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May03
Trouble Shooting Guide for Plastic Injection

Trouble Suggested Remedies (Solutions)
DIMENSIONAL PROBLEMS  
Shot-to-shot dimensional variations
  • Increase injection pressure
  • Maintain uniform pad (cushion)
  • Repair leaking back flow value if pad cannot be maintained
  • Increase screw forward time
  • Maintain uniform cycle
  • Eliminate un-melted particles (see below)
  • Use larger machine or screw designed for DELRIN
Warping
彎曲變形
  • Balance mold temperature
  • Decrease mold temperature
  • Increase/decrease screw forward time
  • Increase/decrease injection pressure
  • Clean water channels in mold; improve mold cooling system
  • Improve part design
  • Change or add ejector pin locations
EJECTION PROBLEMS  
Parts stick in mold
黏模
  • Decrease injection pressure
  • Decrease injection rate
  • Decrease screw forward time
  • Increase cycle (possible only temporarily)
  • Use mold release temporarily
  • Correct mold defects (undercuts)
Sprue sticking
澆口堵塞
  • Remove burrs on sprue
  • Correct alignment between sprue and nozzle
  • Decrease screw forward time
  • Increase nozzle temperature
  • Increase mold cooling time
  • Use nozzle orifice smaller than sprue bushing
  • Increase taper of sprue
  • Use mold release temporarily
FILLING PROBLEMS  
Short Shots
短料
  • Maintain uniform pad
  • Repair leaking back flow value if pad cannot be maintained
  • Increase injection pressure
  • Increase injection rate
  • Increase melt temperature
  • Increase mold temperature
  • Enlarge vents
  • Change vent location
  • Increase overall cycle
  • Use screw designed for DELRIN
  • Use larger machine or injection unit
Voids in parts
  • Increase injection pressure
  • Increase screw forward time
  • Decrease injection rate
  • Decrease melt temperature; improve melt uniformity
  • Repair leaking back flow value if pad cannot be maintained
  • Enlarge vents
  • Improve gate size or location
  • Eliminate any restrictions in runner or nozzle
Weak Welds
熔接線
  • Increase injection pressure
  • Increase injection rate
  • Increase melt temperature, but avoid excessive temperature
  • Increase mold temperature
  • Avoid mold release spray
  • Enlarge vents
  • Change vent or gate location
  • Use larger machine or injection unit
MELT QUALITY PROBLEMS
Mold deposit
黏膜
  • Decrease injection rate
  • Decrease melt temperature
  • Avoid resin contamination
  • Correct hold-up spots in cylinder, screw, nozzle assembly
  • Increase gate size, flare gate
  • Enlarge vents
  • Change vent location
  • Use hopper drier to improve reground resin
Odor
氣味
  • Observe melt appearance (gassing) and measure melt temperature
  • Reduce cylinder temperatures if melt temperature is high.
  • Avoid resin contamination
  • Reduce overall cycle to decrease holdup time
  • Correct hold-up spots in cylinder, adaptor, nozzle, screw tip and check value assembly
  • Use smaller injection unit
Un-melted Particles
顆粒未融
  • Increase cylinder temperature
  • Increase back pressure
  • Reduce screw RPM
  • Use hopper drier to preheat resin
  • Increase overall cycle
  • Use screw designed for DELRIN
  • Use larger machine or injection unit
SURFACE PROBLEMS
Black sports or brown streaks
黑點/條紋
  • Decrease cycle
  • Avoid resin contamination
  • Correct hold-up spots in cylinder, screw, nozzle assembly
Blush, Frost, and Folds
變色/折疊
  • Decrease injection rate
  • Increase mold temperature
  • Change gate location
Gate Smear
  • Increase mold temperature
  • Decrease mold temperature
  • Change gate location 
Jetting
擠壓
  • Increase melt temperature
  • Increase or decrease injection rate
  • Increase gate size, flare gate
  • Change gate location
Pits, Orange peel, Wrinkles
傷痕、脫皮、皺摺
  • Increase injection pressure
  • Increase injection rate
  • Increase screw forward time
  • Increase mold temperature
  • Increase melt temperature
  • Enlarge vents
  • Increase gate size
Sinks
下陷
  • Repair leaking back flow value if pad cannot be maintained
  • Increase injection pressure
  • Increase screw forward time
  • Increase or decrease injection rate
  • Decrease mold temperature
  • Decrease melt temperature
  • Increase gate size
  • Change gate location
Splay
  • Decrease melt temperature if it is too high
  • Reduce cycle to decrease holdup time
  • Avoid resin contamination
  • Increase or decrease injection rate
  • Correct hold-up spots in cylinder screw, nozzle assembly
  • Increase size of small gate

Apr07
Solution to the Drop of First-Side Part during the Second Reflow Soldering

Solution to the Drop of First-Side Part during the Second Reflow SolderingFirst of all, with the rapid growth of mobile phone technology, the Electronic Manufacturing Service (EMS) in mainland China sometimes meet serious labor shortage. Second, the Industry 4.0 promotes the requirement of factory automation for each EMS. Therefore, many parts which cannot adopt SMT reflow process are requested to fulfill Paste-In-Hole process (PIH process), such as the type-A USB connectors, Ethernet connector, power supply sockets, transformers, and so on. Originally, most of these kind of devices were touch-up soldered after SMT process.

Because of labor shortage, also for the purpose of saving process cost, and under the consideration of quality, many SI and EMS have requested that the parts which cannot adopt SMD process should fulfill at least PIH process, so that the soldering of all the electronic parts on circuit board can be completed after SMT process.

read more…》

Mar09
Process Impact of Substituting SMD Parts with Paste-In-Hole Parts

SMD PIHToday, one question from my boss, “Is there any difference or influence on the process and design if we like to convert the SMD parts to DIP type and go through the PIH(Paste-In-Hole) process?”

Later, I realized that the question aimed to avoid the damage of connector caused by customers’ misuse.

Sometimes, Paste-In-Hole (PIH) is also called Pin-In-Paste (PIP).

First, since the traditional insertion parts through PIH process is necessary to be manufactured with high-temperature reflow process, the part design should fulfill the considerations listed as follows:

read more…》

Feb01
Solder Preforms – Another Choice for Solder Volume Increasing Solution

Today, most of electronic parts are developed into smaller size. The small chips are downsized from 1206 to 0805, 0603, 0402, 0201, even to 01005. The size of chip is smaller; the required solder volume is less.

Moreover, the required stencil thickness becomes thinner from 0.18mm to 0.10mm. Some parts, however, cannot be downsized unlimitedly, such as external connectors. For example, a line socket of telephone, a network line socket, a smart card reader, and other devices require a certain amount of solder volume to ensure the soldering strength and quality. In addition, some traditional insertion parts (Dual in line package process, DIP) with paste-in-hole process require extra solder volume as well.

read more…》

Jan04
What is Step-up & Step-down Stencil? Selective Solder Paste Volume Increasing Solution

Step_down_stencilToday, the SMD parts become smaller and smaller. Their sizes can be developed to 0402, 0201, and even 01005 (Note 1). Moreover, the pitch between the pins of a common IC (integrated circuit) is shorten to fine pitch of 0.5mm, even 0.3 mm. The improvement becomes a challenge for the SMT process.

A great challenge for each SMT engineer is how to weld these thin electronic parts on circuit boards without any non-wetting or short-circuit. In addition, it is more difficult to solder few larger parts and a lot of thin ones on a circuit board than to solder thin parts without any larger ones.

read more…》

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