Most of what I've read lately about using lasers is about making tiny vias and other advanced packaging applications. But lasers can do a lot of great stuff for garden-variety flex circuits too!

One of the best uses of lasers is to cut circuit outlines, holding tolerances down to +/-0.001. This is super for making prototypes and low volume applications that need these tight tolerances without spending tens of thousands of dollars for hard tooling. And if the outline changes, you just modify the CAM program and the change is complete. No expensive tooling modifications!

Lasers can also produce very precise coverfilm openings after lamination. By using a low power setting, laser beams will burn through polyimide and adhesive but will be reflected by copper. This creates coverfilm openings with no adhesive squeezeout that are registered very precisely to the etched circuitry. The picture on the left shows a single-sided flex with coverfilm openings made by laser. It would have been virtually impossible to make this part with a regular punched coverfilm because the squeezeout would have left no annular ring for soldering. As you can see all the holes have ample solder for assembly, and yet there are as many as three traces passing between pads.

With these smaller coverfilm openings the designer can stuff more surface mounted components in a smaller space. This can be very significant when designing with small components, such as 0402 caps and resistors. This same method can be used to create backside access to the copper, allowing components to be placed on both sides of a single-sided circuit.

Lasers can also cut coverfilm prior to lamination with the same precision they cut circuit outlines, and they can be used to repair or rework circuits.

Finally, lasers can create unsupported leads in a conventional circuit by burning away the polyimide and adhesive, leaving the lead suspended in air. This allows the flex to be soldered directly to a rigid board or another component. The picture below shows unsupported leads in a circular pattern.

There are two flex shops in the USA that I know of that have lasers in-house: M-Flex in Southern California, and ADFlex in Arizona. Mektec in Northern California has access to laser processing at their main factory in Japan, but they have no laser processing here. They can be reached at:

ADFlex
2001 W. Chandler Blvd.
Chandler, AZ
602-963-4584
Fax 786-8490
www.adflexsolutions.com

M-Flex
1301 North Dynamics Street
Anaheim, CA 92086
714-996-1248
Fax 996-3834
www.mflex.com

Mektec
1740 McCandless Drive
Milpitas, CA 95035
408-945-6666
Fax 945-0118
www.mektec.om

There are several laser specialists that do job-shop work for the flex circuit industry. The best known in the industry is D Squared in Arizona. Dale Ristedt and Dale Lockwood both used to work for ADFlex, and their company specializes in using laser processing flex circuits. I have used them many times and they do fine work.

Applied Laser Technology in Beaverton, OR also has a lot of experience with flex. Sig Jensen worked with lasers at the old flex division of Tektronix.

Allflex, a super flex proto shop in Northfield, Minnesota, also uses SPECTRAlytics in Minneapolis for laser processing. Allflex said they do a good job.

Other companies I have heard of: at Flexcon this year I met the folks from Neuman MicroTechnologies in New Hampshire. They sell lasers to flex manufacturers as well as doing job-shop work. Another laser manufacturer, Electro Scientific Industries (ESI) in Portland, is beginning to accept job-shop work, especially from flex manufacturers interested in evaluating their machines. Finally, the folks at ESI told me about Microsound in the Seattle area. Microsound is a small laser shop that uses ESI lasers. They can handle prototype quantities and quick turn work.

If you know of other laser shops that can process flex circuits let me know and I will add them to the list.

D Squared
1125 N. Mondel Drive
Gilbert, AZ 85233
602-813-5850
Fax 813-5998
www.primenet.com/~dsquared

SPECTRAlytics
7456 West 78th Street
Minneapolis, MN 55439
612-942-5853
Fax 942-5682
www.spectralytics.com

Neuman MicroTechnologies
26 South Main Street, #112
Concord, NH 03301
603-228-6862
Fax 228-6894
tlneusales@AOL.com

ESI
13900 NW Science Park Drive
Portland, OR 97229
503-641-4141
Fax 643-8873
www.esio.comr

Microsound
420 NW Gilman Blvd. Suite 2651
Issaquah, WA 98027
425-392-7784
Fax 392-2551

Applied Laser Technology
14155 SW Brigadoon Court
Beaverton, OR 97005
503-641-4400
Fax 641-6696

Tom Woznicki is the owner of Flex Circuit Design Company, a consulting company in Silicon Valley that specializes in designing flex circuits. He can be reached at TWoznicki@AOL.com or 1-888-FLEXMAN.

This article was published in the November/December 1997 issue of Flexible Circuits Engineering magazine. It was edited slightly for this website.
Photos are courtesy of D Squared.

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©1997 Tom Woznicki. All rights reserved.