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May12
Humidity Temperature Cycle Profile

Humidity Temperature Cycle Profile

The humidity test is designed to determine the effects of humidity on the product and assure that the product will meet published specifications while being subjected to high humidity conditions. This is an accelerated test to uncover failure modes in components, assemblies and process, which may appear in the field during normal service, while keeping test time at a minimum. Performance tests are made at various intervals of the test duration and each test must pass for the design to meet the requirements of this section.

Hygroscopic materials (e.g., printed circuit boards, molded plastics, sealed components, etc.) will absorb moisture proportional to the applied vapor pressure and time of application. Excessive moisture penetration may cause swelling of material or contamination actions, destroying functional ability as well as causing leakage paths between sensitive circuits, result when moisture reacts with trapped chemicals from construction processes causing corrosion or severe etching of metal surfaces. In some cases dendritic growth can cause short circuits or high voltage flashover between closely spaced traces or pin spacing. The following humidity test is designed to accelerate the occurrence of these failure mechanisms if they exist.

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May05
Why Burn/In(B/I) still cannot screen out the DDR soldering fail?

Recently we met a DDR memory BGA (Ball Grid Array) soldering fail issue. Actually the is HIP (Head-In-Pillow) that two balls under the BGA package. We sent a people to field to check how customer do the operation and found the product can’t be powered on. The interesting is the product will be powered on once use finger to press the DDR memory component.

How come this happen? Production line said these products had implemented the power on B/I (Burn/In) for 12 hours at 40°C. Why we still see this kind of BGA soldering defect in field?

Before answer this question, we must understand how the HIP defect happen. The HIP is a solder joint defect where the solder paste deposit wets the pad, but does not fully wets the ball. It is usually caused by the deformation of PCB resin and BGA substrate during reflow high temperature. The deformation make the solder paste on pad and ball on BGA separately while solder become liquid phase. Once the parts start cooling and the deformation will gradually back to normal condition but the liquid solder also back to solid and make two balls as HIP.

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May01
How come the screw boss crack after mold-in screw insert?

screw boss brokenActually this is long ago issue and WorkingBear write down this article just for a record.

One day we received a complaint from field and complained our product had plastic house broken issue. Actually this crack can be saw from outside of the plastic case. So the crack is really terrible.

As checked the defect plastic parts and found the crack all came from the screw boss from inside to outside of plastic house. There is a mold-in screw INSERT be installed inside the plastic boss. We think the potential cause shall come from the screw boss design and plastic inject condition.

Here WorkingBear will try to list out  the screw boss crack potential causes for your reference and also take a memo for myself:

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Apr29
How to design LCM gasket/cushion for manufacture?

The gasket/cushion went outside of LCM

The LCM (LCD Module) is a common component for the electronic products. Almost of the LCM was made by glass and it is brittle and  break easily while hit or drop on the floor due to handle careless. As product design we will install a rubber gasket or cushion locate between the glass and plastic case or metal bezel to prevent it from squeezing due to press or careless hitting.

Although this kind of rubber gasket is a simple design but if the gasket didn’t design well then the installation will be a big challenge in manufacturer. We often see the gasket go outside of the display view area. If this is a touch panel product then it will result the touch function fail. If this kind of issue happens in filed then we will get big trouble.

Therefore, this article attempts to look for the rubber gasket design methods.

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Apr27
How EMS fabricate a PCB Assembly?

How EMS (Electronic Manufacturing Services) fabricate a PCB (Printed Circuit Board) Assembly?

This article is writing for the people who still not yet really under what is the PCB Assembly. Because WorkingBear found there are many people just come to this EMS area and still not yet well understand what is SMT (Surface Mount Technology) and what is Wave Soldering.

The PCB Assembly is a very popular technology in modem industry.  For example, the cell phone, Tablet, Computer, Television, Remote toy car, etc. all have the PCB Assembly module  inside. The  invention of PCB Assembly technology is really help the electric products development trend to small size and multi-function.

So, how EMS fabricate a PCB Assembly? It is almost automatic production line now through SMT or wave soldering process to solder the electronic components on the board to instead of hand soldering by iron. Of course, you still can hand solder all electronic components on the board as manual by yourself but you must take high risk for the poor solderability quality and can’t do it mass production. Besides, the 0201 small chip are hard to be hand soldered on board and some of the package that design the soldering point under the package body can’t be hand soldered. For example BGA, QFN, LGA package.

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