Nov 2010 Vol. 2, Iss. 35
Treating PCBs as MSD Devices?
As a general rule it is a good idea to bake out PCBs being used for lead free rework. A general rule of thumb for rework of FR4 and flex based materials is 125 degrees C for 8 to 12 hours to insure that all moisture absorbed into the PCB materials are driven out.
One needs to be careful to consider all of the components on the already-populated PCB that will be subject to the bakeout. Batteries, underfilled or glued components and connectors are the most common components which will need to be investigated for their heat withstand characteristics. Either parts will need to be removed or one must decrease the temperature while increasing the length of bake out at a lower temperature in order to get around this limitation.
With the higher incidence of delaminating due to moisture absorption inside the laminate during lead free rework process the boards need to be handled as MSD devices. The presence of moisture and higher peak reflow temperatures simply compound the problem.
|Does the Metal Used in SMT Stencils Matter?|
PHD material is a high Nickel content stainless alloy used by BEST to make SMT metal stencils. The grain structure is smaller, the heat withstand properties are superior to standard stainless steel and the thermal stability is better than other stainless steels.
The BEST material gets you better print results. The superior release characteristics means that you get higher print resolution. The smoother walls and the lack of grain bias means there are fewer areas for the solder paste to "hang up". The paste is more easily released, and results in a superior print quality.
Different Turkeys for Thanksgiving
Looking for something different to serve this Turkey Day? Shaped like a turkey, the perfect addition when nonvegetarians like Steve Jobs comes over for dinner for the holidays.
On the complete opposite side of the spectrum how about a pre-stuffed turkey with alligator meat. Pure carnivorous eats!
|TABLE OF CONTENTS|
|PCBs as MSD Devices?|
|Superior Metal Stencils|
|A Different Kind of Turkey|
|BGA Reballing Preforms|
|PCB Repair Kit|
|Last JSTD-001 and IPCA-610 and IPC7711/21 Classes for 2010 |
|BEST will be holding the following instructor (CIT) classes in the last several weeks of 2010: |
JSTD-001 11/29 -12/ 3
IPC 7711/21 12/13-12/17
Call (847) 797-9250 and speak with Katy.
|"StikNPeel(TM)" Rework Stencil |
|BEST has developed a new "StikNPeel" rework stencil which insures board to stencil coplanarity. It is flexible for tight space fit requirements and does not need to be cleaned. This makes for a more repeatable, faster rework process. |
These stencils are available in either 4,5 or 6 mil thicknesses.
COST: ONLY $80.00 for a package of (10) stencils.
|VOCAB- Word of the Month |
"hag-ee-OL-uh-tree, hay-jee- " which is a noun
The vocabulary you use tells others your level of intellect.
1. The worship of saints, OR
2. Treating someone with undue reverence.
" The doctor will still occupy a good position in our national pantheon even if we discard hagiolatry and subject him to a more mature historical evaluation."
|Custom Thermal Shields from BEST |
These custom insulators are available in mica, fish paper, aramid paper, kapton, polyimides as well as a host of others. Maximum sizes which can be processed are 200 x 200mm with minimum features sizes of 0.15mm.