The electronic industry grows quickly. Each vendor takes responsible to his own component only to make it good and low cost. Take a flashlight manufacturer as example. There are bulb, wires, switch, spring, and plastic or metal housing make up the flashlight. The manufacturer buys all the sub-components from each supplier and assembles them together to fabricate the flashlight then sell to end-user.
All the sub-components are delivery by air, ocean, or truck to destination. It is important to prevent the delivery parts without damage during transferring. Most of the packaging uses corrugated paper carton and cardboard to hold inside components and prevent it from damage by falling or throwing down by porter or carrier.
The purpose of temperature environmental test is that the good are shipped by various types of carriers and experience a wide range of storage temperatures, depending on the customer environment, hence the need for this kind of testing. Further, certain components and assemblies are sensitive to these temperature extremes and could be weakened due to induced stresses. Therefore, it is important that a logical sequence of testing be followed in order to observe these effects and assure the product’s performance under various temperature conditions and after temperature extremes have been applied.
(Note: This test didn’t include the humidity.)
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.
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.
Actually 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 on plastic is really terrible.
As checked the defect plastic parts and found the crack all locate at screw boss location and broke from inside to outside of plastic house. There is a mold-in screw INSERT parts was installed inside the plastic boss. We thought the potential cause shall come from this 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: