An Unanswered Question

I’ve been reading through my Virtual PCB chat session transcript from Tuesday. It was a fun session and I have a much better idea of how the virtual shows work now. I think I may just be getting it.

The chat session had a lot of interesting questions and dialog. I did notice, however, that I missed one question and thus didn’t answer it. Oops.

Owen asked if I am of the opinion that all footprints should have rounded pads (probably stencil cutouts, too) to help with paste release. Sorry I missed your question.

I’m not of that opinion. There are a lot of factors that come out of stencil decisions. Paste release is one of them. There are others, some more important. For example, the shape of a pad and stencil cut out can either encourage or discourage solder balls. The size of the opening can put too much or too little paste on the pad. Wide open cut-outs over heat slugs can cause float.Bad QFN paste w caption

The pads themselves, should follow the part manufacturers recommendation for shape and size. Most are rectangular. BGAs have round pads. Unless you have a very good and very specific reason, I would not deviate far from the part manufacturer’s recommended footprint.

Some of the factors that influence paste release are the stencil thickness, whether it’s polished or not, the angle of the cut, ratio of thickness to width and paste properties. How long the paste has been exposed to air as well as the room’s temperature and humidity can also have an impact. Lots of permutations.

If you’re reading this Owen, sorry I missed your question in the chat. I hope this answers it for you.

Duane Benson
If it’s going to the EU, make sure it’s peanut butter-free.

March Madness and Printed Circuits

March is traditionally known for the promise of spring and for the madness that accompanies college basketball. But in the world of printed circuit boards March means the Virtual PCB event. Yes, it’s already that time again. Virtual PCB is live next week, March 8 and 9 on a computer near you.

If you have not visited the show in the past, this year you owe it to yourself to check it out. It’s easy, you can look at things at your own pace, and you never even have to get on a plane or worry about parking. All the travel is through the wonders of the internet.

I’m not going to get into all of the things that will be going on at Virtual PCB, Mike Buetow’s post on here does a good job of that. But I want to make everyone aware that Virtual PCB is live March 9 and 9 and that we all hope to “see” you there.

Stay in touch,

Virtual Show, Real Value

We are eagerly looking forward to next week’s Virtual PCB trade show. It’s the fourth year we’ve produced the Web-based event, and we’ve learned a few things along the way.

1. Although the attendees are online, they usually act as if they are in the flesh. There’s plenty of the “how are you doing,” “great to see you,” and gentle ribbing that takes place when we run into each other at PCB West, SMTAI, Apex or one of the other “bricks and mortar” shows. It’s social. (Perhaps that’s why they call it “social” media.)
2. People are polite to the point of near invisibility. Just like a physical show, some attendees do lots of talking, while others never utter a peep. That’s OK. Lurk away. Everyone learns in their own way.
3. Speaking of learning, it’s almost impossible to attend Virtual PCB and not take away something. Nearly 3,000 people registered last year! These are your peers across the entire electronics manufacturing spectrum, from design to assembly to test. The same experts you might see at a physical show — folks like signal integrity expert Dr. Eric Bogatin or reliability guru Werner Engelmaier, will be there, holding court and sharing their wisdom. More than that, it’s a chance to meet folks from all over the world. These are potential future colleagues and employers. Insofar as networking is concerned, it’s tough to beat.

We hope you take a moment to register (it’s free!) at and log-on to Virtual PCB, March 8-9. It’s a fresh way to stay up on our industry — without ever leaving your desk.

A Show of Hands

I recently heard report on NPR about multitasking that said humans are just not that effective at it. If we try to work on two things at once, the reporter said, one will suffer.

Now, I’m kinda mixed on this one. On the one hand, I like to think that I can keep at least three balls in the air at the same time. On the other, I realize more and more every day that when I try to do this, something is not getting my full attention and will suffer. Of course, getting older doesn’t help.

But in my defense, right now I have two computers open to Virtual PCB, viewing the show as both and exhibitor and an attendee. And to top it off, I’m writing this blog. None of this is brain surgery, so there is the level of attention required for each to be considered. What I really want to find out is why attendees at Virtual PCB get shy and reluctant to contribute in the scheduled chats. One of the chats this morning had 20 or more people in the “room,” but every time the host or moderator asked a question, no one had anything to contribute. No wonder PCB people outside of design say that we are apathetic.

It is true for most things I can think of: You get out of it in equal measure what you contribute. Get off your hands, people, and quit being so passive.