In a past life we used CEM-3 material and had problems with it's expansion
rate. What we saw was that as the board was manufactured it would
grow/shrink ~.001/linear inch. This gave our assy people quite a bit of
frustration not to mention our incoming inspection department went mad
trying to inspect the boards. Personally I would stick to the FR-4 material
since the cost difference between the material is close but the assy &
manufaturability of the material causes some problems.
Steve Collins
----------
> From: Christopher Jorgensen <[log in to unmask]>
> To: [log in to unmask]
> Subject: [TN] Specification for Laminate Based on End Usage
> Date: Tuesday, March 02, 1999 10:29 AM
>
> TechNetters,
>
> Can anyone out there give Tim some recommendations based on your
experiences?
>
> +++++++++++++++++++++++++++++
>
> Name: Tim Bowe
> Company: Diebold, Inc
> E-Mail: [log in to unmask]
>
> Comments:
>
> I am looking for some direction on what type of laminate base material
should be
> specified for rigid printed circuit boards used in Diebold products.
After reviewing
> numerous IPC and UL documents, I do not clearly understand the pros and
cons of
> various laminate grades and their specific applications and am asking
you, who use
> these materials on a daily basis, for assistance and recommendation.
>
> We have qualified a new color monitor for our ATM machines from a
domestic and
> off-shore supplier. Monitor performance is categorized as Class 2
Dedicated Service
> Electronics Products classification listed in IPC-6011 where high
performance and
> extended life is required and for which uninterrupted service is desired
but not
> critical.
>
> The monitor PWB is single-sided, approximately eight-inches square,
supported by
> corner stand-offs in a metal chassis. Components are all thru-hole
connection. Some
> of the power transistors require free-standing heat sinks. Other bulky
components
> include coils and transformers. This AC operated device incorporates an
internal
> universal switching type power supply integrated onto the PWB. AC input
voltage
> range is: 100-vac to 240-vac. There is also several hundred volts
present on other
> circuit traces required by the CRT (cathode ray tube).
>
> To meet our reliability requirements, the domestic supplier plans on
using FR-4
> laminate with plated-thru-holes; the off-shore supplier contends
equivalent
> reliability with their CEM-3 laminate material without plated-thru-holes.
The
> following Diebold requirements need to be considered in making this
supplier
> selection:
>
> 1) Operating Temperature: 0C to 60C @ 95% RH (max). For reliability
predictions, the
> operating temperature is 30C, 90% of the time and at the extremes 5% of
the time.
>
> 2) Shipping/Storage Temperature: -40C to +70C. Absolute humidity content
not to
> exceed 100% at 32C. The off-shore supplier will probably ship product by
boat to a
> domestic warehouse facility until required by Diebold for "just in time"
delivery.
> Is laminate moisture absorption of CEM-3 vs. FR-4 a product reliability
concern
> during this transit process? Specifically, storage in possibly hot/humid
shipping
> holds for a number of weeks.
>
> 3) Transit Vibration: This product is shipped from Diebold either
installed in an ATM
> or individually boxed for field service replacement. In either case,
this product
> may ship anywhere internationally. How does the laminate flexural
strength
> characteristics of CEM-3 vs. FR-4 affect product reliability due to
transit vibration
> effects? What about product reliability during various "handling
processes" of the
> individually boxed version?
>
> 4) Flame Retardency: What is the difference between the NEMA FR-4 and
CEM-3 ratings
> for these laminate materials? Which is best suited for Diebold's needs?
>
> Our annual volume requirement is 10K - 12K. If the off-shore supplier is
selected,
> there is an additional annual cost savings of a couple hundred thousand
dollars.
> Although cost is an issue, Diebold's primary mission is delivering
defect-free
> competitive products and services on time to our customers. What is your
> recommendation on the PWB laminate material type we should specify?
>
> Your assistance in this matter is greatly appreciated.
>
> Sincerely,
> Diebold, Inc.
>
> Tim Bowe
> Module and System Development
> Diebold, Inc.
>
> Voice: 330.490.4668
> FAX: 330.490.4508
> em@il: [log in to unmask]
>
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