1. No open vias in pads. QFNs and BGAs have pins/pads under the part, often completely inaccessible. That’s fine for a reflow oven, but what if you’re soldering it by hand?

A common hand-soldering practice is to put large vias in the pad. Fix the part onto the board with tape. Then, turn the board over and stick solder and a small tipped soldering iron through the via. By doing this, you can hand solder almost any leadless surface mount part.

You can probably guess that I’m going to tell you open vias in pads will not work with automated assembly. The solder will flow down the via and end up on the back side of the board. You may end up with shorts on the back side, and parts that fall off of the front side, or just don’t connect with all their pads.

If you use the open via hand solder technique, you’ll need to re-layout your board without any open vias in the pads before sending it for manufacture.

0. Go for it! It wasn’t that many years ago when the tools and services necessary to get an electronic product manufactured were so complex and expensive as to pretty much make it impossible for DIYers to turn a hobby project into a small business. Times have changed, and with those changes, the hardware startup is back — and within just about anyone’s reach.

Duane Benson
Breaker, breaker, one nine, clear the line, we’ve got boards to build

Electronics Manufacturing Files: What We Need

Manufacturing is all about taking data from you and delivering some good working circuit boards. Well, it can be just data — as in full turnkey — or data plus some parts and or PCBs, as in a partial turnkey or a kitted job. Regardless of whether you’re sending parts and boards, or having the us as the EMS buy everything, we need good data, and a lot of it.

That data are the difference between the working boards you want and need and a random jumble of expensive paperweights.

We need a bill of materials (BoM), the job specifications (which you give us by ordering and describing any special instructions on our website), and the CAD design files. Fab and assembly drawings are always a good idea too. A little extra time spent on the files sent reduces risk, and that’s a very good thing.

The CAD design files include Gerbers, a centroid (aka pick-and-place or XYRLS file), and intelligent CAD files, such as ODB++ or IPC-2581. In some cases, such as Eagle CAD, we can use the native CAD board file.

The ODB++ and IPC-2581 file formats are the future of electronics manufacturing. They come with more data, and more accurate data, than do Gerbers. If you can send either of these two, please do so. Even if you have those, still send us the Gerber files. Gerbers are the lowest common denominator, and provide a base that we and PCB fabricators can work from.


The Gerbers are a set of files used to create the various layers of the board. Each layer requires an individual file, so a six-layer board (six copper layers) will typically require at least 13 distinct files: one for each copper layer, top solder mask, bottom solder mask, top silkscreen, bottom silkscreen, the drills holes, and solder paste for the top, and bottom if the board has SMT parts on both sides.

The drill file is combined with the Gerber files to line up the via and through-hole component holes with the appropriate spots in the PCB. Then the pick-and-place file will tell the assembler where to put each component, what angle to place it at, and which side of the board it goes in.

Fab drawings hold a human-readable, often in PDF format, description of the board and any special instructions needed by the fabricator. The assembly drawing would be the same, but for the assembler.

Sometimes the parts are too densely packed for the reference designators and polarity marks to show up on the actual board, or for aesthetic reasons, the designer doesn’t want them on the board. In such cases, all that information would be put into a set of assembly drawings; PDF files showing all of the necessary reference information.

As of this writing, the ODB++ and IPC-2581 file formats aren’t universally accepted, but are getting more so all the time. Use of these new intelligent CAD output file formats helps to reduce the number of manual steps and human interpretation, and will eventually lead to better quality and faster manufacturing times.

Duane Benson
What do we need?
What does it really matter?
Matter converts to energy
E=(what we need)C2

Power Distribution – To Route, or to Plane PCBs

Power distribution on a PCB can come in a number of forms. The three most common methods are:

  • Route power and ground.
  • Use surface layer floods.
  • Use internal planes.

After component positioning, you’ll need to look at power and ground distribution. With a two-layer board, your options are limited to individually routing power and ground, or using a polygon fill, also called a flood or pour.

 

 

 

 

For simple low-speed layouts, it’s common to route power just like any other signal. You’ll typically use a wider trace, which you can set manually, or with design rules. Drawing a polygon in the board shape, and giving it the same name as your power or ground signals may make the job easier. Keep in mind though, that you can end up with parts of a ground plane disconnected from the rest of the board. This is called an orphan. Some CAD error checks will spot such a problem and some won’t.

I made that mistake not long ago, as describe in this blog post.

If you have a four (or more) layer board, common practice is to designate one of the internal layers for ground, and one for power.

 

 

 

 

 

 

Doing so can leave more room for signal routing, can reduce EMI, and can leave a cleaner-looking, easier-to-debug board. It also reduces the chances of having orphan ground or power areas, as I warned against in the prior post.

Duane Benson
Chocolate layer cake with coconut frosting will not help with EMI

http://blog.screamingcircuits.com/

Basic Layout — Aligning Components

Not long ago, I designed an Arduino compatible clock board. The board has 12 NeoPixel (digital addressed RGB LEDs) arranged around the board to act as hour hands. The minutes and seconds are represented by an external ring of 60 NeoPixels.

 

 

 

 

 

 

 

 

 

 

How did I go about positioning the 12 NeoPixels, and what does it matter? For aesthetic reasons, I do want each NeoPixel in the proper place. If any are off a bit, I’ll notice every time I look at the clock.

I created a triangle, with all of the correct distances, and drew in in my CAD software’s Document layer. The Document layer looks just like a silk screen layer, when visible, but it won’t be printed on the board. You can use this layer to put in extra information for yourself, or for the manufacturer.

 

 

 

 

 

 

 

 

 

 

You’ll notice that I also wrote in the document layer “No tabs here.” That’s an instruction to the board fabricator to not put a panel tab where the micro USB connector goes. If it did, the board wouldn’t be buildable when panelized.

Some create a fabrication document layer and an assembly document layer. An example might pertain to reference designators. If the board is too compact for reference designators, of if, for aesthetic reasons, you want to leave them off the finished board, You can put the reference designators in an Assembly Documentation layer. Then be sure to let your assembler know what you’ve done.

The other things I did here is to keep all the LEDs aligned with the baseline of the PCB. In theory, you can place a component at any rotation angle you want. But, like any system, manufacturing works better when there are fewer variables.

You reduce the probability of error if you keep components aligned at factors of 90 degrees. It also helps to keep polarities oriented the same way, as much as possible. For example, if you can, have all the diode polarities facing the same direction.

Duane Benson
Time flies like an arrow; fruit flies like a banana

http://blog.screamingcircuits.com

The Ideal Bill of Materials

A good portion of a quality build is simply the result of clear information. One of the more important pieces of information we deal with is the bill of materials, called “the BoM.”

The BoM is a list of all the components to be placed on the PCB. The file typically includes an index number, the number of times a specific component will be used on the board, the reference designator from the schematic, the component manufacturer, and the manufacturer’s part number.

If a specific component is used more than once – a common bypass capacitor, for example – it will still only take up one line in the BoM. One field in the BoM will list the number of times the component is used, and another field will list all the reference designators for that part number.

For example, line 5 in my BOM on this slide, is a 0.1 microfarad, 10V capacitor.

The first field in the table has a line item index, 5, because this is the fifth unique part number in my BoM. The next field has a quantity of this component used on the board, which is 5. Field three holds reference designators C1, C2, C3, C4 and C5. The next field has the manufacturer, and the final field has the manufacturer’s part number.

You will likely have additional fields, such as a distributor part number, a description, the package type and other tidbits, as I have here.

But the first five columns in this example show what is generally considered to be the minimum data set for a good bill of materials.

Note the three lines at the bottom highlighted in red with the label “DNS” in the Type column.

DNS means “do not stuff.” That’s an instruction to the manufacturer to not install that component during the assembly phase. Some people use DNP, for do not place, or DNI, for do not insert. It’s always best to consult with your manufacturer to get their preferred labeling.

You may also want to include alternate parts for components likely to go out of stock. Passives, such as capacitors and resistors, are notorious for going out of stock without notice. Invariably, though, a half dozen nearly identical parts will fit the bill just as well.

Create an alternates list so the purchasing folks or manufacturer won’t get stuck not knowing if a substitute is valid or not.

Duane Benson
In the 90’s, when people said good things were “the bom”, this is what they were talking about

 

Mistakes Were Made — Too Much Ground Isolation

I recently ran a batch of my Neo Pixel clock boards through the factory here. It’s an Arduino UNO-based design that I made for myself not long ago. It sports an Atmega328P, with bootloader, an FT231X USB chip, and a DS3231 real time clock (RTC) chip. Pretty standard stuff. It doesn’t even use small parts. All the passives are 0805 size. There’s nothing exotic here. So, where did I go wrong?

I also used my 3D printer to make a clock frame to hold this board and a 60-pixel ring of NeoPixels, from Adafruit. I found that with the micro USB connector on the top of the board, it’s a little awkward to plug in the USB cable, so I put pads for the connector on the back side of the board. Depending on exactly where and how the board will be used, the micro-USB, button switches, and clock backup battery can all go on either the front or back surface of the board.

Programming the bootloader worked as expected, so I assumed it was just a job well done. Except it wasn’t. When I plugged in the micro USB cable, the RX and TX LEDs flickered briefly, but the board wasn’t recognized by my PC.

Take a look at the back side of the PCB and see if you can find my mistake (spoilers after the photo).

I ran a 24 mil trace around the back side of the board to supply power to the NeoPixels. That’s not a problem, except that I closed the loop on that trace, and didn’t put a path for the ground to get across the trace.

Follow it around, and notice that the ground connections to the u-USB connector don’t go anywhere except to this part of the plane. Ugh.

Duane Benson
Cassini’s gone now.