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Many large Original Equipment Manufacturers (OEMs) have a detailed procedure and a significant capital investment in
place for the selection of printed circuit board suppliers. This approval process typically involves one or more site audits
(which,as we know,now involves a significant amount of overseas travel) and non-destructive and destructive qualification
testing by a third party laboratory.
This is all well and good if your company has what seems like unlimited funding to carry out this process,but where does
this leave the small OEM? This paper is intended to assist smaller OEM’s get the most for their money and purchase a
quality product. I was recently in a meeting with a new IPC member who was also new to the electronics industry,and he
made the following statement regarding qualifying their suppliers,“We go to the PCB supplier’s facility for a tour,they take
us to lunch,and they are approved.” He also asked in this same meeting,where in IPC can I go for help to better understand
what I should do,and we did not have a good answer to his question.
Within the past year and a half a blue ribbon committee has been started to assess the feasibility of IPC having a printed
circuit board (PCB) Qualified Suppliers List similar to that of the military for MIL-PRF-31032,MIL-PRF-55110,and MILP-
50884. This will most likely take a few years before we see this listing on IPC’s website. This paper will provide some
basic guidelines in assessing your supplier’s board at a cost that is reasonable to your company.

Recent global environmental regulations affecting consumer electronics and electrical equipment,such as the European Union’s RoHS Directive,China ‘RoHS’ and others,have driven electronics manufacturers to identify the presence and concentration of regulated hazardous substances in their supply chain. These efforts have generally included a close examination of the product supply chain to the homogeneous material level. While the majority of investigatory efforts have relied on supply-chain self-reporting of materials composition,actual materials testing can be of benefit in those instances when supply-chain information is lacking or suspect or if verification testing of final products is desired. While a variety of internationally recognized test methodologies exist there are clear benefits and drawbacks regarding the analytical options available. This paper details the comparison of non-destructive and destructive test methods for the analysis of various plastics and polymers used in electronics. A common non-destructive testing option is x-ray fluorescence (XRF) technology. This approach,while relatively inexpensive and fast,has the added benefit of mirroring the screening testing which regulatory authorities are most likely to use. Destructive testing of materials,on the other hand,provides a more definitive approach. A detailed comparison of the results obtained from testing materials by both technologies is discussed. While clear benefits can be seen from the data presented,it is important to understand the good laboratory practices such as test equipment calibration,duplicate analysis and method blank determination that can greatly impact the results obtained. A thorough analysis of all of this data,not merely the results obtained,is essential in the critical evaluation of the materials tested.

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The proposed revision of IPC-4101 - Specification for Base Materials for Rigid and Multilayer Printed Boards contains new
slash sheets describing FR-4 base materials compatible with lead free assembly. It has been reported in countless papers and
presentations that the new silver/tin/copper and other lead free solders mandate processing temperatures 20-30°C higher than
the time proven tin/lead solder. The six new lead free specifications were developed and incorporated into the IPC-4101B
document in order specify FR-4 base materials with more robust processing windows for lead free assembly. While it is true
that some “more mature” FR-4 products can be used successfully in lead free assembly,most fabricators and assemblers have
found that no single FR-4 product works in all situations.
This paper discusses the new tests incorporated into IPC-4101B,the development of the requirements for lead free FR-4 and
the solutions to various requirements / issues that have surfaced due to the lead free assembly movement.

The regulation requiring lead-free solders for printed circuit boards (PCBs) has presented a number of challenges to our industry at virtually every stage of the process. For the brominated epoxy resins used to make a large fraction of the laminates that serve as the starting material for PCBs,the requirement for higher thermal stability has led to increased use of phenolic curing agents in place of dicy. The good news is that brominated formulations are available that can be used to make laminates that meet the highest IPC specifications for glass transition temperature (Tg > 170 °C) and decomposition temperature (Td > 340 °C). However,phenolic curing agents lead to some compromises in other properties,especially toughness and copper adhesion. A general comparison of the properties of phenolic cure vs dicy cure will be made,along with some guidelines for application. The thermal stability of non-brominated resins is inherently greater than that of brominated resins,and meeting the highest Td specifications is not a challenge,even with dicy cure. Therefore non-brominated resins are well suited for lead free applications. Furthermore,unfilled non-brominated resins have improved dielectric properties and lower densities. However,non-halogenated resins are more expensive and exhibit greater water absorption. Achieving high Tg’s (> 170 °C) can be a challenge,but this is now possible with commercially available materials. A comparison between brominated and non-brominated resins will be made.

Silicones are often used to protect electronic applications designed for cold environments. The low temperature flexibility
of silicones is well recognized,but not as well understood. While the actual Tg of silicones is about -120°C,they do
transition from a soft rubber to a harder rubber around -45°C. At the transition their hardness,strength and modulus
increase slightly while elongation decreases slightly. Very soft silicone gels show the greatest change,becoming more
rubbery and in some cases showing tears. These tears can self-heal within a few weeks at warmer temperatures.
The specific temperature where these changes take place is shown to be dependant on the rate of cooling. Slow cooling
will show this transition around -45°C for many silicone elastomers. Analytical tests may indicate performance limits that
are too conservative. On the other hand,rapid cooling and short dwell times often used in thermal shock and cycling tests
may not detect stress changes that could occur in slower cooling conditions unless a sufficiently long low temperature soak
is included in the testing regime. Lower temperature versions of silicones are available that do not show property
transitions until -80°C or even until -120°C.

While glass fibers are commonly used to reinforce circuit board substrates,they have a high dielectric constant and loss.
Cyclic olefin copolymer fibers have a lower dielectric constant and loss. By combining these fibers with glass fibers in
unique hybrid cloths,we have made circuit board substrate materials with a dielectric constant of 3.08 and loss tangent of
0.013 using standard epoxy resins that are common in FR-4 glass reinforced substrates. The comparative glass materials had
a dielectric constant of 4.49 and loss of 0.019. In another embodiment,the cyclic olefin copolymer fibers were melted to
form the resin component,yielding a substrate with dielectric constant of 3.25 and loss tangent of 0.0013. In the last
example,a special low dielectric resin was used,giving a substrate with dielectric constant of 2.8 and loss tangent of 0.0009.
Substrates made from this fiber have passed Peel Strength,Solder Float,Water Uptake,and have a low coefficient of thermal
expansion.