Archive for the ‘Dry Baking’ Category

Simple Yield Improvement. (Part 2)

Sunday, January 6th, 2013

In the previous post we discussed what happens to the printed circuit board structure when it is heated. We discussed how different materials expand at different rates and the effect the expansion rates have on the warp and twist of a Printed Circuit Board (PCB). We also discussed how moisture absorption can increase the degree of warp and twist and the adverse effect it has on assembly yields and potential field failures. We also discussed how dry baking removes moisture from the PCB and how it minimizes if not eliminates potential problems.

In this post we shall discuss the stabilizing effect that (more…)

Simple Yield Improvement. (Part 1)

Monday, December 31st, 2012

Over the past 15 years we have seen some very amazing advancements in technology. Our electronic devices have become smaller, faster and more powerful. The capabilities of these new devices have brought science fiction to life for many of us. What the common consumer does not realize is that these advancements have occurred in a more destructive Lead-Free assembly process. Lead Free assembly methods consisting of higher assembly temperatures (around 260ºC) for longer dwell times at temperature along with a smaller processing window for success. The assembly methods today are challenged to not only maintain yields but to improve them. All the while cutting costs where ever possible. The desire to cut cost is where we see the result of unintended consequences.

I have been asked repeatedly by customers for my opinion on methods to improve yields. I evaluate designs and work with designers and assemblers on solutions to help them improve yields. This includes in process and post process yields. In other words build it right the first time and make sure it lasts in the field. A common question I am asked by customers is…

What is the one thing that we can do that can  improve our yields?

The answer is very simple… (more…)

Dry bake test results.

Saturday, August 29th, 2009

Printed circuit boards shall absorb moisture to the point of equilibrium. This shall occur as long as there is a source of moisture. Relative humidity provides an ample source of moisture for the absorption process. It is common for contract manufacturers to maintain a controlled environment that often relies on humidity to minimize static charge build up. Electro-static discharge (ESD) is damaging to assembled electronic components. Humidifiers are employed to maintain a 50% relative humidity environment. However, in minimizing one problem another is introduced. The humidity that is introduced to minimize ESD is absorbed into the printed circuit board and components alike.

In a production setting on a manufacturing shop floor, (more…)

Dry Bake Oxidation

Saturday, August 8th, 2009

As with any baking operation it is important to realize that the surface finish shall start to oxidize. There are many bake operations employed in printed circuit board manufacturing. When bare copper is baked at 300  deg F for an hour the copper turns color. The copper has become oxidized and must be cleaned prior to continued processing. The final solderable finish shall oxidize as well when exposed to heat. At the time of this posting the IPC and its members are currently working on a specification that deals directly with baking of printed circuit boards. The preliminary specification can be found posted on the IPC web site at… (more…)

Dry baking printed circuit boards.

Sunday, July 19th, 2009

What most people don’t realise is that printed circuit boards are hygroscopic. They absorb moisture from the atmosphere like a sponge does water. Although the absorption process is much slower it does happen. The amount of moisture absorbed is measured and provided on material data sheets provided by most laminate manufacturers. For example  the moisture absorption limit listed on the Isola FR406 data sheet is 0.20 % measured on a .028 inch thick piece of stock laminate. Lead free assembly compliant laminates are even more hygroscopic. For example, Isola IS410 is 0.45 % measured on the same thickness material per the data sheet. Different grades of material from different manufacturers have different moisture absorption ratings. The percentage of moisture absorption increases when you add inner layer circuity and through holes. A low humidity environment results in a slow absorption rate. A high humidity environment results in a fast absorption rate. Moisture shall be absorbed to the point of equilibrium. Once equilibrium is achieved the absorption stops.

Printed circuit boards that have moisture in them can become (more…)