Apr23
The benefit to use shielding clips to instead of shielding frame

post on April 23, 2015

SMT can clipFor almost of the frequency radio apparatus, the Printed Circuit board must design the shielding frame/can to prevent the EMI (Electromagnetic Disturbance Interference) effect. The regular design will apply one shielding frame to mount on PCB by solder and another shielding can to cover on the frame to isolate the RF.

That means there will be two press tools cost before implement this solution. Beside, the shielding frame must be mounted on the PCB by SMT process. It requires lower flatness specification to keep the solder joint well. Most of the shielding frame asks its flatness meet 0.12mm maximum. Some of the shielding frame even asks the flatness must lower than 0.10mm maximum. Because of current stencil thickness is around 0.10~0.127mm only. It brings more difficult to form the shielding frame and raise its cost.

read more…》

Design, SMT, Soldering     WorkingBear    Views (5,994)     comment (0)

Apr23
How many dimple need to be used for keypad metal dome?

post on April 23, 2015

metal_dome_5_dimplesLast article I mentioned that my company applied the metal dome without dimple as keypad contact solution just like the cell phone but we had trouble and met keypad press insensitive  issue. Now we solved the problem by adding the dimple back to the metal dome and still reach 1,000,000 (one millions) times of finger press cycle life.

We did some failure analysis and found the keypad insensitive defect was caused by two major issues.

  • One is the foreign contamination, include dust and fiber, that I mentioned at last article.
  • Another one is the oxidation show on the immersion gold finished surface on the ENIG board pads.

We found the oxidation particles look like the chemical of Phosphorus (P) exuded from base material of PCB. The P is one of the major element for the ENIG fabrication process. So we only can control less P but can’t remove it from the board.

read more…》

Design, Keypad, Quality     WorkingBear    Views (5,044)     comment (0)
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Apr22
The Importance of Dimples in Metal Dome Keypads

post on April 22, 2015

Keypad contact pad with fiber contaminationforeign dust contaminate inside metal dome and make contact fail.

Recently, our company introduced metal dome technology as a contact solution for rubber keypads, a trend also seen in many cell phone keypad designs. The advantages of using metal domes include a better key press experience, extended lifespan, and improved reliability. According to data, metal dome keypads can endure 2,000,000 finger presses compared to the 300,000 presses of poly-dome keypads. read more…》

Design, Keypad, Quality     WorkingBear    Views (5,692)     comment (0)

Apr22
HotBar FPC Design Notices

post on April 22, 2015

Hot_bar_thermodeThe HotBar soldering is a kind of selective soldering solution where connect two pre-fluxed, solder coated parts by pulse heating element, call a “thermode”, with proper temperature to melt the solder and re-solder.

Applying a pressure and contacting on the soldering target is necessary to melt the solder and insure that components stay in place during cooling.

The regular HotBar reflow process is to pre-print the solder paste on the PCB then go SMT reflow to make the solder on the PCB. After that then stick the FPC on the board and melt the solder again through thermode to connect the FPC on PC board. It may need to apply the flux on the solder since original flux had gone during high temperature of reflow oven.

In order to mount FPC on PCB, a thermal-conductor inside FPC to transfer heat from thermode to PCB to melt the printed solder on PCB is necessary.

read more…》

Design, PCB/FPC/PTF     WorkingBear    Views (10,883)     comment (0)
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Apr21
Design Guideline for Flex cable(FPC) Trace Pattern

post on April 21, 2015

FPCMany FPCB designers may not be well-versed in the manufacturing process and its limitations. Workingbear have often come across designs that don’t meet DFx requirements, where designers insist on their approach, leading to numerous quality issues during mass production.

In an effort to prevent future quality failures and high costs due to yield losses, I propose that FPCB suppliers share some manufacturing insights regarding flex cable (FPCB) design capabilities.

read more…》

Design, PCB/FPC/PTF, Quality     WorkingBear    Views (5,352)     comment (0)